ELECTRODE ASSEMBLY, BATTERY, AND BATTERY PACK AND VEHICLE INCLUDING THE SAME

An electrode assembly, a battery, a battery pack and a vehicle including the same are provided. The first electrode of the electrode assembly includes a first active material portion coated with an active material layer and a first uncoated portion not coated with an active material layer along a winding direction, the first uncoated portion includes a plurality of segments independently bendable along the winding direction and exposed beyond a the separator of the electrode assembly, the plurality of segments are aligned along a radial direction of the electrode assembly to define a plurality of segment alignments spaced apart in a circumferential direction of the electrode assembly, and an electrolyte impregnation portion in which an end of the first active material portion is exposed between winding turns of the separator is included between adjacent segment alignments of the first uncoated portion in the circumferential direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Korean Patent Application No. 10-2021-0160490 filed on Nov. 19, 2021, and Korean Patent Application No. 10-2021-0160823 filed on Nov. 19, 2021, in the Republic of Korea, the disclosures of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to an electrode assembly, a battery, and a battery pack and a vehicle including the same.

BACKGROUND ART

Secondary batteries that are easily applicable to various product groups and have electrical characteristics such as high energy density are universally applied not only to portable devices but also to electric vehicles (EVs) or hybrid electric vehicles (HEVs) driven by an electric drive source.

These secondary batteries are attracting attention as a new energy source to improve eco-friendliness and energy efficiency because they have the primary advantage that they can dramatically reduce the use of fossil fuels as well as the secondary advantage that no by-products are generated from the use of energy.

Secondary batteries currently widely used in the art include lithium ion batteries, lithium polymer batteries, nickel cadmium batteries, nickel hydrogen batteries, nickel zinc batteries, and the like. A unit secondary battery cell, namely a unit battery, has an operating voltage of about 2.5V to 4.5V. Therefore, when a higher output voltage is required, a battery pack may be configured by connecting a plurality of batteries in series. In addition, a plurality of batteries may be connected in parallel to form a battery pack according to the charge/discharge capacity required for the battery pack. Accordingly, the number of batteries included in the battery pack and the form of electrical connection may be variously set according to the required output voltage and/or charge/discharge capacity.

Meanwhile, as a kind of unit secondary battery cell, there are known cylindrical, rectangular, and pouch-type batteries. In the case of a cylindrical battery, a separator serving as an insulator is interposed between a positive electrode and a negative electrode, and they are wound to form an electrode assembly in the form of a jelly roll, which is inserted into a battery housing to configure a battery. In addition, a strip-shaped electrode tab may be connected to an uncoated portion of each of the positive electrode and the negative electrode, and the electrode tab electrically connects the electrode assembly and an electrode terminal exposed to the outside. For reference, the positive electrode terminal is a cap plate of a sealing body that seals the opening of the battery housing, and the negative electrode terminal is the battery housing. However, according to the conventional cylindrical battery having such a structure, since current is concentrated in the strip-shaped electrode tab coupled to the uncoated portion of the positive electrode and/or the uncoated portion of the negative electrode, the current collection efficiency is not good due to large resistance and large heat generation.

For small cylindrical batteries with a form factor1865or a form factor2170, resistance and heat are not a major issue. However, when the form factor is increased to apply the cylindrical battery to an electric vehicle, the cylindrical battery may ignite while a lot of heat is generated around the electrode tab during the rapid charging process.

In order to solve this problem, there is provided a cylindrical battery (so-called tab-less cylindrical battery) in which the uncoated portion of the positive electrode and the uncoated portion of the negative electrode are designed to be positioned at the top and bottom of the jelly-roll type electrode assembly, respectively, and the current collecting plate is welded to the uncoated portion to improve the current collecting efficiency.

FIGS.1to3are diagrams showing a process of manufacturing a tab-less cylindrical battery.FIG.1shows the structure of an electrode,FIG.2shows a process of winding the electrode, andFIG.3shows a process of welding a current collecting plate to a bending surface region of an uncoated portion.

Referring toFIGS.1to3, a positive electrode10and a negative electrode11have a structure in which a current collector sheet20is coated with an active material21, and include an uncoated portion22at one long side along the winding direction X. The long side means a relatively long side in a direction parallel to the x-axis direction.

An electrode assembly A is manufactured by sequentially stacking the positive electrode10and the negative electrode11together with two sheets of separators12as shown inFIG.2and then winding them in one direction X. At this time, the uncoated portions of the positive electrode10and the negative electrode11are arranged in opposite directions.

After the winding process, the uncoated portion10aof the positive electrode10and the uncoated portion11aof the negative electrode11are bent toward the core. After that, current collecting plates30,31are welded and coupled to the uncoated portions10a,11a, respectively.

An electrode tab is not separately coupled to the positive electrode uncoated portion10aand the negative electrode uncoated portion11a, the current collecting plates30,31are connected to external electrode terminals, and a current path is formed with a large cross-sectional area along the winding axis direction of electrode assembly A (see arrow), which has an advantage of lowering the resistance of the battery. This is because resistance is inversely proportional to the cross-sectional area of the path through which the current flows.

In the tab-less cylindrical battery, in order to improve the welding characteristics between the uncoated portions10a,11aand the current collecting plates30,31, a strong pressure must be applied to the welding regions of the uncoated portions10a,11ato bend the uncoated portions10a,11aas flat as possible.

When the welding regions of the uncoated portions10a,11aare bent, the shapes of the uncoated portions10a,11amay be irregularly distorted and deformed. In this case, the deformed portion may contact an electrode of the opposite polarity to cause an internal short circuit or cause fine cracks in the uncoated portions10a,11a.

In addition, when the electrode assembly is manufactured in a state where the uncoated portions10a,11aare bent, there is a problem in that the process efficiency is lowered in the electrolyte injection process that proceeds after inserting the electrode assembly into the battery housing. Since there are not enough gaps on the bent surfaces of the uncoated portions10a,11a, it takes a lot of time for the electrolyte to permeate into the inner space of the electrode assembly.

Therefore, it is necessary to improve the structure of the uncoated portions10a,11a, which may improve the bending quality of the uncoated portions10a,11aand improve the electrolyte impregnation rate.

DISCLOSURE

Technical Problem

The present disclosure is designed to solve the problems of the related art, and therefore the present disclosure is directed to providing an electrode assembly having an uncoated portion structure that is improved to relieve stress applied to uncoated portions when the uncoated portions exposed at both ends of an electrode assembly are bent.

The present disclosure is also directed to providing an electrode assembly in which a plurality of segments are provided to the uncoated portion of the electrode, the plurality of segments are arranged in a predetermined direction when the electrode is wound, and an end of the active material layer formed on the electrode is exposed in an area where the segments are not disposed to increase the impregnation rate of the electrolyte.

The present disclosure is also directed to providing an electrode assembly in which the electrolyte injection passage is not blocked even when the uncoated portion is bent.

The present disclosure is also directed to providing an electrode assembly with improved properties of the welding region by applying a segment structure to the uncoated portion of the electrode and sufficiently increasing the segment stack number in the area used as the welding target area.

The present disclosure is also directed to providing an electrode assembly with improved energy density and reduced resistance by applying a structure in which a current collecting plate is welded to the bending surface region formed by bending the segments.

The present disclosure is also directed to providing a battery including a terminal and a current collecting plate with an improved design so that electrical wiring may be performed at the upper portion.

The present disclosure is also directed to providing a battery including the electrode assembly having an improved structure, a battery pack including the battery, and a vehicle including the battery pack.

The technical objects to be solved by the present disclosure are not limited to the above, and other objects not mentioned herein will be clearly understood by those skilled in the art from the following disclosure.

Technical Solution

In one aspect of the present disclosure, there is provided an electrode assembly having a first electrode, a second electrode, and a separator interposed therebetween, the first electrode, the second electrode, and the separator being wound around a winding axis to define a core and an outer circumference of the electrode assembly, wherein the first electrode includes a first active material portion coated with an active material layer and a first uncoated portion not coated with an active material layer along the winding direction, the first uncoated portion includes a plurality of segments independently bendable along the winding direction and extending beyond the separator, the plurality of segments are aligned to overlap each other along a radial direction of the electrode assembly to define a plurality of segment alignments spaced apart in a circumferential direction of the electrode assembly, and an electrolyte impregnation portion in which an end of the first active material portion is exposed between winding turns of the separator is included between adjacent segment alignments of the first uncoated portion in the circumferential direction.

The fact that the plurality of segments included in the segment alignment overlap in the radial direction means that, when a predetermined straight line passing through the segment alignment is drawn from the center of the core, all segments intersect the corresponding straight line.

Preferably, the segments of each segment alignment may be bent along the radial direction of the electrode assembly.

The plurality of segment alignments may extend radially along the radial direction of the electrode assembly.

The plurality of segment alignments may be spaced at regular intervals along the circumferential direction of the electrode assembly.

An angle between adjacent segment alignments along the circumferential direction of the electrode assembly may be 90 degrees, 120 degrees or 180 degrees.

The plurality of segments may have the same length in the winding direction.

Lengths of the plurality of segments in the winding direction may increase gradually from the core toward the outer circumference.

Each segment alignment may have a rectangular or fan shape when viewed along the winding axis of the electrode assembly.

When viewed along the winding axis of the electrode assembly, an area of the electrolyte impregnation portion may be larger than an area of the plurality of segment alignments.

When viewed in a cross section of the electrolyte impregnation portion taken along the winding axis, an end of the first active material portion may be spaced apart from an end of the separator toward a center of the electrode assembly.

A distance by which the end of the first active material portion is spaced apart from the end of the separator may be 0.6 mm to 1.0 mm.

Lengths and pitches of the plurality of segments in the winding direction may be assigned with values substantially equal to values mathematically designed using a predetermined length of a segment in the winding direction and a predetermined angle between adjacent segment alignments in the circumferential direction based on an approximate winding turn structure in which semicircles having periodically increasing radii are connected in the winding direction.

An n+1thpitch (Dn+1) adjacent to an n+1thsegment along the winding direction may be assigned with a value substantially equal to a value determined using the following formulas:

(n is an integer greater than or equal to 0; a start point of a first semicircle corresponds to a location of the first segment in the winding direction; Rnis a radius of an nthsemicircle; Rn+1is a radius of an n+1thsemicircle; θAn+1is a circumferential angle of the n+1thsegment; θDn+1is a circumferential angle for a pitch of the n+1thsegment; the formula of Case 1 is applied when an arc corresponding to the n+1thpitch (Dn+1) is located in the n+1thsemicircle; the formula of Case 2 is applied when the arc corresponding to the n+1thpitch (Dn+1) is located over the nthsemicircle and the n+1thsemicircle).

The semicircles may have radii increasing by Δ/2 (Δ is an interval between adjacent winding turns) at every ½ winding turn.

Δ may have a value substantially equal to a sum of a thickness of the first electrode, a thickness of the second electrode, and two times a thickness of the separator.

A cut groove may be interposed between adjacent segments along the winding direction, and a lower portion of the cut groove may include a bottom portion, and a round portion configured to connect opposite ends of the bottom portion and sides of the adjacent segments.

The bottom portion of the cut groove may be spaced apart from the active material layer by a predetermined distance.

A separation distance between a lower end of the cut groove and the active material layer may be 0.2 mm to 4 mm.

An insulating coating layer may be located at a boundary between the active material layer and an area of the uncoated portion in a region where the bottom portion of the cut groove and the active material layer are spaced apart.

Each segment alignment may include a radial region in which heights of the segments increase from the core of the electrode assembly toward the outer circumference of the electrode assembly.

Each segment alignment may include a height variable region in which heights of the segments increase stepwise from a first height (h1) to an N−1thheight (hN−1), N is a natural number of 3 or more) from the core of the electrode assembly toward the outer circumference of the electrode assembly, and a height uniform region in which heights of the segments are kept uniform as an Nthheight (hN, greater than hN−1).

When a starting radius of a winding turn containing a segment with a height hk(k is a natural number of 1 to N) is defined as rk, 90% or more of a diameter of the core of the electrode assembly may not be covered by the diameter by the bent portion of the segment located at the rk.

When a starting radius of a winding turn containing a segment with a height hk(k is a natural number of 1 to N) is defined as rkand the radius of the core is rc, the height hkof the segment may satisfy the following formula:

Based on a cross section along the winding axis, sequentially along the radial direction, each segment alignment may include a segment skip region having no segment, a height variable region where heights of the segments vary, and a height uniform region where heights of the segments are uniform, and the plurality of segments may be disposed in the height variable region and the height uniform region and be bent along the radial direction of the electrode assembly to define a bending surface region extending along the radial direction.

When the number of segments meeting an imaginary line parallel to the winding axis direction at an arbitrary radius location of the bending surface region based on the center of the core of the electrode assembly is defined as a stack number of the segments at the corresponding radius location, the bending surface region may include a stack number uniform region where the stack number of the segments is uniform from the core toward the outer circumference of the electrode assembly and a stack number decreasing region located at an outer side of the stack number uniform region in which the stack number of the segments decreases toward the outer circumference of the electrode assembly.

In the stack number uniform region, the stack number of the segments may be10to35.

The first electrode may be a positive electrode, and a stack thickness of the segments in the stack number uniform region may be in the range of 100 μm to 875 μm.

The first electrode may be a negative electrode, and a stack thickness of the segments in the stack number uniform region may be in the range of 50 μm to 700 μm.

The second electrode may include a second active material portion coated with an active material layer and a second uncoated portion not coated with an active material layer along the winding direction, the second uncoated portion may include a plurality of segments independently bendable along the winding direction and extending beyond the separator, the plurality of segments of the second uncoated portion may be aligned along the radial direction of the electrode assembly to define a plurality of segment alignments spaced apart in the circumferential direction, and an electrolyte impregnation portion in which an end of the second active material portion is exposed between winding turns of the separator may be included between adjacent segment alignments of the second uncoated portion in the circumferential direction of the electrode assembly.

In another aspect of the present disclosure, there is also provided a battery, comprising: an electrode assembly as described above; a battery housing including an open end and a bottom portion facing the open end, the battery housing being configured to accommodate the electrode assembly in a space between the open end and the bottom portion, the battery housing being electrically connected to one of the first electrode and the second electrode to have a first polarity; a sealing body configured to seal the open end of the battery housing; and a terminal having a surface exposed outside the battery housing, the terminal being electrically connected to another of the first electrode and the second electrode to have a second polarity.

The battery may further comprise a first current collecting plate electrically connected to the first uncoated portion, the bottom portion of the battery housing may include a perforation hole, and the terminal may be a rivet terminal insulated from the battery housing in the perforation hole and electrically connected to the first current collecting plate to have the second polarity.

The battery may further comprise an insulator interposed between an inner surface of the bottom portion of the battery housing and an upper surface of the first current collecting plate to electrically insulate the inner surface of the bottom portion of the battery housing from the first current collecting plate.

The rivet terminal may include a flat portion at a lower end, the insulator may include an opening that exposes the flat portion, and the flat portion may be welded to the first current collecting plate through the opening.

The second electrode may include a second active material portion coated with an active material layer and a second uncoated portion not coated with an active material layer along the winding direction. The second electrode may have the first polarity. The battery may further comprise a second current collecting plate electrically connected to the second uncoated portion, and at least a part of an edge of the second current collecting plate may be coupled to a sidewall of the battery housing.

The battery housing may include a beading portion adjacent to the open end, and the edge of the second current collecting plate may be electrically connected to the beading portion.

The battery may include a cap plate having an edge supported by the beading portion and having no polarity, a gasket interposed between the edge of the cap plate and the open end of the battery housing, and a crimping portion extending toward an inner side of the open end of the battery housing to surround and fix the edge of the cap plate together with the gasket. The edge of the second current collecting plate may be interposed and fixed between the beading portion and the gasket by the crimping portion.

Based on a cross section along the winding axis direction, sequentially along the radial direction, the electrode assembly may include a segment skip region having no segment, a height variable region where heights of the segments vary, and a height uniform region where heights of the segments are uniform, and the plurality of segments may be disposed in the height variable region and the height uniform region and be bent along the radial direction of the electrode assembly to define a bending surface region.

When the number of segments meeting an imaginary line parallel to the winding axis direction at an arbitrary radius location of the bending surface region based on the center of the core of the electrode assembly is defined as a stack number of the segments at the corresponding radius location, the bending surface region may include a stack number uniform region where the stack number of the segments is uniform from the core toward the outer circumference and a stack number decreasing region located adjacent to the stack number uniform region in which the stack number of the segments decreases away from the stack number uniform region.

In the stack number uniform region, the stack number of the segments may be 10 to 35.

The first electrode may be a positive electrode, and a stack thickness of the segments in the stack number uniform region may be in the range of 100 μm to 875 μm.

The first electrode may be a negative electrode, and a stack thickness of the segments in the stack number uniform region may be in the range of 50 μm to 700 μm.

The battery may further comprise a current collecting plate welded to the bending surface region, and in the radial direction of the electrode assembly, at least 50% of a welding region of the current collecting plate may overlap with the stack number uniform region.

Preferably, the battery may be cylindrical and have a ratio of a diameter to a height greater than 0.4.

Preferably, the battery may be cylindrical and have a form factor of 46110, 4875, 48110, 4880 or 4680.

Preferably, the battery may have a resistance of 4 milliohm or below.

In another aspect of the present disclosure, there is also provided a battery pack, comprising a plurality of batteries described above.

In an aspect, in the battery pack, the plurality of batteries may be arranged in a predetermined number of columns, and the electrode terminal of each battery and an outer surface of the bottom portion of the battery housing may be arranged to face upward.

In another aspect, the battery pack may comprise a plurality of bus bars configured to connect the plurality of batteries in series and parallel.

Preferably, the plurality of bus bars may be disposed at an upper portion of the plurality of batteries, and each bus bar may include a body portion configured to extend between electrode terminals of adjacent batteries; a plurality of first bus bar terminals configured to extend in a first direction from the body portion and electrically coupled to electrode terminals of the batteries located in the first direction; and a plurality of second bus bar terminals configured to extend in a second direction from the body portion and electrically coupled to outer surfaces of the bottom portions of the battery housings of the batteries located in the second direction.

In another aspect of the present disclosure, there is also provided a vehicle, comprising the battery pack.

Advantageous Effects

According to one aspect of the present disclosure, the internal resistance of the battery may be reduced and the energy density may be increased by using the uncoated portion itself protruding at the upper portion and the lower portion of the electrode assembly as an electrode tab.

According to another aspect of the present disclosure, the uncoated portion may be prevented from being torn when the uncoated portion is bent by improving the structure of the uncoated portion of the electrode assembly, and the welding strength of the current collecting plate may be improved by sufficiently increasing the number of overlapping layers of the uncoated portion.

According to another aspect of the present disclosure, a plurality of segments is applied to the uncoated portion of the electrode, and when the electrode is wound, the plurality of segments are disposed to be aligned in a predetermined direction, and the end of the active material layer formed on the electrode is exposed between the winding turns of the separator in an area where the segments are not disposed, so that it is possible to increase the impregnation rate of the electrolyte.

According to another aspect of the present disclosure, physical properties of an area to which a current collecting plate is welded may be improved by sufficiently increasing the segment stack number of the area used as a welding target area.

According to another aspect of the present disclosure, an electrode assembly having improved energy density and reduced resistance may be provided by applying a structure in which a current collecting plate is welded to the bending surface region formed by bending the segments.

According to another aspect of the present disclosure, a cylindrical battery having an improved design so that electrical wiring can be performed at the upper portion thereof may be provided.

According to another aspect of the present disclosure, by improving the structure of the uncoated portion adjacent to the core of the electrode assembly, the cavity in the core of the electrode assembly is prevented from being blocked when the uncoated portion is bent, so that the electrolyte injection process and the process of welding the battery housing (or, rivet terminal) and the current collecting plate may be easily performed.

According to another aspect of the present disclosure, it is possible to provide a cylindrical battery having a structure in which the internal resistance is low, an internal short circuit is prevented, and the welding strength between the current collecting plate and the uncoated portion is improved, and a battery pack and a vehicle including the cylindrical battery.

In particular, the present disclosure may provide a cylindrical battery having a ratio of diameter to height of 0.4 or more and a resistance of 4 milliohm or less, and a battery pack and a vehicle including the cylindrical battery.

In addition, the present disclosure may have several other effects, and such effects will be described in each embodiment, or any description that can be easily inferred by a person skilled in the art will be omitted for an effect.

BEST MODE

In addition, in order to help understanding of the present disclosure, the accompanying drawings are not drawn to scale, and the dimensions of some components may be exaggerated. In addition, the same reference numerals may be assigned to the same elements in different embodiments.

When it is explained that two objects are ‘identical’, this means that these objects are ‘substantially identical’. Accordingly, the substantially identical objects may include deviations considered low in the art, for example, deviations within 5%. Also, when it is explained that certain parameters are uniform in a predetermined region, this may mean that the parameters are uniform in terms of an average in the corresponding region.

In addition, the terms such as “about” or “approximately” refer to cases where the term has a deviation of about 1%, 2%, 3%, . . . , 20% based on the number for which the corresponding term is used.

Although the terms first, second or the like are used to describe different elements, these elements are not limited by the terms. These terms are used to distinguish one element from another, and unless stated to the contrary, a first element may be a second element.

Throughout the specification, unless stated otherwise, each element may be singular or plural.

When an element is “above (or under)” or “on (or below)” another element, the element can be on an upper surface (or a lower surface) of the other element, and intervening elements may be present between the element and the other element on (or below) the element.

Additionally, when an element is referred to as being “connected”, “coupled” or “linked” to another element, the element can be directly connected or coupled to the other element, but it should be understood that intervening elements may be present between each element, or each element may be “connected”, “coupled” or “linked” to each other through another element.

Throughout the specification, “A and/or B” refers to either A or B or both A and B unless expressly stated otherwise, and “C to D” refers to C or greater and D or smaller unless expressly stated otherwise.

A direction that goes along a lengthwise direction of a winding axis of an electrode assembly wound in a roll shape is herein referred to as an axis direction Y. Additionally, a direction around the winding axis is herein referred to as a circumferential or peripheral direction X. Additionally, a direction that gets closer to or faces away from the winding axis is referred to as a radial direction. Among them, in particular, the direction that gets closer to the winding axis is referred to as a centripetal direction, and the direction that faces away from the winding axis is referred to as a centrifugal direction.

First, an electrode assembly according to an embodiment of the present disclosure will be described. The electrode assembly is a jelly-roll type electrode assembly in which a first electrode and a second electrode having a sheet shape and a separator interposed therebetween are wound in one direction.

Preferably, at least one of the first electrode and the second electrode includes an uncoated portion not coated with an active material at a long side end in the winding direction. At least a part of the uncoated portion is used as an electrode tab by itself. That is, a tab in the form of a strip is not separately attached to the uncoated portion, and a part of the uncoated portion is used as the tab.

FIG.4is a plan view showing a structure of an electrode40according to an embodiment of the present disclosure.

Referring toFIG.4, the electrode40of the first embodiment includes a sheet-shaped current collector41and an active material layer42. The current collector41may be made of a metal foil. The metal foil may be a conductive metal, such as aluminum or copper. The current collector41may be appropriately selected according to the polarity of the electrode40. The metal foil can be replaced with a metal mesh or the like. The metal foil may have a structure in which metal thin films are coated on both surfaces of a substrate made of an insulating film. The active material layer42is formed on at least one surface of the current collector41. The active material layer42is formed along the winding direction X. The electrode40includes an uncoated portion43at a long side end in the winding direction X. The uncoated portion43is a partial area of the current collector41that is not coated with an active material. In the electrode40, an area of the current collector41on which the active material layer42is formed may be referred to as an active material portion.

A width of the electrode40in a direction along the short side of the current collector41may be 60 mm to 70 mm, and a length in a direction along the long side of the current collector41may be 3 m to 5 m. Therefore, the ratio of the short side to the long side of the electrode40may be 1.2% to 2.3%. This ratio is significantly smaller than the 6% to 11% that is a ratio of the short side to the long side of electrodes used in cylindrical batteries with1865or2170form factors.

Preferably, an insulating coating layer44may be formed at a boundary between the active material layer42and the uncoated portion43. The insulating coating layer44is formed such that at least a part thereof overlaps with the boundary between the active material layer42and the uncoated portion43. The insulating coating layer44prevents a short circuit between two electrodes having different polarities and facing each other with a separator interposed therebetween. The insulating coating layer44may cover a boundary between the active material layer42and the uncoated portion43with a width of 0.3 mm to 5 mm. The insulating coating layer44may include a polymer resin and an inorganic filler such as Al2O3or SiO2. Since the portion of the current collector41covered by the insulating coating layer44is not an area coated with an active material layer, it may be regarded as an uncoated portion.

The uncoated portion43includes a first portion B1adjacent to the core, a second portion B3adjacent to the outer circumference, and a third portion B2interposed between the first portion B1and the second portion B3. The core and the outer circumference refer to a central area and an outer circumference of the electrode assembly when the electrode40is wound as an electrode assembly.

Among the first portion B1, the second portion B3and the third portion B2, the third portion B2has the longest length and occupies most of the length of the electrode40. The first portion B1may form a plurality of winding turns adjacent to the core of the electrode assembly. The second portion B3may form one or more winding turns adjacent to the outer circumference of the electrode assembly.

The third portion B2includes a plurality of segments45. Preferably, the segment45may have a rectangular shape. Alternatively, the segment45may have a trapezoidal shape, a parallelogram shape, a semicircular shape, or the like. The geometry of the segment45may be modified in many ways.

The plurality of segments45may be laser notched. Alternatively, the segment45may be formed by a known metal foil cutting process such as ultrasonic cutting or punching. In the winding direction X, the interval (pitch) between the segments45may increase from the core toward the outer circumference.

A cut groove46is interposed between segments45adjacent in the winding direction X. The cut groove46is formed in the process of notching the segment45. The cut groove46includes a flat bottom portion46a, a round portion46badjacent thereto, and a side portion46cof the segment45. Here, the round portion46bmay prevent cracks from occurring at the lower end of the segment45by relieving stress when the segment45is bent.

In order to prevent the active material layer42and/or the insulating coating layer44from being damaged when bending the segment45, it is preferable to leave a predetermined gap between the bottom portion46aof the cut groove46and the active material layer42. This is because stress is concentrated near the bottom portion46aof the cut groove46when the segment45is bent. The gap is 0.2 mm to 4 mm, preferably 1.5 mm to 2.5 mm. When the gap is adjusted to the corresponding numerical range, it is possible to prevent the active material layer42and/or the insulating coating layer44near the lower end of the cut groove46from being damaged due to stress generated during the process of bending the segment45. In addition, the gap may prevent the active material layer42and/or the insulating coating layer44from being damaged due to tolerance when notching or cutting the segment45. The lower end of the cut groove46and the insulating coating layer44may be spaced apart by 0.5 mm to 1.0 mm. When the electrode40is wound, the end of the insulating coating layer44in the winding axis Y direction may be located in the range of −2 mm to 2 mm along the winding axis direction based on the end of the separator. The insulating coating layer44may prevent a short circuit between two electrodes having different polarities and facing each other with a separator interposed therebetween, and may support a bending point when the segment45is bent. In order to improve the short circuit prevention effect between the two electrodes, the insulating coating layer44may be exposed to the outside of the separator. In addition, in order to further maximize the effect of preventing a short circuit between the two electrodes, the width of the insulating coating layer44may be increased so that the end of the insulating coating layer44in the winding axis Y direction is located above the bottom portion46aof the cut groove46. In one embodiment, the end of the insulating coating layer44in the winding axis direction may be located within a range of −1 mm to +1 mm based on the bottom portion46aof the cut groove46.

FIG.5is a top plan view showing an electrode assembly JR manufactured by winding a positive electrode and a negative electrode having a structure of the electrode40shown inFIG.4together with a separator,FIG.6is a perspective view partially showing an upper portion of the electrode assembly JR, andFIG.7is a partial cross-sectional view, taken along line7-7′ inFIG.5. The upper portion of the electrode assembly JR shown in the drawings is the positive electrode.

Referring toFIGS.4to7together, the plurality of segments45protrude to the outside of the separator and protrude in the winding axis direction Y. In addition, the plurality of segments45are radially arranged based on the center of the core C of the electrode assembly JR to form a segment alignment50. The segment alignment50refers to an assembly of the segments45in which the segments45located in different winding turns are arranged while overlapping in the radial direction of the electrode assembly JR.

The fact that the plurality of segments45included in the segment alignment50overlap in the radial direction means that, when a predetermined straight line passing through the segment alignment50is drawn from the center of the core, all segments45intersect the corresponding straight line.

The segment alignment50has a structure extending by a predetermined length along the radial direction of the electrode assembly JR, and in the segment alignment50, the segments45in the winding turns adjacent in the radial direction may have overlapping circumferential angles.

Four, three or two segment alignments50may be provided, but the number of segment alignments50is not limited thereto. When a plurality of segment alignments50are provided, the segment alignments50may be arranged at equal intervals or unequal intervals in the circumferential direction.

When the number of segment alignments50is four, the angle between segment alignments50adjacent in the circumferential direction may be 80 degrees to 100 degrees, preferably 85 degrees to 95 degrees, more preferably 90 degree. When the number of segment alignments50is three, the angle between segment alignments50adjacent in the circumferential direction may be about 110 degrees to 130 degrees, preferably about 115 degrees to 125 degrees, and more preferably about 120 degree. When the number of segment alignments50is two, the angle between segment alignments50adjacent in the circumferential direction may be about 170 degrees to 190 degrees, preferably about 175 to 185 degrees, and more preferably about 180 degree.

The angle (θ) between the segment alignments50adjacent in the circumferential direction is defined as an angle formed by a lateral extension line of one segment alignment50and a lateral extension line of another segment alignment50closest to the segment alignment50when the electrode assembly JR is viewed in the winding axis direction Y. When an imaginary line (see the dashed-dotted line) passing through the center of the segment alignment50is drawn from the center of the core C of the electrode assembly JR, the angle (θ) is substantially the same as an angle formed by the imaginary lines adjacent in the circumferential direction.

The pitches of the segments45increase in the winding direction X of electrode assembly JR from the core toward the outer circumference, but may be determined according to a preset rule so that the segment alignment50may be formed in the radial direction of the electrode assembly JR. The rule for changing the pitches of the segments45in the winding direction X will be described later.

An electrolyte impregnation portion60is formed between the segment alignments50adjacent in the circumferential direction of the electrode assembly JR. The electrolyte impregnation portion60is formed by winding the area of the uncoated portion43where the cut groove46is formed.

As shown inFIG.7, the electrolyte impregnation portion60is a region in which the electrolyte EL may be mainly impregnated, and has a lower height than the segment alignment50in the winding axis direction Y. In the electrolyte impregnation portion60, the segment45protruding to the outside of the separator Se does not exist. In addition, in the electrolyte impregnation portion50, the ends of the active material layer a1of the positive electrode E1and the active material layer a2of the negative electrode E2are spaced apart by a predetermined interval below the end of the separator Se between the separators Se adjacent in the radial direction of the electrode assembly JR. Thus, the insulation between the positive electrode E1and the negative electrode E2may be maintained. In an embodiment, the separation distance may be 0.6 mm to 1 mm. An insulating coating layer44may be formed on at least one of the ends of the positive electrode E1and the negative electrode E2. The end of the positive electrode E1may include a sliding portion in which the thickness of the active material layer a1gradually decreases. The arrangement structure of the electrode and the separator shown inFIG.7may also be applied to the lower portion of the electrode assembly JR. Preferably, the insulating coating layer44and the sliding portion may be formed at the end of the negative electrode E2in the lower portion of the electrode assembly JR.

The electrolyte EL may be impregnated into the electrode assembly JR while directly contacting the positive electrode E1and the negative electrode E2through the gap provided between the ends of the separators Se. Specifically, the electrolyte EL dropped to the top of the electrode assembly JR quickly permeates into the electrode assembly JR while simultaneously contacting the ends of the positive electrode E1and the negative electrode E2and the end of the separator Se. As a result, the electrolyte impregnation rate may be significantly improved.

The width (W) of the segment45may be set to an appropriate value considering the size of the welding region of the current collecting plate and the impregnation rate of the electrolyte EL. Preferably, the width (W) of the segment45may be set in the range of 3 mm to 11 mm. If the width (W) of the segment45is less than 3 mm, the welding region of the current collecting plate is too reduced, thereby deteriorating the efficiency of the welding process and increasing the possibility of tab folding failure while the electrode is transferred. Meanwhile, if the width (W) of the segment45is greater than 11 mm, the area of the electrolyte impregnation portion60is reduced so that the impregnation rate of the electrolyte may be reduced correspondingly, and the possibility of defects increases in the subsequent process of bending (forming) the segment45.

Preferably, the heights (H) of the segments45may be substantially the same in the radial direction of electrode assembly JR. In one example, the segment45may have a height of 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, or 10 mm. Alternatively, the heights (H) of the segments45may increase stepwise from the core of the electrode assembly JR toward the outer circumference. In one example, the heights of the segments45may increase stepwise in the range of 2 mm to 10 mm. In one example, when the core diameter of the electrode assembly JR is 8 mm, the heights of the segments45may increase from 2 mm to 10 mm by 1 mm in the radial region of 6 mm to 14 mm. When the heights (H) of the segments45increase stepwise, the stack number of the segments45may be increased on the bending surface of the segments45, and the length of the area where the stack number is uniform may be increased in the radial direction of the electrode assembly JR. This will be explained later.

Referring toFIG.4, the width (dB1) of the first portion B1is designed by applying the condition that the core of the electrode assembly is not covered when the segment45closest to the first portion B1among the segments45of the third portion B2is bent toward the core. Preferably, the width (dB1) of the first portion B1may be designed so that the core of the electrode assembly JR is open to the outside by 90% or more based on the diameter when the segment45of the third portion B2is bent toward the core.

Preferably, the heights (H) of the segments45may increase from the core toward the outer circumference depending on the radius of the winding turn and the radius of the core where the segments45are located.

In one embodiment, when the heights (H) of the segments45increase stepwise over N steps from h1to hNas the radius of the winding turn increases, assuming that the kthheight of the segment45is hk(k is a natural number from 1 to N), the starting radius of the winding turn including the segment45having the height hkis rkand the radius of the core is rc, the heights h1to hNof the segments45may be determined to satisfy Formula 1 below.

If the heights (hk) of the segments45meet Formula 2, even if the segments45of the segment alignment50are bent toward the core, 90% or more of the diameter of the core may be open to the outside.

In one example, the radius of the entire winding turns of the electrode60is 22 mm, the heights of the segments45start from 3 mm, and the heights of segments45are increased sequentially to 3 mm, 4 mm, 5 mm and 6 mm whenever the radius of the winding turn including the segment45increases by 1 mm, and the heights may be maintained substantially identically at 6 mm in the remaining winding turns. That is, among the radii of the entire winding turns, the width of the height variable region of the segment45is 3 mm, and the remaining radial region corresponds to the height uniform region.

In this case, when a is 1 and the equal sign condition is applied in the right inequality, the starting radius r1, r2, r3, r4of the winding turns including the segments45having heights of 3 mm, 4 mm, 5 mm, and 6 mm depending on the radius (rc) of the core of the electrode assembly may be as shown in Table 1 below.

When the segments45are arranged at the radius locations shown in Table 1, the core is not blocked even if the segments45are bent toward the core. Meanwhile, r1, r2, r3, r4shown in Table 1 may be shifted toward the core according to the value of α. In one example, when α is 0.90, r1, r2, r3, r4may be shifted toward the core by 10% of the core radius. In this case, when the segment45is bent toward the core, 10% of the core radius is blocked by the segment45. r1, r2, r3, r4shown in Table 1 are limit values of the location where the segment45starts. Therefore, the location of the segment45may be shifted toward the outer circumference by a predetermined distance rather than the radius shown in Table 1.

FIG.8is a diagram schematically showing the relationship of the heights h1, h2, h3, h4of the segments45, the core radius (rc), and the radii r1, r2, r3, r4of the winding turns where the segments45begins to appear.

Referring to Table 1 andFIG.8together, for example, when the radius (rc) of the core C is 3 mm, the starting radii r1, r2, r3and r4of the winding turns including the segments45having heights of 3 mm (h1), 4 mm (h2), 5 mm (h3) and 6 mm (h4) may be 6 mm, 7 mm, 8 mm, and 9 mm, respectively, and the heights of the segments45may be maintained at 6 mm from the radius 9 mm to the last winding turn. Also, the segment45may not be included in the winding turn having a radius smaller than 6 mm (r1). In this example, since the segment45having a height of 3 mm (h1) closest to the core C is located from the winding turn having a radius of 6 mm, even if the segments45are bent toward the core C, the segments45cover only the radial region of 3 mm to 6 mm and substantially does not block the core C. According to the a value of Formula 1, the location of the segment45may be shifted toward the core C within 10% of the core radius (rc).

The width (dB1) of the first portion B1may increase in proportion to the bending length of the segment45of the third portion B2closest to the first portion B1. The bending length corresponds to a length from the bending point47(FIG.7) to the upper end side of the segment45. Preferably, when the electrode40is used to manufacture an electrode assembly of a cylindrical battery having a form factor of 4680, the width (dB1) of the first portion B1may be set to 180 mm to 350 mm depending on the core diameter of the electrode assembly JR and the height of the segment45of the third portion B2.

The bending point47of the segment45may be set at a line passing through the bottom portion46aof the cut groove46or a point spaced upward from the line by a predetermined distance. When the segment45is bent toward the core at a point spaced from the lower end of the cut groove46by a certain distance, the segments are overlapped better in the radial direction. When the segments45are bent, a segment at an outer side presses a segment at an inner side based on the center of the core. At this time, if the bending point47is spaced apart from the lower end of the cut groove46by a predetermined distance, the segment at the inner side is pressed in the winding axis direction by the segment at the outer side, and the segments45are overlapped better. The separation distance of the bending point47may be 3 mm or less, preferably 2 mm or less.

The pitch of the segment45corresponds to the width of the cut groove46in the winding direction X and may be determined in advance so that the segment alignment50may be formed in the radial direction of the electrode assembly JR in a preset area when the electrode40is wound. The predetermined pitch information of the segment45may be referred to when forming a plurality of segments45by notching the uncoated portion43of the electrode40using a notching device.

When the electrode40is wound, a spiral winding turn structure is formed. When the winding turn increases by 1, the radius of the electrode assembly JR increases quite small. Therefore, the spiral winding structure of the electrode40may be approximated as a continuous connection structure of semicircles whose radii constantly increase at every ½ winding turn. The approximation structure of the spiral winding turn may be used to determine the pitch of the segment45in advance. Hereinafter, the winding turn structure approximated by continuous connection of semicircles is named an approximate winding turn structure.

FIG.9ais a diagram showing an approximate winding turn structure in which semicircles C1, C2, C3, C4, C5, C6. . . whose radii increase at every ½ winding turn are continuously connected to determine the pitches of the segments45.

Referring toFIG.9a, the line of the approximate winding turn structure approximately corresponds to a line where the plane passing through the central location in the thickness direction of the current collector41included in the electrode40and the plane perpendicular to the winding axis of the electrode assembly JR meet.

The approximate winding turn structure is a structure in which semicircles whose radii increase by ‘Δ/2’ are connected in a counterclockwise direction. That is, semicircles C1(R1), C2(R2), C3(R3), C4(R4), C5(R5) . . . whose radii increase by ‘Δ/2’ are connected in a counterclockwise direction to form the approximate winding turn structure. The symbol in parentheses is a symbol representing the radius. R2is R1+Δ/2, R3is R1+Δ, R4is R1+3Δ/2, and R5is R1+2Δ.

In the drawing, Δ corresponds to the interval between winding turns adjacent in the radial direction in the winding turn structure of the electrode assembly JR. Referring toFIG.7, one positive electrode E1, one negative electrode E2, and two separators Se are included between the winding turns passing through the center in the thickness direction of the current collector (foil) e1, e2. Therefore, Δ is the sum of the thickness of the positive electrode E1, the thickness of the negative electrode E2, and the thickness of two separators Se. The thickness of the positive electrode E1is the sum of the thicknesses of the current collector (foil) e1and the active material layer a1coated on both surfaces thereof, and the thickness of the negative electrode E2is the sum of the thicknesses of the current collector (foil) e2and the thicknesses of the active material layer a2coated on both surfaces thereof.

InFIG.9a, a point where the semicircle C1having radius R1and the positive x-axis meet corresponds to a boundary between the first portion B1and the third portion B2, namely a location where the first segment45appears based on the winding direction X. InFIG.9a, the winding turn structure formed by the first portion B1of the electrode40is not explicitly shown. A semicircle C6with radius R6is shown as a dotted line. This means that the semicircles are continuously connected until the sum of the lengths of all semicircles becomes equal to the sum of the lengths of the second portion B3and the third portion B2of the electrode40. As explained above, the radius of the semicircle increases by ‘Δ/2’. Coddrepresents the centers of the semicircles C1, C3, C5, and the like to which odd indices are assigned, and Cevenrepresents the centers of the semicircles C2, C4, C6, and the like to which even indices are assigned. The centers of the semicircles to which odd indices are assigned are the same as Codd, and the centers of the semicircles to which even indices are assigned are the same as Ceven.

FIG.9bis a diagram for deriving a formula for determining the pitch of the segment45using the approximate winding turn structure shown inFIG.9a. For convenience of description, an embodiment in which the segments45are arranged in a cross shape as shown inFIG.5so that an angle between segment alignments50adjacent in the circumferential direction is substantially 90 degrees will be described.

InFIG.9b, the parameter indicated by each symbol is as follows.A1: length of the first segment in the winding direction (or, arc length in the semicircle C1)A2: length of the second segment in the winding direction (or, arc length in the semicircle C1)A3: length of the third segment in the winding direction (or, arc length in the semicircle C2)D1: pitch between the first segment and the second segment (or, arc length in the semicircle C1)D2: pitch between the second segment and the third segment (or, arc length spanning the semicircle C1and the semicircle C2)θA1: circumferential angle of the first segment in the semicircle C1containing the arc corresponding to the first segmentθA2: circumferential angle of the second segment in the semicircle C1containing the arc corresponding to the second segmentθA3: circumferential angle of the third segment in the semicircle C2containing the arc corresponding to the third segmentθD1: circumferential angle of the first pitch D1in the semicircle C1containing the arc corresponding to the first pitch D1θD2: circumferential angle of the second pitch D2in the semicircles C1and C2containing the arc corresponding to the second pitch D2

When the segments45are arranged radially in a cross shape as shown inFIGS.5and6, the sum of the circumferential angle (θA1) of the first segment and the circum ferential angle (θD1) of the first pitch (D1) may be set to 90 degrees. For reference, inFIG.9b, since the circumferential angle (θA1) and the circumferential angle (θD1) are generalized angles, the sum of the circumferential angle (θA1) and the circumferential angle (θD1) does not appear to be 90 degrees. Similarly, the sum of the circumferential angle (θA2) of the second segment and the circumferential angle (θD2) of the second pitch (D2) may be set to 90 degrees. If the angle between segment alignments50adjacent in the circumferential direction is 120 degrees, the 90 degrees may be replaced with 120 degrees. In addition, when the angle between segment alignments50adjacent in the circumferential direction is 180 degrees, the 90 degrees may be replaced with 180 degrees.

According to geometry, the circumferential angle of an arc may be expressed as “arc length/radius”. In addition, when an arc is located between two semicircles connected to each other, the circumferential angle of the arc may be approximated as “arc length/(average radius of two semicircles)”.

According to the above, the circumferential angles θA1, θA2, θD1and θD2may be expressed as Formula 2 below.

In Formula 2, π/2 (90 degrees) may be replaced with 2π/3 (120 degrees), π (180 degrees), or the like according to the angle between the segment alignments50adjacent in the circumferential direction.

Meanwhile, since the length of the arc corresponding to the first pitch (D1) is equal to the product of the circumferential angle θD1and the radius R1of the semicircle C1, the pitch (D1) may be expressed as Formula 3 below.

Similarly, since the length of the arc corresponding to the second pitch (D2) is equal to the product of the circumferential angle θD2and the average radius of the semicircles C1and C2, the pitch (D2) may be expressed as Formula 4 below.

In Formulas 3 and 4, A1and A2correspond to the lengths of the first segment and the second segment in the winding direction and are values that can be known in advance. Preferably, A1and A2may be identical to each other. In addition, R1is a value that can be known in advance according to the design conditions of the electrode assembly, and R2is a value determined by Δ.

Referring to the above, the n+1thpitch (Dn+1) adjacent to the n+1thsegment along the winding direction may be generalized and expressed as Formula 5 below.

Dn+1=θDn+1*(Rn+Rn+1)/2=(90°−θAn+1)*(Rn+Rn+1)/2  Case 2:(n is an integer greater than or equal to 0)

In Formula 5, the formula of Case 1 is a formula applied when the arc corresponding to the n+1thpitch (Dn+1) is located at the n+1thsemicircle Cn+1, similarly to the arc corresponding to the first pitch (D1).

Meanwhile, the formula of Case 2 is a formula applied when the arc corresponding to the n+1thpitch (Dn+1) is located over the nthsemicircle Cnand the n+1thsemicircle Cn+1, similarly to the arc corresponding to the second pitch (D2).

In the winding direction X, the lengths of the segments45A1, A2, A3. . . and the radius R1of the semicircle where the arc of the first segment is located is a value that can be known in advance according to design conditions, and Δ, which is a factor that determines the radius of the semicircle, is also a value that can be known in advance by the thickness of the electrode and the thickness of the separator.

Therefore, by using the known values and the general formula Dn+1for the pitch of the segment, the segment45may be formed at an accurate location by determining the notching location of the segment45in the uncoated portion43of the electrode40. In addition, when the electrode in which the segments45are formed in this way is wound to form an electrode assembly, a segment alignment50extending radially may be formed at the upper and lower portions of the electrode assembly.

Specifically, a region of the uncoated portion43of the electrode40corresponding to the first portion B1is cut. Subsequently, cutting of the region corresponding to the length A1of the first segment is skipped from the point where the cutting of the first portion B1ends. Next, the region of the uncoated portion43corresponding to the first pitch (D1) is cut from the point where the cutting skip region ends. Subsequently, cutting of the region corresponding to the length of the second segment is skipped, and the region of the uncoated portion43corresponding to the second pitch (D2) is cut from the point where the cutting skip region ends. The process of cutting the region of the uncoated portion corresponding to the pitch of the segment and skipping the cutting of the region of the uncoated portion where the segment is to be formed as above may be repeated until the notching process for the entire uncoated portion is completed. When a jelly-roll type electrode assembly is manufactured using a positive electrode and a negative electrode prepared through this notching process and a separator, a segment alignment50extending radially may be formed at the upper and lower portions of the electrode assembly, as shown inFIG.5.

The values that can be known in advance and the pitch values determined in advance by the formulas, which are used in the segment notching process, may be recorded on a storage medium of a computer device. In addition, the segment notching device may be connected to the computer device through a network and/or data line. In addition, the segment notching device may form a segment at a desired location by reading the data A1, A2, A3, . . . , Anrelated to the lengths of the segments in the winding direction and the data D1, D2, D3, . . . , Dnrelated to the pitch, which are recorded on the storage medium of the computer device, and controlling the operation and movement of a notching unit (e.g., a laser cutter).

The notching device capable of forming a segment on the uncoated portion is known in the art and thus will not be described in detail here.

Meanwhile, in the winding direction X, the lengths of the segments45do not necessarily have to be the same and may gradually increase from the core toward the outer circumference. In this case, the lengths of the segment45A1, A2, A3, . . . , Anin the winding direction may be set to increase according to a certain rule. When the lengths of the segments45in the winding direction increase from the core toward the outer circumference, the shape of the segment alignment50may be deformed into a fan shape8as shown inFIG.10a. In addition, if the lengths of the segments45increases in the winding direction X, when the segments45are bent toward the core of the electrode assembly, the bending is not smoothly performed. Thus, as shown inFIG.9b, a plurality of sub segments45′ may be formed in the uncoated portion region where one segment45is to be formed.

Although not shown in the drawing, it is obvious to those skilled in the art that the shape of the segment alignment50may be deformed into other geometric shapes such as a parallelogram and trapezoid by adjusting the lengths of the segments45in the winding direction and the pitch to various conditions.

In the present disclosure, the segment45may be deformed into various shapes while satisfying at least one of the following conditions.Condition 1: the width of the lower portion is greater than the width of the upper portionCondition 2: the width of the lower portion is the same as the width of the upper portionCondition 3: the width is kept uniform from the upper portion to the lower portionCondition 4: the width decreases from the lower portion to the upper portionCondition 5: the width decreases and then increases from the lower portion to the upper portionCondition 6: the width increases and then decreases from the lower portion to the upper portionCondition 7: the width increases from the lower portion to the upper portion and then is kept uniformCondition 8: the width decreases from the lower portion to the upper portion and then is kept uniformCondition 9: the interior angle of one side and the interior angle of the other side of the lower portion are equal

Here, the interior angle may be defined as an angle formed by the side portion of the segment based on the width direction of the lower portion of the segment. If the side portion is a curve, the interior angle is defined as the angle between the tangent drawn at the lowest end of the curve and the width direction of the lower portion of the segment.Condition 10: the interior angle of one side of the lower portion and the interior angle of the other side are differentCondition 11: the interior angle of one side of the lower portion and the interior angle of the other side of the lower portion have an acute angle, a right angle, or an obtuse angle, respectivelyCondition 12: symmetrical in the left and right direction based on the winding axis directionCondition 13: asymmetrical in the left and right direction based on the winding axis directionCondition 14: the side portion is straightCondition 15: the side portion is curvedCondition 16: the side portion is convex outwardCondition 17: the side portion is convex inwardCondition 18: the corner of the upper portion and/or the lower portion has a structure where straight lines meetCondition 19: the corner of the upper portion and/or the lower portion has a structure where a straight line and a curve meetCondition 20: the corner of the upper portion and/or the lower portion has a structure where curves meetCondition 21: the corner of the upper portion and/or the lower portion has a round structure

FIG.11is a diagram exemplarily showing the shapes of segments according to various modifications of the present disclosure.

As shown in the drawing, the segment45may have various geometric shapes in which a dotted line connecting the bottom portions46aof both cut grooves46is a base. The geometric shape has a structure in which at least one straight line, at least one curved line, or a combination thereof are connected. In one example, the segment45may have a polygonal shape, a round shape, or various combinations thereof.

Specifically, the segment45may have a left-right symmetrical trapezoidal shape ({circle around (a)}); a left-right asymmetric trapezoidal shape ({circle around (b)}); a parallelogram shape ({circle around (c)}); a triangular shape ({circle around (l)}); a pentagonal shape ({circle around (k)}); an arc shape ({circle around (e)}); or an elliptical shape ({circle around (f)}).

Since the shape of the segment45is not limited to those shown inFIG.11, it may be transformed into other polygonal shapes, other round shapes, or combinations thereof to satisfy at least one of the conditions 1 to 21 described above.

In the polygonal shapes {circle around (a)}, {circle around (b)}, {circle around (c)}, {circle around (k)} and {circle around (l)} of the segment45, the corners of the upper portion and/or the lower portion may have a shape where straight lines meet or a round shape (see the enlarged view of the corners of the upper portion and/or the lower portion of the shape {circle around (a)}).

In the polygonal shapes {circle around (a)}, {circle around (b)}, {circle around (c)}, {circle around (k)}, and {circle around (l)} of the segment45and the curved shapes {circle around (e)} and {circle around (f)} of the segment45, the interior angle (θ1) at one side and the interior angle (θ2) at the other side of the lower portion may be the same or different, and the interior angle (θ1) at one side and the interior angle (θ2) at the other side of the lower portion may be an acute angle, a right angle, or an obtuse angle, respectively. The interior angle is an angle at which the base and the side of a geometric figure meet. When the side is curved, the straight line may be replaced by a tangent line extending from the point where the base meets the side.

The shape of the side portion of the segment45having a polygonal shape may be modified in various ways.

In one example, the side portion of the segment shape {circle around (a)} may be transformed into an outwardly convex curve, such as the shape {circle around (d)}, or may be transformed into an inwardly curved segment, such as the shape {circle around (g)} or {circle around (j)}.

In another example, the side portion of the segment shape {circle around (a)} may be transformed into a bent straight line curved indented into the segment, such as the shape {circle around (h)} or {circle around (i)}. Although not shown, the side portion of the segment shape {circle around (a)} may be transformed into a straight line convexly bent to the outside.

In the segment shapes {circle around (d)}, {circle around (g)}, {circle around (j)}, {circle around (h)}, and {circle around (i)} in which the side portion is modified in various ways, the interior angle (θ1) at one side and the interior angle (θ2) at the other side of the lower portion may be the same or different, and the interior angle (θ1) at one side and the interior angle (θ2) at the other side of the lower portion may be any one of an acute angle, a right angle, and an obtuse angle, respectively.

The width (length in the winding direction) of the segment45may have various change pattern of from the bottom to the top.

In one example, the width of the segment45may be kept uniform from the bottom to the top (shape {circle around (c)}). In another example, the width of the segment45may gradually decrease from the bottom to the top (shapes {circle around (a)}, {circle around (b)}, {circle around (d)}, {circle around (e)}, {circle around (f)}, and {circle around (g)}). In still another example, the width of the segment45may gradually decrease and then increase from the bottom to the top (shapes {circle around (i)} and {circle around (j)}). In still another example, the width of the segment45may gradually increase and then decrease from the bottom to the top (shape {circle around (k)}). In still another example, the width of segment45may gradually decrease from the bottom to the top and then be kept uniform (shape {circle around (h)}). Although not shown, the width of the segment45may gradually increase from the bottom to the top and then be kept uniform.

Meanwhile, among the shapes of the segment45illustrated inFIG.11, the polygonal shape with a flat top may be rotated by 180 degrees. In one example, when the segment shape {circle around (a)}, {circle around (b)}, {circle around (d)} or {circle around (g)} rotates by 180 degrees, the width of the segment45may gradually increase from the bottom to the top. In another example, when the segment shape {circle around (h)} is rotated by 180 degrees, the width of the segment45may be kept uniform from the bottom to the top and then gradually increase.

In the embodiments (modifications) described above, according to another aspect of the present disclosure, it is possible to differently change the shape of the segment45according to the area of the third portion B2. In one example, for a region in which stress is concentrated, a round shape (e.g., semicircle, ellipse, etc.) that is advantageous for stress distribution may be applied, and for a region in which stress is relatively low, a polygonal shape (e.g., square, trapezoid, parallelogram, etc.) having a wide area as much as possible may be applied.

In the embodiments (modifications), the segment structure of the third portion B2may also be applied to the first portion B1. However, when the segment structure is applied to the first portion B1, a reverse forming phenomenon in which the end of the first portion B1is curved toward the outer circumference when the segment45of the third portion B2is bent according to the radius of curvature of the core may occur. Therefore, even if there is no segment structure in the first portion B1, or even if the segment structure is applied, it is desirable to adjust the width and/or height and/or separation pitch of the segment45as small as possible to a level where reverse forming does not occur in consideration of the radius of curvature of the core.

According to still another aspect of the present disclosure, after the electrode40is wound into the electrode assembly JR, the segments45exposed on the upper portion and the lower portion of the electrode assembly JR to form the segment alignment50may be overlapped into several layers along the radial direction of the electrode assembly JR to form the bending surface regions.

FIG.12ais a schematic diagram showing a cross section of the bending surface region F formed by bending the segments45included in the segment alignment50toward the core C of the electrode assembly JR. The cross-sectional structure of the bending surface region F shows the structure when the segment alignment50is cut in the radial direction. The bending surface region F is formed by bending the segments45whose heights change stepwise from the core of the electrode assembly JR toward the outer circumference. InFIG.12a, the cross section of the bending surface region F is shown only at the left side based on the winding axis of the electrode assembly JR. The bending surface region F may be formed at both the upper portion and the lower portion of the electrode assembly JR.

Referring toFIG.12a, the bending surface region F has a structure in which the segments45are overlapped into a plurality of layers in the winding axis direction. The overlapping direction is the winding axis direction Y. The region {circle around (1)} is a segment skip region (first portion) with no segment, and the regions {circle around (2)} and {circle around (3)} are regions where winding turns containing the segments45are located. The region {circle around (2)} is a height variable region in which the heights of the segments45vary, and the region {circle around (3)} is a height uniform region in which the heights of the segments are maintained uniformly until the outer circumference of the electrode assembly. As will be described later, the lengths of the region {circle around (2)} and the region {circle around (3)} in the radial direction may be variable. Meanwhile, the uncoated portion (second portion) included in at least one winding turn including an outermost winding turn may not include a segment structure. In this case, the second portion may be excluded in the region {circle around (3)}.

In the region {circle around (2)}, the heights of the segments45may be changed stepwise from the minimum height h1(=hmin) to the maximum height hN(=hmax) in the radius r1to rNregion of the electrode assembly JR. The height variable regions where the heights of the segments45vary are r1to rN. From the radius rNto the radius R of the electrode assembly JR, the heights of the segments45are maintained uniformly at hN. Uniform heights means that the deviation of heights is within 5%.

At any radius location in the region {circle around (2)} and the region {circle around (3)}, the stack number of the segments45varies depending on the radius location. In addition, the stack number of the segments45may vary depending on the width of the region {circle around (2)}, the minimum height (h1) and maximum height (hN−1) of the segments in the height variable region of the segments45, and the height change range (Δh) of the segments45. The stack number of the segments45is the number of segments that meet an imaginary line when the imaginary line is drawn in the winding axis direction from an arbitrary radius location of the electrode assembly JR.

Preferably, the stack number of the segments45at each location of the bending surface region F may be optimized according to the required welding strength of the current collecting plate by adjusting the height, width (length in the winding direction) and separation pitch of the segments45according to the radius of the winding turn containing the segment45.

First, in the height variable region ({circle around (2)}) of the segments45, when the minimum height (h1) of the segments is the same, it will be described through specific embodiments how the stack number of the segments45varies along the radial direction of the bending surface region F according to the change in the maximum height (hN) of the segments45.

The electrode assemblies of the embodiments1-1to1-7are prepared. The electrode assemblies of the embodiments have a radius of 22 mm and a core diameter of 4 mm. The positive electrode and the negative electrode included in the electrode assembly have the electrode structure shown inFIG.4. The second portion B3of the positive electrode and the negative electrode does not contain a segment. The length of the second portion B3is 2% to 4% of the total length of the electrode. The positive electrode, the negative electrode, and the separator are wound by the method described inFIG.2. The winding turns are between 48 turns and 56 turns, but the winding turns of the embodiments are 51 turns. The thickness of the positive electrode, the negative electrode and the separator are 149 μm, 193 μm and 13 μm, respectively. The thickness of the positive electrode and the negative electrode is the thickness including the thickness of the active material layer. The thicknesses of the positive electrode current collecting plate and the negative electrode current collecting plate are 15 μm and 10 μm, respectively. The lengths of the positive and negative electrodes in the winding direction are 3948 mm and 4045 mm, respectively.

In each embodiment, the minimum height of the segments45is set to 3 mm so that the height variable region ({circle around (2)}) of the segments45starts with a radius of 5 mm. In addition, in each embodiment, the heights of the segments45are increased by 1 mm per 1 mm increase in radius, and the maximum height of the segments45is changed variously from 4 mm to 10 mm.

Specifically, in the embodiment1-1, the height variable region ({circle around (2)}) of the segments45is 5 mm to 6 mm, and the heights of the segments45are variable from the radius 3 mm to 4 mm. In the embodiment1-2, the height variable region ({circle around (2)}) of the segments45is 5 mm to 7 mm, and the heights of the segments45are variable from 3 mm to 5 mm. In the embodiment1-3, the height variable region ({circle around (2)}) of the segments45is 5 mm to 8 mm, and the heights of the segments45are variable from 3 mm to 6 mm. In the embodiment1-4, the height variable region ({circle around (2)}) of the segments45is 5 mm to 9 mm, and the heights of the segments45are variable from 3 mm to 7 mm. In the embodiment1-5, the height variable region ({circle around (2)}) of the segments45is 5 mm to 10 mm, and the heights of the segments45are variable from 3 mm to 8 mm. In the embodiment1-6, the height variable region ({circle around (2)}) of the segments45is 5 mm to 11 mm, and the heights of the segments45are variable from 3 mm to 9 mm. In the embodiment1-7, the height variable region ({circle around (2)}) of the segments45is 5 mm to 12 mm, and the heights of the segments45are variable from 3 mm to 10 mm. In the embodiment1-1to1-7, the heights of the segments45are uniform from the radius corresponding to the upper limit of the height variable region ({circle around (2)}) to the outer circumference. In one example, in the embodiment1-7, the heights of the segments45are uniform at 10 mm from radius 12 mm to 22 mm. Meanwhile, in the electrode assembly of the comparative example, the heights of the segments45are maintained at a single height of 3 mm from the radius of 5 mm to the radius of 22 mm.

FIG.12bis graphs showing the results of counting the stack number of segments along the radial direction in the bending surface region F of the positive electrode formed at the upper portion of the electrode assemblies according to the embodiments1-1to1-7and the comparative example. The bending surface region F is formed by bending the segments45included in the segment alignment50toward the core of the electrode assembly JR. The bending surface region of the negative electrode also shows substantially the same results. The horizontal axis of the graph is the radius based on the center of the core, and the vertical axis of the graph is the stack number of segments counted at each radius point, which is also applied in the same way toFIGS.12cand12d, explained later.

Referring toFIG.12b, the stack number uniform region b1of the segments is commonly shown in the embodiments1-1to1-7and the comparative example 1. The stack number uniform region b1is a radial region of a flattened area in each graph. The length of the stack number uniform region b1increases as the maximum height of the segments decreases, and the stack number uniform region b1′ of the comparative example is longest. Meanwhile, the stack number of segments increases as the maximum height (hN) of the segments increases. That is, when the maximum height (hN) of the segments increases so that the width of the height variable region ({circle around (2)}) of the segments increases, the stack number of segments increases while the width of the stack number uniform region b1decreases. At the outer side of the stack number uniform region b1, the stack number decrease region b2appears, in which the stack number of segments decreases as the radius increases. The stack number decrease region b2is a radial region in which the stack number of segments decreases as the radius of the electrode assembly increases. The stack number uniform region b1and the stack number decrease region b2are adjacent in the radial direction and complementary to each other. That is, when the length of one region increases, the length of the other region decreases. In addition, in the stack number decrease region b2, the stack number decreases in proportion to the distance away from the stack number uniform region b1.

From the point of view of the stack number of the segments, in the embodiments1-1to1-7, the stack number of the segments is 10 or more in the stack number uniform region b1. An area where the stack number of segments is 10 or more may be set as a desirable welding target area. The welding target area is a region to which at least a part of the current collecting plate can be welded.

In the embodiments1-1to1-7, the stack number uniform region b1starts from the radius point where the height variable region ({circle around (2)}) of the segments starts. That is, the height variable region ({circle around (2)}) starts with the radius of 5 mm and extends toward the outer circumference.

In the embodiments1-1to1-7and the comparative example 1, for the positive electrode, Table 2 below shows the results of calculating a ratio of the length of the segment skip region (c) to the radius (b-a) of the electrode assembly excluding the core, a ratio (e/f) of the length of the stack number uniform region b1to the length (f) from the radius point (5 mm) where the stack number uniform region starts to the outermost point (22 mm) of the electrode assembly, a ratio (d/f) of the length of the height variable region (d) of the segment to the length (f) from the radius point (5 mm) where the stack number uniform region starts to the outermost point (22 mm) of the electrode assembly, a ratio (h) of the length of the electrode area corresponding to the segment skip region to the entire length of the electrode, a ratio (i) of the length of the electrode area corresponding to the height variable region to the entire length of the electrode, and a ratio (j) of the length of the electrode area corresponding to the height uniform region to the entire length of the electrode, and the like.

Except that the negative electrode shows a difference of 0.1& to 1.2% for the parameter h, the other parameters are substantially the same as the positive electrode. The sum of the proportions h, i and j is slightly different from 100%. The reason is that there is a region with no segment in the second portion B3corresponding to the uncoated portion at the outer circumference of the electrode. For example, in the embodiment1-1, a segment does not exist in the second portion B3corresponding to approximately 3% of the entire length of the electrode. In Table 2, a to f are parameters based on the length in the radial direction, and h, i, and j are parameters based on the length in the winding direction of the electrode. Also, the parameters corresponding to the ratio (%) are values rounded at one decimal place. These points are substantially the same in Tables 3 and 4, explained later.

Seeing the embodiments1-1to1-7of Table 2, the stack number of segments is11to27, and the ratio (d/f) of the height variable region (d) to the radial region f containing segments is 6% to 41%. In addition, the ratio (e/f) of the stack number uniform region (e) to the radial region f containing segments is 47% to 82%. In addition, the ratio (c/(b-a)) of the segment skip region (c) to the radius (b-a) of the electrode assembly excluding the core is 15%. In addition, the ratio of the length of the electrode area corresponding to the segment skip region to the entire length of the electrode is 6%, the ratio of the length of the electrode area corresponding to the height variable region to the entire length of the electrode to is 3% to 32%, and the ratio of the length of the electrode area corresponding to the height uniform region to the entire length of the electrode is 59% to 87%. The stack number (g) of the stack number uniform region is 10 or more in all of the embodiments1-1to1-7. The stack number uniform region (e) decreases as the height variable region (d) of the segments increases, but the stack number (g) of the segments increases in the stack number uniform region (e). Preferably, the stack number uniform region (e) in which the stack number (g) of segments is 10 or more may be set as a welding target area.

In the cylindrical batteries with form factors of1865and2170, the radius of the electrode assembly is approximately 9 mm to 10 mm. Therefore, for a conventional cylindrical battery, as in the embodiments1-1to1-7, the length of the segment region (f) in the radial direction cannot be secured at the level of 17 mm, and the length of the stack number uniform region (e) cannot be secured at the level of 8 mm to 14 mm. This is because, in a conventional cylindrical battery, when the radius of the core is designed to be 2 mm, which is the same as in the embodiments1-1to1-7, the radial region in which segments can be disposed is substantially only 7 mm to 8 mm. In addition, in the conventional cylindrical battery, the length of the electrode in the winding direction is about 600 mm to 980 mm. This short length of the electrode is only about 15% to 24% of the length of the electrode (positive electrode 3948 mm, negative electrode 4045 mm) used in the embodiments1-1to1-7. Therefore, the numerical ranges for the parameters h, i, and j cannot be easily derived from design specifications of the conventional cylindrical battery.

Next, when the maximum height (hN) of the segments is the same in the height variable region ({circle around (2)} inFIG.12a) of the segments, it will be explained through specific embodiments how the stack number of the segments varies along the radial direction of the bending surface region F according to the change in the minimum height (h1) of the segments.

The electrode assemblies of the embodiments2-1to2-5have a radius of 22 mm and a diameter of core C of 4 mm. In the height variable region ({circle around (2)} inFIG.12a) of the segments45, the minimum height (h1) is the same as 4 mm, and the maximum height (hN) varies from 6 mm to 10 mm in increments of 1 mm. Therefore, in the electrode assemblies of the embodiments2-1to2-5, the height variable region ({circle around (2)} inFIG.12a) of the segments has a width of 2 mm, 3 mm, 4 mm, 5 mm, and 6 mm, respectively, and the segment skip region ({circle around (1)} inFIG.12a) is a radial region with a radius of 2 mm to 6 mm.

The electrode assemblies of the embodiments3-1to3-4have a radius of 22 mm and a diameter of core C of 4 mm. In the height variable region ({circle around (2)} inFIG.12a) of the segments45, the minimum height (h1) is the same as 5 mm, and the maximum height (hN) varies from 7 mm to 10 mm in increments of 1 mm. Therefore, in the electrode assemblies of the embodiments3-1to3-4, the height variable region ({circle around (2)} inFIG.12a) of the segments has a width of 2 mm, 3 mm, 4 mm, and 5 mm, respectively, and the segment skip region ({circle around (1)} inFIG.12a) is a radial region with a radius of 2 mm to 7 mm.

The electrode assemblies of the embodiments4-1to4-3have a radius of 22 mm and a diameter of core C of 4 mm. In the height variable region ({circle around (2)} inFIG.12a) of the segments45, the minimum height (h1) is the same as 6 mm, and the maximum height (hN) varies from 8 mm to 10 mm in increments of 1 mm. Therefore, in the electrode assemblies of the embodiments4-1to4-3, the width of the height variable region ({circle around (2)} inFIG.12a) of the segments is 2 mm, 3 mm, and 4 mm, respectively, and the segment skip region ({circle around (1)} inFIG.12a) is a radial region with a radius of 2 mm to 8 mm.

The electrode assemblies of the embodiments5-1to5-2have a radius of 22 mm and a diameter of core C of 4 mm. In the height variable region ({circle around (2)} inFIG.12a) of the segments45, the minimum height (h1) is the same as 7 mm, and the maximum height (hN) varies from 9 mm to 10 mm in 1 mm increments. Therefore, in the electrode assemblies of the embodiments5-1to5-2, the width of the height variable region ({circle around (2)} inFIG.12a) of the segments is 2 mm and 3 mm, respectively, and the segment skip region ({circle around (1)} inFIG.12a) is a radial region with a radius of 2 mm to 9 mm.

FIG.12cis graphs showing the results of counting the stack number of segments along the radial direction in the bending surface region F of the positive electrode formed at the upper portion of the electrode assemblies according to the embodiments2-1to2-5, the embodiments3-1to3-4, the embodiments4-1to4-3, and the embodiments5-1to5-2. The bending surface region of the negative electrode also shows substantially the same results.

InFIG.12c, the graph (a) shows the result of counting the stack number of segments along the radial direction in the bending surface region F for the embodiment2-1to2-5, the graph (b) is for the embodiment3-1to3-4, the graph (c) is for the embodiment4-1to4-3, and the graph (d) is for the embodiments5-1to5-2.

Referring toFIG.12c, the stack number uniform region b1of the segments appears in common in all embodiments. The stack number uniform region b1is a radial region of the flat area in the graph. The length of the stack number uniform region b1increases as the maximum height (hN) of the segments decreases when the minimum height (h1) of the segments is the same. Also, the length of the stack number uniform region b1increases as the minimum height (h1) of the segments decreases when the maximum height (hN) of the segments is the same. Meanwhile, in the stack number uniform region b1, the stack number of segments increases as the maximum height (h) of the segments increases. Even in the embodiments above, the stack number decrease region b2appears near the stack number uniform region b1.

In all of the embodiments, the stack number of segments in the stack number uniform region b1is 10 or more. Preferably, an area where the stack number of segments is 10 or more may be set as a desirable welding target area.

In the embodiments, the stack number uniform region b1starts from the radius point where the height variable region ({circle around (2)} inFIG.12a) of the segments starts. In the embodiments2-1to2-5, the height variable region ({circle around (2)} inFIG.12a) of the segments starts from 6 mm and extends toward the outer circumference. In the embodiments3-1to3-4, the height variable region ({circle around (2)} inFIG.12a) of the segments starts from 7 mm and extends toward the outer circumference. In the embodiments4-3to4-3, the height variable region ({circle around (2)} inFIG.12a) of the segments starts from 8 mm and extends toward the outer circumference. In the embodiments5-1to5-2, the height variable region ({circle around (2)} inFIG.12a) of the segments starts from 9 mm and extends toward the outer circumference.

Table 3 below shows the results of calculating various parameters for the embodiments2-1to2-5, the embodiments3-1to3-4, the embodiments4-1to4-3, and the embodiments5-1to5-2, including a ratio (e/f) of the length of the stack number uniform region to the length from the radius point (6 mm, 7 mm, 8 mm, 9 mm) where the stack number uniform region starts to the outermost point (22 mm) of the electrode assembly, a ratio (d/f) of the length of the segment height variable region ({circle around (2)}) to the length from the radius point (6 mm, 7 mm, 8 mm, 9 mm) where the stack number uniform region starts to the outermost point (22 mm) of the electrode assembly, and the like.

Referring to the embodiments2-5,3-4,4-3, and5-2of Table 3 together withFIGS.12(a) to12(d), the maximum height (hN) of the segments in the height variable region ({circle around (2)}) of the segments is the same as 10 mm, but the minimum height (h1) of the segments increases to 4 mm, 5 mm, 6 mm, and 7 mm by 1 mm, and the length of the height variable region ({circle around (2)}) decreases to 6 mm, 5 mm, 4 mm, and 3 mm by 1 mm. In the four embodiments, the ratio (e/f) of the stack number uniform region is largest in the embodiments2-5as 69% and is smallest in the embodiment5-1as 31%, and the stack numbers of the stack number uniform regions are all the same. From the results shown in Table 3, when the maximum height (hN) of the segments is the same, it may be understood that as the width of the height variable region ({circle around (2)}) of the segment increases since the minimum height (h1) of the segments decreases, the width of the stack number uniform region also increases proportionally. The reason is that as the minimum length (h1) of the segments is smaller, the radius point at which the segment starts is closer to the core, and thus the area where the segments are stacked expands toward the core.

Seeing Table 3, it may be found that the stack number of the segments is 16 to 27, the ratio (d/f) of the height variable region ({circle around (2)}) of the segments is 13% to 38%, and the ratio (e/f) of the stack number uniform region is 31% to 69%. In addition, the ratio (c/(b-a)) of the segment skip region (c) to the radius (b-a) of the electrode assembly excluding the core is 20% to 35%. In addition, the ratio of the length of the electrode area corresponding to the segment skip region to the entire length of the electrode is 10% to 20%, the ratio of the length of the electrode area corresponding to the height variable region to the entire length of the electrode is 6% to 25%, and the ratio of the length of the electrode area corresponding to the height uniform region to the entire length of the electrode is 62% to 81%.

In the cylindrical batteries with form factors of1865and2170, the electrode assembly has a radius of approximately 9 mm to 10 mm. Therefore, different from the embodiments, it is not possible to secure the length of the segment region (f) in the radial direction at the level of 13 mm to 16 mm, and it is not possible to secure the length of the stack number uniform region (e) where the stack number of the segments is 10 or more at the level of 5 mm to 11 mm while securing the length of the segment skip region (c) at the level of about 4 mm to 7 mm. This is because, in the conventional cylindrical battery, when the radius of the core is designed to be 2 mm, which is the same as the embodiments, the radial region in which segments can be disposed is substantially only 7 mm to 8 mm. In addition, in the conventional cylindrical battery, the length of the electrode in the winding direction is about 600 mm to 980 mm. This short length of the electrode is only about 15% to 24% of the length of the electrode (positive electrode 3948 mm, negative electrode 4045 mm) in the embodiments. Therefore, the numerical ranges for the parameters h, i, and j cannot be easily derived from design specifications of the conventional cylindrical batteries.

Next, when the minimum height (h1) and the maximum height (hN) of the segments are the same in the segment height variable region ({circle around (2)} inFIG.12a), it will be explained through specific embodiments how the stack number of the segments according to the diameter of the core C of the electrode assembly changes along the radial direction of the bending surface region F.

The electrode assemblies of the embodiments6-1to6-6have a radius of 22 mm, and the radius of the core C is 4 mm. In the height variable region ({circle around (2)} inFIG.12a) of the segments45, the minimum height (h1) of the segments is the same as 3 mm, and the maximum height (hN) of the segments varies from 5 mm to 10 mm in increments of 1 mm. Therefore, in the electrode assemblies of the embodiments6-1to6-6, the width of the height variable region ({circle around (2)} inFIG.12a) of the segments is 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, and 7 mm, respectively, and the segment skip region ({circle around (1)} inFIG.12a) is a radial region with a radius of 4 mm to 7 mm.

The electrode assemblies of the embodiments7-1to7-6have a radius of 22 mm, and the radius of the core C is 2 mm. In the height variable region ({circle around (2)} inFIG.12a) of the segments45, the minimum height (h1) of the segments is the same as 3 mm, and the maximum height (hN) of the segments varies from 5 mm to 10 mm in increments of 1 mm. Therefore, in the electrode assemblies of the embodiments7-1to7-6, the height variable region ({circle around (2)} inFIG.12a) of the segments has a width of 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, and 7 mm, respectively, and the segment skip region ({circle around (1)}) is all the same as a radial region with a radius of 2 mm to 5 mm.

FIG.12dis graphs showing the results of counting the stack number of segments measured along the radial direction in the bending surface region F of the positive electrode formed at the upper portion of the electrode assembly according to the embodiments6-1to6-6and the embodiments7-1to7-6. Substantially the same results appear in the bending surface region of the negative electrode.

InFIG.12d, the graph (a) shows the result of counting the stack number of segments measured along the radial direction in the bending surface region F for the embodiments6-1to6-6, and the graph (b) is for the embodiments7-1to7-6.

Referring toFIG.12d, the stack number uniform region b1of the segments appears in common in all embodiments. The stack number uniform region b1is a radial region of the flat area in the graph. The length of the stack number uniform region b1in the radial direction increases as the maximum height (hN) of the segments decreases when the minimum height (h1) of the segments is the same. Meanwhile, in the stack number uniform region b1, the stack number of segments increases as the maximum height (hN) of the segments increases. In the embodiments, the stack number decrease region b2is identified near the stack number uniform region b1.

In all of the embodiments, the stack number of the segments is 10 or more in the stack number uniform region b1. Preferably, an area where the stack number of segments is 10 or more may be set as a desirable welding target area.

In the embodiments, the stack number uniform region b1starts from the radius point where the height variable region ({circle around (2)} inFIG.12a) of the segments starts. In the embodiments6-1to6-6, the radius where the height variable region ({circle around (2)} inFIG.12a) of the segment starts is 7 mm, and in the embodiments7-1to7-6, the radius where the height variable region ({circle around (2)} inFIG.12a) of the segments starts is 5 mm.

Table 4 below shows the results of calculating various parameters for the embodiments6-1to6-6and the embodiments7-1to7-6, including a ratio (e/f) of the length of the stack number uniform region to the length from the radius point (7 mm, 5 mm) where the stack number uniform region starts to the outermost point (22 mm) of the electrode assembly, a ratio (d/f) of the length of the segment height variable region ({circle around (2)}) to the length from the radius point (7 mm, 5 mm) where the stack number uniform region starts to the outermost point (22 mm) of the electrode assembly, and the like.

Seeing the embodiments6-6and7-6ofFIG.12dand Table 4, the minimum height (h1) and the maximum height (hN) of the segments in the height variable region ({circle around (2)}) of the segments are the same as 3 mm and 10 mm, respectively. However, in the embodiment6-6, the radius of the core is larger by 2 mm than that in the embodiment7-6. Therefore, in the embodiment6-6, the stack number uniform region (e) and the segment region (f) are smaller by 2 mm than those in the embodiment7-6, and the stack number of segments is the same in the stack number uniform region. This result comes from the difference in the radius of the core. From the results shown in Table 4, when the width of the height variable region ({circle around (2)}) of the segments is the same, it may be understood that, as the radius (a) of the core is smaller, the ratio (d/f) of the height variable region ({circle around (2)}) decreases, but the ratio (e/f) of the stack number uniform region increases. Seeing Table 4, it may be found that the stack number of segments is13to27, the ratio (d/f) of the height variable region ({circle around (2)}) of the segments is 12% to 47%, and the ratio (e/f) of the length of the stack number uniform region is 40% to 76%. In addition, the ratio (c/(b-a)) of the segment skip region (c) to the radius (b-a) of the electrode assembly excluding the core is 15% to 17%. In addition, the ratio of the length of the electrode area corresponding to the segment skip region to the entire length of the electrode is 6%, the ratio of the length of the electrode area corresponding to the height variable region to the entire length of the electrode is 7% to 32%, and the ratio of the length of the electrode area corresponding to the height uniform region to the entire length of the electrode is 59% to 83%.

For cylindrical batteries with form factors of1865and2170, the radius of the electrode assembly is approximately 9 mm to 10 mm. Therefore, different from the embodiments, the length of the segment region (f) in the radial direction is not secured at the level of 15 mm to 17 mm, and at the same time the length of the stack number uniform region (e) where the stack number of segments is 10 or more cannot be secured at the level of 6 mm to 13 mm, while securing the length of the segment skip region (c) at the level of about 3 mm. This is because, in the conventional cylindrical battery, when the radius of the core is designed to be 2 mm to 4 mm, which is the same as the embodiments, the radial region in which segments can be disposed is substantially only 5 mm to 8 mm. In addition, in the conventional cylindrical battery, the length of the electrode in the winding direction is about 600 mm to 980 mm. This short length of the electrode is only about 15% to 24% of the length of the electrode (positive electrode 3948 mm, negative electrode 4045 mm) in the embodiments. Therefore, the numerical ranges for the parameters h, i, and j cannot be easily derived from design specifications of the conventional cylindrical batteries.

Comprehensively considering the data in Tables 2 to 4, the stack number of segments may be 11 to 27 in the stack number uniform region of the segments. In addition, the ratio (d/f) of the height variable region ({circle around (2)}) of the segments may be 6% to 47%. Also, the ratio (e/f) of the stack number uniform region may be 31% to 82%. In addition, the ratio (c/(b-a)) of the length of the segment skip region to the radius of the electrode assembly excluding the core may be 15% to 35%. In addition, the ratio of the length of the electrode area corresponding to the segment skip region to the entire length (length in the winding direction) of the electrode may be 6% to 20%. In addition, the ratio of the length of the electrode area corresponding to the height variable region of the segments to the entire length of the electrode may be 3% to 32%. In addition, the ratio of the length of the electrode area corresponding to the height uniform region of the segments to the entire length of the electrode may be 59% to 87%.

Meanwhile, the parameters described in Tables 2 to 4 may be varied according to design factors including the radius (a) of the core; the radius of the electrode assembly (b); the minimum height (h1) and the maximum height (hN) in the height variable region of the segments; the height change range (Δh) of the segments per 1 mm increment of the radius; the thickness of the positive electrode, the negative electrode and the separator, and the like.

Therefore, in the stack number uniform region of the segments, the segment stack number may be extended as10to35. The ratio (d/f) of the height variable region ({circle around (1)}) of the segments may be extended as 1% to 50%. Also, the ratio (e/f) of the stack number uniform region may be extended as 30% to 85%. In addition, the ratio (c/(b-a)) of the length of the segment skip region to the radius of the electrode assembly excluding the core may be extended as 10% to 40%. In addition, the ratio of the length of the electrode area corresponding to the segment skip region to the entire length (length in the winding direction) of the electrode may be expanded as 1% to 30%. In addition, the ratio of the length of the electrode area corresponding to the height variable region of the segments to the entire length of the electrode may be expanded as 1% to 40%. In addition, the ratio of the length of the electrode area corresponding to the height uniform region of the segments to the entire length of the electrode may be expanded as 50% to 90%.

In the bending surface region F formed at the upper portion and the lower portion of the electrode assembly, the stack number uniform region may be used as the welding target area of the current collecting plate.

Preferably, the welding region of the current collecting plate overlaps the stack number uniform region by at least 50% in the radial direction of the electrode assembly, and a higher overlapping ratio is more preferred.

Preferably, the rest area of the welding region of the current collecting plate that does not overlap with the stack number uniform region may overlap with the stack number decrease region adjacent to the stack number uniform region in the radial direction.

More preferably, the rest area of the welding region of the current collecting plate that does not overlap with the stack number uniform region may overlap with the area of the stack number decrease region in which the segment stack number is 10 or more.

If the current collecting plate is welded to the area where the segment stack number is 10 or more, it is desirable in terms of the welding strength and prevention of damage to the separator or the active material layer during welding. In particular, it is useful when welding the current collecting plate using a high-power laser with high transmission characteristics.

If the stack number uniform region where 10 or more of the segments are stacked and the current collecting plate are welded with a laser, even if the output of the laser is increased to improve welding quality, the stack number uniform region absorbs most of the laser energy to form a welding bead, so it is possible to prevent the separator and the active material layer below the bending surface region F from being damaged by the laser.

In addition, since the segment stack number is 10 or more in the area where the laser is irradiated, welding beads are formed with sufficient volume and thickness. Therefore, sufficient welding strength may be secured and the resistance of the welding interface may be reduced to a level suitable for rapid charging.

When welding the current collecting plate, the output of the laser may be determined by the desired welding strength between the bending surface region F and the current collecting plate. The welding strength increases in proportion to the stack number of segments. This is because the volume of the welding beads formed by the laser increases as the stack number increases. The welding beads are formed as the material of the current collecting plate and the material of the segment are melted together. Therefore, when the volume of the welding bead is large, the current collecting plate and the bending surface region are coupled stronger and the contact resistance of the welding interface is lowered.

Preferably, the welding strength may be 2 kgf/cm2or more, more preferably 4 kgf/cm2or more. Also, the welding strength may be preferably set to 8 kgf/cm2or less, more preferably 6 kgf/cm2or less.

When the welding strength satisfies the above numerical range, even if severe vibration is applied to the electrode assembly along the winding axis direction and/or the radial direction, the properties of the welding interface do not deteriorate, and the resistance of the welding interface may be reduced since the volume of the welding beads is sufficient.

The power of the laser to meet the welding strength condition differs depending on the laser equipment, and may be appropriately adjusted in the range of 250W to 320W or in the range of 40% to 90% of the laser maximum output provided by the equipment.

The welding strength may be defined as a tensile force (kgf/cm2) per unit area of the current collecting plate when the current collecting plate starts to separate from the bending surface region F. Specifically, after the current collecting plate is completely welded, a tensile force may be applied to the current collecting plate while gradually increasing the magnitude of the tensile force. When the tensile force exceeds a threshold value, the segment starts to separate from the welding interface. At this time, the value obtained by dividing the tensile force applied to the current collecting plate by the area of the current collecting plate corresponds to the welding strength.

In the bending surface region F, the segments are stacked in a plurality of layers, and according to the above embodiments, the stack number of segments may increase to 10 at minimum to 35 at maximum.

The thickness of the positive electrode current collector is 10 μm to 25 μm, and the thickness of the negative electrode current collector may be selected in the range of 5 μm to 20 μm. Therefore, the bending surface region F of the positive electrode may include an area where the total stack thickness of the segments is 100 μm to 875 μm. In addition, the bending surface region F of the negative electrode may include an area where the total stack thickness of the segments is 50 μm to 700 μm.

FIG.12eis a top plan view of the electrode assembly showing the stack number uniform region b1and the stack number decrease region b2in the bending surface region F of the segments45according to an embodiment of the present disclosure.

Referring toFIG.12e, the bending surface region F of the segments45is formed as the segments45included in the segment alignment50are bent toward the core C of the electrode assembly JR. InFIG.12e, the area between the two circles indicated by the dashed-dotted line corresponds to the stack number uniform region b1in which the stack number of the segments45is 10 or more, and the outer area of the stack number uniform region b1corresponds to the stack number decrease region b2.

In one example, when the current collecting plate (Pc) is welded in the bending surface region F formed by the segment alignment50, a welding pattern (Wp) is generated on the surface of the current collecting plate (Pc). The welding pattern (Wp) may have an array of line patterns or dot patterns. The welding pattern (Wp) corresponds to the welding region and may overlap by 50% or more with the stack number uniform region b1of the segments along the radial direction. Therefore, a part of the welding pattern (Wp) may be included in the stack number uniform region b1, and the rest of the welding pattern (Wp) may be included in the stack number decrease region b2outside the stack number uniform region b1. Of course, the entire welding pattern (Wp) may overlap with the stack number uniform region b1.

Preferably, the edge of the portion where the current collecting plate (Pc) contacts the bending surface region F may cover the end of the segment45bent toward the core C in the last winding turn. In this case, since the welding pattern (Wp) is formed in a state where the segments45are pressed by the current collecting plate (Pc), the current collecting plate (Pc) and the bending surface region F are strongly coupled. As a result, since the segments45stacked in the winding axis direction come into close contact with each other, the resistance at the welding interface may be lowered and lifting of the segments45may be prevented.

Meanwhile, the bending direction of the segments may be opposite to that described above. That is, the segments may be bent from the core toward the outer circumference. In this case, the pattern in which the heights of the segments change along the winding direction (X-axis direction) may be opposite to that of the embodiments (modifications) described above. For example, the heights of the segments may gradually decrease from the core toward the outer circumference. Also, the structure applied to the first portion B1and the structure applied to the second portion B3may be switched with each other. Preferably, the height change pattern may be designed such that the heights of the segments are gradually decreased from the core toward the outer circumference, but when the segment closest to the outer circumference of the electrode assembly is bent toward the outer circumference, the end of the segment does not protrude out of the outer circumference of the electrode assembly.

The electrode structure of the above embodiments (modifications) may be applied to at least one of the first electrode and the second electrode having different polarities included in the jelly-roll type electrode assembly. In addition, when the electrode structure of the above embodiments (modifications) is applied to any one of the first electrode and the second electrode, the conventional electrode structure may be applied to the other one. In addition, the electrode structures applied to the first electrode and the second electrode may not be identical but be different from each other.

For example, when the first electrode and the second electrode are a positive electrode and a negative electrode, respectively, any one of the above embodiments (modifications) may be applied to the first electrode and the conventional electrode structure (seeFIG.1) may be applied to the second electrode.

As another example, when the first electrode and the second electrode the second electrode are a positive electrode and a negative electrode, respectively, any one of the above embodiments (modifications) may be selectively applied to the first electrode and any one of the above embodiments (modifications) may be selectively applied to the second electrode.

In the present disclosure, a positive electrode active material coated on the positive electrode and a negative electrode active material coated on the negative electrode may employ any active material known in the art without limitation.

In one example, the positive electrode active material may include an alkali metal compound expressed by a general formula A[AxMy]O2+z(A includes at least one element among Li, Na and K; M includes at least one element selected from is Ni, Co, Mn, Ca, Mg, Al, Ti, Si, Fe, Mo, V, Zr, Zn, Cu, Al, Mo, Sc, Zr, Ru, and Cr; x≥0, 1≤x+y≤2, −0.1≤z≤2; and the stoichiometric coefficients x, y and z are selected so that the compound maintains electrical neutrality).

In another example, the positive electrode active material may be an alkali metal compound xLiM1O2-(1-x)Li2M2O3disclosed in U.S. Pat. Nos. 6,677,082, 6,680,143, et al., wherein M1includes at least one element having an average oxidation state3; M2includes at least one element having an average oxidation state4; and 0≤x≤1).

In still another example, the positive electrode active material may be lithium metal phosphate expressed by a general formula LiaM1xFe1-xM2yP1-yM3zO4-z(M1includes at least one element selected from the Ti, Si, Mn, Co, Fe, V, Cr, Mo, Ni, Nd, Al, Mg and A1; M2includes at least one element selected from Ti, Si, Mn, Co, Fe, V, Cr, Mo, Ni, Nd, Al, Mg, Al, As, Sb, Si, Ge, V and S; M3includes a halogen element optionally including F; 0<a≤2, 0≤x≤1, 0≤y<1, 0≤z<1; the stoichiometric coefficient a, x, y and z are selected so that the compound maintains electrical neutrality), or Li3M2(PO4)3(M includes at least one element selected from Ti, Si, Mn, Fe, Co, V, Cr, Mo, Ni, A1, Mg and A1).

Preferably, the positive electrode active material may include primary particles and/or secondary particles in which the primary particles are aggregated.

In one example, the negative electrode active material may employ carbon material, lithium metal or lithium metal compound, silicon or silicon compound, tin or tin compound, or the like. Metal oxides such as TiO2and SnO2with a potential of less than 2V may also be used as the negative electrode active material. As the carbon material, low-crystalline carbon, high-crystalline carbon or the like may be used.

The separator may employ a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, ethylene/methacrylate copolymer, or the like, or laminates thereof. As another example, the separator may employ a common porous nonwoven fabric, for example, a nonwoven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, or the like.

A coating layer of inorganic particles may be included in at least one surface of the separator. It is also possible that the separator itself is made of a coating layer of inorganic particles. Particles in the coating layer may be coupled with a binder so that an interstitial volume exists between adjacent particles.

The inorganic particles may be made of an inorganic material having a dielectric constant of 5 or more. As a non-limiting example, the inorganic particles may include at least one material selected from the group consisting of Pb(Zr,Ti)O3(PZT), Pb1-xLaxZr1-yTiyO3(PLZT), PB(Mg3Nb2/3)O3—PbTiO3(PMN-PT), BaTiO3, hafnia (HfO2), SrTiO3, TiO2, Al2O3, ZrO2, SnO2, CeO2, MgO, CaO, ZnO and Y2O3.

Hereinafter, the structure of the electrode assembly according to an embodiment of the present disclosure will be described in detail.

FIG.13is a cross-sectional view of a jelly-roll type electrode assembly100in which the electrode40according to an embodiment is applied to a first electrode (positive electrode) and a second electrode (negative electrode), taken along the Y-axis direction (winding axis direction) to pass through the segment alignment50.

Referring toFIG.13, the uncoated portion43aof the first electrode includes a first portion B1adjacent to the core of the electrode assembly100, a second portion B3adjacent to the surface of the outer circumference of the electrode assembly100, and a third portion B2interposed between the first portion B1and the second portion B3.

The height of the uncoated portion of the first portion B1is relatively smaller than the height of the segments45. In addition, in the third portion B2, the bending length of the innermost segment45is equal to or smaller than the radial length R of the first portion B1. The bending length H corresponds to the distance from the point where the innermost segment45is bent to the top end of the segment45. In one modification, the bending length H may be smaller than the sum of the radial length R of the winding turn formed by the first portion B1and 10% of the radius of the core102.

Therefore, even if the segments45included in the segment alignment50are bent, 90% or more of the diameter of the core102of the electrode assembly100is open to the outside. The core102is a cavity at the center of the electrode assembly100. If the core102is not closed, there is no difficulty in the electrolyte injection process, and the electrolyte injection efficiency is improved. In addition, by inserting a welding jig through the core102, the welding process may be easily performed between the current collecting plate of the negative electrode (or, positive electrode) and the battery housing (or, rivet terminal).

The height of the uncoated portion of the second portion B3is relatively smaller than the height of the segment45. Therefore, it is possible to prevent the phenomenon that the beading portion and the upper edge of the electrode assembly100contact each other to cause an internal short circuit while when the beading portion of the battery housing is being pressed near the winding turn of the second portion B3.

In one modification, the second portion B3may include segments45forming the segment alignment50, and the heights of the segments45of the second portion B3may decrease gradually or stepwise, unlikeFIG.13. In addition, inFIG.13, the heights of the segments45of the segment alignment50are the same in a part of the outer circumference. However, the heights of the segments45of the segment alignment50may increase gradually or stepwise from the boundary between the first portion B1and the third portion B2to the boundary between the third portion B2and the second portion B3. In the segment alignment50, the region where the heights of the segments45change corresponds to the height variable region ({circle around (2)} inFIG.12a) of the segments.

The second uncoated portion43bhas the same structure as the first uncoated portion43a. In one modification, the second uncoated portion43bmay have a conventional electrode structure or an electrode structure of other embodiments (modifications).

The end101of the segments45included in the segment alignment50may be bent in the radial direction of the electrode assembly100, for example from the outer circumference toward the core. At this time, the uncoated portions of the first portion B1and the second portion B3are not substantially bent.

Since the segment alignment50includes a plurality of segments45aligned in the radial direction, the bending stress is alleviated to prevent the uncoated portions43a,43bnear the bending point from being torn or abnormally deformed. In addition, when the width and/or height and/or separation pitch of the segments45is adjusted according to the numerical range of the above embodiment, the segments45are bent toward the core and overlapped in several layers enough to secure sufficient welding strength and an empty hole (gap) is not formed in the bending surface region F.

FIG.14is a cross-sectional view of an electrode assembly110according to still another embodiment of the present disclosure, taken along the Y-axis direction (winding axis direction) to pass through the segment alignment50.

Referring toFIG.14, the electrode assembly110is substantially identical to the electrode assembly100ofFIG.13, except that segments45forming the segment alignment50are also included in the second portion B3and the heights of the segments45of the second portion B3are substantially the same as the height of the segment45at the outermost side of the third portion B2.

In the electrode assembly110, the height of the uncoated portion of the first portion B1is relatively smaller than the height of the segments45included in the segment alignment50. In addition, in the segment alignment50, the bending length H of the segment45located at the innermost side is equal to or smaller than the radial length R of the winding turns formed by the first portion B1. Preferably, the winding turns formed by the first portion B1may be the segment skip region ({circle around (1)} inFIG.12a) with no segment. In one modification, the bending length H may be less than the sum of the radial length R of the winding turns formed by the first portion B1and 10% of the radius of the core112.

Therefore, even if the segments45included in the segment alignment50are bent, 90% or more of the diameter of the core112of the electrode assembly110is open to the outside. If the core112is not blocked, there is no difficulty in the electrolyte injection process, and the electrolyte injection efficiency is improved. In addition, by inserting a welding jig through the core112, the welding process may be easily performed between the current collecting plate of the negative electrode (or, positive electrode) and the battery housing (or, rivet terminal).

In one modification, a structure in which the heights of the segments45included in the segment alignment50increase gradually or stepwise from the core toward the outer circumference may extend to the winding turns formed by the second portion B3. In this case, the heights of the segments45included in the segment alignment50may increase gradually or stepwise from the boundary between the first portion B1and the third portion B2to the outermost surface of the electrode assembly110.

The second uncoated portion43bhas the same structure as the first uncoated portion43a. In one modification, the second uncoated portion43bmay have a conventional electrode structure or an electrode structure in other embodiments (modifications).

The end111of the segments45included in the segment alignment50may be bent in the radial direction of the electrode assembly110, for example from the outer circumference toward the core. At this time, the uncoated portion of the first portion B1is substantially not bent.

Since the segment alignment50includes a plurality of segments45aligned in the radial direction, the bending stress may be alleviated to prevent the uncoated portions43a,43bnear the bending point from being torn or abnormally deformed. In addition, when the width and/or height and/or separation pitch of the segments45is adjusted according to the numerical range of the above embodiment, the segments45are bent toward the core and overlapped in several layers enough to secure sufficient welding strength and an empty hole (gap) is not formed in the bending surface region.

FIG.15is a cross-sectional view showing the electrode assembly120according to still another embodiment of the present disclosure, taken along the Y-axis direction (winding axis direction) to pass through the segment alignment50.

Referring toFIG.15, the electrode assembly120is substantially identical to the electrode assembly100ofFIG.13, except that the heights of the segments45included in the segment alignment50have a pattern of increasing gradually or stepwise and then decreasing. The radial region in which the heights of the segments45change may be regarded as the height variable region ({circle around (2)} inFIG.12a) of the segments. Even in this case, the height variable region of the segments45may be designed so that the stack number uniform region in which the stack number of the segments45is 10 or more appears in the desirable numerical range described above in the bending surface region F formed by bending the segments45.

In the electrode assembly120, the height of the uncoated portion of the first portion B1is relatively smaller than the height of the segments45. In addition, the bending length H of the segment45closest to the core122is equal to or smaller than the radial length R of the winding turns formed by the first portion B1. The region corresponding to the winding turns formed by the first portion B1corresponds to the segment skip region ({circle around (1)} inFIG.12a) with no segment. In one modification, the bending length H may be less than the sum of the radial length R of the winding turns formed by the first portion B1and 10% of the radius of the core122.

Therefore, even if the segments45included in the segment alignment50are bent toward the core, 90% or more of the diameter of the core122of the electrode assembly120is open to the outside. If the core122is not blocked, there is no difficulty in the electrolyte injection process, and the electrolyte injection efficiency is improved. In addition, by inserting a welding jig through the core122, the welding process may be easily performed between the current collecting plate of the negative electrode (or, positive electrode) and the battery housing (or, rivet terminal).

Also, the height of the uncoated portion of the second portion B3is relatively smaller than the heights of the segments45, and preferably, the segment45may not be formed in the second portion B3. Therefore, it is possible to prevent the phenomenon that the beading portion and the edge of the end of the electrode assembly120come into contact with each other to cause an internal short circuit while the beading portion of the battery housing is being pressed near the winding turns formed by the second portion B3. In one modification, the second portion B3may include segments forming the segment alignment50, and the heights of the segments of the second portion B3may decrease gradually or stepwise toward the outer circumference.

The second uncoated portion43bhas the same structure as the first uncoated portion43a. In one modification, the second uncoated portion43bmay have a conventional electrode structure or an electrode structure of other embodiments (modifications).

The end121of the segments45included in the segment alignment50may be bent from the outer circumference of the electrode assembly120toward the core. At this time, the uncoated portions of the first portion B1and the second portion B3are substantially not bent.

Since the segment alignment50includes a plurality of segments45aligned in the radial direction, the bending stress is alleviated to prevent the uncoated portions43a,43bfrom being torn or abnormally deformed. In addition, when the width and/or height and/or separation pitch of the segments45is adjusted according to the numerical range of the above embodiment, the segments45are bent toward the core and overlapped in several layers enough to secure sufficient welding strength and an empty hole (gap) is not formed in the bending surface region F.

FIG.16is a cross-sectional view showing the electrode assembly130according to still another embodiment of the present disclosure, taken along the Y-axis direction (winding axis direction) to pass through the segment alignment50.

Referring toFIG.16, the electrode assembly130is substantially identical to the electrode assembly120ofFIG.15, except that segments45forming the segment alignment50are included in the second portion B3, and the heights of the segments45have a pattern of decreasing gradually or stepwise from the boundary point of the second portion B3and the third portion B2toward the outermost surface of the electrode assembly130.

In the electrode assembly130, the height of the uncoated portion of the first portion B1is relatively smaller than the height of the segments45. In addition, the bending length H of the segment45closest to the core132is equal to or smaller than the radial length R of the winding turns formed by the first portion B1. The winding turns formed by the first portion B1corresponds to the segment skip region ({circle around (1)} inFIG.12a) with no segment. In one modification, the bending length H may be less than the sum of the radial length R of the winding turns formed by the first portion B1and 10% of the radius of the core132.

Therefore, even if the segments45included in the segment alignment50are bent toward the core, 90% or more of the diameter of the core132of the electrode assembly130is open to the outside. If the core132is not blocked, there is no difficulty in the electrolyte injection process, and the electrolyte injection efficiency is improved. In addition, by inserting a welding jig through the core132, the welding process may be easily performed between the current collecting plate of the negative electrode (or, positive electrode) and the battery housing (or, rivet terminal).

The second uncoated portion43bhas the same structure as the first uncoated portion43a. In one modification, the second uncoated portion43bmay have a conventional electrode structure or an electrode structure of other embodiments (modifications).

The end131of the segments45included in the segment alignment50may be bent from the outer circumference of the electrode assembly130toward the core. At this time, the uncoated portion of the first portion B1is substantially not bent.

Since the segment alignment50includes a plurality of segments45aligned in the radial direction, the bending stress is alleviated to prevent the uncoated portions43a,43bnear the bending point from being torn or abnormally deformed. In addition, when the width and/or height and/or separation pitch of the segments45is adjusted according to the numerical range of the above embodiment, the segments45are bent toward the core and overlapped in several layers enough to secure sufficient welding strength and an empty hole (gap) is not formed in the bending surface region F.

Meanwhile, in the above embodiments (modifications), the ends of the segments45included in the segment alignment50may be bent from the core toward the outer circumference. In this case, it is preferable that the winding turns formed by the second portion B3are designed as the segment skip region (o inFIG.12a) with no segment and not bent toward the outer circumference. In addition, the radial width of the winding turns formed by the second portion B3may be equal to or greater than the bending length of the outermost segment. In this case, when the outermost segment is bent toward the outer circumference, the end of the bent portion does not protrude toward the inner surface of the battery housing beyond the outer circumference of the electrode assembly. In addition, the structural change pattern of the segments included in the segment alignment50may be opposite to the above embodiments (modifications). For example, the heights of the segments may increase stepwise or gradually from the core toward the outer circumference. That is, by sequentially arranging the segment skip region ({circle around (1)} inFIG.12a), the height variable region ({circle around (2)} inFIG.12a), and the height uniform region ({circle around (3)} inFIG.12a) from the outer circumference of the electrode assembly toward the core, in the bending surface region F, the stack number uniform region in which the stack number of segments is 10 or more may appear in a desirable numerical range.

Various electrode assembly structures according to an embodiment of the present disclosure may be applied to a jelly-roll type cylindrical battery.

Preferably, the cylindrical battery may be, for example, a cylindrical battery whose form factor ratio (defined as a value obtained by dividing the diameter of the cylindrical battery by height, namely a ratio of diameter (Φ) to height (H)) is greater than about 0.4. Here, the form factor means a value indicating the diameter and height of a cylindrical battery.

Preferably, the cylindrical battery may have a diameter of 40 mm to 50 mm and a height of 70 mm to 90 mm. The cylindrical battery according to an embodiment of the present disclosure may be, for example, a46110battery, a4875battery, a48110battery, a4880battery, and a4680battery. In the numerical value representing the form factor, first two numbers indicate the diameter of the battery, and the remaining numbers indicate the height of the battery.

When an electrode assembly having a tab-less structure is applied to a cylindrical battery having a form factor ratio of more than 0.4, the stress applied in the radial direction when the uncoated portion is bent is large, so that the uncoated portion may be easily torn. In addition, when welding the current collecting plate to the bending surface region of the uncoated portion, it is necessary to sufficiently increase the number of stacked layers of the uncoated portion in the bending surface region in order to sufficiently secure the welding strength and lower the resistance. This requirement may be achieved by the electrode and the electrode assembly according to the embodiments (modifications) of the present disclosure.

A battery according to an embodiment of the present disclosure may be an approximately cylindrical battery, whose diameter is approximately 46 mm, height is approximately 110 mm, and form factor ratio is 0.418.

A battery according to another embodiment may be an approximately cylindrical battery, whose diameter is about 48 mm, height is about 75 mm, and form factor ratio is 0.640.

A battery according to still another embodiment may be an approximately cylindrical battery, whose diameter is approximately 48 mm, height is approximately 110 mm, and form factor ratio is 0.436.

A battery according to still another embodiment may be an approximately cylindrical battery, whose diameter is approximately 48 mm, height is approximately 80 mm, and form factor ratio is 0.600.

A battery according to still another embodiment may be an approximately cylindrical battery, whose diameter is approximately 46 mm, height is approximately 80 mm, and form factor ratio is 0.575.

Conventionally, batteries having a form factor ratio of about 0.4 or less have been used. That is, conventionally, for example, 1865 battery, 2170 battery, etc. were used. The1865battery has a diameter of approximately 18 mm, height of approximately 65 mm, and a form factor ratio of 0.277. The2170battery has a diameter of approximately 21 mm, a height of approximately 70 mm, and a form factor ratio of 0.300.

Hereinafter, the cylindrical battery according to an embodiment of the present disclosure will be described in detail.

FIG.17is a cross-sectional view showing a cylindrical battery190according to an embodiment of the present disclosure, taken along the Y-axis direction to pass through the bending surface region F (FIG.12a) formed by bending the segments included in the segment alignment50(FIG.5).

Referring toFIG.17, the cylindrical battery190according to an embodiment of the present disclosure includes an electrode assembly110having a first electrode, a separator and a second electrode, a battery housing142for accommodating the electrode assembly110, and a sealing body143for sealing an open end of the battery housing142.

The battery housing142is a cylindrical container with an opening at the top. The battery housing142is made of a conductive metal material such as aluminum, steel or stainless steel. A nickel coating layer may be formed on the surface of the battery housing142. The battery housing142accommodates the electrode assembly110in the inner space through the top opening and also accommodates the electrolyte.

The electrode assembly110may have a jelly-roll shape. The electrode assembly110may be manufactured by winding a laminate formed by sequentially laminating a lower separator, a first electrode, an upper separator, and a second electrode at least once, based on the winding center C, as shown inFIG.2.

The first electrode and the second electrode have different polarities. That is, if one has positive polarity, the other has negative polarity. At least one of the first electrode and the second electrode may have an electrode structure according to the above embodiments (modifications). In addition, the other of the first electrode and the second electrode may have a conventional electrode structure or an electrode structure according to embodiments (modifications). The electrode pair included in the electrode assembly110is not limited to one electrode pair, two or more electrode pairs may be included.

As shown inFIG.5, in the upper portion and the lower portion of the electrode assembly110, the segment alignment50(FIG.5) formed by the segments respectively included in the first uncoated portion146aof the first electrode and the second uncoated portion146bof the second electrode is provided.

The segments included in the segment alignment50are bent in the radial direction of the electrode assembly110, for example from the outer circumference toward the core, to form the bending surface region F.

The first portion B1has a lower height than the other portion and corresponds to the segment skip region a1with no segment, so it is not bent toward the core.

Preferably, the bending surface region F may include a segment skip region a1, a segment height variable region a2, and a segment height uniform region a3from the core toward the outer circumference.

As shown inFIGS.12b,12c, and12d, the bending surface region F includes a stack number uniform region b1having the stack number of 10 or more adjacent to the segment skip region a1.

The bending surface region F may also include a stack number decrease region b2adjacent to the outer circumference of the electrode assembly110, where the stack number of segments decreases toward the outer circumference. Preferably, the stack number uniform region b1may be set as a welding target area.

In the bending surface region F, the preferred numerical range of the ratio (a2/c) of the segment height variable region a2and the ratio (b1/c) of the segment stack number uniform region b1based on the radial length c where segments exist, and the ratio of the area of the stack number uniform region b1to the area of the bending surface region F are already described above and thus will not be described again.

The first current collecting plate144may be laser-welded to the bending surface region F of the first uncoated portion146a, and the second current collecting plate145may be laser-welded to the bending surface region F of the second uncoated portion146b. The welding method may be replaced by ultrasonic welding, resistance welding, spot welding, and the like.

Preferably, an area of 50% or more of the welding regions W of the first current collecting plate144and the second current collecting plate145may overlap with the stack number uniform region b1of the bending surface region F. Optionally, the remaining area of the welding region W may overlap with the stack number decrease region b2of bending surface region F. In terms of high welding strength, low resistance of the welding interface, and prevention of damage to the separator or the active material layer, it is more preferable that the entire welding region W overlaps the stack number uniform region b1.

Preferably, in the stack number uniform region b1and, optionally, the stack number decrease region b2overlapping with the welding region W, the stack number of segments may be 10 to 35.

Optionally, when the segment stack number of the stack number decrease region b2overlapping with the welding region W is less than 10, the laser output of the stack number decrease region b2may be lowered than the laser output of the stack number uniform region b1. That is, when the welding region W overlaps with the stack number uniform region b1and the stack number decrease region b2at the same time, the laser output may be varied according to the stack number of segments. In this case, the welding strength of the stack number uniform region b1may be greater than the welding strength of the stack number decrease region b2.

In the bending surface region F formed on the upper portion and the lower portion of the electrode assembly110, the radial length of the segment skip region a1and/or the height variable region a2of the segments and/or the height uniform region a3of the segments may be the same or different.

In the electrode assembly110, the uncoated portion of the first portion B1has a relatively smaller height than other portions. In addition, as shown inFIG.14, the bending length H of the segment closest to the core is smaller than the sum of the radial length R of the winding turns formed by the first portion B1and 10% of the radius of the core112.

Therefore, even if the segments included in the segment alignment50are bent toward the core, 90% or more of the diameter of the core112of the electrode assembly110may be open to the outside. If the core112is not blocked, there is no difficulty in the electrolyte injection process, and the electrolyte injection efficiency is improved. In addition, by inserting a welding jig through the core112, the welding process may be easily performed between the second current collecting plate145and the battery housing142.

If the width and/or height and/or separation pitch of the segments is adjusted to satisfy the numerical range of the above embodiment, when the segments are bent, the segments are overlapped in several layers enough to secure sufficient welding strength and an empty hole (gap) is not formed in the bending surface region F.

Preferably, the first current collecting plate144and the second current collecting plate145may have outer diameters covering the end of the segment45(FIG.12e) bent at the last winding turn of the first electrode and the second electrode. In this case, welding is possible in a state while the segments forming the bending surface region F are uniformly pressed by the current collecting plate, and the tightly stacked state of the segments may be well maintained even after welding. The tightly stacked state means a state where there is substantially no gap between the segments as shown inFIG.12a. The tightly stacked state contributes to lowering the resistance of the cylindrical battery190to a level suitable for rapid charging (for example, 4 milliohms or less).

The sealing body143may include a cap plate143a, a first gasket143bfor providing airtightness between the cap plate143aand the battery housing142and having insulation, and a connection plate143celectrically and mechanically coupled to the cap plate143a.

The cap plate143ais a component made of a conductive metal material, and covers the top opening of the battery housing142. The cap plate143ais electrically connected to the bending surface region F of the first electrode, and is electrically insulated from the battery housing142by means of the first gasket143b. Accordingly, the cap plate143amay function as the first electrode (for example, positive electrode) of the cylindrical battery190.

The cap plate143ais placed on the beading portion147formed on the battery housing142, and is fixed by a crimping portion148. Between the cap plate143aand the crimping portion148, the first gasket143bmay be interposed to secure the airtightness of the battery housing142and the electrical insulation between the battery housing142and the cap plate143a. The cap plate143amay have a protrusion143dprotruding upward from the center thereof.

The battery housing142is electrically connected to the bending surface region F of the second electrode. Therefore, the battery housing142has the same polarity as the second electrode. If the second electrode has negative polarity, the battery housing142also has negative polarity.

The battery housing142includes the beading portion147and the crimping portion148at the top thereof. The beading portion147is formed by press-fitting the periphery of the outer circumferential surface of the battery housing142. The beading portion147prevents the electrode assembly110accommodated inside the battery housing142from escaping through the top opening of the battery housing142, and may function as a support portion on which the sealing body143is placed.

The second portion B3of the first electrode may not include a segment and may be notched in the same structure as the first portion B1. Preferably, the inner circumference of the beading portion147may be spaced apart from the winding turns formed by the second portion B3of the first electrode by a predetermined interval. This is because the second portion B3is notched like the first portion B1. More specifically, the lower end of the inner circumference of the beading portion147is separated from the winding turns formed by the second portion B3of the first electrode by a predetermined interval. In addition, since the uncoated portion of the second portion B3has a low height, the winding turns of the second portion B3are not substantially affected even when the battery housing142is press-fitted at the outside to form the beading portion147. Therefore, the winding turns of the second portion B3are not pressed by other components such as the beading portion147, and thus partial shape deformation of the electrode assembly110is prevented, thereby preventing a short circuit inside the cylindrical battery190.

Preferably, when the press-fit depth of the beading portion147is defined as D1and the radial length from the inner circumference of the battery housing142to the boundary point between the second portion B3and the third portion B2is defined as D2, the relational expression D1≤D2may be satisfied. In this case, when press-fitting the battery housing142to form the beading portion147, it is possible to substantially prevent the winding turns formed by the second portion B3from being damaged.

The crimping portion148is formed on the beading portion147. The crimping portion148has an extended and bent shape to cover the outer circumference of the cap plate143adisposed on the beading portion147and a part of the upper surface of the cap plate143a.

The cylindrical battery190may further include a first current collecting plate144and/or a second current collecting plate145and/or an insulator146.

The first current collecting plate144is coupled to the upper portion of the electrode assembly110. The first current collecting plate144is made of a conductive metal material such as aluminum, copper, steel, nickel and so on, and is electrically connected to the bending surface region F of the first electrode. The electric connection may be made by welding. A lead149may be connected to the first current collecting plate144. The lead149may extend upward above the electrode assembly110and be coupled to the connection plate143cor directly coupled to the lower surface of the cap plate143a. The lead149may be connected to other components by welding.

Preferably, the first current collecting plate144may be integrally formed with the lead149. In this case, the lead149may have an elongated plate shape extending outward from near the center of the first current collecting plate144.

The first current collecting plate144and the bending surface region F of the first electrode may be coupled by, for example, laser welding. Laser welding may be performed by partially melting a base material of the current collecting plate. In one modification, the first current collecting plate144and the bending surface region F may be welded with a solder interposed therebetween. In this case, the solder may have a lower melting point compared to the first current collecting plate144and the first uncoated portion146a. The laser welding may be replaced with resistance welding, ultrasonic welding, spot welding, or the like.

The second current collecting plate145may be coupled to the lower surface of the electrode assembly110. One side of the second current collecting plate145may be coupled by welding to the bending surface region F of the second electrode, and the other side may be coupled to the inner bottom surface of the battery housing142by welding. The coupling structure between the second current collecting plate145and the bending surface region F of the second electrode may be substantially the same as the coupling structure between the first current collecting plate144and the bending surface region F of the first electrode.

The insulator146may cover the first current collecting plate144. The insulator146may cover the first current collecting plate144at the upper surface of the first current collecting plate144, thereby preventing direct contact between the first current collecting plate144and the inner circumference of the battery housing142.

The insulator146has a lead hole151so that the lead149extending upward from the first current collecting plate144may be withdrawn therethrough. The lead149is drawn upward through the lead hole151and coupled to the lower surface of the connection plate143cor the lower surface of the cap plate143a.

A peripheral region of the edge of the insulator146may be interposed between the first current collecting plate144and the beading portion147to fix the coupled body of the electrode assembly110and the first current collecting plate144. Accordingly, the movement of the coupled body of the electrode assembly110and the first current collecting plate144may be restricted in the height direction of the battery190, thereby improving the assembly stability of the battery190.

The insulator146may be made of an insulating polymer resin. In one example, the insulator146may be made of polyethylene, polypropylene, polyimide, or polybutylene terephthalate.

The battery housing142may further include a venting portion152formed at a lower surface thereof. The venting portion152corresponds to a region having a smaller thickness compared to the peripheral region of the lower surface of the battery housing142. The venting portion152is structurally weak compared to the surrounding area. Accordingly, when an abnormality occurs in the cylindrical battery190and the internal pressure increases to a predetermined level or more, the venting portion152may be ruptured so that the gas generated inside the battery housing142is discharged to the outside. The internal pressure at which the venting portion152is ruptured may be approximately 15 kgf/cm2to 35 kgf/cm2.

The venting portion152may be formed continuously or discontinuously while drawing a circle at the lower surface of the battery housing142. In one modification, the venting portion152may be formed in a straight pattern or other patterns.

FIG.18is a cross-sectional view showing a cylindrical battery200according to an embodiment of the present disclosure, taken along the Y-axis direction to pass through the bending surface region F (FIG.12a) formed by bending the segments included in the segment alignment50(FIG.5).

Referring toFIG.18, the structure of the electrode assembly of the cylindrical battery200is substantially the same as that of the cylindrical battery190of inFIG.17, and the other structure except for the electrode assembly is changed.

Specifically, the cylindrical battery200includes a battery housing171through which a rivet terminal172is installed. The rivet terminal172is installed through a perforation hole formed in the closed surface (the upper surface in the drawing) of the battery housing171. The rivet terminal172is riveted to the perforation hole of the battery housing171in a state where a second gasket173made of an insulating material is interposed therebetween. The rivet terminal172is exposed to the outside in a direction opposite to the direction of gravity.

The rivet terminal172includes a terminal exposing portion172aand a terminal insert portion172b. The terminal exposing portion172ais exposed to the outside of the closed surface of the battery housing171. The terminal exposing portion172amay be located approximately at a central portion of the closed surface of the battery housing171. The maximum diameter of the terminal exposing portion172amay be larger than the maximum diameter of the perforation hole formed in the battery housing171. The terminal insert portion172bmay be electrically connected to the uncoated portion146aof the first electrode through approximately the central portion of the closed surface of the battery housing171. The lower edge of the terminal insert portion172bmay be riveted onto the inner surface of the battery housing171. That is, the lower edge of the terminal insert portion172bmay have a shape curved toward the inner surface of the battery housing171. A flat portion172cis included at the inner side of the lower edge of the terminal insert portion172b. The maximum diameter of the lower portion of the terminal insert portion172bmay be larger than the maximum diameter of the perforation hole of the battery housing171.

The flat portion172cof the terminal insert portion172bmay be welded to the center portion of the first current collecting plate144connected to the bending surface region F of the first electrode. The laser welding may be adopted as a preferable welding method, but the laser welding may be replaced with other welding methods such as ultrasonic welding.

An insulator174made of an insulating material may be interposed between the first current collecting plate144and the inner surface of the battery housing171. The insulator174covers the upper portion of the first current collecting plate144and the top edge of the electrode assembly110. Accordingly, it is possible to prevent the second portion B3of the electrode assembly110from contacting the inner surface of the battery housing171having a different polarity to cause a short circuit.

The thickness of the insulator174corresponds to or is slightly greater than the distance between the upper surface of the first current collecting plate144and the inner surface of the closed portion of the battery housing171. Accordingly, the insulator174may contact the upper surface of the first current collecting plate144and the inner surface of the closed portion of the battery housing171.

The terminal insert portion172bof the rivet terminal172may be welded to the first current collecting plate144through the perforation hole of the insulator174. A diameter of the perforation hole formed in the insulator174may be larger than a diameter of the riveting portion at the lower end of the terminal insert portion172b. Preferably, the perforation hole may expose the lower portion of the terminal insert portion172band the second gasket173.

The second gasket173is interposed between the battery housing171and the rivet terminal172to prevent the battery housing171and the rivet terminal172having opposite polarities from electrically contacting each other. Accordingly, the upper surface of the battery housing171having an approximately flat shape may function as the second electrode (for example, negative electrode) of the cylindrical battery200.

The second gasket173includes a gasket exposing portion173aand a gasket insert portion173b. The gasket exposing portion173ais interposed between the rivet terminal exposing portion172aof the terminal172and the battery housing171. The gasket insert portion173bis interposed between the terminal insert portion172bof the rivet terminal172and the battery housing171. The gasket insert portion173bmay be deformed together when the terminal insert portion172bis riveted, so as to be in close contact with the inner surface of the battery housing171. The second gasket173may be made of, for example, a polymer resin having insulation property.

The gasket exposing portion173aof the second gasket173may have an extended shape to cover the outer circumference of the terminal exposing portion172aof the rivet terminal172. When the second gasket173covers the outer circumference of the rivet terminal172, it is possible to prevent a short circuit from occurring while an electrical connection part such as a bus bar is coupled to the upper surface of the battery housing171and/or the rivet terminal172. Although not shown in the drawings, the gasket exposing portion173amay have an extended shape to cover not only the outer circumference surface of the terminal exposing portion172abut also a part of the upper surface thereof.

When the second gasket173is made of a polymer resin, the second gasket173may be coupled to the battery housing171and the rivet terminal172by thermal fusion. In this case, airtightness at the coupling interface between the second gasket173and the rivet terminal172and at the coupling interface between the second gasket173and the battery housing171may be enhanced. Meanwhile, when the gasket exposing portion173aof the second gasket173has a shape extending to the upper surface of the terminal exposing portion172a, the rivet terminal172may be integrally coupled with the second gasket173by insert injection molding.

In the upper surface of the battery housing171, a remaining area175other than the area occupied by the rivet terminal172and the second gasket173corresponds to the second electrode terminal having a polarity opposite to that of the rivet terminal172.

The second current collecting plate176is coupled to the lower portion of the electrode assembly110. The second current collecting plate176is made of a conductive metal material such as aluminum, steel, copper or nickel, and is electrically connected to the bending surface region F of the second electrode.

Preferably, the second current collecting plate176is electrically connected to the battery housing171. To this end, at least a portion of the edge of the second current collecting plate176may be interposed and fixed between the inner surface of the battery housing171and a first gasket178b. In one example, at least a portion of the edge of the second current collecting plate176may be fixed to the beading portion180by welding in a state of being supported on the lower surface of the beading portion180formed at the bottom of the battery housing171. In one modification, at least a portion of the edge of the second current collecting plate176may be directly welded to the inner wall surface of the battery housing171.

Preferably, the second current collecting plate176and the bending surface region F of the second electrode may be coupled by, for example, laser welding. In addition, the welded portion of the second current collecting plate176and the bending surface region F may be spaced apart by a predetermined interval toward the core C based on the inner circumference of the beading portion180.

A sealing body178for sealing the lower open end of the battery housing171includes a cap plate178aand a first gasket178b. The first gasket178belectrically separates the cap plate178aand the battery housing171. A crimping portion181fixes the edge of the cap plate178aand the first gasket178btogether. The cap plate178ahas a venting portion179. The configuration of the venting portion179is substantially the same as the above embodiment (modification). The lower surface of the cap plate178amay be located above the lower end of the crimping portion181. In this case, a space is formed under the cap plate178ato smoothly perform venting. In particular, it is useful when the cylindrical battery200is installed so that the crimping portion181faces the direction of gravity.

Preferably, the cap plate178ais made of a conductive metal material. However, since the first gasket178bis interposed between the cap plate178aand the battery housing171, the cap plate178adoes not have electrical polarity. The sealing body178seals the open end of the lower portion of the battery housing171and mainly functions to discharge gas when the internal pressure of the battery200increases over a critical value. A threshold value of the pressure is 15 kgf/cm2to 35 kgf/cm2.

Preferably, the rivet terminal172electrically connected to the bending surface region F of the first electrode is used as the first electrode terminal. In addition, in the upper surface of the battery housing171electrically connected to the bending surface region F of the second electrode through the second current collecting plate176, a part175except for the rivet terminal172is used as the second electrode terminal having a different polarity from the first electrode terminal. If two electrode terminals are located at the upper portion of the cylindrical battery200as above, it is possible to arrange electrical connection components such as bus bars at only one side of the cylindrical battery200. This may bring about simplification of the battery pack structure and improvement of energy density. In addition, since the part175used as the second electrode terminal has an approximately flat shape, a sufficient bonding area may be secured for bonding electrical connection components such as bus bars. Accordingly, the cylindrical battery200may reduce the resistance at the bonding portion of the electrical connection components to a desirable level.

FIG.19is a cross-sectional view showing a cylindrical battery210according to an embodiment of the present disclosure, taken along the Y-axis direction to pass through the bending surface region F (FIG.12a) formed by bending the segments included in the segment alignment50(FIG.5).

Referring toFIG.19, the cylindrical battery210includes the electrode assembly100shown inFIG.13, and other components except for the electrode assembly100are substantially the same as those of the cylindrical battery190shown inFIG.17. Accordingly, the configuration described with reference toFIGS.13and17may be substantially equally applied to this embodiment.

Preferably, the first and second uncoated portions146a,146bof the electrode assembly100include a plurality of segments. The plurality of segments form a segment alignment50(FIG.5) at the upper portion and the lower portion of the electrode assembly100. The segments45included in the segment alignment50are bent in the radial direction of the electrode assembly100, for example from the outer circumference toward the core. At this time, since the first portion B1of the first uncoated portion146aand the uncoated portion of the second portion B3have a lower height than the other portions and do not include segments, they are not substantially bent. This is also identical in the case of the second uncoated portion146b.

Also in this embodiment, the bending surface region F formed by the segments included in the segment alignment50(FIG.5) may include a segment skip region a1, a segment height variable region a2, and a segment height uniform region a3from the core toward the outer circumference. However, since the uncoated portion of the second portion B3is not bent, the radial length of the bending surface region F may be shorter than in the case of the above embodiment.

As shown inFIGS.12b,12c, and12d, the bending surface region F includes a stack number uniform region b1having the stack number of 10 or more adjacent to the segment skip region a1.

The bending surface region F may also include a stack number decrease region b2adjacent to the winding turns of the second portion B3of the electrode assembly100, in which the stack number of segments decreases toward the outer circumference. Preferably, the stack number uniform region b1may be set as a welding target area.

In the bending surface region F, the preferred numerical range of the ratio (a2/c) of the segment height variable region a2of the segments, the ratio (b1/c) of the segment stack number uniform region b1of the segments, and the ratio of the area of the stack number uniform region b1to the area of the bending surface region F are already described above and thus will not be described again.

The first current collecting plate144may be welded to the bending surface region F of the first uncoated portion146a, and the second current collecting plate145may be welded to the bending surface region F of the second uncoated portion146b.

The overlapping relationship between the stack number uniform region b1and the stack number decrease region b2and the welding region W, the outer diameters of the first current collecting plate144and the second current collecting plate145, and the configuration in which the first portion B1does not block the core are substantially the same as described above.

Meanwhile, the second portion B3does not include segments, and the height of the uncoated portion is lower than the segments of the third portion B2. Therefore, when the segments of the third portion B2are bent, the second portion B3is not substantially bent. In addition, since the winding turns of the second portion B3are sufficiently spaced from the beading portion147, the problem of damage to the winding turns of the second portion B3may be solved while the beading portion147is press-fitted.

FIG.20is a cross-sectional view showing a cylindrical battery220according to an embodiment of the present disclosure, taken along the Y-axis direction to pass through the bending surface region F (FIG.12a) formed by bending the segments included in the segment alignment50(FIG.5).

Referring toFIG.20, the cylindrical battery220includes the electrode assembly100shown inFIG.13, and other components except for the electrode assembly100are substantially the same as those of the cylindrical battery200shown inFIG.18. Accordingly, the configuration described with reference toFIGS.13and18may be substantially equally applied to this embodiment.

Preferably, the first and second uncoated portions146a,146bof the electrode assembly100include a plurality of segments, and the plurality of segments are aligned in the radial direction to form segment alignment50(FIG.5). In addition, the segments included in the segment alignment50are bent from the outer circumference of the electrode assembly100toward the core to form the bending surface region F. At this time, the first portion B1and the second portion B3of the first uncoated portion146aare not substantially bent toward the core because the uncoated portion has a lower height than the other portions and does not include a segment. This is also the same in the case of the second uncoated portion146b.

Therefore, in this embodiment, the bending surface region F may also include a segment skip region a1, a segment height variable region a2, and a segment height uniform region a3from the core toward the outer circumference. However, since the uncoated portion of the second portion B3is not bent, the radial length of the bending surface region F may be shorter than in the case of the above embodiment.

As shown inFIGS.12b,12c, and12d, the bending surface region F includes a stack number uniform region b1having the stack number of 10 or more adjacent to the segment skip region a1.

The bending surface region F may also include a stack number decrease region b2adjacent to the winding turns of the second portion B3of the electrode assembly100, in which the stack number of segments decreases toward the outer circumference. Preferably, the stack number uniform region b1may be set as a welding target area.

In the bending surface region F, the preferred numerical range of the ratio (a2/c) of the segment height variable region a2of the segments based on the radial length c where the segments exist, the ratio (b1/c) of the segment stack number uniform region b1of the segments, and the ratio of the area of the stack number uniform region b1to the area of the bending surface region F are already described above and thus will not be described again.

The first current collecting plate144may be welded to the bending surface region F of the first uncoated portion146a, and the second current collecting plate176may be welded to the bending surface region F of the second uncoated portion146b.

The overlapping relationship between the stack number uniform region b1and the stack number decrease region b2and the welding region W, the outer diameters of the first current collecting plate144and the second current collecting plate176, and the configuration in which the first portion B1does not block the core are substantially the same as described above.

In the embodiments (modifications), the first current collecting plate144and the second current collecting plate176included in the cylindrical batteries200,220including the rivet terminal172may have an improved structure as shown inFIGS.21and22.

The improved structure of the first current collecting plate144and the second current collecting plate176may contribute to lowering the resistance of the cylindrical battery, improving vibration resistance, and improving energy density. In particular, the first current collecting plate144and the second current collecting plate176are more effective when used in a large cylindrical battery whose ratio of diameter to height is greater than 0.4.

FIG.21is a top plan view showing the structure of the first current collecting plate144according to an embodiment of the present disclosure.

Referring toFIGS.20and21together, the first current collecting plate144may include an edge portion144a, a first uncoated portion coupling portion144b, and a terminal coupling portion144c. The edge portion144ais disposed on the electrode assembly100. The edge portion144amay have a substantially rim shape having an empty space (Sopen) formed therein. In the drawings of the present disclosure, only a case in which the edge portion144ahas a substantially circular rim shape is illustrated, but the present disclosure is not limited thereto. The edge portion61may have a substantially rectangular rim shape, a hexagonal rim shape, an octagonal rim shape, or other rim shapes, unlike the illustrated one. The number of the edge portion144amay be increased to two or more. In this case, another edge portion in the form of a rim may be included inside the edge portion144a.

The terminal coupling portion144cmay have a diameter equal to or greater than the diameter of the flat portion172cformed on the bottom surface of the rivet terminal172in order to secure a welding region for coupling with the flat portion172cformed on the bottom surface of the rivet terminal172.

The first uncoated portion coupling portion144bextends inward from the edge portion144aand is coupled to the bending surface region F of the uncoated portion146aby welding. The terminal coupling portion144cis spaced apart from the first uncoated portion coupling portion144band is positioned inside the edge portion144a. The terminal coupling portion144cmay be coupled to the rivet terminal172by welding. The terminal coupling portion144cmay be located, for example, approximately at the center of the inner space (Sopen) surrounded by the edge portion144a. The terminal coupling portion144cmay be provided at a position corresponding to the hole formed in the core C of the electrode assembly100. The terminal coupling portion144cmay be configured to cover the hole formed in the core C of the electrode assembly100so that the hole formed in the core C of the electrode assembly100is not exposed out of the terminal coupling portion144c. To this end, the terminal coupling portion144cmay have a larger diameter or width than the hole formed in the core C of the electrode assembly100.

The first uncoated portion coupling portion144band the terminal coupling portion144cmay not be directly connected, but may be disposed to be spaced apart from each other and indirectly connected by the edge portion144a. Since the first current collecting plate144has a structure in which the first uncoated portion coupling portion144band the terminal coupling portion144care not directly connected to each other but are connected through the edge portion144cas above, when shock and/or vibration occurs at the cylindrical battery220, it is possible to disperse the shock applied to the coupling portion between the first uncoated portion coupling portion144band the first uncoated portion146aand the coupling portion between the terminal coupling portion144cand the rivet terminal172. In the drawings of the present disclosure, only a case in which four first uncoated portion coupling portions144bare provided is illustrated, but the present disclosure is not limited thereto. The number of the first uncoated portion coupling portions144bmay be variously determined in consideration of manufacturing difficulty according to the complexity of the shape, electric resistance, the inner space (Sopen) inside the edge portion144aconsidering electrolyte impregnation, and the like.

The first current collecting plate144may further include a bridge portion144dextending inward from the edge portion144aand connected to the terminal coupling portion144c. At least a part of the bridge portion144dmay have a smaller sectional area compared to the first uncoated portion coupling portion144band the edge portion144a. For example, at least a part of the bridge portion144dmay be formed to have a smaller width and/or thickness compared to the first uncoated portion coupling portion144b. In this case, the electric resistance increases in the bridge portion144d. Therefore, when a current flows through the bridge portion144d, the relatively large resistance causes a part of the bridge portion144dto be melted due to overcurrent heating. Accordingly, the overcurrent is irreversibly blocked. The sectional area of the bridge portion144dmay be adjusted to an appropriate level in consideration of the overcurrent blocking function.

The bridge portion144dmay include a taper portion144ewhose width is gradually decreased from the inner surface of the edge portion144atoward the terminal coupling portion144c. When the taper portion144eis provided, the rigidity of the component may be improved at the connection portion between the bridge portion144dand the edge portion144a. When the taper portion144eis provided, in the process of manufacturing the cylindrical battery220, for example, a transfer device and/or a worker may easily and safely transport the first current collecting plate144and/or a coupled body of the first current collecting plate144and the electrode assembly100by gripping the taper portion144e. That is, when the taper portion144eis provided, it is possible to prevent product defects that may occur by gripping a portion where welding is performed with other components such as the first uncoated portion coupling portion144band the terminal coupling portion144c.

The first uncoated portion coupling portion144bmay be provided in plural. The plurality of first uncoated portion coupling portions144bmay be disposed substantially at regular intervals from each other in the extending direction of the edge portion144a. An extension length of each of the plurality of first uncoated portion coupling portions144bmay be substantially equal to each other. The first uncoated portion coupling portion144bmay be coupled to the bending surface region F of the uncoated portion146aby laser welding. The welding may be replaced by ultrasonic welding, spot welding, or the like.

A welding pattern144fformed by welding between the first uncoated portion coupling portion144band the bending surface region F may have a structure extending along the radial direction of the electrode assembly100. The welding pattern144fmay be an array of line patterns or dot patterns.

The welding pattern144fcorresponds to the welding region. Therefore, it is desirable that the welding pattern144foverlaps with the stack number uniform region b1of the bending surface region F by 50% or more. The welding pattern144fthat does not overlap with the stack number uniform region b1may overlap with the stack number decrease region b2. More preferably, the entire welding pattern144fmay overlap with the stack number uniform region b1of the bending surface region F. In the bending surface region F below the point where the welding pattern144fis formed, the stack number uniform region b1and, optionally, the stack number decrease region b2preferably have the stack number of 10 or more.

The terminal coupling portion144cmay be disposed to be surrounded by the plurality of first uncoated portion coupling portions144b. The terminal coupling portion144cmay be coupled to the flat portion172cof the rivet terminal172by welding. The bridge portion144dmay be positioned between a pair of first uncoated portion coupling portions144badjacent to each other. In this case, the distance from the bridge portion144dto any one of the pair of first uncoated portion coupling portions144balong the extending direction of the edge portion144amay be substantially equal to the distance from the bridge portion144dto the other one of the pair of first uncoated portion coupling portions144balong the extending direction of the edge portion144a. The plurality of first uncoated portion coupling portions144bmay be formed to have substantially the same sectional area. The plurality of first uncoated portion coupling portions144bmay be formed to have substantially the same width and thickness.

Although not shown in the drawings, the bridge portion144dmay be provided in plural. Each of the plurality of bridge portions144dmay be disposed between a pair of first uncoated portion coupling portions144badjacent to each other. The plurality of bridge portions144dmay be disposed substantially at regular intervals to each other in the extending direction of the edge portion144a. A distance from each of the plurality of bridge portions144dto one of the pair of first uncoated portion coupling portions144badjacent to each other along the extending direction of the edge portion144amay be substantially equal to a distance from each of the plurality of the bridge portion144dto the other first uncoated portion coupling portion144b.

In the case where the first uncoated portion coupling portion144band/or the bridge portion144dis provided in plural as described above, if the distance between the first uncoated portion coupling portions144band/or the distance between the bridge portions144dand/or the distance between the first uncoated portion coupling portion144band the bridge portion144dis uniformly formed, a current flowing from the first uncoated portion coupling portion144btoward the bridge portion144dor a current flowing from the bridge portion144dtoward the first uncoated portion coupling portion144bmay be smoothly formed.

The bridge portion144dmay include a notching portion N formed to partially reduce a sectional area of the bridge portion144d. The sectional area of the notching portion N may be adjusted, for example, by partially reducing the width and/or thickness of the bridge portion144d. When the notching portion N is provided, electric resistance is increased in the region where the notching portion N is formed, thereby enabling rapid current interruption when overcurrent occurs.

The notching portion N is preferably provided in a region corresponding to the stack number uniform region of the electrode assembly100in order to prevent foreign substances generated during rupturing from flowing into the electrode assembly100. This is because, in this region, the number of overlapping layers of the segments of the uncoated portion146ais maintained to the maximum and thus the overlapped segments may function as a mask.

The notching portion N may be wrapped with an insulating tape. Then, since the heat generated in the notching portion N is not dissipated to the outside, the notching portion N may be ruptured more quickly when an overcurrent flows through the bridge portion144d.

FIG.22is a perspective view showing the structure of the second current collecting plate176according to an embodiment of the present disclosure.

Referring toFIGS.20and22together, the second current collecting plate176is disposed below the electrode assembly100. In addition, the second current collecting plate176may be configured to electrically connect the uncoated portion146bof the electrode assembly100and the battery housing171. The second current collecting plate176is made of a metal material with conductivity and is electrically connected to the bending surface region F of the uncoated portion146b. In addition, the second current collecting plate176is electrically connected to the battery housing171. The edge portion of the second current collecting plate176may be interposed and fixed between the inner surface of the battery housing171and the first gasket178b. Specifically, the edge portion of the second current collecting plate176may be interposed between the lower surface of the beading portion180of the battery housing171and the first gasket178b. However, the present disclosure is not limited thereto, and the edge portion of the second current collecting plate176may be welded to the inner wall surface of the battery housing171in a region where the beading portion180is not formed.

The second current collecting plate176may include a support portion176adisposed below the electrode assembly100, a second uncoated portion coupling portion176bextending from the support portion176aapproximately along the radial direction of the electrode assembly100and coupled to the bending surface region F of the uncoated portion146b, and a housing coupling portion176cextending from the support portion176atoward the inner surface of the battery housing171approximately along an inclined direction based on the radial direction of the electrode assembly100and coupled to the inner surface of the battery housing171. The second uncoated portion coupling portion176band the housing coupling portion176care indirectly connected through the support portion176a, and are not directly connected to each other. Therefore, when an external shock is applied to the cylindrical battery220of the present disclosure, it is possible to minimize the possibility of damage to the coupling portion of the second current collecting plate176and the electrode assembly100and the coupling portion of the second current collecting plate176and the battery housing171. However, the second current collecting plate176of the present disclosure is not limited to the structure where the second uncoated portion coupling portion176band the housing coupling portion176care only indirectly connected. For example, the second current collecting plate176may have a structure that does not include the support portion176afor indirectly connecting the second uncoated portion coupling portion176band the housing coupling portion176cand/or a structure in which the uncoated portion146band the housing coupling portion176care directly connected to each other.

The support portion176aand the second uncoated portion coupling portion176bare disposed below the electrode assembly100. The second uncoated portion coupling portion176bis coupled to the bending surface region F of the uncoated portion146b. In addition to the second uncoated portion coupling portion176b, the support portion176amay also be coupled to the uncoated portion146b. The second uncoated portion coupling portion176band the bending surface region F of the uncoated portion146bmay be coupled by welding. The welding may be replaced with ultrasonic welding or spot welding. The support portion176aand the second uncoated portion coupling portion176bare located higher than the beading portion180when the beading portion180is formed on the battery housing171.

The support portion176ahas a current collecting plate hole176dformed at a location corresponding to the hole formed at the core C of the electrode assembly100. The core C of the electrode assembly100and the current collecting plate hole176dcommunicating with each other may function as a passage for inserting a welding rod for welding between the rivet terminal172and the terminal coupling portion144cof the first current collecting plate144or for irradiating a laser beam.

The current collecting plate hole176dmay have a radius of 0.5rcor more compared to the radius (rc) of the hole formed in the core C of the electrode assembly100. If the radius of the current collecting plate hole176dis 0.5rcto 1.0rc, when a vent occurs in the cylindrical battery220, the phenomenon that the winding structure of the separator or electrodes near the core C of the electrode assembly100is pushed out of the core C due to the vent pressure is prevented. When the radius of the current collecting plate hole176dis larger than 1.0rc, the opening of the core C is maximized, so the electrolyte may be easily injected in the electrolyte injection process.

When the second uncoated portion coupling portion176bis provided in plural, the plurality of second uncoated portion coupling portions176bmay have a shape extending approximately radially from the support portion176aof the second current collecting plate176toward the sidewall of the battery housing171. The plurality of second uncoated portion coupling portions176bmay be positioned to be spaced apart from each other along the periphery of the support portion176a.

The housing coupling portion176cmay be provided in plural. In this case, the plurality of housing coupling portions176cmay have a shape extending approximately radially from the center of the second current collecting plate176toward the sidewall of the battery housing171. Accordingly, the electrical connection between the second current collecting plate176and the battery housing171may be made at a plurality of points. Since the coupling for electrical connection is made at a plurality of points, the coupling area may be maximized, thereby minimizing electric resistance. The plurality of housing coupling portions176cmay be positioned to be spaced apart from each other along the periphery of the support portion176a. At least one housing coupling portion176cmay be positioned between the second uncoated portion coupling portions176badjacent to each other. The plurality of housing coupling portions176cmay be coupled to, for example, the beading portion180in the inner surface of the battery housing171. The housing coupling portions176cmay be coupled, particularly, to the lower surface of the beading portion180by laser welding. The welding may be replaced with, for example, ultrasonic welding, spot welding, or the like. By coupling the plurality of housing coupling portions176con the beading portion180by welding in this way, the current path may be distributed radially so that the resistance level of the cylindrical battery220is limited to about 4 milliohms or less. In addition, as the lower surface of the beading portion180has a shape extending in a direction approximately parallel to the upper surface of the battery housing171, namely in a direction approximately perpendicular to the sidewall of the battery housing171, and the housing coupling portion176calso has a shape extending in the same direction, namely in the radial direction and the circumferential direction, the housing coupling portion176cmay be stably in contact with the beading portion180. In addition, as the housing coupling portion176cis stably in contact with the flat portion of the beading portion180, the two components may be welded smoothly, thereby improving the coupling force between the two components and minimizing the increase in resistance at the coupling portion.

The housing coupling portion176cmay include a contact portion176ecoupled onto the inner surface of the battery housing171and a connection portion176ffor connecting the support portion176aand the contact portion176e.

The contact portion176eis coupled onto the inner surface of the battery housing171. In the case where the beading portion180is formed on the battery housing171, the contact portion176emay be coupled onto the beading portion180as described above. More specifically, the contact portion176emay be electrically coupled to the flat portion formed at the lower surface of the beading portion180formed on the battery housing171, and may be interposed between the lower surface of the beading portion180and the first gasket178b. In this case, for stable contact and coupling, the contact portion176emay have a shape extending on the beading portion180by a predetermined length along the circumferential direction of the battery housing171.

The connection portion176fmay be bent at an obtuse angle. The bending point may be higher than the middle point of the connection portion176f. When the connection portion176fis bent, the contact portion176emay be stably supported on the flat surface of the beading portion180. The connection portion176fis divided into a lower portion and an upper portion based on the bending point, and the lower portion may have a greater length than the upper portion. In addition, the lower portion of the bending point may have a greater inclination angle based on the surface of the support portion176athan the upper portion. When the connection portion176fis bent, a pressure (force) applied in the vertical direction of the battery housing171may be buffered. For example, in the process of sizing the battery housing171, when a pressure is transmitted to the contact portion176eso that the contact portion176emoves vertically toward the support portion176b, the bending point of the connection portion176fmoves upward, so that the shape of the connection portion176is deformed to buffer the stress.

Meanwhile, the maximum distance from the center of the second current collecting plate176to the end of the second uncoated portion coupling portion176balong the radial direction of the electrode assembly100is preferably equal to or smaller than the inner diameter of the battery housing171in a region where the beading portion180is formed, namely the minimum inner diameter of the battery housing171. This is to prevent the end of the second uncoated portion coupling portion176bfrom pressing the edge of electrode assembly100during the sizing process of compressing the battery housing171along the height direction.

The second uncoated portion coupling portion176bincludes a hole176g. The hole176gmay be used as a passage through which the electrolyte may move. The welding pattern176hformed by welding between the second uncoated portion coupling portion176band the bending surface region F may have a structure to extend along the radial direction of the electrode assembly100. The welding pattern176hmay be a line pattern or a dot array pattern.

The welding pattern176hcorresponds to the welding region. Therefore, it is preferable that the welding pattern176hoverlaps by 50% or more with the stack number uniform region b1of the bending surface region F located in the lower portion of the electrode assembly100. The welding pattern176hthat does not overlap with the stack number uniform region b1may overlap with the stack number decrease region b2. More preferably, the entire welding pattern176hmay overlap with the stack number uniform region b1of the bending surface region F. In the bending surface region F at the upper portion of the point where the welding pattern176his formed, the stack number uniform region b1and, optionally, the stack number decrease region b2preferably have the stack number of 10 or more.

The outer diameters of the first current collecting plate144and the second current collecting plate176described above are different from each other. The outer diameter is an outer diameter of the contact area between the bending surface region F and the current collecting plate. The outer diameter is defined as a maximum value of the distance between two points where a straight line passing through the center of the core C of the electrode assembly meets the edge of the contact area. Since the second current collecting plate176is located inside the beading portion, its outer diameter is smaller than that of the first current collecting plate144. In addition, the length of the welding pattern144fof the first current collecting plate144is longer than the length of the welding pattern176hof the second current collecting plate176. Preferably, the welding pattern144fand the welding pattern176hmay extend toward the outer circumference from substantially the same point based on the center of the core C.

The cylindrical battery200,220according to an embodiment of the present disclosure have an advantage in that electrical connection can be performed at the upper portion thereof.

FIG.23is a top plan view illustrating a state in which a plurality of cylindrical batteries200are electrically connected, andFIG.24is a partially enlarged view ofFIG.23. The cylindrical battery200may be replaced with a cylindrical battery220having a different structure.

Referring toFIGS.23and24, a plurality of cylindrical batteries200may be connected in series and in parallel at an upper portion of the cylindrical batteries200using a bus bar210. The number of cylindrical batteries200may be increased or decreased in consideration of the capacity of the battery pack.

In each cylindrical battery200, the rivet terminal172may have a positive polarity, and the flat surface171aaround the rivet terminal172of the battery housing171may have a negative polarity, or vice versa.

Preferably, the plurality of cylindrical batteries200may be arranged in a plurality of columns and rows. Columns are provided in a vertical direction with respect to the drawing, and rows are provided in a left and right direction with respect to the drawing. In addition, in order to maximize space efficiency, the cylindrical batteries200may be arranged in a closest packing structure. The closest packing structure is formed when an equilateral triangle is formed by connecting the centers of the rivet terminals172exposed out of the battery housing171to each other. Preferably, the bus bar210connects the cylindrical batteries200arranged in the same column in parallel to each other, and connects the cylindrical batteries200arranged in two neighboring columns in series with each other.

Preferably, the bus bar210may include a body portion211, a plurality of first bus bar terminals212and a plurality of second bus bar terminals213for serial and parallel connection.

The body portion211may extend along the column of the cylindrical batteries200between neighboring rivet terminals172. Alternatively, the body portion211may extend along the column of the cylindrical batteries200while being regularly bent like a zigzag shape.

The plurality of first bus bar terminals212may extend in one side direction of the body portion211and may be electrically coupled to the rivet terminal172of the cylindrical battery200located in one side direction. The electrical connection between the first bus bar terminal212and the rivet terminal172may be achieved by laser welding, ultrasonic welding, or the like.

The plurality of second bus bar terminals213may extend in the other side direction of the body portion211and may be electrically coupled to the flat surface171aaround the rivet terminal172located in the other side direction. The electrical coupling between the second bus bar terminal213and the flat surface171amay be performed by laser welding, ultrasonic welding, or the like.

Preferably, the body portion211, the plurality of first bus bar terminals212and the plurality of second bus bar terminals213may be made of one conductive metal plate. The metal plate may be, for example, an aluminum plate or a copper plate, but the present disclosure is not limited thereto. In a modified example, the body portion211, the plurality of first bus bar terminals212and the second bus bar terminals213may be manufactured as separate pieces and then coupled to each other by welding or the like.

The cylindrical battery200of the present disclosure as described above has a structure in which resistance is minimized by enlarging the welding region by means of the bending surface region F, multiplexing current paths by means of the second current collecting plate176, minimizing a current path length, or the like. The AC resistance of the cylindrical battery200measured through a resistance meter between the positive electrode and the negative electrode, namely between the rivet terminal172and the flat surface171aaround the terminal172, may be approximately 4 milliohms or below, suitable for fast charging.

In the cylindrical battery200according to the present disclosure, since the rivet terminal172having a positive polarity and the flat surface171ahaving a negative polarity are located in the same direction, it is easy to electrically connect the cylindrical batteries200using the bus bar210.

In addition, since the rivet terminal172of the cylindrical battery200and the flat surface171aaround the terminal172have a large area, the coupling area of the bus bar210may be sufficiently secured to sufficiently reduce the resistance of the battery pack including the cylindrical battery200.

In addition, since electrical wiring may be performed on the upper portion of the cylindrical battery200, there is an advantage in maximizing the energy density per unit volume of the battery module/pack.

The cylindrical battery according to the above embodiments (modifications) may be used to manufacture a battery pack.

FIG.25is a diagram schematically showing a battery pack according to an embodiment of the present disclosure.

Referring toFIG.25, a battery pack300according to an embodiment of the present disclosure includes an aggregate in which cylindrical batteries301are electrically connected, and a pack housing302for accommodating the aggregate. The cylindrical battery301may be any one of the batteries according to the above embodiments (modifications). In the drawing, components such as a bus bar for electrical connection of the cylindrical batteries301, a cooling unit, an external terminal, and so on are not depicted for convenience of illustration.

The battery pack300may be mounted to a vehicle. The vehicle may be, for example, an electric vehicle, a hybrid electric vehicle, or a plug-in hybrid vehicle. The vehicle includes a four-wheeled vehicle or a two-wheeled vehicle.

FIG.26is a diagram schematically showing a vehicle including the battery pack300ofFIG.25.

Referring toFIG.26, a vehicle V according to an embodiment of the present disclosure includes the battery pack300according to an embodiment of the present disclosure. The vehicle V operates by receiving power from the battery pack300according to an embodiment of the present disclosure.

According to the present disclosure, the internal resistance of the battery may be reduced and the energy density may be increased by using the uncoated portion itself protruding at the upper portion and the lower portion of the electrode assembly as an electrode tab.

According to another aspect of the present disclosure, by improving the structure of the uncoated portion of the electrode assembly so that the electrode assembly and the inner circumference of the battery housing do not interfere in the process of forming the beading portion of the battery housing, it is possible to prevent a short circuit from occurring inside the cylindrical battery due to partial deformation of the electrode assembly.

According to another aspect of the present disclosure, by improving the structure of the uncoated portion of the electrode assembly, it is possible to prevent the uncoated portion from being torn when the uncoated portion is bent, and it is possible to improve the welding strength of the current collecting plate by sufficiently increasing the number of overlapping layers of the uncoated portion.

According to another aspect of the present disclosure, a plurality of segments is formed in the uncoated portion of the electrode, and when the electrode is wound, the plurality of segments are disposed to be aligned in a predetermined direction, and the end of the active material layer formed on the electrode is exposed between the winding turns of the separator in an area where the segments are not disposed, so that it is possible to increase the impregnation rate of the electrolyte.

According to another aspect of the present disclosure, by applying a segment structure to the uncoated portion of the electrode and optimizing the dimensions (width, height, separation pitch) of the segments to sufficiently increase the segment stack number of the area used as the welding target area, it is possible to improve the properties of the area where the current collecting plate is welded.

According to another aspect of the present disclosure, an electrode assembly having improved energy density and reduced resistance may be provided by applying a structure in which a current collecting plate is welded to a broad area of the bending surface region formed by bending the segments.

According to another aspect of the present disclosure, a cylindrical battery having an improved design so that electrical wiring can be performed at the upper portion thereof may be provided.

According to another aspect of the present disclosure, by improving the structure of the uncoated portion adjacent to the core of the electrode assembly, the cavity in the core of the electrode assembly is prevented from being blocked when the uncoated portion is bent, so that the electrolyte injection process and the process of welding the battery housing (or, rivet terminal) and the current collecting plate may be easily performed.

According to another aspect of the present disclosure, it is possible to provide a cylindrical battery having a structure in which the internal resistance is low, an internal short circuit is prevented, and the welding strength between the current collecting plate and the uncoated portion is improved, and a battery pack and a vehicle including the cylindrical battery.

In particular, the present disclosure may provide a cylindrical battery having a ratio of diameter to height of 0.4 or more and a resistance of 4 milliohm or less, and a battery pack and a vehicle including the cylindrical battery.