Patent Description:
As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. Accordingly, many studies have been conducted on secondary batteries that can meet various needs.

Secondary batteries are attracting a lot of attention as an energy source for powerdevices(means of transportation) , such as electric bicycles, electric vehicles, and hybrid electric vehicles, as well as mobile devices, such as mobile phones, digital cameras, and notebook computers.

A small battery pack in which one battery cell is packed is used for small devices, such as mobile phones and cameras, but a medium-sized or large-sized battery pack in which two or more battery cells connected in parallel and/or in series are packed is used in middle to large-sized devices, such as notebook computers and electric vehicles.

For the secondary battery, there is a high demand for a prismatic secondary battery and a pouch-type secondary battery that are applicable to products, such as mobile phones, with a thin thickness in terms of shape. In the case of a prismatic lithium secondary battery, it is advantageous to protect the electrode assembly from external impact, and the liquid injection process is easy, but it is difficult to reduce the volume because the shape is fixed. On the other hand, in the case of a pouch-type lithium secondary battery, there are no restrictions on shape and size, so the pouch-type lithium secondary battery is suitable for manufacturing thin cells, and the pouch-type lithium secondary battery is easily assembled through thermal fusion, and easily releases gas or liquid when abnormal behavior occurs, so that there is a high advantage of high safety.

However, in the pouch-type secondary battery, decomposition of the electrolyte may occur due to factors, such as overcharging, exposure to high temperature, and internal short circuit, and accordingly, a large amount of gas may be generated, and in this case, a swelling phenomenon in which the battery case swells may occur due to the generation of the gas in the battery case.

This swelling phenomenon may cause a high pressure inside the sealed battery case and further promote the decomposition of the electrolyte to further lead to explosion of the battery cell. In addition, the central portion of the battery case swells due to the gas, which causes a shape deformation of the battery cell, thereby having a problem of the occurrence of an electrical short.

Therefore, in order to solve this problem, when the swelling phenomenon occurs, it is necessary to efficiently discharge the gas generated inside the battery case to the outside to ensure safety.

From <CIT> there is known a secondary battery as defined by the preamble of claim <NUM>.

The technical problem of the exemplary embodiments is to provide a secondary battery which is a pouch-type and is capable of preventing explosion by safely discharging gas in an intended direction even if a large amount of gas is generated inside the secondary battery.

However, the problem to be solved in the exemplary embodiments of the present invention is not limited to the foregoing problem.

A secondary battery according to an exemplary embodiment of the present invention includes: an electrode assembly; and a pouch case in which the electrode assembly is embedded, in which the pouch case includes a first case part formed with a first accommodating part in which a part of the electrode assembly is embedded, and a second case part formed with a second accommodating part in which the remaining part of the electrode assembly is accommodated, the first case part and the second case part are in contact with each other in an edge portion surrounding the first and second accommodating parts and are sealed by a sealing part formed in a band shape on at least a part of the edge portion, the sealing part includes a first sealing part having a first width and a second sealing part having a second width smaller than the first width, and a central portion of the second sealing part in a longitudinal direction coincides with a central portion of a long side of the electrode assembly.

The sealing part further includes a first inclined portion which connects the first sealing part and the second sealing part and has a shape inclined toward the electrode assembly from the outside of the pouch case, and a second inclined portion which connects the first sealing part and the second sealing part and has a shape inclined toward the outside of the pouch case from the electrode assembly.

A length of the first inclined portion may be larger than a length of the second inclined portion.

The second width may be <NUM>/<NUM> or less of the first width.

A width of the edge portion may be maintained constant at a place at which the first sealing part is located and a place at which the second sealing part is located.

Each of the first case part and the second case part may include a base layer, a metal layer, and a sealing layer, and the sealing part may be a region in which a sealing layer of the first case part and a sealing layer of the second part are thermally fused to each other and integrally formed.

The sealing layer of the first case part and the sealing layer of the second case part each may include a thermoplastic resin.

The electrode assembly may include a pair of long sides facing each other, and the second sealing part may be located only to correspond to any one long side of the pair of long sides.

The electrode assembly may include a pair of long sides facing each other, and the second sealing part may be located to correspond to both long sides of the pair of long sides.

When thermal runaway occurs inside the pouch case, the second sealing part may act as a vent part of a generated gas.

A battery module according to another exemplary embodiment of the present invention includes the foregoing secondary battery.

According to the exemplary embodiments, it is possible to provide the secondary battery with improved safety, which is a pouch type and is capable of preventing explosion by inducing gas to be safely discharged in an intended direction even if a large amount of gas is generated inside the pouch-type secondary battery.

In the following detailed description, only certain exemplary embodiments of the present invention have been shown and described, simply by way of illustration. However, the present invention can be variously implemented and is not limited to the following embodiments.

Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification.

In addition, the size and thickness of each configuration shown in the drawings are arbitrarily shown for understanding and ease of description, but the present invention is not limited thereto. In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. In the drawings, for understanding and ease of description, the thickness of some layers and areas is exaggerated.

Further, It will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present. Further, when an element is "on" a reference portion, the element is located above or below the reference portion, and it does not necessarily mean that the element is located "on" in a direction opposite to gravity.

In addition, unless explicitly described to the contrary, the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of stated elements but not the exclusion of any other elements.

Further, in the entire specification, when it is referred to as "on a plane" it means when a target part is viewed from above, and when it is referred to as "on a cross-section", it means when the cross-section obtained by cutting a target part vertically is viewed from the side.

<FIG> is an exploded perspective view illustrating a secondary battery according to an exemplary embodiment of the present invention, <FIG> is as diagram illustrating an assembling state of the secondary battery of <FIG>, <FIG> is an enlarged cross-sectional view of part A of <FIG>, <FIG> is a diagram schematically illustrating the secondary battery of <FIG> viewed from the front, and <FIG> is a cross-sectional view taken along line B-B'.

First, referring to <FIG> and <FIG>, a secondary battery <NUM> according to an exemplary embodiment of the present invention includes a pouch case <NUM> and an electrode assembly <NUM>. The pouch case <NUM> includes a first case part <NUM> and a second case part <NUM>. <FIG> illustrates that the first case part <NUM> and the second case part <NUM> are connected to each other and integrally formed, but the first case part <NUM> and the second case part <NUM> may be separated from each other. The shape of the pouch case <NUM> is not limited to that illustrated in <FIG>, and any shape is possible as long as the shape is capable of accommodating and sealing the electrode assembly <NUM>.

The electrode assembly <NUM> may be configured in a form in which a positive electrode plate and a negative electrode plate are disposed with a separator interposed therebetween. In this case, the electrode assembly <NUM> may have a structure in which one positive electrode plate and one negative electrode plate are wound with a separator interposed therebetween, or a structure in which a plurality of positive electrode plates and a plurality of negative electrode plates are stacked with a separator interposed therebetween. The positive electrode plate and the negative electrode plate may be formed in a structure in which an active material slurry is applied to an electrode current collector, respectively, and the slurry may be typically formed by stirring an active material, a conductive material, a binder, and a plasticizer in a state in which a solvent is added.

In the electrode assembly <NUM>, there may be an uncoated region to which the slurry is not applied in the electrode plate, and an electrode tab corresponding to each electrode plate may be formed in the uncoated region. Specifically, as illustrated in <FIG>, a positive electrode tab <NUM> may be attached to the positive electrode plate of the electrode assembly <NUM>, and a negative electrode tab <NUM> may be attached to the negative electrode plate of the electrode assembly <NUM>. The positive electrode tab <NUM> and the negative electrode tab <NUM> are electrically connected to a positive electrode lead <NUM> and a negative electrode lead <NUM> to form electrode terminal <NUM> and electrode terminal <NUM>. In this case, as illustrated in <FIG>, the positive electrode lead <NUM> and the negative electrode lead <NUM> may be drawn out of the pouch case <NUM>.

The first case part <NUM> and the second case part <NUM> of <FIG> include a first accommodating part <NUM> and a second accommodating part <NUM> each having a concave shape, respectively, and the first accommodating part <NUM> and the second accommodating part <NUM> may accommodate the electrode assembly <NUM> and the electrolyte.

The secondary battery <NUM> of <FIG> exemplarily illustrates a pouch-type secondary battery in which the first case part <NUM> and the second case part <NUM> illustrated in <FIG> are bonded to each other and sealed.

<FIG> is an enlarged cross-sectional view of part A of <FIG>, and <FIG> is a diagram illustrating the secondary battery of <FIG> viewed from the front. Referring to <FIG>, the first case part <NUM> and the second case part <NUM> configuring the pouch case <NUM> according to the exemplary embodiment of the present invention include a sealing part <NUM> formed on an edge portion <NUM> of the pouch case <NUM> surrounding the first accommodating part <NUM> and the second accommodating part <NUM> in which the electrode assembly <NUM> of <FIG> is accommodated. The sealing part <NUM> is formed in a band shape on at least a part of the edge portion <NUM> along the edge of the pouch case <NUM>, whereby the first case part <NUM> and the second case part <NUM> may be joined to each other. The first case part <NUM> and the second case part <NUM> are thermally fused to form the sealing part <NUM>, so that the pouch case <NUM> may be sealed.

<FIG> is a cross-sectional view along line B-B' of <FIG>. As illustrated in <FIG>, the first case part <NUM> includes a first base layer <NUM>, a second metal layer <NUM>, and a first sealing layer <NUM> sequentially stacked from the outside, and the second case part <NUM> includes a second base layer <NUM>, a second metal layer <NUM>, and a second sealing layer <NUM> sequentially stacked from the outside.

The first base layer <NUM> and the second base layer <NUM> may be made of an insulating material, such as polyethylene terephthalate (PET) resin or nylon resin, to ensure insulation performance between the secondary battery and the outside and moldability. The first metal layer <NUM> and the second metal layer <NUM> may include one selected from the group consisting of copper, aluminum, nickel, iron, carbon, chromium, manganese, and alloys thereof. The first sealing layer <NUM> and the second sealing layer <NUM> may include a thermoplastic resin, such as polypropylene (PP).

The first case part <NUM> and the second case part <NUM> are bonded so that the first sealing layer <NUM> and the second sealing layer <NUM> are in contact with each other at the edge portion <NUM>. In this state, the first sealing layer <NUM> and the second sealing layer <NUM> are integrally coupled to each other by being pressurized and thermally fused by a heated mold or the like so as to correspond to the sealing part <NUM>, to form the sealing part140, so that the pouch case <NUM> may be sealed.

In this case, the sealing part <NUM> includes a first sealing part <NUM> having a first width W1 and a second sealing part <NUM> having a second width W2 that is smaller than the first width W1. In addition, the second sealing part <NUM> may be formed so that the central portion of the length h2 matches the length h1 of the long side of the electrode assembly <NUM> accommodated in the first accommodating part <NUM> and the second accommodating part <NUM>. That is, in <FIG>, the center of the long side of the electrode assembly <NUM> and the center of the length of the second sealing part <NUM> are both located on the center line C.

The second sealing part <NUM> may act as a vent part for gas generated when the temperature inside the pouch case <NUM> rises. That is, when exposed to high temperature conditions, the separator inside the electrode assembly <NUM> contracts, and the battery expands or the electrode is deformed due to vaporization of the electrolyte, thereby causing a short circuit between the positive electrode and the negative electrode. In particular, when the electrode and the current collector come into contact, the battery reaches a thermal runaway state in which heat generation is greater than heat discharge and the battery is ignited. However, in this case, even if a short circuit occurs between the positive electrode and the negative electrode, when all the electrolyte inside the battery is drained, the movement of ions and electrons in the battery is restricted, so that ignition may be prevented. That is, safety may be improved by inducing the electrolyte to be vaporized and escape at a faster time than batteries in the related art.

In the exemplary present embodiment, the second sealing portion <NUM> having a smaller width than that of another sealing part, that is, the first sealing part <NUM>, acts as a vent part, so that the vent of the vaporized electrolyte proceeds quickly, thereby preventing ignition and explosion to improve safety. That is, when the battery expands, the portion where deformation and expansion occurs most is the central portion C in the longitudinal direction of the electrode assembly <NUM>, and the second sealing part <NUM> is disposed in response to this, the vent through the second sealing part <NUM> may be induced more quickly.

In this case, the second sealing part <NUM> may be disposed to be more biased toward the electrode assembly <NUM> from the center of the first sealing part <NUM> in the width direction. That is, as illustrated in <FIG>, the sealing part <NUM> includes a first inclined portion <NUM> which connects the first sealing part <NUM> and the second sealing part <NUM> and has a shape inclined toward the electrode assembly <NUM> from the outside of the pouch case <NUM>, and includes a second inclined portion <NUM> which connects the first sealing part <NUM> and the second sealing part <NUM> and has having a shape inclined toward the outside of the pouch case <NUM> from the electrode assembly <NUM>. Also, in this case, the length of the first inclined portion <NUM> may be formed to be longer than the length of the second inclined portion <NUM>.

With such a structure, the second sealing part <NUM> is disposed to be relatively close to the inner side, so that even though the width W2 of the second sealing part <NUM> is small, the second sealing part <NUM> may have a sufficient sealing effect. In addition, by including the second inclined portion <NUM> inside, the gas generated inside may be more easily induced toward the corresponding portion, that is, the second inclined portion <NUM> in the recessed form, so that it is possible to more quickly induce breakage and gas discharge of the second sealing part <NUM>.

The second width W2 of the second sealing part <NUM> may have a value of <NUM>/<NUM> or less of the first width W1 of the first sealing part <NUM>, but is not particularly limited. When the second width W2 of the second sealing part <NUM> is too small, sealing performance may be deteriorated, and preferably, the second width W2 of the second sealing part <NUM> may be <NUM>/<NUM> or more and <NUM>/<NUM> or less of the first width W1 of the first sealing part <NUM>.

In addition, as described above, the second sealing part <NUM> is not a configuration obtained through deformation, such as cutting, of the edge portion <NUM>, but is the configuration obtained by deforming only a pressing form of a corresponding portion, that is, reducing the width of the mold, during the sealing process by thermal fusion. Therefore, the width of the edge portion <NUM> is the same in the first sealing part <NUM> and the second sealing part <NUM>, and it is possible to simply obtain the configuration of the second sealing part <NUM> by changing only the width to be thermally fused, that is, the width of the sealing part <NUM>.

As described above, an experiment was conducted in which the secondary battery <NUM> according to the example of the present invention and the secondary battery of the comparative example were exposed to high temperatures, and the results are illustrated in <FIG>.

<FIG> is a graph illustrating the results of an experiment conducted for the secondary batteries of the example and the comparative example of the present invention left at a high temperature.

In the secondary battery <NUM> according to the example, as illustrated in <FIG>, the second sealing part <NUM> was formed, and in the secondary battery according to the comparative example, the second sealing part <NUM> was not formed, and a sealing part of a constant width was formed.

As a result of leaving the secondary battery at a temperature of <NUM>. , as illustrated in <FIG>, it was confirmed that an explosion occurred when about <NUM> minutes had elapsed in the case of the comparative example. On the other hand, in the secondary battery <NUM> of the example, no explosion occurred when <NUM> minutes had elapsed, so it was confirmed that the electrolyte was rapidly discharged even when the battery was exposed to high temperature, thereby improving safety.

<FIG> is a diagram schematically illustrating the secondary battery according to another exemplary embodiment of the present invention viewed from the front.

In the secondary battery <NUM> according to another exemplary embodiment of the present invention, only the number of second sealing parts <NUM> is different and the rest of the configuration is the same as that of the secondary battery <NUM> according to the exemplary embodiment, so that the description of overlapping configurations will be omitted.

As illustrated in <FIG>, in the secondary battery <NUM> according to another exemplary embodiment, the second sealing part <NUM> is positioned to correspond to both long sides of the pair of long sides facing each other of the electrode assembly <NUM>. In this case, even when gas is rapidly generated inside the secondary battery <NUM>, vent of the gas may occur at both sides at the same time, so that the electrolyte may be discharged more quickly. Accordingly, it is possible to prevent an explosion at a high temperature, thereby improving safety.

Meanwhile, a plurality of pouch-type secondary batteries according to the exemplary embodiment of the present invention may be assembled to form a battery module, and one or more of the battery modules may be packaged in a pack case to form a battery pack.

The above-described battery module and battery pack including the same may be applied to various devices. As the device, transport means, such as an electric bicycle, an electric vehicle, and a hybrid vehicle, are applicable, but the present invention is not limited thereto, and the present invention is applicable to various devices capable of using a battery module and a battery pack including the same, which also belongs to the scope of the present invention.

Claim 1:
A secondary battery (<NUM>, <NUM>), comprising:
an electrode assembly (<NUM>); and
a pouch case (<NUM>) in which the electrode assembly (<NUM>) is embedded,
wherein the pouch case (<NUM>) includes a first case part (<NUM>) formed with a first accommodating part (<NUM>) in which a part of the electrode assembly (<NUM>) is embedded, and a second case part (<NUM>) formed with a second accommodating part (<NUM>) in which the remaining part of the electrode assembly (<NUM>) is accommodated,
the first case part (<NUM>) and the second case part (<NUM>) are in contact with each other in an edge portion (<NUM>) surrounding the first and second accommodating parts (<NUM>, <NUM>) and are sealed by a sealing part (<NUM>) formed in a band shape on at least a part of the edge portion (<NUM>),
the sealing part (<NUM>) includes a first sealing part (<NUM>) having a first width (W1) and a second sealing part (<NUM>) having a second width (W2) smaller than the first width (W1), and
a central portion of the second sealing part (<NUM>) in a longitudinal direction coincides with a central portion of a long side of the electrode assembly (<NUM>),
wherein:
the sealing part (<NUM>) further includes a first inclined portion (<NUM>) which connects the first sealing part (<NUM>) and the second sealing part (<NUM>) and has a shape inclined toward the electrode assembly (<NUM>) from the outside of the pouch case (<NUM>),
characterised by a second inclined portion (<NUM>) which connects the first sealing part (<NUM>) and the second sealing part (<NUM>) and has a shape inclined toward the outside of the pouch case (<NUM>) from the electrode assembly (<NUM>).