Secondary battery, battery pack, and device including the same

Abstract

The present invention relates to a secondary battery including an electrode assembly having an electrode lead attached thereto, a case for accommodating the electrode assembly, a seal part formed for sealing the electrode assembly in the case, and a lead film wrapping a part of an outer surface of the electrode lead and interposed between the electrode lead and the seal part, the lead film including a first region configured to be primarily broken when the battery swells, and a second region configured to be secondarily broken when the battery swells.

Description

Technical Field

[0001] The present invention relates to a secondary battery, a battery pack including the same, and a device including the same, and more particularly, to a secondary battery with improved safety, a battery pack including the same, and a device including the battery pack.

[0002] This application claims priority based on Korean Patent Application No. 10-2022-0005176 filed on January 13, 2022, and all of the content disclosed in the specification and drawings of the application is incorporated herein.

Background Art

[0003] Mobile IT devices such as mobile phones, laptops, and tablet PCs are closely related to modern life, and along with the growth of the IT industry market, the need for secondary batteries, which are core components, is also increasing rapidly. The above secondary battery can be repeatedly used through charging and discharging, and is an environmentally friendly battery technology that does not use harmful substances such as lead, nickel, and cadmium. It has the advantage of having a high energy density that can store a large amount of energy in a small volume while being light, and thus forms the core of future new growth driver industries. In particular, lithium secondary batteries are not only most widely used as power sources for mobile IT that is closely related to human life, but recently, their utilization has also been continuously expanded as power sources for electric vehicles and power storage devices for new renewable energy.

[0004] Generally, a secondary battery is composed of a positive electrode, a negative electrode, a separator that separates them, an electrolyte that transmits lithium ions through the separator, a case that houses them, and an electrode lead that serves as a current path to the outside of the case. Further, a lead film may be included, and the lead film is bonded to the electrode lead to prevent a short circuit between the electrode lead and the battery case while sealing the electrode lead and the battery case.

[0005] In the case of such a secondary battery, since it tends to be vulnerable to internal pressure caused by gas or the like generated during the operation of the battery, etc., at present, the development of a secondary battery having sufficient rigidity against such internal pressure is desired. Summary of the Invention Problems to be Solved by the Invention

[0006] Therefore, the problem to be solved by the present invention is to provide a secondary battery with improved safety. Means for Solving the Problems

[0007] In order to solve the above problems, according to one aspect of the present invention, secondary batteries, battery packs, and devices of the following aspects are provided.

[0008] A secondary battery according to an embodiment of the present invention includes an electrode assembly to which an electrode lead is attached, a case that houses the electrode assembly, a seal portion formed to seal the electrode assembly in the case, and a lead film that wraps a part of the outer surface of the electrode lead and is interposed between the electrode lead and the seal portion. The lead film may include a first region configured to break primarily when the battery swells and a second region configured to break secondarily when the battery swells.

[0009] The first region may be located relatively close to the electrode assembly, and the second region may be located relatively far from the electrode assembly.

[0010] The first region may be located at one end of the seal portion in the inner direction of the case.

[0011] The second region may be located at one end of the seal portion in the outer direction of the case.

[0012] The first region and the second region may be spaced apart from each other in the width direction of the seal portion.

[0013] In the first region and the second region, the lead film can be fused to the case, and in the region located between the first region and the second region, there is a possibility that it may not be fused to the case.

[0014] The distance between the first region and the second region can be 20% to 80% of the width of the seal portion.

[0015] The lead film may include a first lead film and a second lead film provided separately from the first lead film.

[0016] The first lead film is located relatively close to the electrode assembly, and the second lead film can be located relatively far from the electrode assembly.

[0017] The first region is located within the region where the first lead film and the seal portion overlap, and the second region can be located within the region where the second lead film and the seal portion overlap.

[0018] A part of the first lead film can be located at the end of the seal portion in the inner direction of the case.

[0019] A part of the second lead film can be located at the end of the seal portion in the outer direction of the case.

[0020] The first lead film and the second lead film can be spaced apart from each other in the width direction of the seal portion.

[0021] The second lead film can have a shape extending along the extending direction of the seal portion.

[0022] The first lead film can have a shape extending along a direction forming a predetermined angle with respect to the extending direction of the second lead film.

[0023] The first lead film can form an angle of 15° to 60° with the second lead film.

[0024] The extension length of the first lead film in the direction parallel to the extension direction of the electrode lead can be 10% to 80% of the width of the seal portion.

[0025] The extension width of the second lead film in the direction parallel to the extension direction of the electrode lead can be 10% to 50% of the width of the seal portion.

[0026] The extension length of the first region in the direction parallel to the extension direction of the electrode lead can be 10% to 50% of the width of the seal portion.

[0027] The extension width of the second region in the direction parallel to the extension direction of the electrode lead can be 10% to 50% of the width of the seal portion.

[0028] The battery pack according to an embodiment of the present invention may include the secondary battery according to an embodiment of the present invention described above.

[0029] The device according to an embodiment of the present invention includes the battery pack according to an embodiment of the present invention described above.

Advantages of the Invention

[0030] The secondary battery according to an embodiment of the present invention can improve the strength against internal pressure, thereby improving safety.

[0031] The drawings attached to this specification illustrate the preferred embodiments of the present invention and serve to further understand the technical idea of the present invention together with the content of the invention. Therefore, the present invention is not construed as being limited only to the matters described in the drawings.

Brief Description of the Drawings

[0032]

Figure 1

Figure 2

Figure 3

BEST MODE FOR CARRYING OUT THE INVENTION

[0033] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms and words used in this specification and the claims are not to be construed as being limited to ordinary or dictionary meanings, and the inventor should interpret them in accordance with the meaning and concept corresponding to the technical idea of the present invention in accordance with the principle that he can appropriately define the concept of the terms in order to explain his invention in the best way.

[0034] Therefore, it should be understood that the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention, and thus there may be various equivalents and modifications that can replace them at the time of this application.

[0035] A secondary battery according to one aspect of the present invention includes an electrode assembly to which an electrode lead is attached, a case that houses the electrode assembly, a seal portion formed to seal the electrode assembly in the case, and a lead film that wraps a part of the outer surface of the electrode lead and is interposed between the electrode lead and the seal portion, wherein the lead film includes a first region configured to break primarily when the battery swells and a second region configured to break secondarily when the battery swells.

[0036] FIG. 1 is a diagram showing an electrode lead, a lead film, and a seal portion of a secondary battery according to an embodiment of the present invention.

[0037] Referring to FIG. 1, a secondary battery 10 according to an embodiment of the present invention includes an electrode assembly 12 to which an electrode lead 11 is attached and a case.

[0038] The electrode assembly 12 includes a positive electrode plate, a negative electrode plate, and a separator. The electrode assembly 12 may have a structure in which the positive electrode plate and the negative electrode plate are sequentially laminated with the separator interposed therebetween.

[0039] The positive electrode plate may be formed by including a positive electrode current collector made of a metal thin plate with excellent conductivity, such as an aluminum (Al) foil, and a positive electrode active material layer coated on at least one surface thereof. Further, the positive electrode plate may include a positive electrode tab made of a metal material, such as an aluminum (Al) material, at one side end. The positive electrode tab may extend and protrude from one side end of the positive electrode plate, may be welded to one side end of the positive electrode plate, or may be joined using a conductive adhesive.

[0040] The negative electrode plate may be formed by including a negative electrode current collector made of a conductive metal thin plate, such as a copper (Cu) foil, and a negative electrode active material layer coated on at least one surface thereof. Further, the negative electrode plate may include a negative electrode tab made of a metal material, such as copper (Cu) or nickel (Ni) material, at one side end. The negative electrode tab may extend and protrude from one side end of the negative electrode plate, may be welded to one side end of the negative electrode plate, or may be joined using a conductive adhesive.

[0041] The separator is interposed between the positive electrode plate and the negative electrode plate, can electrically insulate the positive electrode plate and the negative electrode plate from each other, and can be in the form of a porous membrane that allows the passage of lithium ions and the like between the positive electrode plate and the negative electrode plate. Such a separator may include, for example, a porous membrane made of polyethylene (PE), polypropylene (PP), or a composite film thereof.

[0042] An inorganic coating layer may be provided on the surface of the separation membrane. The inorganic coating layer may have a structure in which inorganic particles are bonded to each other by a binder to form a pore structure (interstitial volume) between the particles.

[0043] Examples of the electrode assembly 12 include a jelly roll type (winding type) electrode assembly having a structure in which a long sheet-like positive electrode and a negative electrode are wound with a separation membrane interposed therebetween, a stack type (lamination type) electrode assembly in which a plurality of positive electrodes and negative electrodes cut into a predetermined size are sequentially laminated with a separation membrane interposed therebetween, and a stack / folding type electrode assembly having a structure in which a bi cell or a full cell in which a positive electrode and a negative electrode of a predetermined unit are laminated with a separation membrane interposed therebetween is wound.

[0044] The case includes a housing portion 13a for housing the electrode assembly 12 and a seal portion 13b formed for sealing the electrode assembly 12.

[0045] The seal portion 13b refers to a portion that is fused, for example, along the outer peripheral surface of the housing portion 13a in order to seal the electrode assembly 12. The fusion may be heat fusion, fusion by ultrasonic waves, etc., but is not particularly limited as long as the seal portion can be fused.

[0046] In one embodiment of the present invention, the case may be configured in the form of a film having a multilayer structure including an outer layer for protecting against external impact, a metal barrier layer for blocking moisture, and a sealant layer for sealing the case.

[0047] The outer layer may include other polyester-based films such as poly(ethylene terephthalate) (PET), polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolyester, polycarbonate, and nylon, and may be composed of a single layer or multiple layers.

[0048] The metal barrier layer may include aluminum, copper, etc.

[0049] The sealant layer may include a sealant resin and may be composed of a single layer or multiple layers.

[0050] In one embodiment of the present invention, the sealant resin may include polypropylene (PP), acid modified polypropylene (PPa), random polypropylene, ethylene-propylene copolymer, or two or more of these. The ethylene-propylene copolymer may include ethylene-propylene rubber, ethylene-propylene block copolymer, etc., but is not limited thereto.

[0051] In one embodiment of the present invention, the case may be of a pouch type.

[0052] In one embodiment of the present invention, when the case is of a pouch type, it may include an upper pouch and a lower pouch. When the case includes an upper pouch and a lower pouch, the outer peripheral surfaces of the upper pouch and the lower pouch can be fused to each other by heat and pressure to seal the battery.

[0053] When the case is of a pouch type, the seal portion 13b may have a four-sided seal structure or a three-sided seal structure at the edge of the case. The three-sided seal structure means that after forming the upper pouch and the lower pouch with a single pouch sheet, the boundary between the upper pouch and the lower pouch is bent so that the electrode assembly accommodating portions 13a formed in the upper pouch and the lower pouch overlap each other, and the remaining three sides other than the bent portion are sealed. On the other hand, in the present invention, the seal portion 13b may refer to the edges of the upper pouch and the lower pouch facing each other. That is, in the present invention, it is not necessary for all the edges of the upper pouch and the lower pouch facing each other to be fused, and they may be fused only partially.

[0054] Referring to FIG. 1, a part of the electrode lead 11 can be accommodated in the case so that a part thereof is exposed outside the case.

[0055] Referring to FIG. 1, a secondary battery 10 according to an embodiment of the present invention includes a lead film 14.

[0056] The lead film 14 wraps a part of the outer surface of the electrode lead 11 and is interposed between the electrode lead 11 and the seal portion 13b of the case where the electrode lead 11 protrudes. The lead film 14 can be located on at least one surface of the electrode lead 11. By interposing the lead film 14 between the electrode lead 11 and the seal portion 13b of the case where the electrode lead protrudes, the binding between the electrode lead 11 and the seal portion 13b of the case is assisted. Sealing of the battery is performed on the surface where the lead film 14 contacts the seal portion 13b.

[0057] Referring to FIG. 1, the lead film 14 can have a shape extending parallel to the extending direction (the left - right direction with reference to FIG. 1) of the seal portion 13b located in the direction in which the electrode lead 11 is drawn out, for example.

[0058] In a secondary battery, a swelling phenomenon may occur in which the battery expands during the process of repeated charge and discharge, which affects the safety of the battery. When the swelling phenomenon occurs, breakage may occur at the interface between the lead film with slightly weak adhesive force and the seal portion.

[0059] Referring to FIG. 1, the lead film 14 includes a first region A configured to break primarily when the battery swells and a second region B configured to break secondarily. Since the first region A breaks before the second region B, it may be easier to adjust the swelling pressure. Thereby, an increase in the swelling pressure can be prevented and the safety of the battery can be improved. The first region A and the second region B may mean regions where fusion bonding is performed among the regions where the lead film 14 and the seal portion 13b of the case overlap.

[0060] Even after breakage preferentially occurs in the first region A, if the swelling pressure increases, breakage secondarily occurs in the second region B, thereby further preventing an increase in the swelling pressure. By breaking the second region B, the pressure inside the battery can be released to the outside, and the swelling pressure can be adjusted more easily.

[0061] At this time, in the first region A, the interface between the lead film 14 and the seal portion 13b breaks. Further, in the second region B, the interface between the lead film 14 and the seal portion 13b breaks.

[0062] After primarily sealing the seal portion 13b and the first region A of the lead film 14, and then secondarily sealing the second region B of the lead film 14, the first region A and the second region B that are fused to the case can be formed on the lead film 14. Therefore, a difference can be made in the sealing strength between the first region A and the second region B, and thereby the breakage timing of the first region A and the second region B can be adjusted. Of course, it is also possible to primarily seal the second region B and secondarily seal the first region A.

[0063] Referring to FIG. 1, the first region A may be located relatively close to the electrode assembly 12, and the second region B may be located relatively far from the electrode assembly 12.

[0064] When a swelling phenomenon occurs, the sealing portion in the inner direction of the case receives the most pressure. When the first region A is located more inwardly of the case than the second region B, when a swelling phenomenon occurs, the first region A, which is relatively located more inwardly of the case, may be more likely to break than the second region B.

[0065] In one embodiment of the present invention, it may further include a sensor part (not shown) and a control part (not shown) connected to the first region A and / or the second region B. The sensor part measures the swelling pressure and transmits it to the control part, and the control part can cause breakage to occur in the first region A and / or the second region B when a specific pressure threshold is exceeded.

[0066] Referring to FIG. 1, the first region A may be located at one end of the sealing portion 13b in the inner direction of the case, and the second region B may be located at one end of the sealing portion 13b in the outer direction of the case. When the first region A is located at one end of the sealing portion 13b in the inner direction of the case, when a swelling phenomenon occurs, breakage preferentially occurs at one end of the sealing portion 13b in the inner direction of the case, which is the portion that receives the most pressure, so that the swelling pressure can be adjusted more easily. When the second region B is located at one end of the sealing portion 13b in the outer direction of the case, by breaking the second region B, the pressure inside the battery can be discharged to the outside, and the swelling pressure can be adjusted more easily.

[0067] Referring to FIG. 1, the first region A and the second region B may be positioned apart from each other in the width direction of the seal portion 13b (the vertical direction with reference to FIG. 1). In this case, the lead film 14 can be fused to the case in the first region A and the second region B, and may not be fused to the case in the region located between the first region A and the second region B. On the other hand, the distance h between the first region A and the second region B can be about 20% to 80% of the width of the seal portion 13b. When the distance h between the first region A and the second region B satisfies the above range, the breakage times of the first region A and the second region B can be adjusted more easily.

[0068] Here, the distance h between the first region A and the second region B refers to the distance between the outermost end portion facing the outside of the case in the first region A and the innermost end portion facing the inside of the case in the second region B.

[0069] FIG. 2 is a diagram showing an electrode lead, a lead film, and a seal portion of a secondary battery according to another embodiment of the present invention.

[0070] Referring to FIG. 2, the lead film 14 may include a first lead film 14a and a second lead film 14b provided separately from the first lead film 14a. The first lead film 14a and / or the second lead film 14b may have a shape extending parallel to the extending direction of the seal portion 13b (the left-right direction with reference to FIG. 1) located in the direction in which the electrode lead 11 is drawn out. When the lead film 14 includes the first lead film 14a and the second lead film 14b, the design of the lead film 14 for obtaining a desired seal strength may be made easier.

[0071] Referring to FIG. 2, the first lead film 14a may be located relatively close to the electrode assembly 12, and the second lead film 14b may be located relatively far from the electrode assembly 12.

[0072] Referring to FIG. 2, a first region A may be located within a region where the first lead film 14a and the seal portion 13b overlap, and a second region B may be located within a region where the second lead film 14b and the seal portion 13b overlap.

[0073] In one embodiment of the present invention, when the battery swells, after the interface between the first lead film 14a and the seal portion 13b is primarily broken, the interface between the second lead film 14b and the seal portion 13b may be secondarily broken.

[0074] When the first lead film 14a is located more inwardly of the case than the second lead film 14b, when a swelling phenomenon occurs, the first lead film 14a, which is relatively located more inwardly of the case, may be more likely to break earlier than the second lead film 14b.

[0075] Referring to FIG. 2, a part of the first lead film 14a may be located at an end portion of the seal portion 13b in the inner direction of the case, and a part of the second lead film 14b may be located at an end portion of the seal portion 13b in the outer direction of the case. At this time, a part of the first lead film 14a located at the end portion of the seal portion 13b in the inner direction of the case may correspond to the first region A, and a part of the second lead film 14b located at the end portion of the seal portion 13b in the outer direction of the case may correspond to the second region B.

[0076] Referring to FIG. 3, it is a view showing an electrode lead, a lead film, and a seal portion of a secondary battery according to still another embodiment of the present invention.

[0077] Referring to FIG. 3, the second lead film 14b may have a shape extending along the extending direction of the seal portion 13b (the left - right direction with reference to FIG. 3).

[0078] Referring to FIG. 3, the first lead film 14a may have a shape extending along a direction forming a predetermined angle with respect to the extending direction of the second lead film 14b. The first lead film 14a may be connected to or separated from the second lead film 14b.

[0079] In one embodiment of the present invention, there may be a plurality of the first lead films 14a.

[0080] In one embodiment of the present invention, when there are a plurality of the first lead films 14a, a part of the plurality of first lead films 14a may overlap each other. When there are a plurality of the first lead films 14a, a pair of the first lead films 14a may have a shape inclined in opposite directions so as to be separated from each other toward the inside of the case.

[0081] In one embodiment of the present invention, the angle formed by the first lead film 14a and the second lead film 14b may be about 15° to 60°.

[0082] When the first lead film 14a and the second lead film 14b have the above-described forms, the contact area between the lead film 14 and the electrode lead 11 increases, the contact area between the lead film 14 and the seal portion 13b also increases, the adhesive strength between the electrode lead 11 and the seal portion 13b increases, and the seal strength between the electrode lead 11 and the seal portion 13b may increase. By increasing the seal strength between the electrode lead 11 and the seal portion 13b, the strength against the internal pressure of the battery can be increased. Also, the internal pressure of the battery may be easily dispersed.

[0083] Referring to FIG. 3, the extension length h1 of the first lead film 14a in a direction parallel to the extension direction of the electrode lead 11 (the vertical direction with reference to FIG. 3) can be about 10% to 80% of the width of the seal portion 13b. When the extension length h1 of the first lead film 14a along the extension direction of the electrode lead 11 satisfies the above range, the contact area between the first lead film 14a and the electrode lead 11, and the contact area between the first lead film 14a and the seal portion 13b are more likely to increase, and it is more likely to further ensure a seal strength with sufficient strength during the normal operation of the battery.

[0084] In this specification, the width of the seal portion 13b means the maximum value of the distance between one end and the other end of the seal portion 13b along the protruding direction of the electrode lead 11.

[0085] Referring to FIG. 3, the extension width h2 of the second lead film 14b in a direction parallel to the extension direction of the electrode lead 11 can be about 10% to 50% of the width of the seal portion 13b. When the extension width h2 of the second lead film 14b satisfies the above range, the contact area between the second lead film 14b and the electrode lead 11, and the contact area between the second lead film 14b and the seal portion 13b are more likely to increase, and it is more likely to further ensure a seal strength with sufficient strength during the normal operation of the battery.

[0086] In an embodiment of the present invention, the extension length d1 in a direction parallel to the extension direction of the electrode lead 11 in the first region A where breakage due to an increase in the internal pressure of the battery preferentially occurs can be about 10% to 50% of the width of the seal portion 13b. When the extension length d1 of the first region A satisfies the above range, it is possible to ensure a seal strength with sufficient strength during the normal operation of the battery, and it can be more likely to break further when the swelling phenomenon occurs.

[0087] In one embodiment of the present invention, the extension width d2 in the direction parallel to the extension direction of the electrode lead 11 in the second region B where breakage occurs can be about 10% to 50% of the width of the seal portion 13b. When the extension width d2 of the second region B satisfies the above range, it is possible to ensure a sufficient seal strength during normal operation of the battery, and it may be more likely to break when the swelling phenomenon occurs.

[0088] Referring to FIG. 3, the lead film 14 can be substantially K-shaped. For example, the substantially K-shaped lead film 14 can include a pair of first lead films 14a having shapes inclined in opposite directions to each other, and a second lead film 14b having a shape extending along a direction substantially parallel to the extension direction of the seal portion 13b. When the lead film 14 is substantially K-shaped in this way, the contact area between the lead film 14 and the electrode lead 11 can be increased, and the contact area between the lead film 14 and the seal portion 13b can also be increased. Therefore, the adhesion strength between the electrode lead 11 and the seal portion 13b increases, and the seal strength between the electrode lead 11 and the seal portion 13b is more likely to increase. In addition, the internal pressure is uniformly distributed over the entire lead film 14, and the strength against the internal pressure of the battery is more likely to increase.

[0089] Also, the lead film 14 can be configured in a simple linear shape. Compared with a general sealing structure, it is easier to disperse the internal pressure of the battery, the contact area increases, and the seal strength can increase.

[0090] In one embodiment of the present invention, when the lead film 14 is substantially K-shaped, a part of the lead film 14 located relatively close to the electrode assembly 12 may correspond to the first region A. Also, a part of the lead film 14 located relatively far from the direction in which the electrode assembly 12 is accommodated may correspond to the second region B. That is, among the regions where a pair of first lead films 14a having shapes inclined in opposite directions overlap with the seal portion 13b of the case, the region where fusion bonding is performed may correspond to the first region A. Further, among the regions where the second lead film 14b having a shape extending in a direction substantially parallel to the extending direction of the seal portion 13b (the left-right direction with reference to FIG. 3) overlaps with the seal portion 13b of the case, the region where fusion bonding is performed may correspond to the second region B.

[0091] The secondary battery may be a cylindrical secondary battery, a prismatic secondary battery, or a pouch-type secondary battery. Among them, the secondary battery may be a pouch-type secondary battery.

[0092] In the case of a pouch-type secondary battery, since the strength of the pouch case is weak and it has various shapes, it tends to be even weaker against internal pressure. Thus, when the secondary battery according to one embodiment of the present invention is a pouch-type secondary battery, it is considered to be more advantageous in terms of safety.

[0093] A battery pack (not shown) according to one embodiment of the present invention may include the secondary battery according to one embodiment of the present invention described above. The battery pack may include, for example, a plurality of secondary batteries. The plurality of secondary batteries may be electrically connected. The battery pack may include a pack housing (not shown) configured to accommodate the secondary battery. On the other hand, the battery pack of the present invention can be manufactured by a cell-to-pack process that does not include the step of manufacturing a battery module including the secondary battery. In contrast, the battery pack can also be manufactured by a process of first manufacturing a battery module including the secondary battery and then manufacturing a battery pack including at least one such battery module.

[0094] A device according to an embodiment of the present invention may include a battery pack according to an embodiment of the present invention. The device may be, for example, an automobile driven by the battery pack of the present invention. Or, the device may be, for example, an energy storage system (ESS) including a plurality of battery packs of the present invention.

[0095] As described above, the preferred embodiments of the present invention have been illustrated and described. However, the present invention is not limited to the specific embodiments described above, and it goes without saying that various modified embodiments are possible by those having ordinary knowledge in the technical field to which the invention pertains without departing from the gist of the invention claimed in the claims. These embodiments should not be individually understood from the technical idea and prospect of the present invention.

Explanation of Reference Numerals

[0096] 10 Secondary battery 11 Electrode lead 12 Electrode assembly 13a Accommodating portion 13b Sealing portion 14 Lead film A First region B Second region 14a First lead film 14b Second lead film

Claims

1. An electrode assembly to which an electrode lead is attached, a case for housing the electrode assembly, a seal portion formed in the case for sealing the electrode assembly, a lead film that wraps a part of the outer surface of the electrode lead and is interposed between the electrode lead and the seal portion, comprising: the lead film includes a first region configured to primarily break the interface between the lead film and the seal portion during swelling of the battery, and a second region configured to secondarily break the interface between the lead film and the seal portion during swelling of the battery, the first region and the second region are spaced apart from each other in the width direction of the seal portion, a secondary battery.

2. The first region is located relatively close to the electrode assembly, the second region is located relatively far from the electrode assembly, the secondary battery according to claim 1.

3. The first region is located at one end of the seal portion in the inner direction of the case, the secondary battery according to claim 2.

4. The second region is located at one end of the seal portion in the outer direction of the case, the secondary battery according to claim 2.

5. The lead film is fused to the case in the first region and the second region, and is not fused to the case in the region located between the first region and the second region, the secondary battery according to claim 1.

6. The distance between the first region and the second region is 20% to 80% of the width of the seal portion, the secondary battery according to claim 1.

7. The lead film a first lead film, a second lead film provided separately from the first lead film, comprising: the first region is located within a region where the first lead film and the seal portion overlap, the second region is located within a region where the second lead film and the seal portion overlap, the secondary battery according to claim 1.

8. The first lead film is located relatively close to the electrode assembly, the second lead film is located relatively far from the electrode assembly, the secondary battery according to claim 7.

9. A part of the first lead film is located at the end of the seal portion in the inner direction of the case, the secondary battery according to claim 8.

10. The secondary battery according to claim 8, wherein a part of the second lead film is located at an end of the seal portion in the outward direction of the case.

11. The secondary battery according to claim 7, wherein the first lead film and the second lead film are spaced apart from each other in the width direction of the seal portion.

12. The secondary battery according to claim 8, wherein the second lead film has a shape extending along the extending direction of the seal portion.

13. The secondary battery according to claim 8, wherein the first lead film has a shape extending along a direction forming a predetermined angle with respect to the extending direction of the second lead film.

14. The secondary battery according to claim 13, wherein the first lead film forms an angle of 15° to 60° with the second lead film.

15. The secondary battery according to claim 8, wherein the extending length of the first lead film in a direction parallel to the extending direction of the electrode lead is 10% to 80% of the width of the seal portion.

16. The secondary battery according to claim 8, wherein the extending width of the second lead film in a direction parallel to the extending direction of the electrode lead is 10% to 50% of the width of the seal portion.

17. The secondary battery according to claim 8, wherein the extending length of the first region in a direction parallel to the extending direction of the electrode lead is 10% to 50% of the width of the seal portion.

18. The secondary battery according to claim 8, wherein the extending width of the second region in a direction parallel to the extending direction of the electrode lead is 10% to 50% of the width of the seal portion.

19. A battery pack including the secondary battery according to any one of claims 1 to 18.

20. A device including the battery pack according to claim 19.

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