Battery cell and battery module including 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: A battery cell according to an embodiment of the present invention includes: a battery case having an accommodation portion in which an electrode assembly is mounted, and a sealing portion having a structure where an outer periphery is sealed; an electrode lead electrically connected to an electrode tab included in the electrode assembly and protruding out of 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. A dented portion that is recessed in an outer direction of the battery case is formed in the lead film, the dented portion is opened toward the inside of the battery case, the dented portion includes a first dented portion and a second dented portion, and a width of the second dented portion is greater than a width of the first dented portion.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] This application claims priority from Korean Patent Application No. 10-2021-0016111, filed on February 4, 2021.

[0002] 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 that have an improved ability to discharge gas generated inside the battery cell to the outside. [Background technology]

[0003] 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, laptops, and wearable devices, as well as for power devices such as electric bicycles, electric vehicles, and hybrid electric vehicles.

[0004] Depending on the shape of the battery case, such secondary batteries can be divided 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. Here, the electrode assembly housed in the battery case is a power generating element that includes a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes and is capable of charging and discharging. It can be divided into a jelly roll type in which a long sheet-type positive electrode and a negative electrode coated with an active material are wound up 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.

[0005] Among these, pouch-type batteries, which have a structure in which a stacked or stacked / folded 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, light weight, and ease of deformation.

[0006] Fig. 1 is a top view of a conventional battery cell. Fig. 2 is a cross-sectional view taken along line a-a' in Fig. 1. Referring to Figs. 1 and 2, a conventional battery cell 10 includes a battery case 20 having an electrode assembly 11 housed in a housing 21 and a sealing portion 25 with a sealed outer periphery. The battery case 20 includes electrode leads 30 protruding to the outside of the battery case 20 through 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.

[0007] However, in recent years, as the energy density of battery cells has increased, the amount of gas generated inside the battery cell has also increased. Conventional battery cells 10 do not include components for discharging gas generated inside the battery cell, which can lead to venting due to gas generation in the battery cell. Furthermore, moisture can penetrate into the battery cell damaged by the venting, causing side reactions that can lead to reduced battery performance and further gas generation. Therefore, there is a growing demand for the development of battery cells with improved capabilities for discharging gas generated inside the battery cell to the outside. Summary of the Invention [Problem to be solved by the invention]

[0008] SUMMARY OF THE INVENTION An object of the present invention is to provide a battery cell and a battery module including the same, which have an improved ability to discharge gas generated inside the battery cell to the outside.

[0009] The problems to be solved by the present invention are not limited to the above-mentioned problems, 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]

[0010] According to one aspect of the present invention, a battery cell includes: a battery case in which an electrode assembly is attached to a housing and which includes a sealing portion having a sealed outer periphery; an electrode lead electrically connected to an electrode tab included in the electrode assembly and protruding to the outside of the battery case through the sealing portion; and a lead film located at a portion of at least one of an upper part and a lower part of the electrode lead corresponding to the sealing portion, wherein the lead film has a recess formed therein that is recessed toward the outside of the battery case, the recess being open to the inside of the battery case, the recess including a first recess and a second recess, the width of the second recess being wider than the width of the first recess.

[0011] The second recess may be located farther from the electrode assembly than the first recess.

[0012] A portion of the first recess may be located at a position corresponding to the sealing portion.

[0013] A portion of the second recess may be located at a position that does not correspond to the sealing portion.

[0014] The width of the lead film may be wider than the width of the sealing portion and shorter than the length of the electrode lead.

[0015] The second recess may be located between an end of the sealing portion and an end of the lead film.

[0016] The first recessed portion may extend along a protruding direction of the electrode lead, and the second recessed portion may extend along a longitudinal direction of the sealing portion.

[0017] The second recessed portion may have a circular, triangular, rectangular, or irregular shape.

[0018] The inner surface of the recess may be closed based on the protruding direction of the electrode lead.

[0019] The lead film may further include an inner layer covering at least one of the inner surfaces of the recess.

[0020] The material of the inner layer may have a higher melting point than the material of the lead film and may be non-reactive with the electrolyte.

[0021] The lead film may include a polyolefin-based material.

[0022] The inner layer may include at least one material selected from the group consisting of polyolefins, fluorine-based materials, and porous ceramic materials.

[0023] The depression may be located on the electrode lead.

[0024] The length of the lead film may be longer than the width of the electrode lead.

[0025] The recess may be located between an end of the electrode lead and an end of the lead film.

[0026] The lead film may include a first lead film and a second lead film, and the first lead film may be located above the electrode lead, and the second lead film may be located below the electrode lead.

[0027] The electrode lead may be located between the first lead film and the second lead film, and the first lead film and the second lead film may be connected to each other.

[0028] The recess may be located in at least one of the first lead film and the second lead film.

[0029] The outermost end of the recessed portion of the battery case may be located outside the outer surface of the battery case.

[0030] An open end of the recess on the inner side of the battery case may be located inside the inner surface of the battery case.

[0031] The width (W) of the lead film surrounding the front surface of the recessed portion based on the protruding direction of the electrode lead may be 2 mm or more.

[0032] The thickness (H) of the lead film surrounding the upper surface of the recess may be 100 to 300 μm.

[0033] The gas permeability of the lead film may be 20 to 60 barrers at 60°C.

[0034] The lead film may have a moisture permeation capacity of 0.02 to 0.2 g for 10 years at 25° C. and 50% RH.

[0035] A battery module according to another aspect of the present invention includes the above-described battery cells. [Effects of the Invention]

[0036] According to an embodiment of the present invention, a battery cell including an electrode lead to which a lead film is attached, the lead film having a recess formed therein that is recessed toward the outside of the battery case and is open to the inside of the battery case, and a battery module including the same are provided, thereby improving the ability to discharge gas generated inside the battery cell to the outside.

[0037] According to an embodiment of the present invention, the depression includes a first depression and a second depression, and the width of the second depression is wider than the width of the first depression, thereby improving the ability to discharge gas generated inside the battery cell to the outside and improving the durability of the lead film.

[0038] 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 the present specification and the accompanying drawings. [Brief explanation of the drawings]

[0039] [Figure 1] FIG. 1 is a top view of a conventional battery cell. [Figure 2] FIG. 2 is a cross-sectional view taken along a-a' in FIG. [Figure 3] FIG. 2 is a top view of a battery cell according to one embodiment of the present invention. [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 line cc' in FIG. [Figure 6] FIG. 5 is a cross-sectional view taken along the line dd' in FIG. [Figure 7] FIG. 5 is a cross-sectional view taken along the line ee' in FIG. [Figure 8] FIG. 4 is an enlarged view of an electrode lead portion of the battery cell shown in FIG. 3. [Figure 9] FIG. 8(a) is an enlarged view of the electrode lead portion corresponding to the position of the sealing portion. [Figure 10] 4 is an enlarged view of an electrode lead portion of the battery cell shown in FIG. 3 according to another embodiment of the present invention. FIG. [Figure 11] 4 is an enlarged view of an electrode lead portion of the battery cell shown in FIG. 3 according to yet another embodiment of the present invention. FIG. [Figure 12] 4 is an enlarged view of an electrode lead portion of the battery cell shown in FIG. 3 according to yet another embodiment of the present invention. FIG. [Figure 13] FIG. 4 is a cross-sectional view taken along the line bb' in FIG. [Figure 14] FIG. 13 is a diagram showing the flow of gas generated inside the battery cell and discharged to the outside. DETAILED DESCRIPTION OF THE INVENTION

[0040] DETAILED DESCRIPTION OF THE INVENTION The present invention may, however, be embodied in various different forms and should not be construed as limited to the embodiments set forth herein.

[0041] 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.

[0042] Furthermore, the size and thickness of each component shown in the drawings are arbitrarily shown for the sake of convenience, and the present invention is not limited by the drawings. In the drawings, thicknesses are exaggerated to clearly show various layers and regions. In the drawings, thicknesses of some layers and regions are exaggerated for the sake of convenience.

[0043] Furthermore, throughout the specification, when a part is said to "include" a certain component, this does not mean that other components are excluded, and that other components may also be included, unless otherwise specified.

[0044] Furthermore, throughout the specification, a "plan view" means a view of the target part viewed from above, and a "cross-sectional view" means a view of the target part cut vertically from the side.

[0045] Hereinafter, a pouch battery cell 100 according to one 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 description may be applied to the other side.

[0046] FIG. 3 is a top view of a battery cell according to one embodiment of the present invention.

[0047] 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.

[0048] The battery case 200 includes a sealing portion 250 in which the electrode assembly 110 is attached to the receiving portion 210 and the outer periphery is sealed. The sealing portion 250 may be sealed by heat or a laser. The battery case 200 may be made of a laminate sheet including a resin layer and a metal layer. More specifically, the battery case 200 may be made of a laminate sheet and may include an outer resin layer forming the outermost shell, a barrier metal layer that prevents the passage of substances, and an inner resin layer for sealing.

[0049] The electrode assembly 110 may have a jelly roll (wound), stacked, or composite (stacked / folded) structure. More specifically, the electrode assembly 110 may include a positive electrode, a negative electrode, and a separator disposed therebetween.

[0050] The following description will focus on the electrode lead 300 and the lead film 400.

[0051] FIG. 4 is a perspective view of an electrode lead included in the battery cell of FIG.

[0052] 3 and 4, the electrode lead 300 is electrically connected to an electrode tab (not shown) included in the electrode assembly 110 and protrudes to the outside of the battery case 200 through the sealing portion 250. In addition, the lead film 400 is located on at least one of the upper and lower portions of the electrode lead 300 in a portion corresponding to the sealing portion 250. As a result, the lead film 400 can prevent a short circuit from occurring in the electrode lead 300 during sealing and can improve the sealing performance between the sealing portion 250 and the electrode lead 300.

[0053] 5 is a cross-sectional view taken along line cc' in FIG. 4, FIG. 6 is a cross-sectional view taken along line dd' in FIG. 4, and FIG. 7 is a cross-sectional view taken along line ee' in FIG.

[0054] 5, a recess 450 is formed in the lead film 400, recessed toward the outside of the battery case 200, and the recess 450 is open to the inside of the battery case 200. In addition, the inner surface of the recess 450 may be closed based on the protruding direction of the electrode lead 300.

[0055] As a result, when gas generated inside the battery case 200 reaches a predetermined pressure or higher, it is discharged into the recessed portion 450 in the lead film 400, and the gas that has flowed into the recessed portion 450 is discharged to the outside of the battery due to the pressure difference between the inside and outside. Furthermore, the recessed portion 450 of the lead film 400 is open toward the inside, and the inner surface of the recessed portion that is recessed toward the outside of the lead film 400 is closed, so the airtightness and durability of the pouch can be ensured. Furthermore, the recessed portion 450 of the lead film 400 maximizes the gas permeation area, allowing a large amount of gas to be discharged.

[0056] 6 and 7, the recess 450 includes a first recess 451 and a second recess 455, and the width of the second recess 455 is wider than the width of the first recess 451.

[0057] In this specification, the width of the second recessed portion 455 means the maximum distance between one end and the other end of the second recessed portion 455 in a direction perpendicular to the protruding direction of the electrode lead 300, and the width of the first recessed portion 451 means the maximum distance between one end and the other end of the first recessed portion 451 in a direction perpendicular to the protruding direction of the electrode lead 300.

[0058] When gas inside the battery case 200 flows into the recess 450 and the lead film 400 expands outward due to the pressure, the resulting curvature increases, and the stress applied to the interface between the lead film 400 and the electrode lead 300 also increases.

[0059] If the recessed portion 450 consists of only portions having the same width, the durability of the lead film 400 may be weakened due to stress applied to the interface between the lead film 400 and the electrode lead 300 due to the increased curvature of the expanded lead film 400.

[0060] On the other hand, when the recess 450 includes a first recess 451 and a second recess 455 having different widths, the curvature of the lead film 400 expanded at the relatively narrow first recess 451 is smaller than the curvature of the lead film 400 expanded at the relatively wide second recess 455, and the stress applied to the interface between the lead film 400 and the electrode lead 300 is reduced, thereby improving durability and increasing gas emission.

[0061] 5 to 7, the lead film 400 may further include an inner layer 410 that covers at least one of the inner surfaces of the recessed portion 450.

[0062] 5(a) to 7(a), for example, the inner layer 410 may cover the entire surface of the lead film 400 in the recess 450. That is, the inner layer 410 may be formed on the entire inner surface of the recess 450 except for the open surface.

[0063] Therefore, even if the lead film 400 is sealed together with the sealing portion 250 while being positioned at least on one of the upper and lower portions of the electrode lead 300, the recessed portion 450 can remain unsealed by the inner layer 410.

[0064] 5(b) to 7(b), the inner layer 410 may cover the upper or lower surface of the inner surface of the recessed portion 450. That is, the inner layer 410 may be formed on at least one of the upper and lower surfaces of the recessed portion 450, which face each other.

[0065] As a result, the lead film 400 can minimize the internal layer 410 formed in the recess 450 while keeping the recess 450 unsealed by the internal layer 410. In addition, the manufacturing process can be simplified and costs can be reduced.

[0066] More specifically, the internal layer 410 may be made of a material having a higher melting point than the material of the lead film 400. Furthermore, the internal layer 410 may be made of a material that does not react with the electrolyte contained in the battery case 200. Since the internal layer 410 is made of the above-mentioned material, it does not react with the electrolyte and does not undergo heat fusion or thermal deformation during the high-temperature sealing process, so the recess 450 remains open. Furthermore, gas generated within the battery case 200 can be easily released to the outside.

[0067] In one embodiment of the present invention, the thickness of the inner layer 410 may be 100 μm or less.

[0068] In one embodiment of the present invention, the gas permeability of the inner layer 410 may be 40 barrers or more. For example, the carbon dioxide permeability of the inner layer 410 may satisfy the above range.

[0069] For example, the inner layer 410 may include at least one of polyolefin-based, fluorine-based, and porous ceramic-based materials. For example, the inner layer 410 may include at least one of polyolefin-based, fluorine-based, and porous ceramic-based materials that satisfy the above-mentioned gas permeability requirements. 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 to 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.

[0070] The inner layer 410 may be bonded to the lead film 400 by providing an adhesive material between the inner layer 410 and the lead film 400 or by being extruded together with the lead film 400. The adhesive material may include an acrylic. In particular, when the inner layer 410 is extruded together with the lead film 400, the gas permeability of the inner layer 410 may be 40 barrers or more.

[0071] 4 to 7, 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 may be sealed together 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 may be connected to each other.

[0072] As a result, the lead film 400 can prevent the side surface of the electrode lead 300 from being exposed to the outside, and can also improve the sealing performance between the sealing portion 250 and the electrode lead 300 .

[0073] For example, the recess 450 may be located in at least one of the first and second lead films in the lead film 400. More specifically, the recess 450 may be formed in the first or second lead film relative to the electrode lead 300, or may be formed in both the first and second lead films relative to the electrode lead 300. However, the number of recesses 450 is not limited to the above, and any appropriate number of recesses 450 may be formed in the lead film 400.

[0074] In this way, 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.

[0075] Fig. 8 is an enlarged view of the electrode lead portion of the battery cell shown in Fig. 3. Fig. 9 is an enlarged view of the electrode lead portion according to the position of the sealing portion in Fig. 8(a).

[0076] Referring to FIG. 8, the second recess 455 may be located farther from the side where the electrode assembly 110 is housed than the first recess 451 .

[0077] In this case, the second recess 455 serves to discharge gas generated inside the battery case 200 to the outside of the battery case 200. Since the width of the second recess 455 is wider than the width of the first recess 451, the area for discharging gas to the outside is further increased, and therefore, the amount of gas discharged can be more easily increased.

[0078] In addition, the first recess 451 having a relatively narrow width serves as a passage through which gas generated inside the battery case 200 flows into the recess 450, thereby increasing the durability of the lead film 400.

[0079] 8, a portion of the first recessed portion 451 may be located at a position corresponding to the sealing portion 250. For example, the second recessed portion 455 may be located farther from the side where the electrode assembly 110 is housed than the first recessed portion 451, and a portion of the first recessed portion 451 may be located at a position corresponding to the sealing portion 250.

[0080] 8, a portion of the second recessed portion 455 may be located at a position that does not correspond to the sealing portion 250. In this case, as the area of ​​the second recessed portion 455 that does not correspond to the sealing portion 250 increases, the area through which gas inside the battery case 200 is discharged to the outside of the battery case 200 increases. For example, the second recessed portion 455 may be located farther from the side where the electrode assembly 110 is housed than the first recessed portion 451, and a portion of the second recessed portion 455 may be located at a position that does not correspond to the sealing portion 250.

[0081] In one embodiment of the present invention, the width of the lead film 400 may be wider than the width of the sealing portion 250 and shorter than the length of the electrode lead 300. In this specification, 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. 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. For example, the entire second recess 455 may be located at a position that does not correspond to the sealing portion 250.

[0082] In the lead film 400, the recess 450 may be formed in various shapes.

[0083] 8, the first recess 451 may extend along the protruding direction of the electrode lead 300, and the second recess 455 may extend along the longitudinal direction of the sealing portion 250. In this specification, the longitudinal direction of the sealing portion 250 refers to a direction perpendicular to the protruding direction of the electrode lead 300.

[0084] The recesses 450 in the lead film 400 may be formed at various positions relative to the electrode lead 300 .

[0085] 8(a), in the lead film 400, the recess 450 may be located on the electrode lead 300. More specifically, the recess 450 may be formed at a position corresponding to the center of the electrode lead 300.

[0086] 8(b), the length of the lead film 400 may be longer 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. In this specification, 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 may be 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 any appropriate position within the lead film 400.

[0087] In this way, the durability and airtightness of the lead film 400 can be controlled by adjusting the position of the recess 450 formed in 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.

[0088] 9 , the end of the recessed portion 450 in the lead film 400 that is open toward the inside is formed adjacent to the end of the lead film 400 that faces the inside of the battery case 200, and the end of the recessed portion 450 at the outermost part of the battery case 200 that is recessed toward the outside may be located between the end of the sealing portion 250 and the end of the lead film 400. In this specification, the “end at the outermost part of the battery case 200” refers to the end of the recessed portion 450 that is located outermost based on the protruding direction of the electrode lead 300 among the ends of the recessed portion.

[0089] In addition, the outwardly recessed end of the recessed portion 450 may be located adjacent to or spaced apart from the end of the sealing portion 250 by a predetermined distance.

[0090] For example, comparing (a) and (b) in Figure 9, it can be seen that even if the position of the sealing portion 250 that contacts the lead film 400 changes, there is no effect on the area of ​​the recessed portion 450 located outside the battery case 200.

[0091] As a result, according to this embodiment, the area of ​​the recess 450 positioned outside the battery case 200 can be maintained uniform within the error range due to the positions of the lead film 400 and the sealing part 250 that occurs during the sealing process, and the area through which gas inside the battery case 200 flows into the recess 450 and is discharged to the outside can also be maintained uniform. As a result, the gas discharge effect of the recess 450 can be maintained.

[0092] 10 to 12 are enlarged views of the electrode lead portion of the battery cell shown in FIG. 3 according to another embodiment of the present invention.

[0093] 10 to 12, the shape of the second recess 455 may be circular, triangular, or concave-convex, but is not limited thereto, and may be, for example, a square as shown in FIG.

[0094] In this way, the durability and airtightness of the lead film 400 can be controlled by adjusting the shape of the recess 450 formed in the lead film 400. In addition, the shape of the recess 450 can be changed as needed to simplify the manufacturing process and reduce costs.

[0095] Fig. 13 is a cross-sectional view taken along line bb' in Fig. 3. Fig. 14 is a diagram showing the flow of gas generated inside the battery cell in Fig. 13 as it is discharged to the outside.

[0096] 13, the end of the recessed portion 450 at the outermost side of the battery case 200 may be located outside the outer surface of the battery case 200. In this specification, the outer surface of the battery case 200 refers to the outer end of the sealing portion 250 of the battery case 200. This makes it possible to easily ensure a sufficient area for gas to be discharged to the outside of the battery.

[0097] In addition, the end of the recessed portion 450 that is open toward the inside of the battery case 200 may be located inside the inner surface of the battery case 200. In this specification, the inner surface of the battery case 200 refers to the end of the sealing portion 250 of the battery case 200 that is inside the battery. This allows gas inside the battery to easily flow into the recessed portion 450.

[0098] In the above case, the lead film 400 maximizes the area of ​​the recess 450, thereby maximizing the permeation area of ​​the gas generated inside the battery case 200, and thus allowing a large amount of gas to be discharged.

[0099] 13, the thickness H of the lead film 400 surrounding the upper surface of the depressed portion 450 may be 100 to 300 μm or 100 to 200 μm. When the thickness H of the lead film 400 surrounding the upper surface of the depressed portion 450 satisfies the above range, gas inside the battery case 200 can be more easily discharged to the outside. In this specification, the lead film 400 surrounding the upper surface of the depressed portion 450 refers to the lead film 400 between the depressed portion 450 and the sealing portion 250.

[0100] 13, the width W of the lead film 400 surrounding the front surface of the recessed portion 450 based on the protruding direction of the electrode lead 300 may be 2 mm or more, or 2 mm to 3 mm. In this specification, the width of the lead film 400 surrounding the front surface of the recessed portion 450 refers to the maximum distance between the recessed end at the outermost side of the battery case 200 and the end of the lead film 400 outside the battery case 200. When the width W of the lead film 400 surrounding the front surface of the recessed portion 450 satisfies the above range, it is possible to more easily prevent the lead film 400 from being torn when gas generated inside the battery case 200 is discharged to the outside.

[0101] 14 , gas generated inside the battery cell 100 may be discharged toward the recessed portion 450 of the lead film 400. Here, since the recessed portion 450 is open toward the inside, the internal pressure of the recessed portion 450 may be the same as the internal pressure of the battery case 200.

[0102] The internal pressure of the recess 450 is higher than the external pressure of the battery cell 100, and the resulting pressure difference acts as a driving force for the gas. This allows the gas that has flowed into the recess 450 to be easily discharged to the outside. In addition, the amount of gas generated inside the battery cell 100 that is discharged to the outside can also be increased.

[0103] At this time, gas generated inside the battery case 200 can be discharged in the Z-axis direction through the depressed portion 450 and the lead film 400 surrounding the upper surface of the depressed portion. For example, when the depressed portion 450 is exposed to the outside of the battery case 200, gas generated inside the battery case 200 can be discharged in the Z-axis direction through the depressed portion 450 and the lead film 400 surrounding the upper surface of the depressed portion. In particular, when the recessed end of the depressed portion 450 at the outermost part of the battery case is located outside the outer surface of the battery case 200, gas can be discharged in the Z-axis direction from the depressed portion 450 through the lead film 400 between the recessed end of the depressed portion 450 at the outermost part of the battery case 200 and the outer surface of the battery case 200.

[0104] In one embodiment of the present invention, the gas permeability of the lead film 400 may be 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 having 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 can be more effectively discharged.

[0105] As used herein, gas permeability may be measured by ASTM F2476-20.

[0106] In one embodiment of the present invention, the moisture permeation amount of the lead film 400 may be 0.02 to 0.2 g, or 0.02 to 0.04 g, or 0.06 g, or 0.15 g for 10 years at 25°C and 50% RH. When the moisture permeation amount of the lead film 400 satisfies the above range, the permeation of moisture entering through the lead film 400 can be more effectively prevented.

[0107] The amount of moisture permeation through the lead film 400 can be measured according to ASTM F 1249. In this case, the measurement can be performed using an officially certified device from MCOON.

[0108] In one embodiment of the present invention, the lead film 400 may have a gas permeability of 20 to 60 Barrers at 60°C and a moisture permeation rate of 0.02 to 0.2 g for 10 years at 25°C and 50% RH. When the gas permeability and moisture permeation rate of the lead film 400 satisfy the above ranges, gas generated inside the secondary battery can be discharged while moisture permeation from the outside can be more effectively prevented.

[0109] 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 amount. The polyolefin-based resin may include one or more materials selected from the group consisting of polypropylene, polyethylene, and polyvinyl difluoride (PVDF). The lead film 400 may include polypropylene, and the gas permeability of the lead film 400 may be 20 to 60 barrers at 60°C. Furthermore, the moisture penetration amount may be 0.06 g to 0.15 g. In this case, not only is it more effective at discharging gas generated inside the secondary battery, but it is also easier to prevent moisture penetration from the outside.

[0110] 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.

[0111] A battery module according to another aspect 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.

[0112] The above-described battery module and a battery pack including the same may be applied to various devices. Such devices may be transportation means such as electric bicycles, electric vehicles, and hybrid vehicles, but the present invention is not limited thereto and may be applied to various devices that can use a battery module and a battery pack including the same, which also fall within the scope of the present invention.

[0113] 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 it goes without saying that various modifications and improvements made by those skilled in the art using the basic concept of the present invention as claimed in the claims also fall within the scope of the present invention. [Explanation of symbols]

[0114] 10 Conventional battery cells 11 Electrode assembly 20 Battery case 21 Storage area 25 Sealing part 30 electrode leads 40 Lead Film 100 pouch 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 sealing portion in which the electrode assembly is attached to a housing portion and the outer periphery is sealed; an electrode lead electrically connected to an electrode tab included in the electrode assembly and protruding to the outside of the battery case through the sealing portion; 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, a recessed portion recessed toward the outside of the battery case is formed in the lead film, the lead film covers at least the upper surface of the recessed portion, The recessed portion includes a first recessed portion and a second recessed portion, The width of the second recessed portion is wider than the width of the first recessed portion, The second recessed portion is located farther from the electrode assembly than the first recessed portion.

2. The battery cell according to claim 1 , wherein the recessed portion is open to the inside of the battery case.

3. The battery cell according to claim 1 or 2, wherein a portion of the first recess is located at a position corresponding to a sealing portion.

4. The battery cell according to claim 1 , wherein a portion of the second recess is located at a position that does not correspond to a sealing portion.

5. 5. The battery cell according to claim 1, wherein the width of the lead film is wider than the width of the sealing portion and shorter than the length of the electrode lead, and the second recess is located between an end of the sealing portion and an end of the lead film.

6. 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.

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

8. The battery cell according to claim 7 , wherein the lead film further includes an inner layer covering at least one of the inner surfaces of the recessed portion.

9. 9. The battery cell according to claim 8, wherein the material of the inner layer has a higher melting point than the material of the lead film and does not react with the electrolyte.

10. 10. The battery cell according to claim 8, wherein the recessed portion is open to the inside of the battery case, and the internal layer is formed on the entire inner surface of the recessed portion excluding the open surface.

11. The battery cell according to claim 8 , wherein the inner layer includes at least one material selected from the group consisting of polyolefin-based, fluorine-based, and porous ceramic-based materials.

12. The inner layer is water (H ２ 12. The battery cell of claim 8, further comprising a getter material that reacts with ZnO.

13. The battery cell according to claim 8 , wherein the internal layer is adhered to the lead film by providing an adhesive material between the internal layer and the lead film.

14. The battery cell according to claim 8 , wherein the inner layer is extruded together with the lead film and is adhered to the lead film.

15. The battery cell according to claim 1 , wherein the lead film is heat-sealed together with the sealing portion, and the recessed portion is kept open by being left unsealed.

16. The battery cell according to claim 1 , wherein the length of the lead film is longer than the width of the electrode lead, and the recess is located between an end of the electrode lead and an end of the lead film.

17. 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.

18. The battery cell according to claim 17 , wherein 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.

19. The battery cell according to claim 17 or 18, wherein the recess is located in at least one of the first lead film and the second lead film.

20. The battery cell according to claim 1 , wherein an end of the recessed portion facing the outermost side of the battery case is located outside an outer surface of the battery case.

21. The battery cell according to claim 1 , wherein an open end of the recessed portion facing the inside of the battery case is located inside an inner surface of the battery case.

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

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