Battery cell and battery module comprising the same

Abstract

To provide a battery cell with improved external emission of gas generated inside the battery cell, and a battery module including the same.SOLUTION: Disclosed is a battery cell, which includes a battery case having an accommodation portion in which an electrode assembly is mounted, and a sealing portion formed by sealing an outer periphery of the accommodation portion by heat fusion; an electrode lead electrically connected to an electrode tap included in the electrode assembly and protruding outside the battery case via the sealing portion; and a lead film located at a portion corresponding to the sealing portion in at least one of an upper portion and a lower portion of the electrode lead. The lead film has a dented portion recessed toward an inside of the battery case, and the dented portion is opened toward an outside of the battery case.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This application claims priority based on Korean Patent Application No. 10-2021-0003184, filed January 11, 2021. The present invention relates to a battery cell and a battery module including the same, and more particularly to a battery cell and a battery module including the same in which gas generated inside the battery cell is improved in terms of external discharge. [Background technology]

[0002] As technological development and demand for mobile devices increase, the demand for secondary batteries as energy sources is rapidly increasing. In particular, secondary batteries are attracting much attention as energy sources for mobile devices such as mobile phones, digital cameras, laptop computers, and wearable devices, as well as for power devices such as electric bicycles, electric vehicles, and hybrid electric vehicles.

[0003] These secondary batteries are classified into cylindrical batteries and prismatic batteries, in which an electrode assembly is housed in a cylindrical or prismatic metal can, and pouch-type batteries, in which an electrode assembly is housed in a pouch-type case made of an aluminum laminate sheet, depending on the shape of the battery case. The electrode assembly housed in the battery case is a power generating element that can be charged and discharged and includes a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes. The electrode assembly is classified into a jelly roll type, in which a long sheet-type positive electrode and a negative electrode coated with an active material are wound with a separator interposed between them, and a stack type, in which multiple positive electrodes and negative electrodes are stacked in sequence with a separator interposed between them.

[0004] Among these, pouch-type batteries, which have a structure in which a stack-type or stack / folding-type electrode assembly is housed in a pouch-type battery case made of an aluminum laminate sheet, are increasingly being used due to their low manufacturing cost, small weight, and easy modification.

[0005] Figure 1 is a top view of a conventional battery cell. Figure 2 is a cross-sectional view taken along the a-a' axis in Figure 1. Referring to Figures 1 and 2, a conventional battery cell 10 includes an electrode assembly 11 mounted in a housing 21 and a battery case 20 including a sealing portion 25 whose outer periphery is sealed by heat fusion. The battery case 20 includes electrode leads 30 protruding outward from the battery case 20 via the sealing portion 25, and lead films 40 are positioned between the upper and lower portions of the electrode leads 30 and the sealing portion 25.

[0006] However, as the energy density of battery cells has increased recently, there has been a problem of an increase in the amount of gas generated inside the battery cell. In the case of a conventional battery cell 10, since no components are included to exhaust gas generated inside the battery cell, the battery cell may experience venting due to gas generation. Similarly, a battery cell damaged by venting may allow moisture to penetrate the inside, causing side reactions, resulting in reduced battery performance and additional gas generation. As a result, there is an increasing need to develop a battery cell that has improved ability to exhaust gas generated inside the battery cell to the outside. Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a battery cell and a battery module including the same, in which gas generated inside the battery cell is discharged to the outside with improved efficiency.

[0008] The problems to be solved by the present invention are not limited to the problems described above, and problems not mentioned will be clearly understood by those skilled in the art from this specification and the accompanying drawings. [Means for solving the problem]

[0009] A battery cell according to one embodiment of the present invention includes a battery case including a receiving portion in which an electrode assembly is mounted and a sealing portion formed by sealing the outer periphery of the receiving portion by heat sealing; an electrode lead electrically connected to an electrode tap included in the electrode assembly and protruding outward from the battery case through the sealing portion; and a lead film located at a portion corresponding to the sealing portion on at least one of an upper portion and a lower portion of the electrode lead, the lead film having a recess formed inward from the battery case, the recess opening toward the outside of the battery case.

[0010] The inner surface of the recess is closed based on the protruding direction of the electrode lead.

[0011] The lead film may further include an inner layer covering at least one of the inner surfaces of the recessed portion of the lead film.

[0012] The material forming the inner layer has a higher melting point than the material forming the lead film and does not react with the electrolyte.

[0013] The lead film may include a polyolefin-based material.

[0014] The inner layer may include at least one of a polyolefin-based material, a fluorine-based material, and a porous ceramic-based material.

[0015] The depression may be located on the electrode lead.

[0016] The length of the lead film is greater than the width of the electrode lead.

[0017] The recess may be located between an end of the electrode lead and an end of the lead film.

[0018] The recessed portion includes a first recessed portion and a second recessed portion, the first recessed portion extending along a protruding direction of the electrode lead, and the second recessed portion extending along a longitudinal direction of the sealing portion.

[0019] The width of the lead film is greater than the width of the sealing portion and less than the length of the electrode lead.

[0020] The second recess may be located between an end of the sealing portion and an end of the lead film.

[0021] The lead film may include a first lead film and a second lead film, the first lead film being positioned above the electrode lead, and the second lead film being positioned below the electrode lead.

[0022] The electrode lead is located between the first lead film and the second lead film, and the first lead film and the second lead film are connected to each other.

[0023] The recess may be located in at least one of the first lead film and the second lead film.

[0024] The end of the recessed portion recessed into the lead film may be located inside the inner surface of the battery case.

[0025] An end of the recess that is open toward the outside of the battery case may be located outside the outer surface of the battery case.

[0026] The width of the lead film surrounding the rear surface of the recessed portion is 2 mm or more based on the protruding direction of the electrode lead.

[0027] The lead film surrounding the upper surface of the recess has a thickness of 100 to 300 μm.

[0028] The lead film has a gas permeability of 20 to 60 barrers at 60°C.

[0029] The lead film has a moisture penetration rate of 0.02 to 0.2 g for 10 years at 25° C. and 50% RH.

[0030] A battery module according to another embodiment of the present invention may include the above-described battery cells. [Effects of the Invention]

[0031] According to an embodiment, the present invention provides a battery cell including an electrode lead to which a lead film is attached, the lead film having a recess formed therein that is indented toward the inside of a battery case and is open toward the outside of the battery case, and a battery module including the same, thereby improving the discharge of gas generated inside the battery cell to the outside.

[0032] The effects of the present invention are not limited to those described above, and effects not mentioned will be clearly understood by those skilled in the art from this specification and the accompanying drawings. [Brief explanation of the drawings]

[0033] [Figure 1] FIG. 1 is a top view of a conventional battery cell. [Figure 2] FIG. 2 is a cross-sectional view taken along the a-a' axis in FIG. [Figure 3] FIG. 2 is a top view of the battery cell according to the present embodiment. [Figure 4] FIG. 4 is a perspective view of an electrode lead included in the battery cell of FIG. 3. [Figure 5] FIG. 5 is a cross-sectional view taken along the cc' axis in FIG. [Figure 6] FIG. 5 is a cross-sectional view taken along the dd' axis in FIG. [Figure 7] 4 is an enlarged view of the electrode lead portion of the battery cell of FIG. 3. [Figure 8] 8 is an enlarged view of the electrode lead portion according to the position of the sealing portion in FIG. 7(a). [Figure 9] FIG. 4 is a cross-sectional view taken along the bb' axis in FIG. [Figure 10] 10 is a diagram showing the flow of gas generated inside the battery cell in FIG. 9 and discharged to the outside. DETAILED DESCRIPTION OF THE INVENTION

[0034] DETAILED DESCRIPTION OF THE INVENTION The present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0035] In order to clearly describe the present invention, parts that are not relevant to the description will be omitted, and the same reference numerals will be used throughout the specification to refer to the same or similar components.

[0036] In addition, the size and thickness of each component shown in the drawings are arbitrarily shown for the convenience of explanation, and the present invention is not necessarily limited to those shown. In the drawings, thicknesses are exaggerated to clearly show various layers and regions. In the drawings, the thicknesses of some layers and regions are exaggerated for the convenience of explanation.

[0037] Furthermore, throughout the specification, when a part "includes" a certain component, this does not mean that it excludes other components, but that it may further include other components, unless otherwise specified to the contrary.

[0038] Also, throughout the specification, when we say "on a plane," this means a top view of the target part, and when we say "on a cross section," this means a side view of a cross section cut vertically through the target part.

[0039] Hereinafter, a pouch battery cell 100 according to an embodiment of the present invention will be described. However, the description will be based on one side of the pouch battery cell 100, but the description is not limited to this, and the same or similar content will be used for the other side.

[0040] FIG. 3 is a top view of the battery cell according to this embodiment.

[0041] Referring to FIG. 3, the battery cell 100 according to this embodiment includes a battery case 200, an electrode lead 300, and a lead film 400.

[0042] The battery case 200 includes a sealing portion 250 in which the electrode assembly 110 is mounted in the receiving portion 210 and the outer periphery is sealed by heat sealing. The battery case 200 is a laminate sheet including a resin layer and a metal layer. More specifically, the battery case 200 is made of a laminate sheet and may be composed of an outer resin layer forming the outermost shell, a metal layer with barrier properties that prevents penetration of materials, and an inner resin layer for sealing.

[0043] The electrode assembly 110 may have a jelly roll type (wound type), stack type (layered type), or composite type (stack / folded type) structure. More specifically, the electrode assembly 110 may include a positive electrode, a negative electrode, and a separator disposed therebetween.

[0044] The following description will focus on the electrode lead 300 and the lead film 400.

[0045] FIG. 4 is a perspective view of an electrode lead included in the battery cell of FIG.

[0046] 3 and 4, the electrode lead 300 is electrically connected to an electrode tap (not shown) included in the electrode assembly 110 and protrudes outward from the battery case 200 via the sealing part 250. In addition, the lead film 400 is located on at least one of the upper and lower parts of the electrode lead 300, in a portion corresponding to the sealing part 250. As a result, the lead film 400 can improve the sealing between the sealing part 250 and the electrode lead 300 while preventing short circuits from occurring in the electrode lead 300 during heat sealing.

[0047] Fig. 5 is a cross-sectional view taken along the c-c' axis in Fig. 4. Fig. 6 is a cross-sectional view taken along the d-d' axis in Fig. 4.

[0048] 5 and 6, the lead film 400 has a recess 450 formed therein that is recessed toward the inside of the battery case 200, and the recess 450 is open toward the outside of the battery case 200. In addition, the inner surface of the recess 450 is closed based on the protruding direction of the electrode lead 300.

[0049] As a result, gas generated inside the battery case 200 is discharged to the recessed portion 450 in the lead film 400 due to the pressure difference between the inside and outside, and the gas that has flowed into the recessed portion 450 is discharged to the outside. In addition, the lead film 400 has an advantage that the recessed portion 450 is open to the outside and is not exposed to the electrolyte inside the battery case 200, thereby ensuring the airtightness and durability of the pouch. In addition, the recessed portion 450 of the lead film 400 maximizes the gas permeation area, allowing it to discharge a large amount of gas.

[0050] 5 and 6, the lead film 400 may further include an inner layer 410 covering at least one of the inner surfaces of the recess 450.

[0051] 5(a) and 6(a), for example, the inner layer 410 covers the entire surface of the lead film 400 in the recess 450. That is, the inner layer 410 is formed on the entire inner surface of the recess 450 except for the open surface.

[0052] As a result, even if the lead film 400 is heat-sealed together with the sealing portion 250 while positioned at at least one of the upper and lower portions of the electrode lead 300, the recessed portion 450 is kept in an unheat-sealed state by the inner layer 410.

[0053] 5(b) and 6(b), the inner layer 410 covers the upper or lower surface of the inner surface of the depression 450. That is, the inner layer 410 is formed on at least one of the upper and lower surfaces of the depression 450, which face each other.

[0054] As a result, the lead film 400 minimizes the inner layer 410 formed in the recess 450, while the recess 450 is kept in a state where it is not heat-sealed by the inner layer 410. In addition, the manufacturing process can be simplified and costs can be reduced.

[0055] More specifically, the inner layer 410 may be made of a material having a higher melting point than the material constituting the lead film 400. Furthermore, the inner layer 410 may be made of a material that does not react with the electrolyte contained in the battery case 200. As a result, the inner layer 410 is made of the above-mentioned material and does not react with the electrolyte, but does not undergo heat fusion or thermal deformation during a high-temperature heat fusion process, and the recess 450 remains empty. Furthermore, gas generated within the battery case 200 can be easily released to the outside.

[0056] In one embodiment of the present invention, the thickness of the inner layer 410 is 100 μm or less.

[0057] In one embodiment of the present invention, the gas permeability of the inner layer 410 is 40 barrers or more. For example, the carbon dioxide permeability of the inner layer 410 may satisfy the above range.

[0058] For example, the lead film 400 may include a polyolefin-based material, and the inner layer 410 may include at least one of a polyolefin-based material, a fluorine-based material, and a porous ceramic-based material. For example, the inner layer 410 may include at least one of a polyolefin-based material, a fluorine-based material, and a porous ceramic-based material that satisfies the above-mentioned gas permeability values. The polyolefin-based material may include one or more materials selected from the group consisting of polypropylene, polyethylene, and polyvinyldifluoride (PVDF). The fluorine-based material may include one or more materials selected from the group consisting of polytetrafluoroethylene and polyvinylidene fluoride. The inner layer 410 may also include a getter material, which may increase gas permeability while minimizing moisture penetration. For example, the getter material may be calcium oxide (CaO), barium oxide (BaO), lithium chloride (LiCl), silica (SiO2), etc., but is not limited thereto. Any material that reacts with water (H2O) may be used.

[0059] The inner layer 410 may have an adhesive material between the lead film 400 and the inner layer 410, or may be extruded together with the lead film 400 to adhere to the lead film 400. The adhesive material may include an acrylic material. In particular, when the inner layer 410 is extruded together with the lead film 400, the gas permeability of the inner layer 410 is 40 barrers or more.

[0060] 4 to 6, the lead film 400 may include a first lead film and a second lead film, and the first lead film may be located on an upper portion of the electrode lead 300, and the second lead film may be located on a lower portion of the electrode lead 300. In this case, the electrode lead 300 is heat-sealed with the sealing part 250 while being located between the first lead film and the second lead film, and the first lead film and the second lead film are connected to each other.

[0061] Therefore, the lead film 400 can improve the sealing performance between the sealing part 250 and the electrode lead 300 while preventing the side surface of the electrode lead 300 from being exposed to the outside.

[0062] For example, the recessed portion 450 may be located in at least one of the first and second lead films in the lead film 400. More specifically, the recessed portion 450 may be formed in the first or second lead film based on the electrode lead 300, or the recessed portion 450 may be formed in both the first and second lead films based on the electrode lead 300. However, the number of recessed portions 450 is not limited to the above, and any appropriate number may be formed in the lead film 400.

[0063] Therefore, the durability and airtightness of the lead film 400 can be controlled by adjusting the number of recesses 450 formed in the lead film 400. In addition, the number of recesses 450 can be minimized as needed to simplify the manufacturing process and reduce costs.

[0064] Figure 7 is an enlarged view of the electrode lead portion of the battery cell of Figure 3. Figure 8 is an enlarged view of the electrode lead portion according to the position of the sealing portion in Figure 7(a).

[0065] Referring to FIG. 7, the recesses 450 are formed in the lead film 400 at various positions based on the electrode lead 300 .

[0066] 7(a), a recess 450 in a lead film 400 may be located on an electrode lead 300. More specifically, the recess 450 is formed at a position corresponding to the center of the electrode lead 300.

[0067] 7(b), the length of the lead film 400 may be greater than the width of the electrode lead 300, and the recess 450 may be located between the ends of the electrode lead 300 and the lead film 400. Here, the length of the lead film 400 refers to the maximum distance between one end and the other end of the lead film 400 in a direction perpendicular to the protruding direction of the electrode lead 300, and the width of the electrode lead 300 refers to the maximum distance between one end and the other end of the electrode lead 300 in a direction perpendicular to the protruding direction of the electrode lead 300. In other words, the recess 450 is formed in the lead film 400 at a position that avoids the electrode lead 300. However, the position of the recess 450 is not limited to the above and may be formed at an appropriate position within the lead film 400.

[0068] Therefore, the position of the recess 450 formed in the lead film 400 can be adjusted to control the durability and airtightness of the lead film 400. Furthermore, the size of the recess 450 can be adjusted according to the position of the recess 450, as needed, thereby simplifying the manufacturing process and reducing costs.

[0069] Referring to FIG. 7, the recesses 450 in the lead film 400 are formed in various shapes.

[0070] For example, the recessed portion 450 includes a first recessed portion 451 and a second recessed portion 455, where the first recessed portion 451 extends along the protruding direction of the electrode lead 300, and the second recessed portion 455 extends along the longitudinal direction of the sealing portion 250. Here, the longitudinal direction of the sealing portion 250 refers to a direction perpendicular to the protruding direction of the electrode lead 300.

[0071] Here, the width of the lead film 400 is greater than the width of the sealing portion 250 but less than the length of the electrode lead 300. Here, the width of the lead film 400 refers to the maximum distance between one end and the other end of the lead film in the protruding direction of the electrode lead 300.

[0072] The width of the sealing portion 250 refers to the maximum distance between one end and the other end of the sealing portion 250 in the protruding direction of the electrode lead 300. The length of the electrode lead 300 refers to the maximum distance between one end and the other end of the electrode lead 300 in the protruding direction of the electrode lead 300. In this case, the second recess 455 may be located between the end of the sealing portion 250 and the end of the lead film 400. As another example, the recess 450 may have a rectangular shape similar to that of the lead film 400. However, the shape of the recess 450 is not limited to the above and may be formed in any appropriate shape within the lead film 400.

[0073] Therefore, the shape of the recess 450 formed in the lead film 400 can be adjusted to control the durability and airtightness of the lead film 400. Also, by varying the shape of the recess 450 as needed, the manufacturing process can be simplified and costs can be reduced.

[0074] 8, the end of the lead film 400 where the recess 450 is open to the outside may be formed adjacent to the end of the lead film 400, and the end that is indented to the inside may be located between the end of the sealing portion 250 and the end of the lead film 400. In addition, the end of the recess 450 that is indented to the inside may be located adjacent to or spaced apart from the end of the sealing portion 250 by a predetermined distance.

[0075] For example, by comparing Figures 8(a) and 8(b), it can be seen that even if the position of the sealing portion 250 that contacts the lead film 400 is changed, there is no effect on the end portion that is curved inward at the recessed portion 450.

[0076] As a result, in this embodiment, within the error range due to the positions of the lead film 400 and the sealing part 250 that occurs during the heat sealing process, the area of ​​the end of the recessed part 450 that is indented inward relative to the battery case 200 can be kept uniform, and the area through which gas within the battery case 200 flows into the recessed part 450 and is discharged to the outside can also be kept uniform. This has the advantage of maintaining the gas discharge effect of the recessed part 450.

[0077] FIG. 9 is a cross-sectional view taken along the bb' axis in FIG.

[0078] 9, an end of the recessed portion 450 recessed into the lead film 400 may be located inside the inner surface of the battery case 200. Here, the inner surface of the battery case 200 refers to the end of the sealing portion 250 of the battery case 200 that is on the inner side of the battery. Also, an end of the recessed portion 450 that is open to the outside of the battery case 200 may be located outside the outer surface of the battery case 200. Here, the outer surface of the battery case 200 refers to the end of the sealing portion 250 of the battery case 200 that is on the outer side of the battery.

[0079] As a result, the lead film 400 can maximize the area of ​​the recess 450 and discharge a large amount of gas.

[0080] 9, the thickness (H) of the lead film 400 surrounding the upper surface of the recessed portion 450 is 100 to 300 μm or 100 to 200 μm. When the thickness (H) of the lead film 400 surrounding the upper surface of the recessed portion 450 satisfies the above-mentioned range, gas inside the battery case 200 can be more easily discharged to the outside.

[0081] 9, the width (W) of the lead film 400 surrounding the rear surface of the depression 450 in the protruding direction of the electrode lead 300 is 2 mm or more, or 2 to 3 mm. Here, the width of the lead film 400 surrounding the rear surface of the depression 450 refers to the maximum distance between the indented end of the depression 450 and the inner end of the lead film 400 in the battery case 200. When the width (W) of the lead film 400 surrounding the rear surface of the depression 450 satisfies the above-mentioned range, it is easier to prevent the lead film 400 from being torn when gas generated inside the battery case 200 is discharged to the outside.

[0082] FIG. 10 is a diagram showing the flow of gas generated inside the battery cell in FIG. 9 and discharged to the outside.

[0083] 10, gas generated inside the battery cell 100 is discharged toward the recessed portion 450 of the lead film 400. Here, the pressure inside the battery cell 100 is higher than the pressure inside the recessed portion 450, and the resulting pressure difference acts as a driving force for the gas. Here, the recessed portion 450 is open to the outside, and the pressure inside the recessed portion 450 is the same as the external pressure.

[0084] As a result, gas generated inside the battery cell 100 is discharged toward the recessed portion 450, and gas that has flowed into the recessed portion 450 is easily discharged toward the outside. In addition, the amount of gas generated inside the battery cell 100 that is discharged to the outside is also increased.

[0085] In one embodiment of the present invention, the gas permeability of the lead film 400 is 20 to 60 barrers or 30 to 40 barrers at 60°C. For example, the carbon dioxide permeability of the lead film 400 may satisfy the above-mentioned range. Furthermore, the gas permeability of the lead film 400 with a thickness of 200 μm may satisfy the above-mentioned range at 60°C. When the gas permeability of the lead film 400 satisfies the above-mentioned range, gas generated inside the secondary battery is more effectively discharged.

[0086] In this specification, the gas permeability can be measured according to ASTM F2476-20.

[0087] In one embodiment of the present invention, the moisture penetration amount of the lead film 400 is 0.02 to 0.2 g, or 0.02 to 0.04 g, or 0.06 g to 0.15 g for 10 years at 25°C and 50% RH. When the moisture penetration amount of the lead film 400 satisfies the above range, it is more effective to prevent the penetration of moisture flowing in from the lead film 400.

[0088] In one embodiment of the present invention, the lead film 400 has a gas permeability of 20 to 60 barrers at 60° C. and a moisture penetration amount of 0.02 to 0.2 g for 10 years at 25° C. and 50% RH. When the gas permeability and moisture penetration amount of the lead film 400 satisfy the above-mentioned ranges, it is more effective to discharge gas generated inside the secondary battery while preventing moisture penetration from the outside.

[0089] The amount of moisture penetration of the lead film 400 can be measured according to ASTM F 1249. In this case, the measurement can be performed using equipment officially certified by MCOON.

[0090] In one embodiment of the present invention, the lead film 400 may include a polyolefin-based resin. For example, the lead film 400 may include a polyolefin-based resin that satisfies the above-mentioned gas permeability and / or moisture penetration values. The polyolefin-based resin may include one or more materials selected from the group consisting of polypropylene, polyethylene, and polyvinylidene fluoride (PVDF). When the lead film 400 includes polypropylene, the gas permeability of the lead film 400 is 20 to 60 barrers at 60°C. In addition, the moisture penetration is 0.06 to 0.15 g. In this case, gas generated inside the secondary battery is more effectively discharged, and moisture penetration from the outside is easily prevented.

[0091] Furthermore, the lead film 400 is made of the above-mentioned material, and can maintain the airtightness of the battery cell 100 and prevent leakage of the internal electrolyte.

[0092] For example, the recess 450 may partially expand toward the top and bottom compared to Fig. 9 due to gas inside the battery cell 100. However, in this embodiment, the recess 450 is open to the outside, so the degree of expansion is relatively small, and the resulting deformation of the components is also small.

[0093] A battery module according to another embodiment of the present invention includes the above-described battery cell. Meanwhile, one or more battery modules according to this embodiment may be packaged in a pack case to form a battery pack.

[0094] The battery module and the battery pack including the same can be applied to various devices, including transportation means such as electric bicycles, electric cars, and hybrid cars, but the present invention is not limited thereto and can be applied to various devices that can use the battery module and the battery pack including the same, which also fall within the scope of the present invention.

[0095] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention. [Explanation of symbols]

[0096] 10 battery cells 11 Electrode assembly 20 Battery case 21 Storage area 25 Sealing part 30 electrode leads 40 Lead Film 100 battery cells 110 Electrode assembly 200 Battery Case 210 Storage area 250 sealing part 300 electrode leads 400 lead film 410 Inner layer 450 Depression 451 First depression 455 Second depression

Claims

1. a battery case including a receiving portion in which the electrode assembly is mounted and a sealing portion formed by sealing an outer periphery of the receiving portion by heat sealing; an electrode lead electrically connected to an electrode tap included in the electrode assembly and protruding toward the outside of the battery case through the sealing part; a lead film located at a portion of at least one of an upper portion and a lower portion of the electrode lead corresponding to the sealing portion, The lead film has a recess formed therein that is recessed toward the inside of the battery case, The recessed portion is open to the outside of the battery case.

2. The battery cell according to claim 1 , wherein an inner surface of the recess is closed relative to a protruding direction of the electrode lead.

3. The battery cell of claim 2 , further comprising an inner layer covering at least one of the inner surfaces of the recessed portion of the lead film.

4. 4. The battery cell according to claim 3, wherein the material forming the inner layer has a higher melting point than the material forming the lead film and is non-reactive with the electrolyte.

5. The battery cell according to claim 1 , wherein the lead film contains a polyolefin-based material.

6. The battery cell according to claim 3 or 4, wherein the inner layer includes at least one of a polyolefin-based material, a fluorine-based material, and a porous ceramic-based material.

7. The battery cell according to claim 1 , wherein the recessed portion is located on the electrode lead.

8. The battery cell according to claim 1 , wherein the length of the lead film is greater than the width of the electrode lead.

9. The battery cell according to claim 8 , wherein the recessed portion is located between an end of the electrode lead and an end of the lead film.

10. The recessed portion includes a first recessed portion and a second recessed portion, the first recessed portion extends along a protruding direction of the electrode lead, The battery cell according to claim 1 , wherein the second recessed portion extends along a longitudinal direction of the sealing portion.

11. The battery cell according to claim 10 , wherein the width of the lead film is greater than the width of the sealing portion and less than the length of the electrode lead.

12. The battery cell of claim 11 , wherein the second recess is located between an end of the sealing portion and an end of the lead film.

13. the lead film includes a first lead film and a second lead film; the first lead film is located on top of the electrode lead, The battery cell according to claim 1 , wherein the second lead film is located below the electrode lead.

14. the electrode lead is located between the first lead film and the second lead film, The battery cell of claim 13 , wherein the first lead film and the second lead film are connected to each other.

15. The battery cell according to claim 13 , wherein the recess is located in at least one of the first lead film and the second lead film.

16. 16. The battery cell according to claim 1, wherein an end of the recessed portion recessed into the lead film is located inside the inner surface of the battery case.

17. The battery cell according to claim 16 , wherein an end of the recessed portion that is open toward the outside of the battery case is located outside an outer surface of the battery case.

18. 18. The battery cell according to claim 1, wherein the width of the lead film surrounding the back surface of the recessed portion is 2 mm or more based on the protruding direction of the electrode lead.

19. 19. The battery cell according to claim 1, wherein the lead film surrounding the upper surface of the recess has a thickness of 100 to 300 μm.

20. 20. The battery cell according to claim 1, wherein the gas permeability of the lead film is 20 to 60 barrers at 60°C.

21. 21. The battery cell according to claim 1, wherein the amount of moisture penetration into the lead film is 0.02 to 0.2 g for 10 years at 25° C. and 50% RH.

22. A battery module comprising the battery cell according to any one of claims 1 to 21.

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