Battery cell and battery pack

Abstract

The invention relates to the technical field of batteries, and discloses a battery cell and a battery pack, and the battery cell comprises a pole group and a packaging film. According to the battery cell with the structure, the length between the main edge folding section and the secondary edge folding section meets # imgabs0, so that the length of the secondary edge folding section can be effectively ensured, the phenomenon that the secondary edge folding section is easy to tilt after being bent due to the fact that the length of the secondary edge folding section is too short is avoided, and enough fitting length between the secondary edge folding section and the main edge folding section after being bent is ensured; the secondary edge folding section can be effectively attached to the main edge folding section, the edge folding effect can be guaranteed, the edge folding structure is stable, and the packaging strength of the packaging film can be improved; after edge folding, all the edge folding sections of the edge folding structure are sequentially attached, the distance between the end of the edge sealing area and the internal pole group is prolonged, meanwhile, the path for external water vapor to enter the packaging film becomes more zigzag and roundabout, the external water vapor can be effectively prevented from entering the packaging film, and the packaging effect of the packaging film can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a battery cell and a battery pack. Background Art

[0002] The soft-pack battery mainly includes a pole group and a packaging film. The packaging film includes a packaging body and a sealing edge area. The packaging body wraps the pole group, and then the packaging film outside the pole group is hot-pressed to seal the pole group in the packaging film. The packaging film after hot pressing forms a sealing edge area, and the sealing edge area extends outward roughly parallel to the large surface of the battery cell. In order to reduce the space occupied by the sealing edge area in the width direction of the battery cell, the sealing edge area is folded toward the side of the battery cell to form a folded edge structure. After folding, the existing folded edge structure is prone to warping and deformation between the sections of the folded edge structure, resulting in the inability to effectively fit between the bent sections, resulting in poor folding, and affecting the packaging strength of the folded edge structure of the packaging film. Summary of the invention

[0003] In view of this, the present invention provides a battery cell and a battery pack to solve the problem in the prior art that the sections of the folded edge structure of the battery cell cannot be effectively fitted together, thus affecting the packaging strength of the folded edge structure of the packaging film.

[0004] In a first aspect, the present invention provides a battery cell, comprising:

[0005] Pole group;

[0006] The packaging film comprises a packaging body and an edge sealing area, wherein the packaging body is coated outside the electrode group, the edge sealing area is located outside the electrode group, the edge sealing area comprises an extension portion and a folding structure, the extension portion extends toward the outside of the electrode group, the folding structure comprises a main folding section and at least two secondary folding sections, one end of the main folding section is connected to an end of the extension portion away from the electrode group, and the other end is connected to the secondary folding section; the main folding section is bent toward one side in the thickness direction of the electrode group, and the secondary folding section is bent toward the inside and / or outside of the main folding section, and the folding sections of the folding structure are sequentially fitted together; the length of the main folding section is L1, and the total length of the secondary folding section is L,

[0007] Beneficial effect: In this structure of the battery cell, the length between the main folding section and the secondary folding section meets The length of the secondary folding edge section can be effectively guaranteed to avoid the secondary folding edge section being too short and causing it to easily curl up after bending, and to ensure that the secondary folding edge section has sufficient fitting length with the main folding edge section after bending. The secondary folding edge section can be effectively fitted on the main folding edge section, which can ensure the folding effect. The folding structure is stable and can improve the packaging strength of the packaging film. Since the edge sealing area contains two layers of packaging film, the two layers of packaging film are hot-pressed to form the packaging area, and water vapor may enter between the two layers of packaging film at the end of the packaging area. After folding, the folding edge sections of the folding edge structure are fitted in turn, which extends the distance between the end of the edge sealing area and the internal pole group, and at the same time makes the path for external water vapor to enter the interior of the packaging film more tortuous, which can effectively prevent external water vapor from entering the interior of the packaging film, and can effectively improve the packaging effect of the packaging film.

[0008] In an optional embodiment, the secondary folding section is bent toward the inner side of the main folding section, and the secondary folding section includes a first folding section, a second folding section and a third folding section connected in sequence, and the first folding section is spaced apart from the main folding section; one end of the first folding section is connected to the main folding section, and the other end is bent toward the extension portion, the second folding section is bent away from the extension portion and the second folding section is attached to the outer wall surface of the first folding section; the third folding section is bent toward the extension portion, the second folding section and the third folding section are located between the main folding section and the first folding section, and the inner and outer wall surfaces of the third folding section are respectively attached to the outer wall surface of the second folding section and the inner wall surface of the main folding section.

[0009] Beneficial effect: The folding structure forms four layers of folding edges, and each folding edge is sequentially attached, which improves the overall stability and strength of the folding edge structure. At the same time, each secondary folding edge segment is bent toward the inside of the main folding edge segment, which can reduce the space occupied by the secondary folding edge segment in the width direction of the battery cell and improve the compactness of the battery cell in the width direction.

[0010] In an optional embodiment, the length of the first folded edge section is L2, The end of the third folding section is spaced apart from the extension portion to form a spacing interval, and the first folding section and the second folding section are bent toward one end of the extension portion toward the main folding portion and are located in the spacing interval.

[0011] Beneficial effect: The cutting edge is located at the end of the third folding edge section, and the length of the first folding edge section is greater than that of the main folding edge section, so that the ends of the first folding edge section and the second folding edge section facing the extension portion can be bent toward the main folding edge portion and located in the interval, and the cutting edge is blocked on the inner side of the ends of the first folding edge section and the second folding edge section, which can effectively prevent the cutting edge from contacting the extension portion and damaging the extension portion, and can effectively ensure the packaging effect of the packaging film. At the same time, the bending area between the first folding edge section and the second folding edge section is located in the interval, which improves the overall compactness of the folding edge structure, effectively improves the overall strength of the folding edge structure, and thus improves the packaging strength of the packaging film.

[0012] In an optional embodiment, the length of the first folded edge section is L2,

[0013] Beneficial effect: This arrangement can ensure that the first folding edge section has sufficient length, which is convenient for bending the double-layer packaging area upward, and at the same time can ensure the fitting length between the folding edge sections after bending, and ensure the stability of the folding edge structure. This arrangement can space the ends of the first folded edge section and the second folded edge section from the extension portion, thereby preventing the packaging films from contacting each other and causing wear.

[0014] In an optional embodiment, a distance between one end of the third folded edge section facing the extension portion and the extension portion is D, and D≥1 mm.

[0015] Beneficial effect: This arrangement can separate the cutting edge at the end of the third folded edge section from the extension portion, thereby preventing the cutting edge from scratching the extension portion, thereby ensuring the packaging effect of the packaging film and improving the safety performance of the battery cell.

[0016] In an optional embodiment, the length of the third folded edge section is L3.

[0017] Beneficial effect: The length L3 of the third folding section satisfies This arrangement can ensure the length of the third folding section, ensure the fitting length between the third folding section and the adjacent folding section after folding, and prevent the folding structure from warping. It can further be ensured that the cutting edge of the third folding edge section is spaced apart from the extension portion, thereby preventing the cutting edge from damaging the extension portion.

[0018] In an optional embodiment, L3≤L2.

[0019] Beneficial effect: This arrangement can prevent the third folding section from exceeding the ends of the first folding section and the second folding section, and avoid the cutting edge of the end of the third folding section from damaging the extension portion.

[0020] In an optional embodiment, the angle between the main folding edge section and the extension portion is θ, 60°≤θ≤120°.

[0021] In an optional embodiment, the secondary folding section includes a first folding section, a second folding section and a third folding section connected in sequence, the first folding section is bent toward the extension portion and affixed to the inner wall surface of the main folding section, the second folding section is bent away from the extension portion and affixed to the inner wall surface of the first folding section; the third folding section is bent toward the extension portion and affixed to the outer wall surface of the main folding section.

[0022] In a second aspect, the present invention further provides a battery pack, comprising any one of the above-mentioned battery cells. The battery pack comprises the battery cell, has the same technical effect as the battery cell, and will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 A side view of a battery cell according to an embodiment of the present invention;

[0025] Figure 2 for Figure 1 A is a partial enlarged schematic diagram;

[0026] Figure 3 for Figure 1 A is a partial enlarged schematic diagram;

[0027] Figure 4 A schematic diagram of a folded edge structure in a battery cell according to an embodiment of the present invention;

[0028] Figure 5 A side view of another battery cell according to an embodiment of the present invention;

[0029] Figure 6 for Figure 5 A partial enlarged view of the middle B part;

[0030] Figure 7 FIG. 4 is a side view of another battery cell according to an embodiment of the present invention.

[0031] Description of reference numerals:

[0032] 1. Packaging film; 11. Packaging body; 12. Edge sealing area; 121. Extension portion; 122. Folding structure; 1221. Main folding section; 1222. Secondary folding section; 12221. First folding section; 12222. Second folding section; 12223. Third folding section. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0034] like Figure 1 , Figure 2 , Figure 3 and Figure 5 As shown, the x direction is called the width direction of the battery cell, the z direction is called the thickness direction of the battery cell, the upper part of the z direction is called the upper part of the battery cell, the lower part of the z direction is called the lower part of the battery cell, the large surface of the battery cell facing upward is its top surface, and the large surface of the battery cell facing downward is its bottom surface.

[0035] Combine the following Figures 1 to 7 , describing an embodiment of the present invention.

[0036] According to an embodiment of the present invention, on the one hand, a battery cell is provided, including an electrode group and a packaging film 1.

[0037] Among them, the packaging film 1 includes a packaging body 11 and a sealing edge area 12, the packaging body 11 is coated outside the electrode group, the sealing edge area 12 is located outside the electrode group, the sealing edge area 12 includes an extension portion 121 and a folding structure 122, the extension portion 121 extends toward the outside of the electrode group, the folding structure 122 includes a main folding section 1221 and at least two secondary folding sections 1222, one end of the main folding section 1221 is connected to one end of the extension portion 121 away from the electrode group, and the other end is connected to the secondary folding section 1222; the main folding section 1221 is bent toward one side of the electrode group thickness direction, and the secondary folding section 1222 is bent toward the inner side and / or outer side of the main folding section 1221, and each folding section of the folding structure 122 is sequentially fitted together; the length of the main folding section 1221 is L1, and the total length of the secondary folding section 1222 is L,

[0038] The length between the main folding edge section 1221 and the secondary folding edge section 1222 satisfies The length of the secondary folding edge section 1222 can be effectively guaranteed, and the secondary folding edge section 1222 can be prevented from being too short and easily curling up after bending, so as to ensure that the secondary folding edge section 1222 has sufficient fitting length with the main folding edge section 1221 after bending, and the secondary folding edge section 1222 can be effectively fitted on the main folding edge section 1221, so as to ensure the folding effect, and the folding structure 122 is stable, which can improve the packaging strength of the packaging film 1; since the edge sealing area 12 contains two layers of packaging film 1, the two layers of packaging film 1 are hot-pressed to form the packaging area, and water vapor may enter between the two layers of packaging film 1 at the end of the packaging area, after the folding, the folding edge sections of the folding edge structure 122 are fitted in sequence, which extends the distance between the end of the edge sealing area 12 and the internal pole group, and at the same time makes the path for external water vapor to enter the interior of the packaging film 1 more tortuous, which can effectively prevent external water vapor from entering the interior of the packaging film 1, and can effectively improve the packaging effect of the packaging film 1.

[0039] like Figures 1 to 4 As shown, the secondary folding section 1222 is bent toward the inner side of the main folding section 1221, and the secondary folding section 1222 includes a first folding section 12221, a second folding section 12222 and a third folding section 12223 connected in sequence, and the first folding section 12221 is spaced apart from the main folding section 1221; one end of the first folding section 12221 is connected to the main folding section 1221, and the other end is bent toward the extension portion, and the second folding section 12222 is back to the extension portion. The extension portion is bent and the second folding edge section 12222 is attached to the outer wall surface of the first folding edge section 12221; the third folding edge section 12223 is bent toward the extension portion, the second folding edge section 12222 and the third folding edge section 12223 are located between the main folding edge section 1221 and the first folding edge section 12221, and the inner and outer wall surfaces of the third folding edge section 12223 are respectively attached to the outer wall surface of the second folding edge section 12222 and the inner wall surface of the main folding edge section 1221. The folding edge structure 122 forms four layers of folding edges, and each folding edge is attached in sequence, which improves the overall stability and strength of the folding edge structure 122. At the same time, each secondary folding edge section 1222 is bent toward the inner side of the main folding edge section 1221, which can reduce the space occupied by the secondary folding edge section 1222 in the width direction of the battery cell and improve the compactness in the width direction of the battery cell.

[0040] In some embodiments, Figures 1 to 3 As shown, the length L1 of the main folding section 1221 is greater than the total length L of the secondary folding section 1222. This arrangement can separate the end of the secondary folding section 1222 facing the extension portion 121 from the extension portion 121 to avoid contact and wear between the two. For example, in some embodiments, Such an arrangement can ensure that the end of the secondary folding edge section 1222 facing the extending portion 121 is sufficiently spaced apart from the extending portion 121 to avoid contact wear.

[0041] In other embodiments, Figure 4As shown, the length L1 of the main folding section 1221 is smaller than the total length L of the secondary folding section 1222. At this time, the length of the third folding section 12223 is smaller than the length of the main folding section 1221, so as to form an accommodating space between the third folding section 12223 and the extension portion 121. The portion of the secondary folding section 1222 that exceeds the main folding section 1221 is bent toward the accommodating space, and the side of the secondary folding section 1222 facing the extension portion 121 abuts against the extension portion 121, and the end of the secondary folding section 1222 facing the main folding section 1221 abuts against the inner wall surface of the main folding section 1221, thereby forming a compact and stable folding structure 122, which can prevent the folding structure 122 from collapsing and can improve the packaging strength of the packaging film 1.

[0042] In some embodiments, Figure 4 As shown, the length of the first folding edge section 12221 is L2. The end of the third folding edge section 12223 is spaced from the extension portion 121 to form a spacing interval, and the first folding edge section 12221 and the second folding edge section 12222 are bent toward the main folding edge section at one end of the extension portion 121 and are located in the spacing interval. Since the outer edge of the edge sealing area 12 is a cutting edge, the cutting edge has a sharp structure, and the cutting edge is easy to damage the packaging film 1 after contacting the packaging film 1. In the battery cell of this structure, the cutting edge is located at the end of the third folding edge section 12223, and the length of the first folding edge section 12221 is greater than the length of the main folding edge section 1221, so that the first folding edge section 12221 and the second folding edge section 12222 at one end of the extension portion 121 can be bent toward the main folding edge section and located in the spacing interval, and the cutting edge is blocked on the inner side of the end of the first folding edge section 12221 and the second folding edge section 12222, which can effectively prevent the cutting edge from contacting the extension portion 121 and damaging the extension portion 121, and can effectively ensure the packaging effect of the packaging film 1. At the same time, the bending area between the first folding section 12221 and the second folding section 12222 is located in the spacing interval, which improves the overall compactness of the folding structure 122 and effectively improves the overall strength of the folding structure 122, thereby improving the packaging strength of the packaging film 1.

[0043] In some embodiments, Figure 2 As shown, the length of the first folding edge section 12221 is L2. When the folded edge structure 122 is bent, the whole edge sealing area 12 is roughly horizontally extended with the large surface of the battery cell. The edge sealing area 12 is first bent upward to form a double-layer packaging area with two layers of mutual adhesion, and then the middle area of ​​the double-layer packaging area is bent upward to form a four-layer structure. Finally, the single-layer extension part 121 inside the four-layer structure is vertically bent upward to form a four-layer folded edge structure 122. Figure 2The x-direction is called the thickness direction of the folding structure 122. If the length of the first folding section 12221 is too short, it is inconvenient to bend the double-layer packaging area upward from the middle. At the same time, the first folding section 12221 and the second folding section are also prone to deformation and warping after bending. The length of the first folding section 12221 is too short. Along the thickness direction of the battery cell, the thickness of the folding structure 122 in the areas of the first folding section 12221, the second folding section 12222 and the third folding section 12223 is relatively thick. Only the thickness of the folding structure 122 at the main folding section 1221 is thin, resulting in the folding structure 122 being thick on the top and thin on the bottom. The first folding section 12221, the second folding section 12222 and the third folding section 12223 are prone to collapse downward, affecting the flatness of the side of the folding structure 122. In order to avoid this problem, the length of the first folding section 12221 of the present application is L2, which satisfies This arrangement can ensure that the first folding edge section 12221 has sufficient length to facilitate the upward bending of the double-layer packaging area, and at the same time can ensure the fitting length between the folding edge sections after bending, thereby ensuring the stability of the folding edge structure 122. This arrangement can separate the ends of the first folding section 12221 and the second folding section 12222 from the extending portion 121 , thereby preventing the packaging films 1 from contacting each other and causing wear.

[0044] In some embodiments, Figure 2 As shown, the distance between one end of the third folded edge section 12223 facing the extension portion 121 and the extension portion 121 is D, and D≥1mm. This arrangement can separate the cutting edge at the end of the third folded edge section 12223 from the extension portion 121, thereby preventing the cutting edge from scratching the extension portion 121, thereby ensuring the packaging effect of the packaging film 1 and improving the safety performance of the battery cell.

[0045] In some embodiments, Figure 2 As shown, the length of the third folding edge section 12223 is L3. If the length of the third folding edge section 12223 is too short, after being bent, the length of the third folding edge section 12223 that is attached to the main folding edge section 1221 and the second folding edge section is insufficient, causing the folding edge structure 122 to easily warp, thereby affecting the packaging strength of the edge sealing area 12 of the packaging film 1. In order to avoid this problem, the length L3 of the third folding edge section 12223 of the present structure satisfies This arrangement can ensure the length of the third folding edge section 12223, ensure the fitting length between the third folding edge section 12223 and the adjacent folding edge section after folding, and prevent the folding edge structure 122 from tilting. It can further ensure that the cutting edge of the third folding edge section 12223 is spaced apart from the extending portion 121 to prevent the cutting edge from damaging the extending portion 121 .

[0046] In some embodiments, Figure 2As shown, L3≤L2, that is, the length of the third folding section 12223 is less than or equal to the length of the first folding section 12221. This arrangement can prevent the third folding section 12223 from exceeding the ends of the first folding section 12221 and the second folding section 12222, thereby preventing the cutting edge at the end of the third folding section 12223 from damaging the extension portion 121.

[0047] In some embodiments, the angle between the main folding section 1221 and the extension portion 121 is θ, 60°≤θ≤120°. The angle between the main folding section 1221 and the extension portion 121 is moderate, which can prevent the folding structure 122 from tilting too much inward or outward along the width direction of the battery cell and occupying too much space.

[0048] For example, in some embodiments, the main folding section 1221 is arranged perpendicular to the extension portion 121. Such an arrangement can further reduce the space occupied by the folding structure 122 in the width direction of the battery cell, improve the compactness of the overall structure of the battery cell, and improve the volume energy density of the battery cell.

[0049] like Figure 2 As shown, in some embodiments, the edge sealing area 12 is arranged on one side in the thickness direction of the battery cell, and the folded edge structure 122 is bent upward. The total thickness of the battery cell is H, and the length of the folded edge structure 122 is less than H. This arrangement can prevent the top of the folded edge structure 122 from exceeding the top surface of the battery cell, which can improve the space utilization and volume energy density of the battery cell.

[0050] In other embodiments, Figure 7 As shown, the edge sealing area 12 is arranged in the middle area in the thickness direction of the electrode group, and the folded edge structure 122 is bent toward the top or bottom of the battery cell.

[0051] like Figure 5 and Figure 6 As shown, the secondary folding section 1222 includes a first folding section 12221, a second folding section 12222 and a third folding section 12223 which are connected in sequence. The first folding section 12221 is bent toward the extension portion and adheres to the inner wall surface of the main folding section 1221, and the second folding section 12222 is bent away from the extension portion and adheres to the inner wall surface of the first folding section; the third folding section is bent toward the extension portion and adheres to the outer wall surface of the main folding section 1221, that is, the first folding section 12221 and the second folding section 12222 are arranged on the inner side of the main folding section 1221, and the third folding section 12223 is arranged on the outer side of the main folding section 1221. This arrangement makes the third folding section 12223 away from the side of the packaging body 11, which can effectively prevent the cutting edge from damaging the side of the packaging body 11 when the third folding section 12223 is deformed and warped, thereby ensuring the integrity of the packaging film 1 and the sealing protection effect of the packaging film 1.

[0052] According to an embodiment of the present invention, on the other hand, a battery pack is provided, comprising the above-mentioned battery cell.

[0053] The length between the main folding edge section 1221 and the secondary folding edge section 1222 satisfies The length of the secondary folding edge section 1222 can be effectively guaranteed to avoid the secondary folding edge section 1222 being too short and causing it to easily curl up after bending, and ensure that the secondary folding edge section 1222 can be effectively bonded to the main folding edge section 1221 after bending, so as to ensure the folding effect. The folding edge structure 122 is stable, which can improve the packaging strength of the packaging film 1, thereby facilitating improving the overall strength of the battery cell and the battery pack; after folding, the folding edge sections of the folding edge structure 122 are bonded in sequence, which extends the distance between the end of the edge sealing area 12 and the internal pole group, and at the same time makes the path for external water vapor to enter the interior of the packaging film 1 more tortuous, which can effectively prevent external water vapor from entering the interior of the packaging film 1, and can improve the safety performance of the battery cell and the battery pack.

[0054] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A battery cell, characterized in that: include: Pole group; The packaging film comprises a packaging body and an edge sealing area, wherein the packaging body is coated outside the electrode group, the edge sealing area is located outside the electrode group, the edge sealing area comprises an extension portion and a folding structure, the extension portion extends toward the outside of the electrode group, the folding structure comprises a main folding section and at least two secondary folding sections, one end of the main folding section is connected to an end of the extension portion away from the electrode group, and the other end is connected to the secondary folding section; the main folding section is bent toward one side in the thickness direction of the electrode group, and the secondary folding section is bent toward the inside and / or outside of the main folding section, and the folding sections of the folding structure are sequentially fitted together; the length of the main folding section is L1, and the total length of the secondary folding section is L, 2. The battery cell according to claim 1, characterized in that: The secondary folding section is bent toward the inner side of the main folding section, and the secondary folding section includes a first folding section, a second folding section and a third folding section connected in sequence, and the first folding section is arranged at an interval with the main folding section; one end of the first folding section is connected to the main folding section, and the other end is bent toward the extension portion, the second folding section is bent away from the extension portion and the second folding section is attached to the outer wall surface of the first folding section; the third folding section is bent toward the extension portion, the second folding section and the third folding section are located between the main folding section and the first folding section, and the inner and outer wall surfaces of the third folding section are respectively attached to the outer wall surface of the second folding section and the inner wall surface of the main folding section.

3. The battery cell according to claim 2, characterized in that: The length of the first folded edge section is The end of the third folding section is spaced apart from the extension portion to form a spacing interval, and the first folding section and the second folding section are bent toward one end of the extension portion toward the main folding portion and are located in the spacing interval.

4. The battery cell according to claim 2, characterized in that: The length of the first folded edge section is L2, 5. The battery cell according to claim 4, characterized in that: A distance between one end of the third folded edge section facing the extending portion and the extending portion is D, where D≥1 mm.

6. The battery cell according to claim 2, 4 or 5, characterized in that: The length of the third folding edge section is L3, 7. The battery cell according to claim 6, characterized in that: L3≤L2.

8. The battery cell according to any one of claims 1 to 5, characterized in that: The included angle between the main folding edge section and the extension portion is θ, 60°≤θ≤120°.

9. The battery cell according to any one of claims 1 to 5, characterized in that: The secondary folding section includes a first folding section, a second folding section and a third folding section connected in sequence, the first folding section is bent toward the extension portion and affixed to the inner wall surface of the main folding section, the second folding section is bent away from the extension portion and affixed to the inner wall surface of the first folding section; the third folding section is bent toward the extension portion and affixed to the outer wall surface of the main folding section.

10. A battery pack, characterized in that: A battery cell comprising the battery cell according to any one of claims 1 to 9.

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