Electrode sheet, electrode assembly and battery

Abstract

An electrode sheet (300), an electrode assembly and a battery. The electrode sheet (300) comprises a first surface perpendicular to the thickness direction of the electrode sheet (300), wherein the first surface comprises a bump region (310), and a plurality of protrusions (311) are formed in the bump region (310); there is a spacing between the bump region (310) and an edge of the first surface; and the area of the bump region (310) is Y, the projected area of the first surface in the thickness direction of the electrode sheet (300) is E, and Y and E satisfy: 0.1≤Y / E≤0.98. The setting of an appropriate area proportion of the plurality of first protrusions (311) is facilitated; the first protrusions (311) can provide effective support for a separator (50), such that the plurality of first protrusions (311) can effectively buffer a winding stress during a winding process of the electrode assembly and an expansion force for expansion of the electrode assembly, thereby improving the electrolytic-solution infiltration effect of the electrode assembly and ameliorating the interface problem of an electrode; and when applied to a battery, the electrode sheet (300) can improve the cycling performance of the battery.

Description

Pole piece, electrode assembly and battery

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the China Patent Office on January 26, 2024, with application number 202410111591.3 and invention name “A pole piece, electrode assembly and battery”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the technical field of chemical devices, and in particular to a pole piece, an electrode assembly and a battery. Background Art

[0004] Cycle life is a key performance of lithium-ion batteries. Improving cycle life is a long-term and continuous research and development direction. In addition to improving the battery material end through optimization and innovation, its cycle life can also be effectively promoted through structural design and improvement. This also places more design requirements on the winding method of the electrode assembly of the battery cell. Summary of the Invention

[0005] The inventors discovered that compression occurs between the layers of the electrode assembly, including between corners and straight sections. This compression is exacerbated during battery charging and discharging, as the electrode assembly expands. This can lead to insufficient electrolyte between the layers, poor wetting, and potentially deteriorating interfaces, leading to poor wetting and cycle failure.

[0006] The embodiments of the present application provide a pole piece, an electrode assembly, and a battery, which can improve the extrusion problem between layers of the electrode assembly.

[0007] In a first aspect, an embodiment of the present application provides a pole piece for a battery, wherein the pole piece includes a first surface perpendicular to a thickness direction of the pole piece, the first surface includes a convex region, and the convex region is formed with a plurality of first convex portions;

[0008] There is a distance between the convex area and the edge of the first surface, the area of ​​the convex area is Y, the projected area of ​​the first surface in the direction perpendicular to the thickness of the pole piece is E, and E and Y satisfy: 0.1≤Y / E≤0.98, preferably, 0.3≤Y / E≤0.9; more preferably, 0.5≤Y / E≤0.9.

[0009] In some exemplary embodiments, the first surface includes an end avoidance area and an edge avoidance area, the end avoidance area is connected to the end of the convex area in the length direction of the pole piece and extends to the edge of the pole piece, and the edge avoidance area is arranged on one side of the convex area in the width direction of the pole piece and extends to the edge of the pole piece.

[0010] In some exemplary embodiments, the pole piece includes a first edge and a second edge oppositely disposed in the length direction of the pole piece, and the convex area includes a first boundary and a second boundary oppositely disposed in the length direction of the pole piece, wherein the first boundary corresponds to the first edge and the second boundary corresponds to the second edge;

[0011] The end avoidance area includes a head avoidance area and a tail avoidance area. The head avoidance area is formed between the first edge and the first boundary, and the tail avoidance area is formed between the second edge and the second boundary. The electrode piece is used to be wound from the head avoidance area and the isolation membrane along the length direction of the electrode piece to form a flat electrode body.

[0012] In some exemplary embodiments, the area of ​​the head air avoidance zone is A, the area of ​​the tail air avoidance zone is D, and the pole piece satisfies at least one of the following conditions:

[0013] (1) 0≤A / E≤0.3, preferably, 0≤A≤0.1E;

[0014] (2)0.06≤D / E≤0.6.

[0015] In some exemplary embodiments, the pole piece includes a third edge and a fourth edge disposed opposite to each other in the width direction of the pole piece, and the convex area includes a third boundary and a fourth boundary disposed opposite to each other in the width direction of the pole piece, the third boundary corresponds to the third edge, and the fourth boundary corresponds to the fourth edge;

[0016] The edge avoidance zone includes a first zone and a second zone, the first zone is formed between the third boundary and the third edge, the second zone is formed between the fourth boundary and the fourth edge, and the first zone and the second zone extend in the length direction of the pole piece to connect to the end avoidance zone.

[0017] In some exemplary embodiments, the area of ​​the first region is S1, and the size of the first region in the width direction of the pole piece is T11; the area of ​​the second region is S2, and the size of the first region in the width direction of the pole piece is T12; the pole piece satisfies at least one of the following conditions:

[0018] Ⅰ, 0.01≤S1 / E≤0.4;

[0019] Ⅱ, 0.01≤S2 / E≤0.4;

[0020] III, 0.9≤S2 / S1≤1.1;

[0021] IV, 1mm≤T11≤30mm;

[0022] Ⅴ, 1mm≤T12≤30mm.

[0023] In some exemplary embodiments, the convex region has a third boundary and a fourth boundary arranged opposite to each other in the width direction of the pole piece;

[0024] The first surface also includes a tab area, which extends from the third boundary toward the side where the fourth boundary is located. The tab area is used to set at least one tab component, and the tab component includes at least one of a tab and a protective glue, and the tab component is spaced apart from the bump area; the spacing setting in this application means that there is a distance.

[0025] The number of the tab regions of the same pole piece is at least one, and the area of ​​each tab region is M, where M satisfies: 0.01≤M / E≤0.2.

[0026] In some exemplary embodiments, the same pole piece has a plurality of tab regions, wherein the tab region includes a tab installation region and a protective glue installation region, the tab installation region is used to set the tab, and the protective glue installation region is used to set the protective glue; the area of ​​the tab installation region is B, and the area of ​​the protective glue installation region is C; the pole piece satisfies at least one of the following conditions:

[0027] a. 0.01≤B / E≤0.2;

[0028] b. 0.01≤C / E≤0.2.

[0029] In some exemplary embodiments, the tab region is spaced apart from the fourth boundary; or, the tab region extends from the third boundary through the convex region along the width direction of the pole piece.

[0030] In some exemplary embodiments, the electrode sheet is used to be wound multiple times with the isolation film along the length direction of the electrode sheet to form an electrode body; each turn of the electrode sheet includes a straight section and corner sections provided at both ends of the straight section; in the length direction of the electrode sheet, the size of the corner section is W5, and the size of the convex area is W6;

[0031] The convex point area is provided at the corner section, wherein W6=W5; or

[0032] The convex point area is arranged at the corner section and extends to the straight section, and the two convex point areas of the same circle of the pole pieces are arranged at intervals, wherein W6>W5.

[0033] In some exemplary embodiments, the electrode sheet includes a current collector and an active material layer; the current collector includes a main body and a hollow foil portion, the hollow foil portion is integrally arranged with the main body, and the hollow foil portion forms a plurality of electrode tabs, the active material layer is arranged on the surface of the main body, and the surface of the active material layer facing away from the main body forms the first surface.

[0034] In some exemplary embodiments, the electrode sheet includes a current collector and an active material layer, wherein the active material layer is disposed on a surface of the current collector; the first protrusion is formed by bending a portion of the current collector and a portion of the active material layer toward the same side; the portion of the current collector used to form the first protrusion is a protrusion base, and the protrusion base has a first peripheral edge line, and the first peripheral edge line has a first circumscribed circle;

[0035] Two adjacent convex bases have a first spacing L1 and a second spacing L2, the first spacing L1 being the spacing between the centers of the first circumscribed circles of the first peripheral edge lines of the two adjacent convex bases in the length direction of the pole piece, and the second spacing L2 being the spacing between the centers of the first circumscribed circles of the first peripheral edge lines of the two adjacent convex bases in the width direction of the pole piece;

[0036] L1 satisfies: 0.5 mm ≤ L1 ≤ 40 mm; and / or, L2 satisfies: 0.5 mm ≤ L2 ≤ 40 mm.

[0037] In a second aspect, an embodiment of the present application provides an electrode assembly comprising a plurality of tab assemblies, the pole pieces as described above, and an isolation membrane disposed between the two pole pieces, wherein the isolation membrane and the two pole pieces are wound along the length direction of the pole pieces to form a flat electrode body.

[0038] In some exemplary embodiments, the tab assembly is spaced apart from the convex area; the tab assembly includes a tab and a protective glue, the tab includes a connecting section connected to the pole piece and a docking section extending out of the edge of the pole piece, and a plurality of second protrusions are protruding from the surface of the connecting section facing away from the pole piece.

[0039] In a third aspect, an embodiment of the present application provides a battery, comprising a housing and the electrode assembly as described above, wherein the electrode assembly is disposed in an internal space of the housing.

[0040] Based on the electrode pieces, electrode assemblies and batteries of the embodiments of the present application, by setting the proportion of the convex area on the first surface in the range of 0.1 to 0.98, it is convenient to set the area proportion of multiple first convex portions to be appropriate. The first convex portions can provide effective support for the isolation membrane, so that the multiple first convex portions can effectively buffer the winding stress during the winding process of the electrode assembly and the expansion force of the electrode assembly, improve the electrolyte wetting effect of the electrode assembly, and improve the interface problem of the electrode, and can improve the cycle performance of the battery when the electrode piece is used in the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0042] FIG1 is a schematic diagram of an expanded structure of a tab assembly installed on a pole piece in a first region according to an embodiment of the present application;

[0043] FIG2 is a schematic diagram of the winding structure of an electrode body according to an embodiment of the present application;

[0044] FIG3 is a schematic structural diagram of an embodiment of the present application in which the tab region and the fourth boundary are spaced apart;

[0045] FIG4 is a schematic structural diagram of a pole piece in which a tab region extends through a convex region according to an embodiment of the present application;

[0046] FIG5 is a schematic diagram of the expanded structure of a pole piece with a convex point area located at a corner section according to an embodiment of the present application;

[0047] FIG6 is a schematic diagram of the expanded structure of a pole piece with gradually increasing width of a convex region according to an embodiment of the present application;

[0048] FIG7 is a schematic structural diagram of a first convex portion of a convex region according to an embodiment of the present application, wherein the size of the first convex portion gradually decreases from the central region to the edge region;

[0049] FIG8 is a schematic diagram of a partial cross-sectional structure of a pole piece according to an embodiment of the present application;

[0050] FIG9 is a schematic diagram of the unfolded structure of the electrode when the coating portion and the hollow foil portion of the current collector are integrally arranged in one embodiment of the present application;

[0051] FIG10 is a schematic structural diagram of a tab assembly installed on a pole piece and having a second protrusion according to an embodiment of the present application.

[0052] Reference numerals: 20, electrode body; 21, straight section; 22, corner section; 100, tab; 110, second convex portion; 200, protective adhesive; 40, tab assembly; 50, separator; 300, pole piece; 310, bump area; 311, first convex portion; 312, main body; 320, tab area; 321, tab mounting area; 322, protective adhesive mounting area; 330, end avoidance area; 3201, first side boundary; 3202, second side boundary; 3203, bottom boundary; 3204, third side boundary; 3205, fourth side boundary; 331, head avoidance area; 332, tail avoidance area; 410, positive electrode piece; 420, negative electrode piece; 3411, first edge; 3421, second edge; 3431, third edge; 3441, fourth edge; 301, bump boundary line; 3101, first boundary; 3102, second boundary; 3103, third boundary; 3104, fourth boundary; 500, current collector; 510, coating portion; 520, hollow foil portion; 340, edge avoidance area; 341, first region; 342, second region; X, length direction; Y, width direction; Z, thickness direction. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0054] The inventors found that during the battery charging and discharging process, the electrode assembly expands and the extrusion of the corner section of the electrode assembly will be further aggravated, resulting in insufficient electrolyte in the corner section, poor infiltration, and easy interface deterioration, and even cycle failure.

[0055] The inventors also discovered that in the process of processing the electrode assembly, the positive electrode sheet, the isolation membrane and the negative electrode sheet are stacked and wound in sequence for multiple turns to form an electrode body with multiple winding units. By increasing the spacing between two adjacent winding units and providing a protrusion on the electrode sheet to support the two adjacent winding units, the extrusion problem caused by the expansion of the electrode assembly can be improved. However, if the position of the protrusion is not set properly and the supporting force of the protrusion is insufficient, there will still be negative problems such as electrode sheet interface problems and insufficient electrolyte, and the improvement effect is still poor.

[0056] Based on this, the embodiments of the present application provide a pole piece, an electrode assembly, and a battery, which are designed with a convex distribution to effectively improve electrolytic wetting and pole piece interface problems.

[0057] As shown in FIG1 , a schematic diagram of the front view of the electrode sheet 300 in an embodiment of the present application is shown in an unfolded state. The electrode sheet 300 has a length direction X, a width direction Y, and a thickness direction Z that are perpendicular to each other. The electrode sheet 300 is used in an electrode assembly. As shown in FIG2 , a schematic diagram of the structure of an electrode assembly in an embodiment of the present application is shown. The electrode assembly includes two electrode sheets 300 of opposite polarity and a separator 50. The length directions X, width directions Y, and thickness directions Z of the two electrode sheets 300 of opposite polarity are consistent. The separator 50 is provided between the two electrode sheets 300 of opposite polarity in the thickness direction Z of the electrode sheets 300. One of the two electrode sheets 300 of opposite polarity is a positive electrode sheet 410, and the other is a negative electrode sheet 420. The separator 50 has insulating properties and is used to separate the positive electrode sheet 410 from the negative electrode sheet 420 to prevent the positive electrode sheet 410 and the negative electrode sheet 420 from short-circuiting.

[0058] The separator 50 and the two electrode pieces 300 are wound multiple times along the length direction X of the electrode piece 300 to form the electrode body 20. The length direction X of the electrode piece is the direction in which the electrode piece is wound, and the width direction Y is perpendicular to the length direction X. The electrode body 20 is flat, and each turn of the electrode piece 300 includes two straight sections 21 and two corner sections 22. The two straight sections 21 are arranged opposite each other in a direction perpendicular to the plate surface of the straight sections 21. The two straight sections 21 are arranged between the two corner sections 22 in a direction parallel to the plate surface of the straight sections 21. The two straight sections 21 and the two corner sections 22 are connected end to end in sequence. Among them, the corner sections 22 of two adjacent circles of electrode pieces 300 are prone to mutual extrusion, and the straight section 21 and the corner section 22 of each circle of electrode pieces 300 are also squeezed. Therefore, the corner section 22 is a high-incidence area for extrusion of the electrode body 20. When the corner section 22 is squeezed, it is easy to have problems such as insufficient electrolyte and poor infiltration, which in turn leads to deterioration of the interface of the corner section 22 and even cycle failure.

[0059] The pole piece 300 includes a first surface perpendicular to the thickness direction Z of the pole piece 300. As shown in FIG1 , the first surface includes a convex region 310. The convex region 310 is formed with a plurality of first protrusions 311. There is a gap between the convex region 310 and the edge of the first surface. Each first protrusion 311 protrudes in the thickness direction Z of the pole piece 300. After the two pole pieces 300 and the isolation membrane 50 are wound multiple times to form the electrode body 20, the first protrusion 311 contacts the isolation membrane 50 to provide support for the isolation membrane 50. When the electrode body 20 expands, the first protrusion 311 can still support the isolation membrane 50. The contact area between the first protrusion 311 and the isolation membrane 50 is small, so that there is space between the portion of the pole piece 300 corresponding to the convex region 310 and the isolation membrane 50 to accommodate electrolyte, thereby preventing abnormal conditions such as insufficient electrolyte and poor wetting between the pole piece 300 and the isolation membrane 50 due to expansion and squeezing.

[0060] Both the straight section 21 and the corner section 22 have a first protrusion 311 to support the isolation membrane 50 corresponding to the straight section 21 and the corner section 22. Optionally, all the first protrusions 311 provided on a single pole piece 300 protrude toward the same side of the pole piece 300 in the thickness direction Z of the pole piece 300. For example, the first protrusion 311 provided on the straight section 21 protrudes toward the side of the winding center of the electrode body 20, and the first protrusion 311 provided on the corner section 22 protrudes toward the side where the winding center of the electrode body 20 is located; or, the first protrusion 311 provided on the straight section 21 protrudes toward the side away from the winding center of the electrode body 20, and the first protrusion 311 provided on the corner section 22 protrudes toward the side away from the winding center of the electrode body 20. Optionally, a portion of the first protrusion 311 provided on a single pole piece 300 protrudes toward one side of the pole piece 300 in the thickness direction Z of the pole piece 300, and another portion of the first protrusion 311 protrudes toward the other side of the pole piece 300 in the thickness direction Z of the pole piece 300. For example, the first protrusion 311 provided on the straight section 21 protrudes toward one side of the winding center of the electrode body 20, and the first protrusion 311 provided on the corner section 22 protrudes toward the side away from the winding center of the electrode body 20; or, the first protrusion 311 provided on the straight section 21 protrudes toward the side away from the winding center of the electrode body 20, and the first protrusion 311 provided on the corner section 22 protrudes toward the side of the winding center of the electrode body 20.

[0061] The above is merely an exemplary introduction. This application does not limit the orientation of the first protrusion 311 of each pole piece 300 , and the orientation can be selected according to actual needs.

[0062] As shown in Figure 1, the convex region 310 is defined by the convex boundary line 301. The first convex portion 311 of the convex region 310 may be located in the inner region defined by the convex boundary line 301, and the first convex portion 311 may also be inscribed in the convex boundary line 301. The area of ​​the convex region 310 is Y, and the projected area of ​​the first surface perpendicular to the thickness direction Z of the pole piece 300 is E. E and Y satisfy: 0.1≤Y / E≤0.98. For example, Y / E may be 0.1, 0.3, 0.4, 0.5, 0.6, 0.8, 0.98, or a range consisting of any two thereof. By setting the proportion of the convex area 310 on the first surface to be in the range of 0.1 to 0.98, it is convenient to set the area proportion of the multiple first protrusions 311 to be appropriate. The first protrusions 311 can provide effective support for the isolation membrane 50, so that the multiple first protrusions 311 can effectively buffer the winding stress of the electrode assembly during the winding process and the expansion force of the electrode assembly, improve the electrolyte infiltration effect of the electrode assembly, and improve the interface problem of the electrode piece 300, and can improve the cycle performance of the battery when the electrode piece 300 is used in the battery.

[0063] Preferably, E and Y satisfy: 0.3≤Y / E≤0.9. Within this region, the pole piece 300 is applied to the battery to achieve a better improvement in the cycle performance of the battery.

[0064] As shown in FIG1 , the first surface includes an end avoidance region 330 and an edge avoidance region 340 . The end avoidance region 330 is connected to the end of the convex region 310 in the length direction X of the pole piece 300 and extends to the edge of the pole piece 300 . The edge avoidance region 340 is provided on one side of the convex region 310 in the width direction Y of the pole piece 300 and extends to the edge of the pole piece 300 . Neither the edge avoidance region 340 nor the end avoidance region 330 is provided with the first protrusion 311 . After the two pole pieces 300 and the isolation film 50 are wound, the surfaces of the pole piece 300 corresponding to the edge avoidance region 340 and the end avoidance region 330 can be spaced apart from the isolation film 50 .

[0065] The end clearance area 330 is provided at the end of the convex area 310 in the length direction X of the pole piece 300 and extends to the edge of the pole piece 300, and the end clearance area 330 also extends to the edge of the pole piece 300 in the width direction Y of the pole piece 300. As shown in Figure 1, the end clearance area 330 includes at least one of a head clearance area 331 and a tail clearance area 332. Preferably, the end clearance area 330 includes both the head clearance area 331 and the tail clearance area 332. In the length direction X of the pole piece 300, the head clearance area 331 is provided at one end of the convex area 310, and the tail clearance area 332 is provided at the other end of the convex area 310.

[0066] After the two pole pieces 300 and the isolation film 50 are wound, the head air avoidance area 331 can be located in the innermost turns of the electrode body 20, which is convenient for the winding and forming of the electrode body 20 and helps to improve the structural stability of the central area of ​​the electrode body 20. The tail air avoidance area 332 can be located in the outermost turns of the electrode body 20. The tail air avoidance area 332 can serve as a buffer area between the first protrusion 311 and the tail end of the electrode body 20, so that the part of the pole piece 300 corresponding to the end air avoidance area 330 can more smoothly form a constraint on the inner layer structure of the electrode body 20, which helps to improve the packaging stability of the electrode body 20. Especially when the electrode body 20 has a tendency to expand, the tail air avoidance area 332 without the first protrusion 311 is used for tailing, which can prevent the tail of the electrode body 20 from slipping due to expansion stress and improve the structural stability of the electrode body 20.

[0067] Specifically, the first surface of the pole piece 300 includes a first edge 3411 and a second edge 3421 arranged opposite to each other in the length direction X of the pole piece 300, and the convex area 310 includes a first boundary 3101 and a second boundary 3102 arranged opposite to each other in the length direction X of the pole piece 300, the first boundary 3101 corresponds to the first edge 3411, and the second boundary 3102 corresponds to the second edge 3421. The head space avoidance area 331 is formed between the first edge 3411 and the first boundary 3101, and the tail space avoidance area 332 is formed between the second edge 3421 and the second boundary 3102. One end of the isolation membrane 50 is flush with the head space avoidance area 331 or extends out of the head space avoidance area 331 to be clamped between two pole pieces 300 with opposite polarity. The pole piece 300 is wound along the length direction X of the pole piece 300 from the head space avoidance area 331 and the isolation membrane 50 to form a flat electrode body 20, that is, the head space avoidance area 331 is in the inner circle of the electrode body 20, and the tail space avoidance area 332 is in the outer circle of the electrode body 20. The other end of the isolation membrane 50 extends out of the tail space avoidance area 332 in the winding direction of the pole piece 300 to prevent the isolation membrane 50 from shrinking and causing the two pole pieces 300 with opposite polarity to short-circuit.

[0068] The area of ​​the tail clearance zone 332 is D, where D and E satisfy the following: 0.06 ≤ D / E ≤ 0.6. For example, D / E can be 0.06, 0.1, 0.2, 0.3, 0.5, 0.6, or any two thereof. Setting D / E within the range of 0.06 to 0.6 improves the connection stability at the tail of the electrode body 20, providing the entire electrode body 20 with good winding stability, thereby improving the ability of the entire electrode body 20 to buffer expansion stress.

[0069] In the winding direction of the electrode sheet 300, the distance between the second boundary 3102 and the second edge 3421 is d', that is, the width of the tail clearance zone 332 is d', and d' satisfies the following: 30mm≤d'≤1000mm. For example, d' can be 30mm, 50mm, 100mm, 150mm, 300mm, 500mm, 1000mm, or a range consisting of any two thereof. When the dimension d' of the tail clearance zone 332 is within the range of 30mm to 1000mm, the tail clearance zone 332 has an appropriate length for the tail, improving the connection stability at the tail of the electrode body 20, thereby ensuring good winding stability for the entire electrode assembly. It also ensures that the first protrusions 311 adjacent to the outer ring are distributed over an appropriate range, providing support for the separator 50 located on the outer ring and improving the extrusion problem of the outer ring of the electrode body 20. Preferably, d' satisfies the following: 100mm≤d'≤500mm.

[0070] The area of ​​the head clearance region 331 is A, and A and E satisfy the relationship: 0 ≤ A / E ≤ 0.3. For example, A / E can be 0, 0.1, 0.15, 0.20, 0.25, 0.3, or a range consisting of any two thereof. Setting A / E within the range of 0 to 0.3 facilitates alignment of the end of the electrode piece 300 with the separator 50, thereby facilitating winding of the electrode piece 300 and the separator 50 starting from the head clearance region 331. This improves the winding yield of the electrode body 20, and the first protrusion 311 can play a supporting role on the inner layer of the electrode body 20, thereby improving the electrolyte infiltration effect of the inner circle of the electrode body 20.

[0071] In the winding direction of the electrode 300, the distance between the first boundary 3101 and the first edge 3411 is a', that is, the width of the head clearance area 331 is a'. a' satisfies the following: 30mm≤a'≤1000mm. For example, a' can be 30mm, 50mm, 100mm, 200mm, 1000mm, or any range consisting of two thereof. When the dimension a' of the head clearance area 331 is within the range of 30mm to 1000mm, it facilitates setting a suitable distribution range of the bump area 310, allowing the first protrusion 311 located in the inner circle to better play a supporting role and improve electrolyte infiltration of the inner circle of the electrode body 20. At the same time, it facilitates coordination with the tail clearance area 332, ensuring that the head clearance area 331 and the tail clearance area 332 have an appropriate spacing for setting the bump area 310, thereby ensuring a suitable distribution range of the bump area 310 and better reducing extrusion problems. Preferably, a' satisfies the following: 60mm≤a'≤500mm.

[0072] The first surface of the pole piece 300 has an edge avoidance area 340, and the edge avoidance area 340 includes a first area 341 and a second area 342. In the width direction Y of the pole piece 300, the first area 341 is connected to one side of the convex area 310, and the second area 342 is connected to the other side of the convex area 310. The first area 341 extends to the edge of the pole piece 300 in a direction away from the second area 342, and the second area 342 extends to the edge of the pole piece 300 in a direction away from the first area 341. That is, the two opposite boundaries of the convex area 310 in the width direction Y of the pole piece 300 are respectively spaced from the corresponding edges of the pole piece 300, so as to prevent the deformation stress when the first protrusion 311 is processed in the convex area 310 from causing abnormal deformation such as wavy edges or wrinkles on the edge of the pole piece 300.

[0073] Specifically, the pole piece 300 includes a third edge 3431 and a fourth edge 3441 that are relatively arranged in the width direction Y of the pole piece 300, and the convex area 310 includes a third boundary 3103 and a fourth boundary 3104 that are relatively arranged in the width direction Y of the pole piece 300, the third boundary 3103 corresponds to the third edge 3431, and the fourth boundary 3104 corresponds to the fourth edge 3441. The first region 341 is formed between the third boundary 3103 and the third edge 3431, and the second region 342 is formed between the fourth boundary 3104 and the fourth edge 3441, and the first region 341 and the second region 342 extend in the length direction X of the pole piece 300 to connect to the end avoidance area 330, that is, the extension line of the first boundary 3101, the extension line of the second boundary 3102, the third boundary 3103 and the third edge 34 31 defines a first area 341, the extension line of the first boundary 3101, the extension line of the second boundary 3102, the fourth boundary 3104 and the fourth edge 3441 define a second area 342, the extension line of the first boundary 3101, the first edge 3411, the third edge 3431 and the fourth edge 3441 define a head avoidance area 331, the extension line of the second boundary 3102, the second edge 3421, the third edge 3431 and the fourth edge 3441 define a tail avoidance area 332, the convex point area 310 is located in the area defined by the first boundary 3101, the second boundary 3102, the third boundary 3103 and the fourth boundary 3104, and the first convex portion 311 can be inscribed in at least one of the first boundary 3101, the second boundary 3102, the third boundary 3103 and the fourth boundary 3104.

[0074] Optionally, the first boundary 3101, the second boundary 3102, the first edge 3411 and the second edge 3421 are parallel to the width direction Y of the pole piece 300, and the third boundary 3103, the fourth boundary 3104, the third edge 3431 and the fourth edge 3441 are parallel to the length direction X of the pole piece 300. At this time, the head avoidance area 331 and the tail avoidance area 332 are each independently rectangular or square, and the first area 341 and the second area 342 are rectangular.

[0075] The area of ​​the first region 341 is S1, and S1 and E satisfy the following: 0.01≤S1 / E≤0.4. For example, S1 / E can be 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, or a range consisting of any two thereof. By setting S1 / E within the range of 0.01 to 0.4, the first protrusion 311 can provide support for the edge area of ​​the isolation membrane 50, while also ensuring that the distance from the first protrusion 311 to the edge of the pole piece 300 is not too close, thereby preventing the edge of the pole piece 300 from abnormal deformation such as bending, unevenness, and wavy edges due to the deformation stress of the first protrusion 311 during processing.

[0076] The area of ​​the second region 342 is S2, where S2 and E satisfy the following: 0.01≤S2 / E≤0.4. For example, S2 / E can be 0.01, 0.1, 0.2, 0.25, 0.3, 0.4, or any two thereof. By setting S1 / E within the range of 0.01 to 0.4, the first protrusion 311 can similarly provide support for the edge region of the other side of the isolation membrane 50, while preventing the edge of the pole piece 300 from deforming abnormally, such as bending, unevenness, or wavy edges, due to the deformation stress of processing the first protrusion 311.

[0077] In the width direction Y of the electrode 300, the minimum distance between the third edge 3431 and the third boundary 3103 is the width T11 of the first region 341 in the width direction Y of the electrode 300, and the minimum distance between the fourth edge 3441 and the fourth boundary 3104 is the width T12 of the second region 342 in the width direction Y of the electrode 300. T11 satisfies the following: 0.5mm≤T11≤30mm, and T12 satisfies the following: 0.5mm≤T12≤30mm. The difference between the width T11 of the first region 341 in the width direction Y of the electrode 300 and the width T12 of the second region 342 in the width direction Y of the electrode 300 is ΔT1, ΔT1=|T11-T112|, and ΔT1 satisfies the following: 0mm≤ΔT1≤29.5mm. When this range is met, the lithium ion migration rate can be kept within an appropriate range during high-rate charge and discharge testing, thereby improving the high and low temperature cycling performance of the battery.

[0078] Optionally, one of the first region 341 and the second region 342 is used to mount the tab assembly 40 of the electrode assembly. As shown in FIG1 , illustratively, the first region 341 is used to mount the tab assembly 40 of the electrode assembly, and the convex region 310 is spaced apart from the tab assembly 40. In this case, the convex region 310 is defined by a first boundary 3101, a second boundary 3102, a third boundary 3103, and a fourth boundary 3104.

[0079] Optionally, as shown in FIG3 , the first surface further includes a tab region 320 , which extends from the third boundary 3103 toward the side where the fourth boundary 3104 is located. The tab region 320 is used to install the tab assembly 40 of the electrode assembly, and the tab assembly 40 is spaced apart from the convex region 310 . When the tab assembly 40 is installed in the tab region 320 , its processing method will affect the installation stability of the tab assembly 40 and the stability of the structure surrounding the tab assembly 40 , thereby affecting the stability of the interface of the electrode piece 300 . For example, when the tab assembly 40 is pressed and installed on the electrode piece 300 by rolling, the tab assembly 40 is pressed together with the area where the first protrusion 311 is provided, or the distance between the tab assembly 40 and the first protrusion 311 is too close, the first protrusion 311 may be deformed, indented, etc., thereby causing the interface of the electrode piece 300 in the area near the tab assembly 40 to deteriorate. In the embodiment of the present application, the tab area 320 is planned for installing the tab assembly 40, which facilitates the installation of the tab assembly 40, reduces the process difficulty, improves the installation stability of the tab assembly 40, and improves the interface stability near the tab assembly 40. It can also make the tab assembly 40 and the first protrusion 311 misaligned in the thickness direction Z of the pole piece 300, which helps to improve the energy density of the battery when the electrode assembly is applied to the battery.

[0080] It is understandable that the wider the distribution range of the multiple first protrusions 311 provided on the electrode piece 300 is, the larger the effective support area of ​​the multiple first protrusions 311 for the entire electrode body 20 is, and thus the fewer problems caused by extrusion. In an embodiment of the present application, a pole ear area 320, an end avoidance area 330 and an edge avoidance area 340 are provided in combination, wherein the provision of the end avoidance area 330 can provide a winding buffer area for the winding of the electrode body 20, thereby improving the winding stability of the electrode body 20, reducing the occurrence of winding instability caused by the area with the first protrusion 311 being the winding starting point or winding end point, protecting the straight section 21, and in this case, combining the pole ear area 320 and the edge avoidance area 340 to prevent the part of the electrode body 20 where the pole ear assembly 40 is installed from expanding and driving the pole ear assembly 40 to squeeze the electrode body 20, thereby reducing mutual damage between the pole ear assembly 40 and the electrode body 20, and the supporting role played by the first protrusion 311 can be extended to the pole ear area 320, so that the pole piece 300 is not easily squeezed in the pole ear area 320, and a part of the area can be reserved to accommodate the electrolyte, which is convenient for the electrolyte to enter and exit the electrode body 20, thereby improving the electrolytic infiltration effect. Therefore, the electrode assembly of the embodiment of the present application can not only improve the interface problems caused by the extrusion of the corner section 22, but also reduce the negative problems caused by the extrusion of the straight section 21. When the electrode assembly is used in the battery, it can improve the performance of the corner position of the battery cell and enhance the overall cycle performance of the battery.

[0081] As shown in Figure 3, the spacing between the tab assembly 40 and the convex area 310 is T2, wherein the spacing between the tab assembly 40 and the convex area 310 includes the spacing in the length direction X of the pole piece 300 and the spacing in the width direction Y, and the spacing in these two directions is T2. T2 satisfies: 0.5mm≤T2≤30mm. For example, T2 can be 0.5mm, 1mm, 2mm, 8mm, 10mm, 15mm, 20mm, 30mm or a range consisting of any two of them. When T2 is in the range of 0.5mm to 30mm, the spacing between the tab assembly 40 and the convex area 310 is appropriate, which can not only meet the support requirements of the first protrusion 311 for the tab assembly 40, but also facilitate processing.

[0082] The number of tab regions 320 in a given electrode 300 is at least one, and the area of ​​each tab region 320 is M, where M satisfies the following: 0.01≤M / E≤0.2. Each tab region 320 is used to accommodate at least one tab assembly 40. For example, the tab assembly 40 includes a tab 100 and a protective adhesive 200. The tab 100 and the protective adhesive 200 can be installed in the same tab region 320; alternatively, the tab 100 can be installed in one tab region 320, and the protective adhesive 200 can be installed in another tab region 320.

[0083] There are multiple tabs 100, some of which are installed on one of the pole pieces 300, and some of which are installed on the other pole piece 300. The tabs 100 installed on the positive pole piece 410 are positive tabs, and the tabs 100 installed on the negative pole piece 420 are negative tabs. The tab area 320 includes a tab mounting area 321, which is used to mount the tabs 100 of the electrode assembly. The area of ​​the tab mounting area 321 is B, and B and E satisfy: 0.01≤B / E≤0.2. For example, B / E can be 0.01, 0.05, 0.08, 0.1, 0.12, 0.15, 0.18, 0.2, or a range consisting of any two thereof.

[0084] Optionally, when only one of the two pole pieces 300 with opposite polarity has a convex point area 310, a tab area 320 and an end avoidance area 330, a portion of the tabs 100 is arranged corresponding to the tab mounting area 321 of one of the pole pieces 300, and the other portion of the tabs 100 is directly mounted on the edge area of ​​the other pole piece 300. Optionally, when both of the two pole pieces 300 with opposite polarity have a convex point area 310, a tab area 320 and an end avoidance area 330, a portion of the tabs 100 is arranged corresponding to the tab mounting area 321 of one of the pole pieces 300, and the other portion of the tabs 100 is arranged corresponding to the tab mounting area 321 of one of the pole pieces 300.

[0085] When lithium ions migrate to the negative electrode tab, there is no graphite or other lithium-intercalating structure at the negative electrode tab, which easily leads to lithium deposition at the negative electrode tab. Optionally, the tab assembly 40 also includes a protective adhesive 200. The number of protective adhesives 200 can be multiple. After the separator 50 and the two electrode sheets 300 are wound to form the flat electrode body 20, each protective adhesive 200 is attached to the surface of the negative electrode tab, separating the positive electrode sheet 410 from the negative electrode tab, and preventing lithium deposition around the negative electrode tab.

[0086] The same electrode piece 300 may have multiple tab regions 320. The tab region 320 further includes a protective adhesive mounting area 322. The protective adhesive mounting area 322 is spaced apart from the tab mounting area 321 and is used to mount the protective adhesive 200 of the electrode assembly. The area of ​​the protective adhesive mounting area 322 is C, where C and E satisfy the following: 0.01 ≤ C / E ≤ 0.2. For example, C / E can be 0.01, 0.05, 0.08, 0.1, 0.12, 0.15, 0.18, 0.2, or a range consisting of any two thereof.

[0087] Optionally, as shown in FIG3 , the pole ear region 320 is spaced apart from the fourth boundary 3104. Specifically, the pole ear region 320 includes a first side boundary 3201, a second side boundary 3202, and a bottom boundary 3203. The first side boundary 3201 and the second side boundary 3202 are arranged between the first boundary 3101 and the second boundary 3102 in the length direction X of the pole piece 300. The first side boundary 3201 and the second side boundary 3202 are arranged opposite to each other and both are connected to the third boundary 3103. The bottom boundary 3203 is arranged in the width direction Y of the pole piece 300. The tab region 320 is defined between the third boundary 3103 and the fourth boundary 3104, and the bottom boundary 3203 is connected between the first side boundary 3201 and the second side boundary 3202. The tab region 320 is defined by the third boundary 3103, the first side boundary 3201, the second side boundary 3202, and the bottom boundary 3203, and the convex region 310 is defined by the first boundary 3101, the second boundary 3102, the third boundary 3103, the fourth boundary 3104, the first side boundary 3201, the second side boundary 3202, and the bottom boundary 3203. The number of tab regions 320 on the first surface of the same pole piece 300 may be multiple.

[0088] Optionally, as shown in Figure 4, the tab region 320 extends from the third boundary 3103 through the convex region 310 along the width direction Y of the pole piece 300. Specifically, the tab region 320 has a third side boundary 3204 and a fourth side boundary 3205, and both the third side boundary 3204 and the fourth side boundary 3205 are located between the first boundary 3101 and the second boundary 3102 in the length direction X of the pole piece 300, and in the width direction Y of the pole piece 300, the opposite ends of the third side boundary 3204 are respectively connected to the third boundary 3103 and the fourth boundary 3104, and the opposite ends of the fourth side boundary 3205 are respectively connected to the third boundary 3103 and the fourth boundary 3104. At this time, the tab region 320 is defined by the third boundary 3103, the fourth boundary 3104, the third side boundary 3204 and the fourth side boundary 3205. Among them, when the number of tab areas 320 of the same pole piece 300 is one, the number of convex areas 310 is two, and the two convex areas 310 are arranged on opposite sides of the tab area 320 in the length direction X of the pole piece 300; when the number of tab areas 320 of the same pole piece 300 is multiple, the number of convex areas 310 is also multiple, and each tab area 320 is located between two adjacent convex areas 310 in the length direction X of the pole piece 300, and each tab assembly 40 can be installed in one of the tab areas 320.

[0089] Optionally, the pole ear area 320 is arranged in the straight section 21, and the convex area 310 is arranged in the corner section 22. In the length direction X of the pole piece 300, the size of the corner section 22 is W5, and the size of the convex area 310 is W6, W6=W5, so that the first protrusion 311 only contacts the corresponding pole piece 300 in the corner section 22 to provide support. In this case, the first protrusion 311 can provide good support, and has a balanced wetting effect on the straight section 21 and the corner section 22, thereby improving the shortcomings of the battery cell and improving the overall cycle performance of the battery cell.

[0090] Optionally, the ear area 320 is provided in the straight section 21, the convex area 310 is provided in the corner section 22 and extends to the straight section 21, and the two convex areas 310 of the same circle of the pole piece 300 are arranged at intervals, as shown in Figure 6. In the length direction X of the pole piece 300, the size of the corner section 22 is W5, and the size of the convex area 310 is W6, W6>W5, so that the first protrusion 311 of the convex area 310 can support more area, improve the wetting channel of the pole piece 300, solve the problem of insufficient electrolyte and premature failure in some areas due to uneven wetting, improve the cycle performance, and then when the electrode assembly is used in the battery, it can improve the charge and discharge cycle life of the battery under 3C / 5C, and can increase the number of stable cycles of the battery.

[0091] Optionally, W5 satisfies the following conditions: 0.5 mm ≤ W5 ≤ 20 mm. For example, W5 may be 0.5 mm, 2 mm, 5 mm, 8 mm, 10 mm, 12 mm, 15 mm, 20 mm, or a range consisting of any two thereof. W6 satisfies the following conditions: 0.5 mm ≤ W6 ≤ 100 mm. For example, W6 may be 0.5 mm, 2 mm, 8 mm, 15 mm, 30 mm, 50 mm, 100 mm, or a range consisting of any two thereof.

[0092] As shown in the pole piece 300 in Figure 5, optionally, the size W6 of all the convex areas 310 in the length direction X of the pole piece 300 is equal. It can be understood that the circumference of each circle of the pole piece 300 gradually increases from the inner circle to the outer circle of the electrode body 20, wherein the size of the corner segment 22 of the outermost circle pole piece 300 in the length direction X of the pole piece 300 is Wmax, W6≥Wmax. In this way, when the size W6 of all the convex areas 310 in the length direction X of the pole piece 300 is equal, each convex area 310 can cover the corresponding corner segment 22, and some of the convex areas 310 can extend to partially cover the straight segment 21 while covering the corner segment 22.

[0093] As shown in FIG6 , the pole piece 300 may optionally have a dimension W6 of the convex area 310 in the length direction X of the pole piece 300 gradually increasing from the inner circle to the outer circle of the electrode body 20. At this time, the dimension W6 of the convex area 310 in the length direction X of the pole piece 300 gradually increases as the dimension of the corner segment 22 in the length direction X of the pole piece 300 increases from the inner circle to the outer circle of the electrode body 20. In this case, the dimension W6 of the convex area 310 in the length direction X of the pole piece 300 may be equal to the dimension of the corresponding corner segment 22 in the length direction X of the pole piece 300, that is, the convex area 310 only covers the corresponding corner segment 22; or, the dimension W6 of the convex area 310 in the length direction X of the pole piece 300 may also be greater than the dimension of the corresponding corner segment 22 in the length direction X of the pole piece 300, that is, the convex area 310 covers the corresponding corner segment 22 while also extending to the straight segment 21.

[0094] In the embodiment of the present application, as shown in FIG8 , the first protrusion 311 has a vertex Q and a base m. The base m of the first protrusion 311 is connected to the surface of the main body 312 of the electrode 300 (which surface may be a flat surface or a convex arc surface). The first protrusion 311 is protruding from the main body of the electrode 300. The vertex Q of the first protrusion 311 is the point of the first protrusion 311 that is farthest from the base m in the thickness direction Z of the electrode 300. The height of the first protrusion 311 is the dimension from the vertex Q of the first protrusion 311 to the base m of the first protrusion 311 in the thickness direction Z of the electrode 300. When the corner section 22 has the first protrusion 311, the height of the first protrusion 311 provided in the corner section 22 is h1. When the straight section 21 has the first protrusion 311, the height of the first protrusion 311 provided in the straight section 21 is h2, where h2 ≤ h1, to improve the electrolyte infiltration effect. Furthermore, h1 satisfies: 55 μm≤h1≤70 μm; the height of the first convex portion 311 provided on the straight section 21 is h2, and h2 satisfies: 10 μm≤h2≤18 μm.

[0095] Optionally, the outer contour of the first protrusion 311 is circular, elliptical or regular polygonal. The top surface of the first protrusion 311 in contact with the isolation membrane 50 is an arc surface to prevent the top of the first protrusion 311 from being too sharp to puncture the isolation membrane 50.

[0096] Optionally, the outer contour dimensions of the first convex portion 311 in a cross section perpendicular to the thickness direction Z of the urinary tract 300 are equal. For example, when the outer contour of the first convex portion 311 is circular, the outer contour radius of each circular first convex portion 311 is equal; when the outer contour of the first convex portion 311 is a regular polygon, the radii of the circumscribed circles of the regular polygon are equal.

[0097] Among them, two pole pieces 300 with opposite polarities and an isolating film 50 are wound to form a flat electrode body 20. The probability of being squeezed in the central area of ​​the convex area 310, resulting in insufficient electrolyte, is higher. In the embodiment of the present application, the outer contour size of the first protrusion 311 in the central area of ​​the convex area 310 is set to be larger, and the distance between the pole piece 300 and the isolating film 50 in the central area of ​​the convex area 310 is increased to improve the insufficient electrolyte in the central area of ​​the convex area 310, thereby improving the electrolyte infiltration effect. The pole pieces 300 in Figures 2 to 6 above can all adopt a design method in which the outer contour size of the first protrusion 311 in the central area of ​​the convex area 310 is relatively large and the outer contour size of the first protrusion 311 in the edge area of ​​the convex area 310 is relatively small to improve the insufficient electrolyte. Optionally, as shown in Figure 7, in the width direction Y of the pole piece 300, the outer contour size of the first protrusion 311 gradually decreases from the central area of ​​the convex area 310 to the edge area; and / or, in the length direction X of the pole piece 300, the outer contour size of the first protrusion 311 gradually decreases from the central area of ​​the convex area 310 to the edge area.

[0098] The pole piece 300 of the embodiment of the present application includes a current collector and an active material layer provided on the surface of the current collector, wherein the surface of the active material layer facing away from the current collector forms a first surface. The first protrusion 311 can be formed by a portion of the current collector and a portion of the active material layer. For example, the first protrusion 311 of the embodiment of the present application can be processed by rolling. Specifically, the method acts on a portion of the pole piece 300 on one side of the pole piece 300, and causes the current collector and the active material layer in the region to deform and bend together, thereby forming the first protrusion 311.

[0099] The portion of the current collector used to form the first protrusion 311 is a protrusion base. The protrusion base has a first outer edge line, and the first outer edge line has a first circumscribed circle. Two adjacent protrusion bases have a first spacing L1 and a second spacing L2. The first spacing L1 is the spacing between the centers of the first circumscribed circle of the first outer edge line of the two adjacent protrusion bases in the length direction of the pole piece. L1 satisfies the following conditions: 0.5mm≤L1≤40mm. Two adjacent protrusion bases have a second spacing L2. The second spacing L2 is the spacing between the centers of the first circumscribed circle of the first outer edge line of the two adjacent protrusion bases in the width direction of the pole piece. L2 satisfies the following conditions: 0.5mm≤L2≤40mm.

[0100] Optionally, the current collector surface includes two coating surfaces arranged opposite to each other in the thickness direction of the electrode, the active material layer is arranged on at least one of the coating surfaces, and the active material layer covers the entire coating surface. Alternatively, as shown in Figure 9, the current collector 500 includes a coating portion 510 and a hollow foil portion 520, the hollow foil portion 520 is arranged on one side of the coating portion 510 in the width direction Y of the electrode 300, and the hollow foil portion 520 is integrally arranged with the coating portion 510, the hollow foil portion 520 forms a plurality of pole tabs 100, the active material layer 600 is arranged on the surface of the coating portion 510, and the surface of the active material layer facing away from the coating portion 510 forms a first surface. Specifically, the coating portion 510 includes two main surfaces arranged opposite to each other in the thickness direction Z of the electrode 300, the active material layer 600 is arranged on at least one of the main surfaces, and the surface of the active material layer 600 facing away from the main surface forms a first surface.

[0101] The electrode sheet 300 includes a positive electrode sheet 410 and a negative electrode sheet 420. The embodiment of the present application has no special restrictions on the positive electrode sheet 410 and the negative electrode sheet 420. Various elements that can be used as electrode assemblies known in the art are applicable to the present application.

[0102] In some exemplary embodiments, the negative electrode plate 420 may include a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector. Exemplarily, the negative electrode current collector may be at least one of copper foil, aluminum foil, nickel foil, or a carbon-based current collector; the thickness of the negative electrode current collector may be 1 μm to 200 μm. The negative electrode active material layer may be disposed on one surface or two opposing surfaces of the negative electrode current collector. Furthermore, the negative electrode active material layer may be coated only on a portion of the negative electrode current collector along the thickness of the negative electrode plate 420. Exemplarily, the thickness of the negative electrode active material layer may be 10 μm to 500 μm.

[0103] The negative electrode active material layer includes a negative electrode active material. Exemplarily, the negative electrode active material includes at least one of lithium metal, natural graphite, artificial graphite, or a silicon-based material. The silicon-based material includes at least one of silicon, a silicon oxide compound, a silicon carbon compound, or a silicon alloy. The negative electrode active material layer may further include a conductive agent and / or a binder. Exemplarily, the conductive agent in the negative electrode active material layer may include at least one of carbon black, acetylene black, Ketjen black, flake graphite, graphene, carbon nanotubes, carbon fibers, or carbon nanowires. The binder in the negative electrode active material layer may include at least one of carboxymethyl cellulose (CMC), polyacrylic acid, polyacrylic acid salt, polyacrylate, polyvinyl pyrrolidone, polyaniline, polyimide, polyamide-imide, polysiloxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin, or polyfluorene.

[0104] In some exemplary embodiments, the positive electrode sheet 410 includes a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector. For example, the positive electrode current collector may be made of aluminum foil, although other common positive electrode current collectors in the art may also be used. The thickness of the positive electrode current collector may be 1 μm to 200 μm. The positive electrode active material layer may be disposed on one surface or two opposing surfaces of the positive electrode current collector. Furthermore, in the thickness direction of the positive electrode sheet 410, the positive electrode active material layer may be coated only on a portion of the positive electrode current collector. The thickness of the positive electrode active material layer may be 10 μm to 500 μm.

[0105] The positive electrode active material layer includes positive electrode active materials, and the positive electrode active materials include LiCoO2, LiNiO2, LiMn2O4, LiCo 1-y MyO2、LiNi 1-y MyO2、LiMn 2-y MyO4、LiNi x Co y Mn z M 1-x-y-zO2, wherein M is selected from at least one of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, or Ti, and 0≤y≤1, 0≤x≤1, 0≤z≤1, and x+y+z≤1. For example, the positive electrode active material may include at least one of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganate, lithium nickel cobalt aluminum oxide, or lithium nickel manganate. The positive electrode active material may be doped and / or coated. The positive electrode active material layer further includes a binder and a conductive agent. Illustratively, the binder in the positive electrode active material layer may include at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, a styrene-acrylate copolymer, a styrene-butadiene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinyl acetate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene; the conductive agent in the positive electrode active material layer may include at least one of conductive carbon black, acetylene black, Ketjen black, flake graphite, graphene, carbon nanotubes or carbon fibers.

[0106] An embodiment of the present application also provides an electrode assembly, which includes multiple tab assemblies 40, the pole pieces 300 as described above, and an isolation membrane 50 arranged between the two pole pieces 300, and the isolation membrane 50 and the two pole pieces 300 are wound along the length direction X of the pole pieces 300 to form a flat electrode body 20.

[0107] Optionally, as shown in FIG10 , the tab assembly 40 includes a connecting section connected to the pole piece 300 and a docking section extending from the edge of the pole piece 300. The surface of the connecting section facing away from the pole piece is provided with a plurality of second protrusions 110. The second protrusions 110 provide support for the structure of the tab assembly 40. For example, the second protrusions 110 contact the separator 50, providing support for the separator 50 and improving the electrolyte infiltration effect of the tab assembly 40. Furthermore, the boundary of the area of ​​the tab assembly 40 provided with the plurality of second protrusions 110 is flush with the second boundary 3102 of the bump area 310. The second protrusions 110 and the first protrusions 311 can be configured to be identical in shape, size, and arrangement. The second protrusions 110 can be formed by rolling, in which case the second protrusions 110 are formed by bending portions of the tab assembly 40 and portions of the pole piece 300 toward the same side.

[0108] The embodiments of the present application have no particular restrictions on the isolation film 50 , the tabs, and the protective glue. Various components that can be used as electrode assemblies that are well known in the art are applicable to the present application.

[0109] In some exemplary embodiments, the separator 50 comprises at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid. For example, the polyethylene may include at least one selected from high-density polyethylene, low-density polyethylene, or ultra-high molecular weight polyethylene. Polyethylene and polypropylene are particularly effective in preventing short circuits and can improve the stability of the electrode assembly through the shutdown effect. The thickness of the separator 50 ranges from approximately 3 μm to 500 μm. The positive and negative tabs are made of a conductive metal material.

[0110] The present application also provides a battery comprising a housing and an electrode assembly as described above, the electrode assembly being disposed within the interior space of the housing. The battery also comprises an electrolyte, which fills the interior space of the housing and impregnates the electrode assembly. The present application also does not particularly limit the electrolyte; any material known in the art for use as an electrolyte is suitable for use in the present application.

[0111] The present application will be further described below using an electrode assembly of a lithium-ion battery as an example and in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and are not intended to limit the scope of the present application.

[0112] In each embodiment and comparative example of the present application, lithium-ion batteries were prepared and their performance was tested using the following method:

[0113] 1. Preparation method of lithium-ion battery

[0114] (1) Preparation of positive electrode sheet 410

[0115] The positive electrode active material, lithium cobalt oxide (LiCoO2), conductive carbon black (conductive agent), and binder, polyvinylidene fluoride (PVDF), were dissolved in an N-methylpyrrolidone (NMP) solution at a weight ratio of 97.9:0.9:1.2 to form a positive electrode slurry. A 9μm aluminum foil was used as the positive electrode current collector. The positive electrode slurry was applied to the positive electrode current collector and dried, cold pressed, and cut to obtain a positive electrode sheet 410. The compacted density of the positive electrode active material layer of the positive electrode sheet 410 was 4.2g / cm 3 .

[0116] In the following embodiments and comparative examples, the positive electrode sheet 410 has a convex point area 310 , a tab area 320 , a head avoidance area 331 , a tail avoidance area 332 , a first area 341 and a second area 342 .

[0117] (2) Preparation of negative electrode sheet 420

[0118] The negative electrode active material, artificial graphite, the binder, styrene-butadiene rubber (SBR), and the thickener, sodium carboxymethyl cellulose (CMC), were dissolved in deionized water at a weight ratio of 97.4:1.4:1.2 to form a negative electrode slurry. A 10μm thick copper foil was used as the negative electrode current collector. The negative electrode slurry was applied to the negative electrode current collector, dried, cold pressed, and cut to obtain the negative electrode sheet 420. The compacted density of the negative electrode active material layer of the negative electrode sheet 420 was 1.8g / cm 3 .

[0119] (3) Preparation of isolation film 50

[0120] The separator substrate is made of 5μm-thick polyethylene (PE). A 2μm-thick alumina ceramic layer is coated on one side of the separator substrate. Finally, a 2.5mg / 1540.25mm² binder (polyvinylidene fluoride) (PVDF) is applied to both sides of the single-layer ceramic-coated separator substrate and dried to form a porous layer. The porous layer of separator 50 has a porosity of 39%.

[0121] (4) Preparation of electrolyte

[0122] In an environment with a water content of less than 10 ppm, ethylene carbonate (abbreviated as EC), propylene carbonate (abbreviated as PC), diethyl carbonate (abbreviated as DEC), ethyl propionate (abbreviated as EP), and propyl propionate (abbreviated as PP) are mixed uniformly in a mass ratio of 1:1:1:1:1, and then the electrolyte salt LiPF6 is dissolved in the above-mentioned non-aqueous solvent. After uniform mixing, an electrolyte is formed, wherein the mass percentage of LiPF6 based on the mass of the electrolyte is 12.5%.

[0123] (5) Assembly of lithium-ion batteries

[0124] The positive tab 100 is installed on the tab installation area of ​​the positive electrode sheet 410 by rolling, the protective glue 200 is pasted on the protective glue installation area of ​​the positive electrode sheet 410, and the negative tab 100 is installed on the edge area of ​​the negative electrode sheet 420 by rolling.

[0125] The positive electrode sheet 410 with the positive electrode tab 100 installed, the separator 50, and the negative electrode sheet 420 with the negative electrode tab 100 installed are stacked in sequence, with the separator 50 positioned between the positive electrode sheet 410 and the negative electrode sheet 420 to provide isolation. The electrodes are then wound to form the electrode body 20. The electrode assembly is placed in an outer aluminum-plastic film package, dehydrated at 80°C, and then injected with the aforementioned electrolyte and packaged. The lithium-ion battery is produced through the following process steps: formation, degassing, and trimming. The following describes the testing methods for various parameters of various embodiments of this application.

[0126] 2. Performance test of lithium-ion batteries

[0127] (1) 25℃ / 45℃ cycle test

[0128] In an environment of 25℃ / 45℃, the electrode assembly is charged at a constant current of 1C to the full charge voltage (the battery is designed for a maximum voltage of 4.5V). Then, constant voltage charging is performed at the maximum voltage until the current reaches 0.02C. Then, constant current discharge is performed at a discharge current of 0.7C until the final voltage reaches 3.0V. The discharge capacity of the first cycle is recorded. The above steps are then repeated for 1000 charge and discharge cycles. The discharge capacity of the lithium-ion battery after 1000 charge and discharge cycles is recorded.

[0129] 25° C. 1C charge / 0.7C discharge cycle capacity retention rate=(discharge capacity at the 1000th cycle / discharge capacity at the first cycle)×100%.

[0130] Cycle capacity retention rate of 45° C. 1C charge / 0.7C discharge=(discharge capacity at the 800th cycle / discharge capacity at the first cycle)×100%.

[0131] (2) Battery cycle and lithium deposition test

[0132] Normal temperature cycle test: In a 25°C environment, the electrode assembly is charged at a constant current of 1C to the full charge voltage (the battery is designed for a maximum voltage of 4.5V). Then, constant voltage charging is performed at the maximum voltage until the current reaches 0.02C. Then, constant current discharge is performed at a discharge current of 0.7C until the final voltage reaches 3.0V. The discharge capacity of the first cycle is recorded. The above steps are then repeated for 1000 charge and discharge cycles. The discharge capacity of the lithium-ion battery after 1000 charge and discharge cycles is recorded.

[0133] High-temperature cycling test: In a 45°C environment, the electrode assembly is charged at a constant current of 1C to the full charge voltage (the battery's maximum design voltage is 4.5V). Then, constant voltage charging is performed at the maximum voltage until the current reaches 0.02C. Then, constant current discharge is performed at a discharge current of 0.7C until the final voltage reaches 3.0V. The discharge capacity of the first cycle is recorded. The above steps are then repeated for 1000 charge and discharge cycles. The discharge capacity of the lithium-ion battery after 1000 charge and discharge cycles is recorded.

[0134] After testing at 25°C and 1000 charge-discharge cycles, the battery was disassembled when it was fully charged (the battery's maximum design voltage was 4.5V) to observe whether there was lithium deposition at the negative electrode interface / ear / protective glue.

[0135] (3) Winding quality

[0136] After the bare cell winding production is completed, use an X-Ray detector to detect the overhang of the bare cell (the width of the negative electrode sheet 420 edge exceeding the positive electrode sheet 410 edge in the width direction of the positive electrode sheet 410). If the excess width is greater than 0.2mm, it is a good product. The total number of test samples is 100, and the winding quality rate = number of good products / total number of samples.

[0137] In Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-2, the electrode 300 shown in FIG3 is used as the positive electrode 410 , and the parameters of the electrode 300 are shown in Table I.

[0138] Table I

[0139] The parameters of Examples 1-1 to 1-9 and Comparative Examples 1-1 to 1-2 and the test results of the lithium-ion batteries are shown in Table 1.

[0140] Table 1

[0141] According to the results in Table 1, it can be seen that the ratio of the area Y of the convex region 310 to the area of ​​the first surface E of the electrode satisfies 0.1≤Y / E≤0.98, the charge and discharge cycle performance of the lithium-ion battery is good, and no lithium deposition occurs on the interface. When Y / E is lower than the lower limit of 0.1 or higher than the upper limit of 0.98, the charge and discharge cycle performance of the lithium-ion battery deteriorates, and lithium deposition occurs. Among them, when Y / E is greater than 0.9, the charge and discharge cycle performance of the lithium-ion battery does not change significantly. Preferably, 0.3≤Y / E≤0.9, the charge and discharge cycle performance of the lithium-ion battery is better. More preferably, 0.5≤Y / E≤0.9.

[0142] The difference between Examples 2-1 to 2-11 and Example 1-1 lies in that the area A of the head avoidance zone 331 and the area D of the tail avoidance zone 332 are different.

[0143] The parameters and test results of the lithium-ion batteries in Examples 2-1 to 2-11 are shown in Table 2.

[0144] Table 2

[0145] According to Examples 1-6, 2-1 to 2-4, and 2-9 in Table 2, it can be seen that the ratio of the area A of the head air gap 331 to the area of ​​the first surface E of the electrode satisfies 0≤A / E≤0.3, the charge and discharge cycle performance of the lithium-ion battery is good, and no lithium deposition occurs at the interface. The smaller the area A of the head air gap 331, the better the charge and discharge cycle performance of the lithium-ion battery. This is because as the area of ​​the head air gap 331 decreases, the area Y of the convex area 310 increases, the wettability improvement effect is better, and the cycle performance is better. When A / E is higher than the upper limit of 0.3, the charge and discharge cycle performance of the lithium-ion battery deteriorates.

[0146] According to Examples 2-2, 2-5, and 2-11 in Table 2, the ratio of the area D of the tail clearance region 332 to the area of ​​the first surface E of the electrode satisfies 0.06 ≤ D / E ≤ 0.6, resulting in good charge-discharge cycle performance for the lithium-ion battery and no lithium deposition at the interface. When D / E is below the lower limit of 0.06 or above the upper limit of 0.6, the charge-discharge cycle performance of the lithium-ion battery is inferior to that within the range, and lithium deposition occurs.

[0147] The difference between Examples 3-1 to 3-11 and Example 1-1 is that the area S1 of the first region 341 and the area S2 of the second region 342 are different.

[0148] The parameters and test results of the lithium-ion batteries in Examples 3-1 to 3-11 are shown in Table 3.

[0149] Table 3

[0150] According to the results in Table 3, it can be seen that the ratio of the area S1 of the first region 341 to the area of ​​the first surface E of the electrode satisfies 0.01≤S1 / E≤0.4, and the ratio of the area S2 of the second region 342 to the area of ​​the first surface E of the electrode satisfies 0.01≤S2 / E≤0.4. The charge and discharge cycle performance of the lithium-ion battery is good, and the winding yield is good.

[0151] The difference between Examples 4-1 to 4-12 and Example 1-1 is that the width T11 of the first region 341 and the width T12 of the second region 342 are different.

[0152] The parameters and test results of the lithium-ion batteries in Examples 4-1 to 4-12 are shown in Table 4.

[0153] Table 4

[0154] According to the results in Table 4, the width T11 of the first region 341 satisfies 1mm≤T11≤30mm, and the width T12 of the second region 342 satisfies 1mm≤T12≤30mm. The lithium-ion battery has good charge and discharge cycle performance and a good winding yield.

[0155] When T11 is less than the lower limit of 1mm or greater than the upper limit of 30mm, and T12 is less than the lower limit of 1mm or greater than the upper limit of 30mm, the charge and discharge cycle performance and winding yield of the lithium-ion battery are reduced. Preferably, T11 satisfies 1mm≤T11≤10mm, and T12 satisfies 1mm≤T12≤10mm.

[0156] The difference between Examples 5-1 to 5-10 and Example 1-1 lies in that the area B of the tab mounting area 321 and the area C of the protective adhesive mounting area 322 are different.

[0157] The parameters and test results of the lithium-ion batteries in Examples 5-1 to 5-10 are shown in Table 5.

[0158] Table 5

[0159] According to the results in Table 5, it can be seen that the ratio of the area B of the tab installation area 321 to the area of ​​the first surface E of the pole piece satisfies 0.01≤B / E≤0.2, and the ratio of the area C of the protective glue installation area 322 to the area of ​​the first surface E of the pole piece satisfies 0.01≤C / E≤0.2. The charge and discharge cycle performance of the lithium-ion battery is good, and no lithium plating occurs at the negative electrode interface, the tab 100 and the protective glue 200.

[0160] When the B / E ratio is lower than the lower limit of 0.01 or higher than the upper limit of 0.2, and the C / E ratio is lower than the lower limit of 0.01 or higher than the upper limit of 0.2, the charge and discharge cycle performance of the lithium-ion battery deteriorates. When the B / E ratio is lower than the lower limit of 0.01, lithium deposition occurs at the tab 100, and when the C / E ratio is lower than the lower limit of 0.01, lithium deposition occurs at the protective adhesive 200. This is because when the B / E and C / E ratio are lower than the lower limit, the first protrusion 311 in the corresponding area directly presses against the tab 100 and protective adhesive 200, damaging them and puncturing the protective adhesive 200, which in turn causes lithium deposition.

[0161] The difference between Examples 6-1 to 6-12 and Example 1-4 is that the first spacing L1 of the first protrusions 311 in the length direction X of the pole piece 300 and the second spacing L2 of the first protrusions 311 in the width direction Y of the pole piece 300 are different.

[0162] The parameters and test results of the lithium-ion batteries in Examples 6-1 to 6-12 are shown in Table 6.

[0163] Table 6

[0164] According to the results in Table 6, it can be seen that the first spacing L1 of the first protrusion 311 in the length direction X of the pole piece 300 satisfies 0.5 mm ≤ L1 ≤ 40 mm, and the second spacing L2 of the first protrusion 311 in the width direction Y of the pole piece 300 satisfies 0.5 mm ≤ L2 ≤ 40 mm, and the charge and discharge cycle performance of the lithium-ion battery at room temperature (25°C) and high temperature (45°C) are both improved.

[0165] The same or similar numbers in the drawings of this embodiment correspond to the same or similar parts; in the description of this application, it should be understood that if the terms "upper", "lower", "left", "right", etc. indicate an orientation or position relationship, they are based on the orientation or position relationship shown in the drawings. This is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as a limitation on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0166] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A pole piece, the pole piece includes a first surface perpendicular to the thickness direction of the pole piece, the first surface includes a bump area, an end clearance area, an edge clearance area and an ear area, the end clearance area is connected to the end of the bump area in the length direction of the pole piece and extends to the edge of the pole piece, the edge clearance area is arranged on one side of the bump area in the width direction of the pole piece and extends to the edge of the pole piece; the bump area has a third boundary and a fourth boundary oppositely arranged in the width direction of the pole piece; the first surface further includes an ear area, and the ear area extends from the third boundary towards the side where the fourth boundary is located; The bump region includes a plurality of first bumps; wherein, The area of the bump area is Y, and the projected area of the first surface in the direction perpendicular to the thickness direction of the pole piece is E, and E and Y satisfy: 0.1 ≤ Y / E ≤ 0.

98.

2. The electrode tab according to claim 1, wherein, The pole piece satisfies: 0.3 ≤ Y / E ≤ 0.

9.

3. The pole piece according to claim 1 or 2, wherein The pole piece satisfies: 0.5 ≤ Y / E ≤ 0.

9.

4. The electrode tab according to any one of claims 1 to 3, wherein, The pole piece includes a first edge and a second edge oppositely arranged in the length direction of the pole piece, the bump area includes a first boundary and a second boundary oppositely arranged in the length direction of the pole piece, the first boundary corresponds to the first edge, and the second boundary corresponds to the second edge; The end clearance area includes a head clearance area and a tail clearance area, the head clearance area is formed between the first edge and the first boundary, the tail clearance area is formed between the second edge and the second boundary, and the pole piece is used to wind with the separator film from the head clearance area along the length direction of the pole piece to form a flat electrode body.

5. The electrode tab according to claim 4, wherein, The area of the head clearance area is A, the area of the tail clearance area is D, and the pole piece satisfies at least one of the following conditions: (1) 0 ≤ A / E ≤ 0.3; (2) 0.06 ≤ D / E ≤ 0.

6.

6. The electrode tab according to claim 5, wherein, 0 ≤ A ≤ 0.1E.

7. The electrode tab according to any one of claims 1 to 6, wherein, The pole piece includes a third edge and a fourth edge oppositely arranged in the width direction of the pole piece, the bump area includes a third boundary and a fourth boundary oppositely arranged in the width direction of the pole piece, the third boundary corresponds to the third edge, and the fourth boundary corresponds to the fourth edge; The edge clearance area includes a first area and a second area, the first area is formed between the third boundary and the third edge, the second area is formed between the fourth boundary and the fourth edge, and the first area and the second area extend in the length direction of the pole piece to be connected to the end clearance area.

8. The electrode tab according to claim 7, wherein, The area of the first area is S1, and the dimension of the first area in the width direction of the pole piece is T11; the area of the second area is S2, and the dimension of the first area in the width direction of the pole piece is T12; the pole piece satisfies at least one of the following conditions: Ⅰ. 0.01 ≤ S1 / E ≤ 0.4; Ⅱ. 0.01 ≤ S2 / E ≤ 0.4; Ⅲ. 0.9 ≤ S2 / S1 ≤ 1.1; Ⅳ. 1mm ≤ T11 ≤ 30mm; Ⅴ. 1mm ≤ T12 ≤ 30mm.

9. The electrode tab according to any one of claims 1 to 8, wherein, The ear area is used to arrange at least one ear component, and the ear component includes at least one of an ear and a protective adhesive; The number of the tab areas of the same electrode tab is at least one, and the area of each tab area is M, where M satisfies: 0.01 ≤ M / E ≤ 0.

2.

10. The pole piece according to claim 9, wherein, The number of the tab areas of the same electrode tab is multiple. Among them, the tab area includes a tab mounting area and a protective adhesive mounting area. The tab mounting area is used to set tabs, and the protective adhesive mounting area is used to set protective adhesives; the area of the tab mounting area is B, and the area of the protective adhesive mounting area is C; the electrode tab satisfies at least one of the following conditions: a. 0.01 ≤ B / E ≤ 0.2; b. 0.01 ≤ C / E ≤ 0.

2.

11. The electrode tab according to claim 9, wherein, the tab area is arranged at an interval from the fourth boundary; or, the tab area penetrates the bump area along the width direction of the electrode tab from the third boundary.

12. The pole piece according to any one of claims 1 to 11, wherein, The electrode tab is used to wind multiple turns along the length direction of the electrode tab with a separator to form an electrode body; each turn of the electrode tab includes a straight section and corner sections arranged at both ends of the straight section; in the length direction of the electrode tab, the size of the corner section is W5, and the size of the bump area is W6; the bump area is arranged in the corner section, where W6 = W5; or, the bump area is arranged in the corner section and extends to the straight section, and the two bump areas of the same turn of the electrode tab are arranged at an interval, where W6 > W5.

13. The pole piece according to any one of claims 1 to 12, wherein, The electrode tab includes a current collector and an active material layer; the current collector includes a main body part and a blank foil part, the blank foil part is integrally arranged with the main body part, and the blank foil part forms multiple tabs, the active material layer is arranged on the surface of the main body part, and the surface of the active material layer facing away from the main body part forms the first surface.

14. The pole piece according to any one of claims 1 to 13, wherein, The electrode tab includes a current collector and an active material layer, and the active material layer is arranged on the surface of the current collector; the first convex part is formed by bending a part of the current collector and a part of the active material layer towards the same side. The part of the current collector used to form the first convex part is a convex part base body, and the convex part base body has a first outer peripheral line, and the first outer peripheral line has a first circumscribed circle. There are a first distance L1 and a second distance L2 between two adjacent convex part base bodies. The first distance L1 is the distance between the centers of the first circumscribed circles of the first outer peripheral lines of two adjacent convex part base bodies in the length direction of the electrode tab, and the second distance L2 is the distance between the centers of the first circumscribed circles of the first outer peripheral lines of two adjacent convex part base bodies in the width direction of the electrode tab; L1 satisfies: 0.5 mm ≤ L1 ≤ 40 mm; and / or, L2 satisfies: 0.5 mm ≤ L2 ≤ 40 mm.

15. An electrode assembly includes a plurality of tab assemblies, the electrode tab according to any one of claims 1 to 14 above, and a separator arranged between the two electrode tabs, and the separator and the two electrode tabs are wound along the length direction of the electrode tab to form a flat electrode body.

16. The electrode assembly according to claim 15, wherein, The tab assembly includes a tab and a protective adhesive. The tab includes a connection section connected to the electrode tab and a docking section extending out of the edge of the electrode tab. A plurality of second convex parts are convexly arranged on the surface of the connection section facing away from the electrode tab.

17. A battery, comprising: a housing; and an electrode assembly as described in claim 15 or 16 above, the electrode assembly being disposed in the internal space of the housing.

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