Battery cell and battery module including the same

Abstract

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; electrode leads electrically connected to electrode taps included in the electrode assembly and protruding outward from the battery case via the sealing portion; and a lead film located at a portion corresponding to the sealing portion on at least one of the upper and lower parts of the electrode lead; the lead film has a recess formed in the lead film that is indented toward the inside of the battery case and is open to the outside of the battery case.

Description

Technical Field

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

Background Art

[0002] As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source has been rapidly increasing. In particular, secondary batteries are attracting much attention not only as an energy source for mobile devices such as mobile phones, digital cameras, notebook computers, and wearable devices, but also as an energy source for power devices such as electric bicycles, electric vehicles, and hybrid electric vehicles.

[0003] Such secondary batteries are classified into cylindrical batteries and prismatic batteries in which an electrode assembly is built into a cylindrical or prismatic metal can depending on the shape of the battery case, and pouch-type batteries in which an electrode assembly is built into a pouch-type case of an aluminum laminate sheet. Here, the electrode assembly built into the battery case is a power generation element composed of a positive electrode, a negative electrode, and a separator structure interposed between the positive electrode and the negative electrode, and is capable of charge and discharge. It is classified into a jelly roll type in which a separator is interposed between a long sheet-type positive electrode and negative electrode coated with an active material and wound, and a stack type in which a large number of positive electrodes and negative electrodes are sequentially stacked with a separator interposed therebetween.

[0004] Among them, in particular, the usage amount of pouch-type batteries having a structure in which a stack-type or stack / folding-type electrode assembly is built into a pouch-type battery case made of an aluminum laminate sheet is gradually increasing due to low manufacturing cost, small weight, easy deformability, etc.

[0005] FIG. 1 is a top view of a conventional battery cell. FIG. 2 is a cross-sectional view taken along the a-a' axis in FIG. 1. Referring to FIGS. 1 and 2, an electrode assembly 11 of a conventional battery cell 10 is mounted in a housing portion 21, and includes a battery case 20 having a sealing portion 25 with a structure in which the outer periphery is sealed by heat fusion. Here, it includes an electrode lead 30 protruding in the outer direction of the battery case 20 via the sealing portion 25, and a lead film 40 is positioned between the upper and lower portions of the electrode lead 30 and the sealing portion 25.

[0006] However, recently, as the energy density of battery cells increases, there is a problem that the amount of gas generated inside the battery cell also increases. In the case of the conventional battery cell 10, there is no component for discharging the gas generated inside the battery cell, and the battery cell may experience a bending phenomenon due to gas generation. Similarly, a damaged battery cell due to the bending phenomenon may allow moisture to penetrate inside, causing side reactions, resulting in problems such as a decrease in battery performance and additional gas generation. Therefore, there is an increasing need to develop a battery cell with improved external discharge of gas generated inside the battery cell.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] The problem to be solved by the present invention is to provide a battery cell with improved external discharge of gas generated inside the battery cell and a battery module including the same.

[0008] The problem to be solved by the present invention is 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 PROBLEMS

[0009] A battery cell according to an embodiment of the present invention includes a battery case including a storage portion in which an electrode assembly is mounted and a sealing portion formed by heat-sealing the outer periphery of the storage portion; an electrode lead electrically connected to an electrode tap included in the electrode assembly and protruding outward from the battery case via the sealing portion; and a lead film located at a portion corresponding to the sealing portion at at least one of the upper and lower portions of the electrode lead. A recessed portion that curves inward in the direction of the battery case is formed in the lead film, and the recessed portion is open toward the outside of the battery case.

[0010] Based on the protruding direction of the electrode lead, the inner surface of the recessed portion is closed.

[0011] It 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 and does not react with the electrolyte compared to the material forming the lead film.

[0013] The lead film may contain a polyolefin-based substance.

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

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

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

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

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

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

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

[0021] The lead film includes a first lead film and a second lead film. The first lead film is located above the electrode lead, and the second lead film may be located 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 recessed portion may be located in at least one of the first lead film and the second lead film.

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

[0025] The end of the recessed portion that is open toward the outside of the battery case may be located outside the outer surface of the battery case.

[0026] Based on the protruding direction of the electrode lead, the width of the lead film surrounding the back surface of the recessed portion is 2 mm or more.

[0027] The thickness of the lead film surrounding the upper surface of the recessed portion is 100 - 300 μm.

[0028] The gas permeability of the lead film is 20 to 60 barrer at 60°C.

[0029] The amount of water ingress into the lead film is 0.02 to 0.2 g over 10 years at 25°C and 50% RH.

[0030] A battery module according to another embodiment of the present invention may include the battery cell described above.

Advantages of the Invention

[0031] According to the 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 so as to bend inward in the battery case and open toward the outside of the battery case, and a battery module including the same, thereby improving the external discharge amount of gas generated inside the battery cell.

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

Brief Description of the Drawings

[0033]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0034] Hereinafter, with reference to the attached drawings, various embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. The present invention is embodied in various different forms and is not limited to the embodiments described herein.

[0035] To clearly explain the present invention, parts not related to the explanation are omitted, and the same reference numerals are given to the same or similar components throughout the specification.

[0036] Also, the size and thickness of each configuration shown in the drawings are arbitrarily shown for the convenience of explanation, and the present invention is not necessarily limited to the places where it is shown. The thickness is enlarged to clearly represent various layers and regions in the drawings. And in the drawings, for the convenience of explanation, the thickness of some layers and regions is exaggerated.

[0037] Also, throughout the specification, when a certain part "includes" a certain component, this means that, unless otherwise stated to the contrary, it does not exclude other components and may further include other components.

[0038] Also, throughout the specification, when it is "on a plane", this means a top view of the target part, and when it is "in a cross-section", this means a side view of the cross-section obtained by cutting the target part vertically.

[0039] Hereinafter, the pouch battery cell 100 according to an embodiment of the present invention will be described. However, here, of the two side surfaces of the pouch battery cell 100, the description is based on one side surface, but it is not necessarily limited to this, and the same or similar content will also be described in the case of the other side surface.

[0040] Figure 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 having a structure in which the electrode assembly 110 is mounted in the storage portion 210 and the outer periphery is sealed by heat fusion. 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 can be composed of an outer resin layer forming the outermost contour, a barrier metal layer preventing the penetration of substances, and an inner resin layer for sealing.

[0043] In addition, the electrode assembly 110 can have a structure of a jelly roll type (winding type), a stack type (laminated type), or a composite type (stack / folding type). More specifically, the electrode assembly 110 can be composed of a positive electrode, a negative electrode, and a separator disposed therebetween.

[0044] Hereinafter, the electrode lead 300 and the lead film 400 will be mainly described.

[0045] FIG. 4 is a perspective view of the electrode lead included in the battery cell of FIG. 3.

[0046] Referring to FIGS. 3 and 4, the electrode lead 300 is electrically connected to an electrode tab (not shown) included in the electrode assembly 110 and protrudes outward from the battery case 200 via the sealing portion 250. Further, the lead film 400 is located at least one of the upper and lower portions of the electrode lead 300 and at a portion corresponding to the sealing portion 250. Thereby, the lead film 400 can improve the sealing performance between the sealing portion 250 and the electrode lead 300 while preventing a short circuit from occurring due to the electrode lead 300 during heat fusion.

[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] Referring to FIGS. 5 and 6, the lead film 400 has a recess 450 that curves inward in the direction of the inside of the battery case 200, and the recess 450 is open to the outside of the battery case 200. Also, with respect to the protruding direction of the electrode lead 300, the inner surface of the recess 450 is closed.

[0049] As a result, with the lead film 400, gas generated inside the battery case 200 is discharged to the recess 450 due to the pressure difference between the inside and the outside, and the gas that has flowed into the recess 450 is discharged outward. Also, the lead film 400 has the advantage that since the recess 450 is open to the outside, the recess 450 is not exposed to the electrolyte inside the battery case 200, and the airtightness and durability of the pouch can be ensured. Further, with the lead film 400, the gas permeation area is maximized by the recess 450, and a large amount of gas can be discharged.

[0050] Also, referring to FIGS. 5 and 6, the lead film 400 may further include an inner layer 410 that covers at least one of the inner surfaces of the recess 450.

[0051] As an example, referring to FIGS. 5(a) and 6(a), inside the recess 450, the inner layer 410 covers the entire surface of the lead film 400. That is, the inner layer 410 is formed on the entire inner surface of the recess 450 excluding the open surface.

[0052] As a result, even when the lead film 400 is heat-sealed together with the sealing portion 250 while being positioned at least at one of the upper and lower portions of the electrode lead 300, the recess 450 is stored in a state where it is not heat-sealed by the inner layer 410.

[0053] As another example, referring to FIGS. 5(b) and 6(b), the inner layer 410 covers the upper surface or the lower surface of the inner surface of the recess 450. That is, the inner layer 410 is formed on at least one of the upper surface and the lower surface that face each other in the recess 450.

[0054] Thereby, the lead film 400 stores the recess 450 in a state where it is not heat-sealed by the inner layer 410 while minimizing the inner layer 410 formed in the recess 450. Also, the manufacturing process can be simplified and costs can be reduced.

[0055] More specifically, the inner layer 410 can be made of a material having a higher melting point than the material forming the lead film 400. Also, the inner layer 410 can be made of a material that does not react with the electrolyte contained in the battery case 200. Thereby, the inner layer 410 is made of the above-described material and does not undergo heat-sealing, heat deformation, etc. during the high-temperature heat-sealing process without reacting separately with the electrolyte, and the recess 450 is held empty. Also, the gas generated in the battery case 200 is easily discharged 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 barrer or more. For example, the carbon dioxide permeability of the inner layer 410 can satisfy the above-described range.

[0058] As an example, the lead film 400 contains a polyolefin-based substance, and the inner layer 410 may contain at least one substance among polyolefin-based, fluorine-based, and porous ceramic-based substances. For example, the inner layer 410 may contain at least one substance among polyolefin-based, fluorine-based, and porous ceramic-based substances that satisfy the above-described gas permeability value. The polyolefin-based substance may include one or more materials selected from the group consisting of polypropylene, polyethylene, and polyvinyldifluoride (PVDF). The fluorine-based substance may include one or more materials selected from the group consisting of polytetrafluoroethylene and polyvinylidene fluoride. Further, the inner layer 410 contains a getter substance, which can increase the gas permeability but minimize the degree of moisture intrusion. As an example, the getter substance is calcium oxide (CaO), barium oxide (BaO), lithium chloride (LiCl), silica (SiO2), etc., but is not limited thereto, and any substance that reacts with water (H2O) can be used.

[0059] The inner layer 410 is provided with an adhesive material between the lead film 400 and the inner layer 410, or can be extruded together with the lead film 400 and adhered to the lead film 400. The adhesive material may include an acrylic-based one. 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 barrer or more.

[0060] Referring to FIGS. 4 to 6, the lead film 400 includes a first lead film and a second lead film. The first lead film is located above the electrode lead 300, and the second lead film may be located below the electrode lead 300. At this time, the electrode lead 300 is heat-sealed together with the sealing portion 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] Thereby, the lead film 400 can improve the sealing performance between the sealing portion 250 and the electrode lead 300 while preventing the exposure of the side surface of the electrode lead 300 to the outside.

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

[0063] Thereby, by adjusting the number of the recessed portions 450 formed in the lead film 400, the durability and airtightness of the lead film 400 can be controlled. Further, if necessary, the number of the recessed portions 450 can be minimized to simplify the manufacturing process and reduce costs.

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

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

[0066] As an example, as shown in FIG. 7(a), with the lead film 400, the recessed portion 450 may be located on the electrode lead 300. More specifically, the recessed portion 450 is formed at a position corresponding to the central portion of the electrode lead 300.

[0067] As another example, as shown in FIG. 7(b), the length of the lead film 400 is larger than the width of the electrode lead 300, and the recessed portion 450 may be located between the end of the electrode lead 300 and the end of the lead film 400. Here, the length of the lead film 400 means the maximum value of the distance between one end and the other end of the lead film 400 in a direction orthogonal to the protruding direction of the electrode lead 300, and the width of the electrode lead 300 means the maximum value of the distance between one end and the other end of the electrode lead 300 in a direction orthogonal to the protruding direction of the electrode lead 300. In other words, with the lead film 400, the recessed portion 450 is formed at a position avoiding the electrode lead 300. However, the position of the recessed portion 450 is not limited to the above-described content and is formed at an appropriate position within the lead film 400.

[0068] Thereby, by adjusting the position of the recessed portion 450 formed in the lead film 400, the durability and airtightness of the lead film 400 can be controlled. Further, if necessary, depending on the position of the recessed portion 450, the size of the recessed portion 450 can be adjusted to simplify the manufacturing process and reduce costs.

[0069] Referring to FIG. 7, with the lead film 400, the recessed portion 450 is formed in various shapes.

[0070] As an example, the recessed portion 450 includes a first recessed portion 451 and a second recessed portion 455. 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 orthogonal to the protruding direction of the electrode lead 300.

[0071] Here, the width of the lead film 400 is larger than the width of the sealing portion 250 but smaller than the length of the electrode lead 300. Here, the width of the lead film 400 means the maximum value of the 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 means the maximum value of the 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 means the maximum value of the distance between one end and the other end of the electrode lead 300 in the protruding direction of the electrode lead 300. At this time, the second recessed portion 455 can be located between the end of the sealing portion 250 and the end of the lead film 400. As another example, the recessed portion 450 can have a rectangular shape similar to the lead film 400. However, the shape of the recessed portion 450 is not limited to the above-described content and is formed in an appropriate shape within the lead film 400.

[0073] Thereby, by adjusting the shape of the recessed portion 450 formed in the lead film 400, the durability and airtightness of the lead film 400 can be controlled. Further, if necessary, the shape of the recessed portion 450 can be made different to simplify the manufacturing process and reduce costs.

[0074] Referring to FIG. 8, in the lead film 400, the end portion of the recessed portion 450 that is open toward the outside is formed adjacent to the end portion of the lead film 400, and the end portion that curves inward can be located between the end portion of the sealing portion 250 and the end portion of the lead film 400. Further, the end portion of the recessed portion 450 that curves inward can be separated from the end portion of the sealing portion 250 by a predetermined distance or can be adjacent thereto.

[0075] As an example, by comparing FIG. 8(a) and FIG. 8(b), it can be confirmed that even if the position of the sealing portion 250 in contact with the lead film 400 is changed, there is no influence on the end portion of the recessed portion 450 that curves inward.

[0076] As a result, in this embodiment, within the error range due to the position of the lead film 400 and the sealing portion 250 generated during the heat fusion process, the area where the end portion that curves inward at the recessed portion 450 is located inside with respect to the battery case 200 can be uniformly maintained, and the area where the gas in the battery case 200 flows into and is discharged to the outside of the recessed portion 450 is also uniformly maintained. Accordingly, there is an advantage that the gas discharge effect by the recessed portion 450 is also maintained.

[0077] FIG. 9 is a cross-sectional view taken along the b-b' axis in FIG. 3.

[0078] Referring to FIG. 9, the end portion of the recessed portion 450 that curves into the lead film 400 can be located inside the inner surface of the battery case 200. Here, the inner surface of the battery case 200 means the inner end portion of the sealing portion 250 of the battery case 200. Also, the end portion of the recessed portion 450 that is open toward the outside of the battery case 200 can be located outside the outer surface of the battery case 200. Here, the outer surface of the battery case 200 means the outer end portion of the sealing portion 250 of the battery case 200.

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

[0080] Referring to FIG. 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-described range, it is even easier for the gas inside the battery case 200 to be discharged to the outside.

[0081] Referring to FIG. 9, based on the protruding direction of the electrode lead 300, the width (W) of the lead film 400 surrounding the back surface of the recessed portion 450 is 2 mm or more, or 2 - 3 mm. Here, the width of the lead film 400 surrounding the back surface of the recessed portion 450 means the maximum value of the distance between the recessed end of the recessed portion 450 and the inner end of the lead film 400 on the battery case 200. When the width (W) of the lead film 400 surrounding the back surface of the recessed portion 450 satisfies the above-mentioned range, it is further easier to prevent the phenomenon that the lead film 400 is torn during the process of the gas generated inside the battery case 200 being discharged to the outside.

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

[0083] Referring to FIG. 10, the 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 the 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] Thereby, the gas generated inside the battery cell 100 is discharged toward the recessed portion 450, and the gas flowing into the recessed portion 450 is easily discharged to the outside. Also, the amount of gas discharged from the inside of the battery cell 100 to the outside increases.

[0085] In one embodiment of the present invention, the gas permeability of the lead film 400 is 20 - 60 barrer, or 30 - 40 barrer at 60°C. For example, the carbon dioxide permeability of the lead film 400 can satisfy the above-mentioned range. Also, based on the thickness of the lead film 400 being 200 μm, the gas permeability can satisfy the above-mentioned range at 60°C. When the gas permeability of the lead film 400 satisfies the above-mentioned range, the discharge of the gas generated inside the secondary battery is more effective.

[0086] In this specification, the gas permeability can be measured in accordance with ASTM F2476-20.

[0087] In one embodiment of the present invention, the amount of water ingress into 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 over 10 years at 25°C and 50% RH. When the amount of water ingress into the lead film 400 satisfies the above-described range, it is more effective to prevent the ingress of water 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 barrer at 60°C and an amount of water ingress of 0.02 to 0.2 g over 10 years at 25°C and 50% RH. When the gas permeability and the amount of water ingress of the lead film 400 satisfy the above-described range, it is more effective to prevent the ingress of moisture from the outside while discharging the gas generated inside the secondary battery.

[0089] The amount of water ingress into the lead film 400 can be measured by adopting the ASTM F 1249 method. At this time, it can be measured using equipment officially certified by MCOON.

[0090] In one embodiment of the present invention, the lead film 400 may contain a polyolefin-based resin. For example, the lead film 400 may contain a polyolefin-based resin that satisfies the above-described gas permeability and / or water ingress amount values. The polyolefin-based resin may contain one or more materials selected from the group consisting of polypropylene, polyethylene, and polyvinylidene fluoride (PVDF). While the lead film 400 contains polypropylene, the gas permeability of the lead film 400 is 20 to 60 barrer at 60°C. Also, the amount of water ingress is 0.06 to 0.15 g. In this case, the discharge of the gas generated inside the secondary battery is more effective, and it is also easy to prevent the ingress of moisture from the outside.

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

[0092] As an example, when compared with FIG. 9, the recessed portion 450 may partially expand upward and downward due to the gas inside the battery cell 100. However, in the case of this embodiment, the recessed portion 450 is open to the outside, the degree of expansion is relatively small, and the deformation of the components due to this is also small.

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

[0094] The above-described battery module and the battery pack including the same are applicable to various devices. Such devices can be applied to transportation means such as electric bicycles, electric vehicles, and hybrid vehicles, but the present invention is not limited thereto, and is applicable to various devices that can use the battery module and the battery pack including the same, and this also belongs to the scope of rights of the present invention.

[0095] As described above, the desirable embodiments of the present invention have been described in detail, but the scope of rights of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention defined in the following claims also belong to the scope of rights of the present invention.

Description of Reference Numerals

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

Claims

1. A battery case including a storage portion in which an electrode assembly is mounted, and a sealing portion formed by heat-sealing the outer periphery of the storage portion; An electrode lead that is electrically connected to an electrode tab included in the electrode assembly and protrudes outward from the battery case via the sealing portion; A lead film located at a portion corresponding to the sealing portion in at least one of the upper and lower portions of the electrode lead; A recessed portion that is recessed inwardly of the battery case is formed in the lead film; The recessed portion is open toward the outside of the battery case; An end portion of the recessed portion that is recessed into the lead film is located inside the inner surface of the battery case; An end portion of the recessed portion that is open toward the outside of the battery case is located outside the outer surface of the battery case; The lead film surrounds the back surface and the upper surface of the recessed portion in the protruding direction of the electrode lead; A battery cell in which gas generated inside the battery case permeates through the lead film due to a pressure difference between the inside and outside and flows into the recessed portion and is discharged to the outside.

2. The battery cell according to claim 1, wherein the entire inner surface of the recessed portion is closed.

3. The battery cell according to claim 2, further including an inner layer covering at least one surface of the inner surface of the recessed portion of the lead film.

4. The battery cell according to claim 3, wherein the material forming the inner layer has a higher melting point and does not react with the electrolyte compared to the material forming the lead film.

5. The battery cell according to claim 3 or 4, wherein the inner layer contains at least one substance selected from the group consisting of polyolefin-based, fluorine-based, and porous ceramic-based substances.

6. The battery cell according to any one of claims 1 to 5, wherein the lead film contains a polyolefin-based substance.

7. The battery cell according to any one of claims 1 to 6, wherein the recessed portion is located on the electrode lead.

8. The battery cell according to any one of claims 1 to 7, wherein the length of the lead film is larger than the width of the electrode lead.

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

10. The recessed portion includes a first recessed portion and a second recessed portion. The first recessed portion extends along the protruding direction of the electrode lead, The second recessed portion extends along the longitudinal direction of the sealing portion. The battery cell according to any one of claims 1 to 9.

11. The width of the lead film is larger than the width of the sealing portion and smaller than the length of the electrode lead. The battery cell according to claim 10.

12. The second recessed portion is located between the end of the sealing portion and the end of the lead film. The battery cell according to claim 11.

13. The lead film includes a first lead film and a second lead film, The first lead film is located above the electrode lead, The second lead film is located below the electrode lead. The battery cell according to any one of claims 1 to 12.

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

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

16. The width of the lead film surrounding the back surface of the recessed portion in the protruding direction of the electrode lead is 2 mm or more. The battery cell according to any one of claims 1 to 15.

17. The thickness of the lead film surrounding the upper surface of the recessed portion is 100 to 300 μm. The battery cell according to any one of claims 1 to 16.

18. The gas permeability of the lead film is 20 to 60 barrer at 60°C. The battery cell according to any one of claims 1 to 17.

19. The amount of water intrusion into the lead film is 0.02 to 0.2 g over 10 years at 25°C and 50% RH. The battery cell according to any one of claims 1 to 18.

20. A battery module including the battery cell according to any one of claims 1 to 19.

Images