Fixing Structure of Electrode Terminal, and Battery, Battery Pack and Vehicle Including the Same

Disclosed is a fixing structure of an electrode terminal, and a battery, a battery pack and a vehicle including the same. The fixing structure of an electrode terminal includes a battery housing having an open end and a bottom portion in which a perforation hole is formed; an electrode terminal installed through the perforation hole not to contact an inner wall of the perforation hole; and a terminal gasket interposed between the electrode terminal and the perforation hole. A hot-melt layer is interposed at the interface between the electrode terminal and the terminal gasket or the interface between the terminal gasket and the battery housing.

TECHNICAL FIELD

The present disclosure relates to a fixing structure of an electrode terminal, and a battery, 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 has an operating voltage of about 2.5 V to 4.5 V. 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 secondary battery, 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 together with the electrolyte 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 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 factor1865(diameter: 18 mm, height: 65 mm) or a form factor2170(diameter: 21 mm, height: 70 mm), 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 collector 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 collector to a bent surface of an uncoated portion.FIG.4is a cross-sectional view showing the tab-less cylindrical battery, taken along the longitudinal direction Y.

Referring toFIGS.1to4, a positive electrode10and a negative electrode11have a structure in which a sheet-shaped current collector20is coated with an active material layer21, and include an uncoated portion22at one long side along the winding direction X. 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 collectors30,31are 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 collectors30,31are 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.

However, as the form factor of the cylindrical battery increases and the magnitude of the charging current during fast charging increases, heat generation problems also occur in tab-less cylindrical batteries.

Specifically, the conventional tab-less cylindrical battery40includes a battery housing41and a sealing body42as shown inFIG.4. The battery housing41is called a battery can. The sealing body42includes a cap42a, a sealing gasket42b, and a connection plate42c. The sealing gasket42bsurrounds the edge of the cap42aand is fixed by a crimping portion43. Also, the electrode assembly A is fixed within the battery housing41by a beading portion44to prevent up and down movement.

Typically, the positive electrode terminal is the cap42aof the sealing body42, and the negative electrode terminal is the battery housing41. Accordingly, the current collector30coupled to the uncoated portion10aof the positive electrode10is electrically connected to a connection plate42cattached to the cap42athrough a strip-shaped lead45. Also, the current collector31coupled to the uncoated portion11aof the negative electrode11is electrically connected to the bottom portion of the battery housing41. The insulator46covers the current collector30to prevent the battery housing41and the uncoated portion10aof the positive electrode10having different polarities from contacting each other and causing a short circuit.

When the current collector30is connected to the connection plate42c, the strip-shaped lead45is used. The lead45is attached separately to the current collector30or manufactured integrally with the current collector30. However, since the lead45is in the form of a thin strip, its sectional area is small, so a lot of heat is generated when the fast charging current flows. Also, excessive heat generated from the lead45may be transferred to the electrode assembly A and shrink the separator12, which may cause an internal short circuit that is the main cause of thermal runaway.

The lead45also occupies a considerable installation space within the battery housing41. Therefore, the cylindrical battery40including the lead45has low space efficiency and has limitations in increasing energy density.

In addition, the top of the crimping portion43has negative polarity, but has a small area. In the drawings, the crimping portion43is shown large, but in reality, the top of the crimping portion43has a very small area, compared to the sealing body42. Therefore, in order to stably connect bus bar components, there is no choice but to connect the positive electrode to the sealing body42crimped to the open end of the battery housing40and connect the negative electrode to the bottom portion of the battery housing40.

As such, in order to connect the conventional tab-less cylindrical batteries40in series and/or parallel, bus bar components must be connected to the cap42aof the sealing body42and the bottom portion of the battery housing41, which reduces space efficiency. The battery pack mounted in an electric vehicle includes hundreds of cylindrical batteries40. Therefore, inefficiencies in electrical wiring cause significant inconvenience during the assembly process of the electric vehicle and during the maintenance of the battery pack.

DISCLOSURE

Technical Problem

The present disclosure is designed to solve the problems of the related art, and therefore the present disclosure is directed to lowering the inner resistance of a cylindrical battery and increasing energy density by improving an electrode terminal structure of the cylindrical battery to increase space efficiency within the battery housing.

The present disclosure is also directed to solving the internal heat generation problem that occurs during fast charging by improving the electrode terminal structure of the cylindrical battery to expand the sectional area of a current path.

The present disclosure is also directed to improving sealing properties along with the improvement of the electrode terminal structure the cylindrical battery.

The present disclosure is also directed to providing a cylindrical battery with an improved structure in which the electrical wiring work for series and/or parallel connection of cylindrical batteries may be performed at one side of the cylindrical battery.

The present disclosure is also directed to providing a battery pack manufactured using the cylindrical battery with an improved structure and a vehicle including the same.

However, 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 a fixing structure of an electrode terminal, comprising: a battery housing having an open end and a bottom portion in which a perforation hole is formed; an electrode terminal installed through the perforation hole not to contact an inner wall of the perforation hole; and a terminal gasket interposed between the electrode terminal and the perforation hole, wherein a hot-melt layer is interposed at the interface between the electrode terminal and the terminal gasket or the interface between the terminal gasket and the battery housing.

The electrode terminal may include a body portion inserted into the perforation hole; an outer flange portion configured to extend from a first side of the body portion along an outer surface of the bottom portion of the battery housing; and an inner flange portion configured to at least partially extend from a second side of the body portion to face the bottom portion of the battery housing.

A welding portion may be provided on an inner side of the inner flange portion.

The welding portion may have a flat surface.

The terminal gasket may include an outer gasket interposed between the outer flange portion and a first plane where the outer surface of the bottom portion of the battery housing is located; an inner gasket interposed between the inner flange portion and a second plane where an inner surface of the bottom portion of the battery housing is located; and an intermediate gasket interposed between the body portion and the perforation hole and configured to connect the outer gasket and the inner gasket.

The hot-melt layer may be located at the interface between the inner flange portion and the inner gasket and is at least partially exposed.

The hot-melt layer may be located at the interface between the outer flange portion and the outer gasket and is at least partially exposed.

The hot-melt layer may be located at the interface between the outer gasket and the first plane and is at least partially exposed.

The hot-melt layer may be located at the interface between the inner gasket and the second plane and is at least partially exposed.

The hot-melt layer may be formed by hardening a hot-melt film with heat.

The hot-melt layer may be formed by hardening a hot-melt coating layer with heat.

The hot-melt layer may be made of silicone-based, epoxy-based, acrylic-based or urethane-based hot-melt material.

The hot-melt layer may have a thickness of several μm several hundred μm.

In another aspect of the present disclosure, there is also provided a battery, comprising: an electrode assembly in which a first electrode and a second electrode are wound with a separator interposed therebetween; a battery housing configured to accommodate the electrode assembly and electrically connected to the first electrode; an electrode terminal installed through a perforation hole formed in a bottom portion of the battery housing not to contact an inner wall of the perforation hole and electrically connected to the second electrode, the electrode terminal including: a body portion inserted into the perforation hole; an outer flange portion configured to extend from a first side of the body portion along an outer surface of the bottom portion of the battery housing; and an inner flange portion configured to at least partially extend from a second side of the body portion to face an inner surface of the bottom portion of the battery housing; a terminal gasket interposed between the electrode terminal and the perforation hole; and a sealing body configured to seal an open end of the battery housing to enable insulation from the battery housing, wherein a hot-melt layer is interposed at the interface between the electrode terminal and the terminal gasket or the interface between the terminal gasket and the battery housing.

The electrode terminal may include a welding portion on an inner side of the inner flange portion. The welding portion may have a flat surface.

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

Advantageous Effects

According to an aspect of the present disclosure, it is possible to lower the inner resistance of a battery and increase energy density by improving an electrode terminal structure of the battery to increase space efficiency within the battery housing.

According to another aspect of the present disclosure, the sealing performance of the electrode terminal may be improved by applying a hot-melt layer to the electrode terminal structure.

According to still another aspect of the present disclosure, it is possible to solve the internal heat generation problem that occurs during fast charging by improving the electrode terminal structure of the battery to expand the sectional area of a current path.

According to still another aspect of the present disclosure, the electrical wiring work for series and/or parallel connection of batteries may be performed at one side of the battery.

According to still another aspect of the present disclosure, it is possible to provide a battery pack manufactured using the battery with an improved structure and a vehicle including the same.

BEST MODE

Also, to aid understanding of the present disclosure, the attached drawings are not drawn to scale and the dimensions of some components may be exaggerated. In addition, the same reference symbols may be assigned to the same components in different embodiments.

Stating that two objects of comparison are ‘the same’ means that they are ‘substantially the same’. Therefore, the term ‘substantially the same’ may include a deviation that is considered low in the art, for example, a deviation of less than 5%. Also, uniformity of a parameter in a region may mean that the parameter is uniform from an average perspective in the corresponding region.

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.

For convenience of description, 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.

A cylindrical battery according to an embodiment of the present disclosure may include an electrode terminal installed in a perforation hole formed in the bottom portion of a battery housing.

FIG.5is a cross-sectional view showing a fixing structure of an electrode terminal50according to an embodiment of the present disclosure, andFIG.6ais an enlarged cross-sectional view showing the portion indicated by a dotted circle inFIG.5.

Referring toFIGS.5and6a, the electrode terminal50may include a body portion50ahaving an upper surface, a lower surface and an outer surface, an outer flange portion50bextending along the outer surface52aof the bottom portion52of the battery housing51from the outer surface of the body portion50a, and an inner flange portion50cextending from the outer surface of the body portion50ato at least partially face the inner surface52bof the bottom portion52of the battery housing51. The upper surface of the body portion50amay be flat and be connected to the current collector, and is located above the inner flange portion50c.

The fixing structure of the electrode terminal50according to an embodiment of the present disclosure may be applied to the structure of the cylindrical battery housing51. Specifically, the fixing structure of the electrode terminal50may include a battery housing51having an open end, an electrode terminal50fixed through the perforation hole53formed in the bottom portion52of the battery housing51, and a terminal gasket54interposed between the electrode terminal50and the perforation hole53.

The battery housing51may include a cylindrical sidewall and a bottom portion52connected to an end of the sidewall. Since the perforation hole53is formed in the bottom portion52, the battery housing51has a structure in which one side is open and the other side is partially closed by the bottom portion52. The battery housing51may also have other shapes than the cylindrical shape, for example a prismatic shape with a rectangular cross section.

The battery housing51is made of a conductive metal material. In one example, battery housing51may be made of steel, but the present disclosure is not limited thereto. The inner and outer surfaces of the battery housing51may be coated with a Ni-plated layer.

The electrode terminal50is made of a conductive metal material. In one example, electrode terminal50may be made of aluminum, but the present disclosure is not limited thereto. The electrode terminal50may be made of 10 series aluminum alloy, which is easy to plasticize and has low resistance. Plastic working is a method of applying a physical force to metal to deform the metal into a desired shape, and may include riveting, caulking, and the like.

The terminal gasket54may be made of polymer resin with insulating and elastic properties. In one example, the terminal gasket54may be made of polypropylene, polybutylene terephthalate, polyfluoroethylene, or the like, but the present disclosure is not limited thereto.

Preferably, the electrode terminal50is installed in the perforation hole53not to contact the inner wall of the perforation hole53.

The electrode terminal50includes a body portion50ainserted into the perforation hole53. The body portion50amay have an upper surface, a lower surface, and an outer surface for connecting the upper surface and the lower surface to each other.

The electrode terminal50may include an outer flange portion50bextending along the outer surface52afrom the periphery of the first side of the body portion50aexposed through the outer surface52aof the bottom portion52of the battery housing51, and an inner flange portion50cextending from the periphery of the second side of the body portion50aexposed through the inner surface52bof the bottom portion52of the battery housing51to at least partially face the inner surface52b.

The electrode terminal50may include a flat portion50dat the inner side of the inner flange portion50c. The flat portion50dis an example of a welding portion. The welding portion is a part welded to another member. The flat portion50dmay be surrounded by the inner flange portion50c.

The flat portion50dcorresponds to the upper surface of the body portion50a. The flat portion50dmay include a flat surface in at least a partial area. At least a partial area of the flat portion50dmay be parallel to the inner surface52bof the bottom portion52of the battery housing51. Here, the term ‘parallel’ means substantially parallel when observed with the naked eye. The flat portion50dmay be a surface already formed before the electrode terminal50is plastic-worked. That is, the flat portion50dmay be a region that is not deformed by plastic working.

Preferably, the electrode terminal50is made of metal, and the inner flange portion50cmay be formed by plastic-working the upper periphery of the body portion50a. Plastic working may be caulking. However, the present disclosure is not limited thereto. In one embodiment, the electrode terminal50may be a rivet terminal riveted through the perforation hole53by the inner flange portion50c.

The inner flange portion50cextends gradually away from the bottom portion52of the battery housing51. The angle (θ) between the surface of the inner flange portion50cfacing the bottom portion52of the battery housing51and the inner surface52bof the bottom portion52of the battery housing51may be 0 degrees to 60 degrees.

The size of the angle (θ) is determined by the caulking strength when the electrode terminal50is installed in the perforation hole53of the battery housing51using the caulking method. In one example, as caulking intensity increases, the angle (θ) may decrease to 0 degrees. If the angle (θ) exceeds 60 degrees, the sealing effect of the terminal gasket54may be deteriorated.

Meanwhile, since the outer flange portion50bis substantially parallel to the bottom portion52of the battery housing51, the angle between the inner flange portion50cand the outer flange portion50bmay also be 0 degrees to 60 degrees.

According to another aspect, a recess portion55may be provided between the inner flange portion50cand the flat portion50d. The recess portion55is a groove recessed toward the central axis of the body portion50a. The groove may have a closed loop shape when viewed from the central axis direction of the body portion50a. The recess portion55may have an asymmetric cross-section. In one example, the asymmetric cross-section may be approximately V-shaped or U-shaped. The asymmetric cross section may include a sidewall55aof the flat portion50dand an inclined surface55bconnected to the end of the sidewall55aand formed by the upper surface of the inner flange portion50c. The outer surface of the body portion50aexposed through the sidewall55amay be referred to as a first surface, and the inclined surface55bmay be referred to as a second surface. The first and second surfaces are asymmetrical. The sidewall55amay be substantially perpendicular to the inner surface52bof the bottom portion52of the battery housing51. The term ‘vertical’ means substantial vertical when observed with the naked eye. As will be described later, the sidewall55amay be inclined toward the flat portion50d. The recess portion55is generated by the shape of the caulking jig when the electrode terminal50is installed in the perforation hole53of the battery housing51using the caulking method.

Preferably, the thickness of the inner flange portion50cmay decrease as being away from the body portion50aof the electrode terminal50.

According to another aspect, the terminal gasket54may include an outer gasket54ainterposed between the outer flange portion50band the first plane P1where the outer surface52aof the bottom portion52of the battery housing51is located, an inner gasket54binterposed between the inner flange portion50cand the second plane P2where the inner surface52bof the bottom portion52of the battery housing51is located, and an intermediate gasket54cinterposed between the body portion50aand the perforation hole53and configured to connect the outer gasket54aand the inner gasket54b.

The thickness of the outer gasket54aand/or the inner gasket54band/or the intermediate gasket54cmay vary depending on location.

Preferably, the thickness of the intermediate gasket54cmay vary depending on the location, and the terminal gasket54may have a minimum thickness at the intermediate gasket54c.

In one aspect, the thickness of the area of the intermediate gasket54cadjacent to the first plane P1may increase as being closer to the first plane P1. Similarly, the thickness of the area of the intermediate gasket54cadjacent to the second plane P2may increase as being closer to the second plane P2. Also, the central area of the intermediate gasket54clocated between the first plane P1and the second plane P2may have a uniform thickness.

Preferably, among the area of the intermediate gasket54c, the area interposed between the inner flange portion50cand the inner edge56of the perforation hole53connected to the inner surface52bof the bottom portion52of the battery housing51may have a relatively small thickness. Preferably, a minimum thickness point may exist in the area of the intermediate gasket54cinterposed between the inner edge56of the perforation hole53and the inner flange portion50c. Also, the inner edge56of the perforation hole53may include an opposing surface57that faces the inner flange portion50c.

Meanwhile, the top and bottom of the inner wall of the perforation hole53, which is perpendicular to the bottom portion52of the battery housing51, are chamfered (corner cutting) to form a surface tapered toward the electrode terminal50. However, the top and/or bottom of the inner wall of the perforation hole53may be transformed into a smooth curved surface with curvature. In this case, the stress applied to the gasket54near the top and/or bottom of the inner wall of the perforation hole53may be further alleviated.

Preferably, the inner gasket54bforms an angle (θ) of 0 degrees to 60 degrees with the inner surface52bof the bottom portion52of the battery housing51and may extend longer than the inner flange portion50c.

In another aspect, the height H1of the flat portion50dmay be equal to or greater than the height H2of the end of the inner gasket54b, based on the inner surface52bof the bottom portion52of the battery housing51. Also, based on the inner surface52bof the bottom portion52of the battery housing51, the height H1of the flat portion50dmay be equal to or greater than the height H3of the end of the inner flange portion50c. Here, the height H2is the maximum height of the end of the inner gasket54bmeasured based on the inner surface52b. Also, the height H3is the maximum height of the upper surface of the inner flange portion50cmeasured based on the inner surface52b.

If the height parameters H1, H2, and H3meet the above conditions, the inner flange portion50cand the inner gasket54bmay be prevented from interfering with other components.

Preferably, the height H3of the inner flange portion50cmay be 0.5 mm to 3.0 mm. If the height H3of the inner flange portion50cis less than 0.5 mm, sufficient sealing performance cannot be secured. Also, if the height H3of the inner flange portion50cexceeds 3 mm, the inner space of the battery housing51that can be occupied by the electrode assembly is reduced.

Preferably, the height H4of the electrode terminal50may be 1.5 mm to 7 mm. The height H4of the electrode terminal50corresponds to the distance from the lower surface of the outer flange portion50bto the flat portion50d. If the height H4of the electrode terminal50is less than 1.5 mm, it is difficult to increase the height of the inner flange portion50cto a level to ensure sealing performance due to the thickness of the bottom portion52of the battery housing51. For reference, the thickness of the bottom portion52of the battery housing51is approximately 0.5 mm to 1 mm. In addition, when the height H4of the electrode terminal50exceeds 7 mm, the inner space of the battery housing51that can be occupied by the electrode assembly decreases and the height of the battery increases, thereby lowering the energy density per unit volume. If H3and H4meet the numerical range, the sealing property of the electrode terminal50may be secured sufficiently without reducing the space inside the battery housing51.

In another aspect, the height H5of the outer flange portion50bmay be 0.8 mm or more based on the outer surface52aof the bottom portion52of the battery housing51. If the height H5of the outer flange portion50bis less than 0.8 mm, the outer flange portion50bmay be deformed when the electrode terminal50is riveted. The thickness of the outer gasket54ais 0.3 mm or more considering insulation and sealing properties. Considering the thickness of the outer gasket54a, if the height of the outer flange portion50bis less than 0.8 mm, the thickness of the outer flange portion50bbecomes thin to a level where it is difficult to secure sufficient mechanical rigidity. This is especially true when the electrode terminal50is made of aluminum. Meanwhile, the height of the outer flange portion50bmay be set appropriately considering the space margin at the upper portion of the battery. In one example, the height of the outer flange portion50bmay be set to 2 mm or less, or 3 mm or less, or 4 mm or less, or 5 mm or less, but the present disclosure is not limited thereto.

In still another aspect, at least a part of the outer gasket54amay be exposed to the outside of the outer flange portion50bof the electrode terminal50. The purpose of exposing the outer gasket54ais to insulate the outer surface52a, which has a polarity opposite to that of the electrode terminal50, and the electrode terminal50from each other. For electrical insulation between the electrode terminal50and the outer surface52a, the exposure width G of the outer gasket54amay be 0.1 mm to 1 mm. If the exposure width G is less than 0.1 mm, the electrical insulation between the electrode terminal50and the outer surface52aon the plane may be destroyed when high c-rate charging and discharging of 300 A or more is performed. In addition, if the exposure width G is larger than 1 mm, the electrical insulation effect does not increase further, but rather the area of the outer surface52aused as a negative electrode area decreases, thereby reducing the contact area of electrical connection components (e.g., bus bar).

In still another aspect, the diameter of the flat portion50dof the electrode terminal50may be determined considering the welding strength between the current collector and the flat portion50d. The tensile force of the welding portion between the flat portion50dand the current collector may be at least 2 kgf or more, or 5 kgf or more, or 6 kgf or more, or 7 kgf or more, or 8 kgf or more, or 9 kgf or more, or 10 kgf or more. It is desirable to increase the tensile force of the welding portion as much as possible within the allowable range by selecting the best welding method.

Referring toFIG.6c, in order to satisfy the tensile force condition of the welding portion, the diameter of the welding pattern Wp formed on the flat portion50dmay be at least 2 mm. The diameter of the welding pattern Wp may be defined as the converted diameter of the circle (2*(S/π)0.5) when the area S of the welding pattern Wp that appears on the surface of the welding area is converted to the area (πr2) of the circle. The welding pattern Wp may be continuous or discontinuous. The welding pattern Wp may not be a circle. When the welding pattern Wp is not a circle, the converted diameter (maximum value*2) may be determined from the maximum value of the distance from the center of the flat portion50dto the edge of the welding pattern Wp.

The flat portion50dof the electrode terminal50includes a weldable area. The diameter of the weldable area may be 3 mm to 14 mm. If the diameter of the weldable area is smaller than 3 mm, it is difficult to secure a welding pattern with a diameter of 2 mm or more. In particular, when forming a welding pattern using laser welding, it is difficult to secure a welding pattern with a diameter of 2 mm or more due to interference of the laser beam. If the diameter of the weldable area exceeds 14 mm, the diameter of the outer flange portion50bof the electrode terminal50becomes too large, and thus it is difficult to sufficiently secure the area of the outer surface52aof the bottom portion52of the battery housing to be used as the negative electrode area.

Considering the above diameter condition of the welding pattern and the diameter condition of the weldable area, the ratio of the area of the welding pattern to the area of the weldable area required to secure a tensile force of the welding portion of 2 kgf or more is preferably 2.04%(π12/π72) to 44.4%(ð12/π1.52).

In another aspect, the radius R1from the center of the body portion50ato the edge of the outer flange portion50bmay be 10% to 70% based on the radius R2of the bottom portion52of the battery housing51.

As R1becomes smaller, the welding space becomes insufficient when welding components (bus bars) used for the electrical connection of the electrode terminal50. Also, as R1increases, the welding space decreases when welding electrical connection components (bus bars) to the outer surface52aof the bottom portion52of the battery housing51excluding the electrode terminal50.

By adjusting the ratio R1/R2between 10% and 70%, the welding space for the electrode terminal50and the outer surface52aof the bottom portion52of the battery housing51may be appropriately secured.

In addition, the radius R3from the center of the body portion50aof the electrode terminal50to the edge of the flat portion50dmay be 4% to 30% based on the radius R2of the bottom portion52of the battery housing51.

If R3becomes smaller, the welding space becomes insufficient when welding the current collector to the flat portion50dof the electrode terminal50, and the welding area of the electrode terminal50decreases, which may increase contact resistance. In addition, R3must be smaller than R1, and if R3becomes larger, the thickness of the inner flange portion50cbecomes thinner and the force with which the inner flange portion50ccompresses the terminal gasket54becomes weaker, which may deteriorate the sealing ability of the terminal gasket54.

If R3/R2is adjusted between 4% and 30%, the welding process may be performed easily by securing a sufficient welding area between the flat portion50dof the electrode terminal50and the current collector, and it is also possible to reduce the contact resistance of the welding area and prevent deterioration of the sealing ability of the terminal gasket54.

According to an embodiment of the present disclosure, the fixing structure of the electrode terminal50may be formed using a caulking jig that moves up and down. First, a preform (not shown) of the electrode terminal50is inserted by interposing the terminal gasket54into the perforation hole53formed in the bottom portion52of the battery housing51. The preform refers to the electrode terminal before the caulking process.

Next, the caulking jig is inserted into the inner space of the battery housing51. The caulking jig has a groove and a protrusion corresponding to the final shape of the electrode terminal50on the surface facing the preform in order to form the electrode terminal50by press-forming the preform.

Next, the caulking jig is moved downward to press-form the upper portion of the preform so that the preform is transformed into the electrode terminal50riveted to the perforation hole53of the battery housing51. The press-fit depth of the caulking jig may be regulated by the flat portion50d. The flat portion50dis formed in advance on the body portion50a, and the caulking jig has a groove into which the flat portion50dis inserted. Therefore, while the preform is being press-formed, if the flat portion50dcontacts the bottom of the groove, the press forming is stopped. Accordingly, even during the mass production process, the shapes of the inner flange portion50cand the recess portion55, which are formed through plastic deformation, may be made uniform. Also, the flat portion50dis not deformed or substantially not deformed while the preform is pressed by the caulking jig. Therefore, the flat portion50dmay also maintain a uniform shape during the mass production process. By doing so, the welding process between the flat portion50dand the current collector, explained later, may be performed more easily, and thus manufacturing variation may be significantly reduced.

While the preform is pressed by the caulking jig and its shape is deformed, the outer gasket54ainterposed between the outer flange portion50band the outer surface52aof the bottom portion52of the battery housing51is elastically compressed and its thickness decreases. In addition, the region of the intermediate gasket54cinterposed between the inner edge56of the perforation hole53and the preform is elastically compressed by the inner flange portion50c, and its thickness is reduced more than other regions. In particular, the area where the thickness of the intermediate gasket54cis intensively reduced is the portion indicated by the dotted circle inFIG.6a. Accordingly, the sealing property and airtightness between the riveted electrode terminal50and the battery housing51are significantly improved.

Preferably, the terminal gasket54is sufficiently compressed to secure the desired sealing strength without being physically damaged while the preform is being riveted through a firing process that is called caulking.

Preferably, the compression ratio of the terminal gasket54may be 30% to 90%. The minimum compression ratio corresponds to the compression ratio if a minimum level to ensure the sealing property of the electrode terminal50. The maximum compression ratio corresponds to the compression ratio of a maximum level that can be achieved without physically damaging the terminal gasket54.

In one example, when the terminal gasket54is made of polybutylene terephthalade, it is desirable that the terminal gasket54has a compression ratio of 50% or more at the point where it is compressed to the minimum thickness.

In the present disclosure, the compression ratio may be defined as the ratio of the change in thickness at the maximum compression point compared to the thickness of the terminal gasket54before compression. The thicknesses of the inner gasket54band the intermediate gasket54cbefore compression may be uniform, and a maximum compression point may exist near the inner edge56. Preferably, the compression ratio may be calculated based on the uniform thickness of the inner gasket54band the intermediate gasket54c.

In another example, when the terminal gasket54is made of polyfluoroethylene, it is desirable that the terminal gasket54has a compression ratio of 60% or more at the point where it is compressed to the minimum thickness. Preferably, the compression ratio may be calculated based on the uniform thickness of the inner gasket54band the intermediate gasket54c.

In still another example, when the terminal gasket54is made of polypropylene, it is desirable that the terminal gasket54has a compression ratio of 60% or more at the point where it is compressed to the minimum thickness. Preferably, the compression ratio may be calculated based on the uniform thickness of the inner gasket54band the intermediate gasket54c.

Preferably, the upper portion of the preform may be press-formed step by step by moving the caulking jig up and down at least twice. In other words, the preform may be deformed several times by performing press forming step by step. At this time, the pressure applied to the caulking jig may be increased step by step. In this way, it is possible to prevent the terminal gasket54from being damaged during the caulking process by dispersing the stress applied to the preform several times. In particular, damage to the gasket is minimized when the region of the intermediate gasket54cinterposed between the inner edge56of the perforation hole53and the preform is intensively compressed by the inner flange portion50c.

After the preform is completely press-formed using the caulking jig, if the caulking jig is separated from the battery housing51, the fixing structure of the electrode terminal50according to an embodiment of the present disclosure may be obtained, as shown inFIG.6a.

According to the above embodiment, the caulking jig press-forms the upper portion of the preform by moving up and down inside the battery housing51. In some cases, a rotary jig used in the prior art may be used for press-forming the preform.

However, the rotary jig rotates in a state of being tilted at a predetermined angle based on the central axis of the battery housing51. Therefore, a rotary jig with a large rotation radius may cause interference with the inner wall of the battery housing51. Also, if the depth of the battery housing51is large, the length of the rotary jig becomes correspondingly longer. In this case, as the rotation radius of the end of the rotary jig increases, the preform may not be press-formed properly. Therefore, press forming using the caulking jig is more effective than using a rotary jig.

Meanwhile, the electrode terminal50may have various structures depending on the design of the preform and/or the caulking jig and/or the terminal gasket54and the magnitude of the pressure applied to the preform during the caulking process.

FIG.6bis a partially enlarged cross-sectional view schematically showing a structure of an electrode terminal50′ according to another embodiment of the present disclosure.

Referring toFIG.6b, the electrode terminal50′ according to another embodiment has a structure in which the inner flange portion50cis riveted toward the inner surface52bof the bottom portion52of the battery housing51.

The inner flange portion50cincludes a first region50clextending gradually away from the bottom portion52of the battery housing51, and a second region50c2connected to the first region50cland extending toward the bottom portion52of the battery housing51.

The angle (δ) between the surface of the second region50c2facing the bottom portion52of the battery housing51and the inner surface52bof the bottom portion52may be 0 degrees to 30 degrees.

Preferably, the angle (δ) may be substantially close to zero to maximize the sealing property of the terminal gasket54. Since the second region50c2strongly compresses the inner gasket54b, the sealing property of the terminal gasket54may be increased. This effect increases as the angle (δ) is close to 0.

The height H3of the inner flange portion53cis greater than the height H2of the inner gasket54b. Also, the inner edge of the perforation hole53has an arc shape with a predetermined curvature. In addition, the sidewall55aat the edge of the flat portion50dhas a structure inclined toward the flat portion50d.

The terminal gasket54may include an outer gasket54ainterposed between the outer flange portion50band the first plane P1where the outer surface52aof the bottom portion52of the battery housing51is located; an inner gasket54binterposed between the inner flange portion50cand the second plane P2where the inner surface52bof the bottom portion52of the battery housing51is located; and an intermediate gasket54cinterposed between the body portion50aand the perforation hole53and configured to connect the outer gasket54aand the inner gasket54b.

Preferably, the thickness of the intermediate gasket54cgradually decreases in a direction away from the outer gasket54a. Also, the inner gasket54bmay decrease to the minimum thickness near the end of the inner flange portion50c, and then the thickness may slightly increase toward the uppermost end. This compression structure of the inner gasket54bmay further improve the sealing property of the electrode terminal50′. The compression ratio of the inner gasket54bmay be calculated at the minimum thickness point near the end of the inner flange portion50c.

Meanwhile, according to the experiment performed by the inventors, when the thermal shock cycle experiment was repeated for a cylindrical battery to which the electrode terminal50,50′ was applied, it was found that a gap was generated between the terminal gasket54and the electrode terminal50,50′ so that the electrolyte was leaked to the outside.

The thermal shock cycle test is an experiment that repeats the process of adjusting the state of charge of the cylindrical battery to 50% and then exposing the cylindrical battery to temperatures between-30° C. and 60° C.

In each thermal shock cycle, the lowest temperature holding time was 60 minutes and the maximum temperature holding time was also 60 minutes. In addition, the speed of changing the temperature from the lowest temperature to the highest temperature or the speed of changing the temperature from the highest temperature to the lowest temperature was set to 2.5° C. or less per minute. The thermal shock cycle for the cylindrical battery was repeated a total of 200 times.

FIG.6dis a photograph showing the surface of a cylindrical battery with the electrode terminal50,50′ exposed after performing a thermal shock cycle test. Stains were observed on the surface of the cylindrical battery. The stain supports electrolyte leakage. As a result of analyzing components of the stain, electrolyte components were found.

FIG.6eis a photograph showing the results of measuring the interval between the terminal gasket54and the electrode terminal50,50′ before and after the thermal shock cycle test.

FIG.6e(a) is a cross-sectional photograph showing the electrode terminal50,50′ and the terminal gasket54before the thermal shock cycle test is performed. The interval between the corner of the perforation hole where the electrode terminal50,50′ is installed and the electrode terminal50,50′ is measured to be 0.25 mm to 0.35 mm.

FIG.6e(b) is a cross-sectional photograph showing the electrode terminal50,50′ and the terminal gasket54taken at a total of 4 points after the thermal shock cycle test is performed. The interval between the corner of the perforation hole where the electrode terminal50,50′ is installed and the electrode terminal50,50′ increases from 0.264 mm to 0.409 mm, and a gap is also found at the interface between the battery housing and the terminal gasket54.

The increase of the interval and the presence of the gap were analyzed as causes of electrolyte leakage. After the thermal shock cycle experiment was performed, the weight of the cylindrical battery was reduced. The leakage amount of the electrolyte was estimated from the weight reduction of the cylindrical battery to be approximately 180 mg to 270 mg.FIG.6fis a cross-sectional view showing the improved structure of the electrode terminal50,50′ to solve the electrolyte leakage problem identified in the thermal shock cycle experiment.

The improved structure of the electrode terminal may also be applied to the embodiment shown inFIG.6a.

A first hot-melt layer (HM1) may be interposed between the electrode terminal50,50′ and the terminal gasket54.

A second hot-melt layer (HM2) may be interposed between the battery housing and the terminal gasket54.

Any one of the first hot-melt layer (HM1) and the second hot-melt layer (HM2) may not be formed.

The hot-melt layer may have a thickness of several μm to several hundred μm.

The first hot-melt layer (HM1) is interposed at the interface between the inner flange portion50cand the inner gasket54band may be at least partially exposed.

The first hot-melt layer (HM1) is interposed between the outer flange portion50band the outer gasket54aand may be at least partially exposed.

The second hot-melt layer (HM2) is interposed at the interface between the outer gasket54aand the first plane P1and may be at least partially exposed.

The second hot-melt layer (HM2) is interposed at the interface between the inner gasket54band the second plane P2and may be at least partially exposed.

The first and second hot-melt layers (HM1, HM2) may be formed using a hot-melt film or a hot-melt coating solution. The hot-melt film may be locally attached to the surface of at least one of two members between which the first hot-melt layer (HM1) and/or the second hot-melt layer (HM2) is interposed. The hot-melt coating solution may be sprayed locally on the surface of at least one of the two members between which the first hot-melt layer (HM1) and/or the second hot-melt layer (HM2) is interposed. The sprayed hot-melt coating solution forms a hot-melt coating layer on the surface.

In one example, the hot-melt film may be locally attached to the surface of the terminal gasket54facing the electrode terminal50and/or the surface of the terminal gasket54facing the battery housing51.

In another example, the hot-melt coating solution may be sprayed locally on the surface of the terminal gasket54facing the electrode terminal50,50′ and/or the surface of the terminal gasket54facing the battery housing51.

In still another example, the hot-melt film may be attached to the surface of the electrode terminal50,50′ facing the terminal gasket54. Alternatively, the hot-melt coating solution may be sprayed on the surface of the electrode terminal50,50′ facing the terminal gasket54.

In still another example, the hot-melt film may be attached to the surface of the battery housing51facing the terminal gasket54. Alternatively, the hot-melt coating solution may be sprayed on the surface of the battery housing51facing the terminal gasket54.

The first and second hot-melt layers (HM1, HM2) may be formed by heating a hot-melt film or a hot-melt coating layer. The hot-melt film or the hot-melt coating layer may be hardened through heating.

The first and second hot-melt layers (HM1, HM2) may be made of hot-melt materials known in the art. The hot-melt materials may be used without limitation as long as they are, for example, silicone-based, epoxy-based, acrylic-based, or urethane-based materials.

The first and second hot-melt layers (HM1, HM2) may improve the sealing property of the terminal gasket54by filling fine irregularities in the interface between the terminal gasket54and the electrode terminal50,50′ and the interface between the terminal gasket54and the battery housing, and in particular, may prevent the lifting (interface peeling) of the terminal gasket54.

As a result, electrolyte leakage may be prevented even if the cylindrical battery is repeatedly charged and discharged in a low or high temperature environment.

Preferably, the fixing structure of the electrode terminal50,50′ according to an embodiment of the present disclosures as described above may be applied to a cylindrical battery with a form factor greater than 2170.

Recently, as cylindrical batteries are applied to electric vehicles, the form factor of cylindrical batteries is increasing compared to the conventional1865,2170, or the like. If the form factor increases, the energy density is increased, the safety against thermal runaway is enhanced, and the cooling efficiency is improved.

In addition, as explained later, electrical wiring may be performed at one side of the cylindrical battery to which the fixing structure of the electrode terminal50,50′ is applied. Also, the electrode terminal50,50′ has low resistance due to a large sectional area and thus is very suitable for rapid charging.

Preferably, the cylindrical battery to which the structure of the electrode terminal50,50′ of the present disclosure 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 (@) 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. The form factor of the cylindrical battery according to an embodiment of the present disclosure may be, for example, 4611, 4875, 48110, 4880, or 4680. In the numerical value representing the form factor, first two numbers indicate the diameter, and the remaining numbers indicate the height.

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

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

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

A battery according to still another embodiment may be a cylindrical battery, whose diameter is about 46 mm, height is about 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.

FIG.7ais a sectional view showing a cylindrical battery70according to an embodiment of the present disclosure, taken along the longitudinal direction Y.

Referring toFIG.7a, the cylindrical battery70according to an embodiment includes a jelly-roll type electrode assembly71, in which a first electrode and a second electrode in a sheet form are wound in a state where a separator is interposed therebetween, the uncoated portion72of the first electrode serving as a first portion of the first electrode is exposed at the lower portion, and the uncoated portion73of the second electrode serving as a second portion of the second electrode is exposed at the lower portion.

Here, the first portion and the second portion may be different portions of the electrode other than the uncoated portion. The other portion may be a metal tab electrically coupled to the uncoated portion of the electrode. Also, it is not excluded that the electrode assembly71has a shape other than a jelly-roll shape. In addition, it is obvious that the battery may have not only a cylindrical shape but also other shapes such as a prismatic shape.

In an embodiment, the first electrode may be a negative electrode and the second electrode may be a positive electrode, or vice versa.

The method of winding the electrode assembly71is substantially the same as the method of winding an electrode assembly used in manufacturing a tab-less cylindrical battery according to the prior art described with reference toFIG.2.

When showing the electrode assembly71, only the uncoated portions72,73that are exposed and extended outside the separator are shown in detail, and the winding structure of the first electrode, the second electrode and the separator is not depicted.

The cylindrical battery70also includes a cylindrical battery housing51configured to accommodate the electrode assembly71and electrically connected to the uncoated portion72of the first electrode.

Preferably, one side (lower portion) of the battery housing51is open. Also, the bottom portion52of the battery housing51has a structure in which the electrode terminal50is riveted to the perforation hole53through a firing (e.g., caulking) process.

Specifically, the electrode terminal50includes a body portion50ainserted into the perforation hole53, an outer flange extending along the outer surface52afrom the periphery of the first side of the body portion50aexposed through the outer surface52aof the bottom portion52of the battery housing51, an inner flange portion50cextending from the periphery of the second side of the body portion50aexposed through the inner surface52bof the bottom portion52of the battery housing51toward the inner surface52b, and, optionally, a flat portion50dprovided at the inner side of the inner flange portion50cand surrounded by the inner flange portion50c.

The electrode terminal50may be replaced with the electrode terminal50′ structure shown inFIG.6b.

The cylindrical battery70may also include a terminal gasket54interposed between the electrode terminal50and the perforation hole53.

The cylindrical battery70may also include a sealing body74that seals the open end of the battery housing51to enable insulation from the battery housing51. Preferably, the sealing body74may include a cap74ahaving no polarity and having a plate shape, and a sealing gasket74binterposed between the edge of the cap74aand the open end of the battery housing51.

The cap74amay be made of a conductive metal material such as aluminum, steel, or nickel. Also, the sealing gasket74bmay be made of polypropylene, polybutylene terephthalate, polyfluoroethylene, or the like, which have insulating and elastic properties. However, the present disclosure is not limited by the materials of the cap74aand the sealing gasket74b.

The cap74amay include a vent notch77that ruptures when the pressure inside the battery housing51exceeds a threshold value. The vent notch77may be formed on both sides of the cap74a. The vent notch77may have a continuous or discontinuous circular, straight, or other pattern on the surface of the cap74a. The depth and width of the vent notch77may be set so that the vent notch77may rupture when the pressure inside battery housing51is in the range of 15 kgf/cm2 to 35 kgf/cm2.

In order to fix the sealing body74, the battery housing51may include a crimping portion75that extends and bends into the battery housing51to surround and fix the edge of the cap74aalong with the sealing gasket74b.

Preferably, the lower surface of the cap74amay be located above the bottom of the crimping portion75. Then, a vent space is formed below the cap74a, so that gas may be discharged smoothly when the vent notch77is ruptured.

The battery housing51may also include a beading portion76press-fitted into the inner side of the battery housing51in an area adjacent the open end. The beading portion76supports the edge of the sealing body74, especially the outer circumferential surface of the sealing gasket74b, when the sealing body74is fixed by the crimping portion75.

The cylindrical battery70may further include a first current collector78that is welded to the uncoated portion72of the first electrode. The first current collector78is made of conductive metal materials such as aluminum, steel, and nickel. Preferably, the first current collector78may be fixed by the crimping portion75in a state that at least a portion78aof the edge thereof that is not in contact with the uncoated portion72of the first electrode is interposed between the beading portion76and the sealing gasket74b. Optionally, the at least a portion78aof the edge of the first current collector78may be fixed to the inner circumference76aof the beading portion76adjacent to the crimping portion75through welding.

The cylindrical battery70may also include a second current collector79that is welded to the uncoated portion73of the second electrode. Preferably, at least a portion of the second current collector79, such as the center portion79a, may be welded to the flat portion50dof the electrode terminal50.

Preferably, when the second current collector79is welded, the welding tool may be inserted through the cavity81present in the core of the electrode assembly71to reach the welding point of the second current collector79. In addition, when the second current collector79is welded to the flat portion50dof the electrode terminal50, the electrode terminal50supports the welding area of the second current collector79, so the welding quality may be improved by applying a strong pressure to the welding area. In addition, the flat portion50dof the electrode terminal50has a wide area, so a large welding area may be secured. As a result, the internal resistance of the cylindrical battery70may be lowered by lowering the contact resistance of the welding area. The face-to-face welding structure of the riveted electrode terminal50and the second current collector79is very useful for fast charging using high c-rate current. This is because the current density per unit area can be lowered in the cross section in the direction in which the current flows, so the amount of heat generated in the current path can be lowered than before.

When welding the flat portion50dof the electrode terminal50and the second current collector79, any one of laser welding, ultrasonic welding, spot welding, and resistance welding can be used.

In one example, when the flat portion50dand the second current collector79are welded with a laser and welded with continuous or discontinuous lines in the form of an are pattern, the diameter of the arc welding pattern is preferably 2 mm or more, preferably 4 mm or more. If the diameter of the arc welding pattern satisfies the corresponding condition, it is possible to secure sufficient welding strength by increasing the tensile force of the welding portion to 2 kgf or more.

In another example, when the flat portion50dand the second current collector79are ultrasonically welded in a circular pattern, the diameter of the circular welding pattern is preferably 2 mm or more. If the diameter of the circular welding pattern satisfies the corresponding condition, it is possible to secure sufficient welding strength by increasing the tensile force of the welding portion to 2 kgf or more.

The diameter of the flat portion50dcorresponding to the weldable area may be adjusted in the range of 3 mm to 14 mm. If the radius of the flat portion50dis smaller than 3 mm, it is difficult to form a welding pattern with a diameter of 2 mm or more using a laser welding tool, an ultrasonic welding tool, or the like. In addition, if the radius of the flat portion50dexceeds 14 mm, the size of the electrode terminal50becomes too large, and the area occupied by the outer surface52aof the bottom portion52of the battery housing51is reduced, which makes it difficult to connect the electrical connection components (bus bars) through the outer surface52a.

Preferably, the diameter of the welding pattern to secure the tensile force of the welding portion of 2 kgf or more is 2 mm or more and the diameter of the weldable area is 3 mm to 14 mm, so the ratio of the area of the welding pattern to the area of the weldable area is 2.04 (100*π12/π72)% to 44.4 (100*π12/π1.52)%.

The cylindrical battery70may also further include an insulator80. The insulator80may be interposed between the second current collector79and the inner surface52bof the bottom portion52of the battery housing51and between the inner circumference51aof the sidewall of the battery housing51and the electrode assembly71.

Preferably, the insulator80may include a welding hole80athat exposes the flat portion50dof the electrode terminal50toward the second current collector79. Also, the welding hole80amay expose the inner flange portion50cand the inner gasket54btogether with the flat portion50dof the electrode terminal.

Preferably, the insulator80may cover at least the surface of the second current collector79and one side (top) edge of the electrode assembly71. Through this, it is possible to prevent the second current collector79, which has a different polarity from the battery housing51, and the uncoated portion73of the second electrode from contacting each other.

Preferably, the insulator80is made of an insulating resin and may include a top plate80band a side sleeve80c. In one example, the top plate80band the side sleeve80cmay be an integrated injection-molded product. Alternatively, the side sleeve80cmay be replaced with an insulating tape or the like. The insulating tape may cover the outer edge of the second current collector79together with the uncoated portion73of the second electrode exposed through the outer circumferential surface of the electrode assembly71.

Preferably, the insulator80and the inner surface52bof the bottom portion52of the battery housing51may be in close contact with each other as shown inFIG.7c. Here, the term ‘close contact’ means that there is no space (gap) visible to the naked eye. To eliminate the space (gap), the distance from the inner surface52bof the bottom portion52of the battery housing51to the flat portion50dof the electrode terminal50may be equal to or slightly smaller than the thickness of the insulator80.

Preferably, the uncoated portion72,73of the first electrode and/or the second electrode may be bent in a radius direction of the electrode assembly71, for example from the outer circumference toward the core, to form a bent surface at the upper and lower portions of the electrode assembly71. Also, the first current collector78may be welded to the bent surface formed by bending the uncoated portion72of the first electrode, and the second current collector79may be welded to the bent surface formed by bending the uncoated portion73of the second electrode.

In order to relieve stress generated when the uncoated portion72,73is bent, the first electrode and/or the second electrode may have an improved structure different from the conventional electrode (seeFIG.1).

FIG.8is a plan view exemplarily showing the structure of an electrode90according to a preferred embodiment of the present disclosure.

Referring toFIG.8, the electrode90includes a sheet-shaped current collector91made of a conductive material foil, an active material layer92formed on at least one side of the current collector91, and an uncoated portion93not coated with an active material and provided at the long side end of the current collector91.

Preferably, the uncoated portion93may include a plurality of notched segments93a. The plurality of segment93aforms a plurality of groups, and the segments93abelonging to each group may have the same height (Y-direction length) and/or width (X-direction length) and/or spacing pitch. The number of segments93abelonging to each group may be increased or decreased from those shown in the drawings. The segment93ahas a geometric shape in which at least one straight line and/or at least one curve are combined. Preferably, the segment93amay have a trapezoidal shape, but may be modified into a rectangular, quadrilateral, semicircular, or semielliptical shape.

Preferably, the height of the segment93amay increase stepwise along a direction parallel to the winding direction of the electrode assembly, for example from the core toward the outer circumference. Also, the core side uncoated portion93′ adjacent to the core may not include the segment93a, and the height of the core side uncoated portion93′ may be smaller than that of other uncoated portion areas. In addition, the outer circumference side uncoated portion93″ adjacent to the outer circumference may not include the segment93a, and the height of the outer circumference side uncoated portion93″ may be smaller than that of other uncoated portion areas.

Optionally, the electrode90may include an insulating coating layer94that covers the boundary between the active material layer92and the uncoated portion93. The insulating coating layer94includes an insulating polymer resin and may optionally further include an inorganic filler. The insulating coating layer94prevents the end of the active material layer92from contacting the active material layer having opposite polarity and facing through the separator and serves to structurally support the bending of the segment93a. To this end, when the electrode90is wound into an electrode assembly, it is preferable that at least a part of the insulating coating layer94is exposed to the outside from the separator.

FIG.9is a cross-sectional view showing an electrode assembly100in which a segmental structure of an uncoated portion of an electrode90according to an embodiment of the present disclosure is applied to a first electrode and a second electrode, taken along a longitudinal direction Y.

Referring toFIG.9, the electrode assembly100may be manufactured using the winding method described with reference toFIG.2. For convenience of explanation, the protruding structure of the uncoated portions72,73extending to the outside of the separator are shown in detail, and the winding structure of the first electrode, the second electrode and the separator is not depicted. The uncoated portion72protruding downward extends from the first electrode, and the uncoated portion73protruding upward extends from the second electrode.

The changing pattern of the height of the uncoated portions72,73is schematically shown. In other words, the height of the uncoated portions72,73may vary irregularly depending on the location where the cross section is cut. For example, when the side portion of trapezoid segment93ais cut, the height of the uncoated portion in the cross section becomes lower than the height of the segment93a. Therefore, it should be understood that the height of the uncoated portions72,73shown in the cross-sectional view of the electrode assembly100correspond to the average of the heights of the uncoated portions included in each winding turn.

The uncoated portions72,73may be bent along the radial direction of the electrode assembly100, for example from the outer circumference toward the core, as shown inFIGS.10aand10b. InFIG.9, the bent portion101is indicated by a dotted box. When the uncoated portions72,73are bent, segments adjacent in the radial direction overlap each other in several layers, thereby forming a bent surface102at the upper and lower portions of the electrode assembly100. At this time, the core side uncoated portion93′ (FIG.8) is not bent due to its low height, and the height (h) of the innermost bent segment is equal to or smaller than the radial length (r) of the winding area formed by the core side uncoated portion93′ without a segment structure. Accordingly, the cavity81in the core of the electrode assembly100is not closed by the bent segments. If the cavity81is not closed, there is no difficulty in the electrolyte injection process, and the electrolyte injection efficiency is improved. In addition, the electrode terminal50and the second current collector79may be easily welded by inserting a welding tool through the cavity81.

In the cylindrical battery70according to an embodiment of the present disclosure, the cap74aof the sealing body74has no polarity. Instead, since the first current collector78is connected to the sidewall of the battery housing51, the outer surface52aof the bottom portion52of the battery housing51has an opposite polarity to the electrode terminal50. Therefore, when connecting a plurality of batteries in series and/or parallel, wiring such as bus bar connection may be performed at the upper portion of the cylindrical battery70using the outer surface52aof the bottom portion52of the battery housing51and the electrode terminal50. Through this, energy density may be improved by increasing the number of batteries that can be mounted in the same space, and electrical wiring work may be easily performed.

FIG.11is a diagram showing a plurality of cylindrical batteries70electrically connected using a bus bar150according to an embodiment of the present disclosure.

Referring toFIG.11, a plurality of cylindrical batteries70may be connected in series and parallel at the upper portion using the bus bar150. The number of cylindrical batteries70may be increased or decreased considering the capacity of the battery pack.

In each cylindrical battery70, the electrode terminal50may have a positive polarity, and the outer surface52aof the bottom portion52of the battery housing51may have a negative polarity, and vice versa.

Preferably, the plurality of cylindrical batteries70may be arranged in a plurality of columns and rows. Columns are oriented up and down based on the drawing, and rows are oriented left and right based on the drawing. Also, to maximize space efficiency, the cylindrical batteries70may be arranged in a closest packing structure. The closest packing structure is formed when the centers of the electrode terminals50form an equilateral triangle when being connected to each other.

Preferably, the bus bar150may be disposed at the upper portion of the plurality of batteries70, more preferably between adjacent columns. Alternatively, the bus bar150may be disposed between adjacent rows.

Preferably, the bus bar150connects batteries disposed in the same column in parallel with each other and connects batteries disposed in two adjacent columns in series.

Preferably, the bus bar150may include a body portion151, a plurality of first bus bar terminals152, and a plurality of second bus bar terminals153for serial and parallel connection.

The body portion151may extend between electrode terminals50of adjacent cylindrical batteries70, preferably between columns of the cylindrical batteries70. Alternatively, the body portion151may extend along the column of the cylindrical batteries70, but the body portion151may be bent regularly, such as in a zigzag shape.

The plurality of first bus bar terminals152protrude and extend from one side of the body portion151toward the electrode terminal50of each cylindrical battery70and may be electrically coupled to the electrode terminal50. Electrical coupling with the electrode terminal50may be achieved through laser welding, ultrasonic welding, or the like. Also, the plurality of second bus bar terminals153protrude and extend from the other side of the body portion151toward the outer surface52aof the bottom portion52of the battery housing51of each cylindrical battery70, and may be electrically coupled to the outer surface52a. Electrical coupling with the outer surface52amay be achieved by laser welding or ultrasonic welding.

Preferably, the body portion151, the plurality of first bus bar terminals152, and the plurality of second bus bar terminals153may be made of one conductive metal plate. The metal plate may be an aluminum plate or a copper plate, but the present disclosure is not limited thereto. In a modified example, the body portion151, the plurality of first bus bar terminals152, and the plurality of second bus bar terminals153may be manufactured as separate piece units and then coupled to each other through welding or the like.

In the cylindrical battery70according to the present disclosure, since the electrode terminal50with positive polarity and the outer surface52aof the bottom portion52of the battery housing51with negative polarity are located in the same direction, the cylindrical batteries70may be electrically connected easily using the bus bar150.

In addition, since the electrode terminal50of the cylindrical battery70and the outer surface52ahave a large area, the resistance of the battery pack including the cylindrical battery70may be sufficiently reduced by securing a sufficient coupling area for the bus bar150.

FIG.12ais an enlarged view showing the electric connection portion of the bus bar150and the cylindrical battery70, andFIGS.12band12care diagrams showing the definitions of various parameters to design upper and lower limits for the diameter of the electrode terminal50and the exposure width of the outer surface52ain consideration of the sizes of the bus bar terminals152,153.

Referring toFIGS.12a,12b, and12c, in the cylindrical battery70, the diameter (E1) of the electrode terminal50and the width (E2) of the ring-shaped outer surface52amay be adjusted adaptively in consideration of the dimension of the contact area of the bus bar terminals152,153.

Here, the width (E2) of the outer surface52ais the width of the exposed surface parallel to the surface of the electrode terminal50. Specifically, the width (E2) of the outer surface52ais defined as the width of the line segment connecting two points at which a straight line (L1) drawn in the radial direction from the center C of the electrode terminal50intersects the inner and outer boundaries of the outer surface52a. The width (E2) of the outer surface52ais the width of the flat exposed surface excluding the round area at the edge of the bottom portion52and the exposed area54a′ of the outer gasket54a.

When viewed from the above, the bottom portion52of the battery housing51may be divided into the electrode terminal50, the exposed area54a′ of the terminal gasket54, and the round area R at the edge of the outer surface52a. The round area R is a processed area (seeFIGS.7aand7b) to smoothly connect the bottom portion52of the battery housing51and the sidewall of the battery housing51, and has a width (Ra) on the plane.

The first bus bar terminal152of the bus bar150branches off to a side different from the traveling direction of the body portion151and is electrically coupled to the electrode terminal50. At this time, the electrode terminal50and the first bus bar terminal152form a first overlapping area (indicated by hatching) on the plane, and the first overlapping area has the first width (W1). Here, the first overlapping area is the area where the electrode terminal50and the first bus bar terminal152overlap on the plane.

The first width (W1) is defined as the maximum distance between any two points selected in the edge of the first overlapping area. The definition of the first width (W1) applies equally to the case where the first overlapping area includes the center of the electrode terminal50(FIG.12b) and the case where the first overlapping area does not include the center of the electrode terminal50(FIG.12c). Referring toFIGS.12band12c, the distance indicated by W1corresponds to the maximum value among the distances between any two points selected in the edge of the first overlapping area.

The second bus bar terminal153of the bus bar150extends in the opposite direction to the first bus bar terminal152based on the traveling direction of the body portion151and is electrically coupled to the outer surface52aof the bottom portion52of the battery housing51. At this time, the second bus bar terminal153and the outer surface52aform a second overlapping area (indicated by hatching) on the plane, and the second overlapping area has a second width (W2). Here, the second overlapping area is the area where the outer surface52aand the second bus bar terminal153overlap on the plane.

The second width (W2) is defined as the maximum width between two points where each straight line meets the edge of the second overlapping area when a plurality of straight lines (L3) are drawn from the center C of the electrode terminal50to pass through the second overlapping area.

Preferably, the diameter (E1) of the electrode terminal50should be at least equal to or greater than the first width (W1) of the first bus bar terminal152. This is because the first overlapping area of the first bus bar terminal152and the electrode terminal50must not deviate to the outside of the electrode terminal50on the plane. Also, the diameter (E1) of the electrode terminal50may be increased to the maximum until the distance between the boundary of the electrode terminal50and the second bus bar terminal153corresponds to the width G of the exposed area54a′ of the outer gasket54a. Therefore, the maximum value of the diameter (E1) of the electrode terminal50is ‘D−2*Ra−2*G−2*W2’.

Preferably, the width (E2) of the outer surface52ais a factor dependent on the diameter (E1) of the electrode terminal50and should be at least equal to or greater than the second width (W2) of the second bus bar terminal153. Only in this case, the overlapping area of the second bus bar terminal153and the outer surface52acan be formed. In addition, the width (E2) of the outer surface52amay be increased to 50% of ‘D−2*Rd−2*G−E1’, which is the value obtained by deducting the diameter (E1) of the electrode terminal50, the width (2*G) of the exposed area of the outer gasket54a, and the width (2*Rd) of the round area from the outer diameter (D) of the battery housing51.

In conclusion, in the cylindrical battery70according to the present disclosure, it is desirable that the diameter (E1) of the electrode terminal50and the width (E2) of the outer surface52aare designed to satisfy the following relational equation.

(E1: diameter of the electrode terminal50, E2: width of the outer surface52a, D: outer diameter of the battery housing51, Rd: width of the round area R measured on the plane, G: width of the exposed area54a′ of the outer gasket54a, W1: width of the first bus bar terminal152, W2: width of the second bus bar terminal153)

In a specific example, when D is 46 mm, W1and W2are 6 mm, G is 0.5 mm, and R is 1 mm, the diameter (E1) of the electrode terminal50is 6 mm to 31 mm and the width (E2) of the outer surface52ais 6 mm to 18.5 mm.

As another example, when D is 46 mm, W1and W2are 6 mm, G is 0.5 mm, and Ra is 1.5 mm, the diameter (E1) of the exposed electrode terminal portion50is 6 mm to 30 mm and the width (E2) of the outer surface20ais 6 mm to 18 mm.

The cylindrical battery70of the present disclosure described above has a structure in which resistance is minimized through expansion of the welding area through a bent surface, multiplexing of current paths using the first current collector, minimization of the current path length, and the like. The AC resistance of the cylindrical battery70, measured using a resistance meter between the positive electrode and the negative electrode, namely between the electrode terminal50and the surrounding flat outer surface52a, may be 0.5 milliohm to 4 milliohm, preferably 1 milliohm to 4 milliohm, suitable for fast charging.

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 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, z and M 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 state 3; M2includes at least one element having an average oxidation state 4; and 0≤x≤1).

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.

At least one surface of the separator may include a coating layer of inorganic particles. It is also possible that the separator itself is made of a coating layer of inorganic particles. The particles constituting the coating layer may have a structure coupled with a binder so that interstitial volumes exist among adjacent particles.

The inorganic particles may be made of an inorganic material having a dielectric constant of 5 or more. 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.

The cylindrical battery70according to the above embodiment may be used to manufacture a battery pack.

FIG.13is a diagram schematically showing a battery pack according to an embodiment of the present disclosure.

Referring toFIG.13, a battery pack200according to an embodiment of the present disclosure includes an aggregate in which cylindrical batteries201are electrically connected, and a pack housing202for accommodating the aggregate. The cylindrical battery201may be the battery according to the above embodiment. In the drawing, components such as a bus bar, a cooling unit, and an external terminal for electrical connection of the cylindrical batteries201are not depicted for convenience of illustration.

The battery pack200may 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.14is a diagram schematically showing a vehicle including the battery pack200ofFIG.13.

Referring toFIG.14, a vehicle V according to an embodiment of the present disclosure includes the battery pack200according to an embodiment of the present disclosure. The vehicle V operates by receiving power from the battery pack200according to an embodiment of the present disclosure.