Electrode sheet, electrode assembly and battery

Abstract

Disclosed in the present application are an electrode sheet, an electrode assembly and a battery. The surface of an active material layer of the electrode sheet facing away from a current collector is provided with a protrusion point area, a tab area and an end clearance area. The electrode sheet comprises a plurality of first protrusion parts distributed in the protrusion point area, the plurality of first protrusion parts protruding towards the same side of the electrode sheet in the thickness direction of the electrode sheet. The end clearance area is arranged at an end part of the protrusion point area in the length direction of the electrode sheet and extends to an edge of the electrode sheet. The tab area extends to an edge of the electrode sheet in the width direction of the electrode sheet, a tab assembly being provided in the tab area and spaced apart from the protrusion point area. Configuring the protrusion point area, the tab area and the end clearance area of the electrode sheet to be combined with each other can effectively ameliorate an interface problem caused by squeezing between electrode layers, thus improving the cycle performance of batteries.

Description

Electrode pieces, electrode assemblies and batteries Technical Field

[0001] The present application relates to the technical field of electrochemical devices, and in particular to a pole piece, an electrode assembly and a battery. Background Art

[0002] 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

[0003] 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.

[0004] 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.

[0005] In a first aspect, an embodiment of the present application provides a pole piece, comprising a current collector and an active material layer arranged on the surface of the current collector, wherein the surface of the active material layer facing away from the current collector has a convex area and an end avoidance area; the pole piece comprises a plurality of first protrusions distributed in the convex area, and the plurality of first protrusions protrude toward the same side of the pole piece in the thickness direction of the pole piece; the end avoidance area is arranged at the end of the convex area in the length direction of the pole piece and extends to the edge of the pole piece; in the width direction of the pole piece, the shortest distance between the convex area and the edge of the active material layer is T1, and T1 satisfies: 0.5mm≤T1≤30mm.

[0006] In some exemplary embodiments, the surface of the active material layer facing away from the current collector includes a tab region, which extends to the edge of the pole piece in the width direction of the pole piece; the tab region is used to set a tab assembly, and the tab assembly is spaced apart from the convex area.

[0007] In some exemplary embodiments, the current collector includes a coating portion and a hollow foil portion, the active material layer is provided on a surface of the coating portion, and the hollow foil portion is provided outside the hollow foil portion in the length direction of the electrode sheet.

[0008] In some exemplary embodiments, the end avoidance area includes a head avoidance area and a tail avoidance area. In the length direction of the pole piece, the head avoidance area is arranged at one end of the convex area, and the tail avoidance area is arranged at the other end of the convex area; the pole piece is used to be wound from the head avoidance area and the isolation membrane along the length direction of the pole piece to form a flat electrode body.

[0009] In some exemplary embodiments, in the length direction of the pole piece, the size of the head avoidance zone is A, and the size of the tail avoidance zone is D, A satisfies: 30mm≤A≤1000mm, and D satisfies: 30mm≤D≤1000mm.

[0010] In some exemplary embodiments, in the length direction of the pole piece, the size of the head avoidance zone is A, and the size of the tail avoidance zone is D, A satisfies: 60mm≤A≤500mm, and D satisfies: 100mm≤D≤500mm.

[0011] In some exemplary embodiments, T1 satisfies: 1 mm ≤ T1 ≤ 30 mm.

[0012] In some exemplary embodiments, T1 satisfies: 3 mm ≤ T1 ≤ 30 mm.

[0013] In some exemplary embodiments, T1 satisfies: 3 mm ≤ T1 ≤ 20 mm.

[0014] In some exemplary embodiments, in the width direction of the pole piece, the surface of the active material layer facing away from the current collector has a first region connected to one side of the convex area and a second region connected to the other side of the convex area, the first region extends to the edge of the active material layer in a direction away from the second region, and the second region extends to the edge of the active material layer in a direction away from the first region; T11 is set as the width of the first region in the width direction of the pole piece, T12 is set as the width of the second region in the width direction of the pole piece, and the difference between the width T11 of the first region in the width direction of the pole piece and the width T12 of the second region in the width direction of the pole piece is △T1, △T1=|T11-T12|, and △T1 satisfies: 0mm≤△T1≤29.5mm.

[0015] In some exemplary embodiments, the interval between the tab assembly and the bump area is T2, and T2 satisfies: 0.5 mm ≤ T2 ≤ 30 mm; the tab assembly includes a tab; and / or the tab assembly includes protective glue.

[0016] In some exemplary embodiments, the number of the tab region is one, and the tab region extends along the length direction of the pole piece to connect with the end free space region.

[0017] In some exemplary embodiments, in the width direction of the pole piece, the surface of the active material layer facing away from the current collector has a first region connected to one side of the convex region, and the first region is located on the side of the convex region facing away from the tab region and extends to the edge of the pole piece; the width of the tab region in the width direction of the pole piece is W1, and W1 satisfies: 2mm≤W1≤40mm.

[0018] In some exemplary embodiments, there are multiple lug regions and convex regions; in the length direction of the pole piece, one lug region is provided between two adjacent convex regions, and each lug region penetrates the pole piece along the width direction of the pole piece.

[0019] In some exemplary embodiments, the convex point area has at least one avoidance opening area, each of the avoidance opening areas extends along the width direction of the pole piece to the edge of the pole piece to form the pole ear area, and multiple avoidance opening areas extend toward the same edge of the pole piece in the width direction of the pole piece.

[0020] In some exemplary embodiments, the dimension of the tab region in the length direction of the pole piece is W3, and W3 satisfies: 10 mm ≤ W3 ≤ 50 mm.

[0021] 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 portion and corner portions provided at both ends of the straight portion, and the tab region is provided on the straight portion; in the length direction of the electrode sheet, the size of the corner portion is W5, and the size of the convex region is W6;

[0022] The convex area is provided at the corner part, wherein W6=W5; or, the convex area is provided at the corner part and extends to the straight part, and the two convex areas of the same circle of the pole piece are spaced apart, wherein W6>W5.

[0023] In some exemplary embodiments, W5 satisfies: 0.5 mm ≤ W5 ≤ 20 mm; and / or, W6 satisfies: 0.5 mm ≤ W6 ≤ 100 mm.

[0024] In some exemplary embodiments, the size W6 of all the convex areas in the length direction of the pole piece is equal; or, the size W6 of the convex areas in the length direction of the pole piece gradually increases from the inner circle to the outer circle of the electrode body.

[0025] In some exemplary embodiments, the electrode piece is used to be wound multiple times with the isolation membrane along the length direction of the electrode piece to form an electrode body; each turn of the electrode piece includes a straight portion and corner portions provided at both ends of the straight portion, and the electrode ear area is provided in the straight portion; the height of the first protrusion provided at the corner portion is h1, and h1 satisfies: 55μm≤h1≤70μm; the height of the first protrusion provided at the straight portion is h2, and h2 satisfies: 10μm≤h2≤18μm.

[0026] In some exemplary embodiments, the pole piece is used to be wound multiple times with the isolation membrane along the length direction of the pole piece to form an electrode body; the multiple first protrusions of the pole piece in each circle are protruded toward the winding center of the electrode body in the thickness direction of the pole piece.

[0027] In some exemplary embodiments, the outer contour of the first protrusion is circular, elliptical or regular polygonal; or, the outer contour dimensions of the first protrusion are equal; or, in the width direction of the pole piece, the outer contour dimensions of the first protrusion gradually decrease from the central area of ​​the convex area to the edge area; or; in the length direction of the pole piece, the outer contour dimensions of the first protrusion gradually decrease from the central area of ​​the convex area to the edge area.

[0028] In a second aspect, the present application provides an electrode assembly, which includes multiple tab assemblies, the pole pieces as described above, and an isolation membrane arranged between the two pole pieces, and the isolation membrane and the two pole pieces are wound along the length direction of the pole pieces to form a flat electrode body.

[0029] In some exemplary embodiments, the tab assembly includes a tab, which is arranged in the tab area of ​​the pole piece; 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 the connecting section is provided with a plurality of second protrusions on the surface facing away from the pole piece.

[0030] In a third aspect, 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.

[0031] Based on the pole piece, electrode assembly and battery of the embodiment of the present application, by setting the end avoidance area, a winding buffer zone can be provided for the winding of the electrode body, thereby improving the winding stability of the electrode body, reducing the occurrence of winding instability caused by the area with the first convex portion as the winding starting point or winding end point, and in this case, combined with the pole ear area, it is prevented that the intermediate layer of the electrode body with the pole ear assembly is expanded and drives the pole ear assembly to squeeze the electrode body, reducing the damage of the pole ear assembly to the electrode body, and the pole ear area extends to the edge of the pole piece. Because of the presence of the first convex portion, the supporting role played by the first convex portion can be extended to the pole ear area, making it less likely for the pole piece to be squeezed, and a part of the area can be reserved to accommodate the electrolyte, thereby improving the electrolytic infiltration effect. Therefore, the electrode assembly of the embodiment of the present application, by setting the convex point area, the pole ear area and the end avoidance area of ​​the pole piece, can not only improve the interface problem caused by the squeezing between the electrode layers, but also effectively improve the cycle performance of the battery when the electrode assembly is used in the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] 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.

[0033] FIG1 is a schematic diagram of a partial side view of an electrode body according to an embodiment of the present application;

[0034] FIG2 is a schematic diagram of the expanded structure of a pole piece having a pole ear region according to an embodiment of the present application;

[0035] FIG3 is a schematic diagram of the expanded structure of a pole piece having a pole ear region according to another embodiment of the present application;

[0036] FIG4 is a schematic diagram of the unfolded structure of a pole piece when the tab region does not penetrate the convex region according to an embodiment of the present application;

[0037] FIG5 is a schematic diagram of the unfolded structure of a pole piece having a second protrusion according to an embodiment of the present application;

[0038] FIG6 is a schematic diagram of the unfolded structure of the electrode piece when the tab region penetrates the convex region according to an embodiment of the present application;

[0039] FIG7 is a schematic diagram of the unfolded structure of a pole piece when multiple convex regions have equal widths in the length direction of the pole piece according to an embodiment of the present application;

[0040] FIG8 is a schematic diagram of the unfolded structure of a pole piece when the width of multiple convex areas gradually increases in the length direction of the pole piece according to an embodiment of the present application;

[0041] FIG9 is a schematic diagram of the unfolded structure of the pole piece when the first convex portion in the central area of ​​the convex region is relatively large in one embodiment of the present application.

[0042] Figure markings: 20, electrode body; 21, straight part; 22, corner part; 100, tab; 110, second convex portion; 200, protective glue; 40, tab assembly; 50, isolation membrane; 300, pole piece; 310, bump area; 311, first convex portion; 320, tab area; 330, end avoidance area; 331, head avoidance area; 332, tail avoidance area; 341, first area; 342, second area; 3411, first edge; 3421, second edge; 3101, first boundary; 3102, second boundary; 301, positive pole piece; 302, negative pole piece; X, length direction; Y, width direction; Z, thickness direction. DETAILED DESCRIPTION

[0043] 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.

[0044] The inventors found that during the charge and discharge process of the battery, the electrode assembly expands and the extrusion of the corner part of the electrode assembly will be further aggravated, resulting in insufficient electrolyte in the corner part, poor infiltration, easy interface deterioration, and even cycle failure.

[0045] The inventors also found 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 support structures such as bumps and adhesive tape to support the two adjacent winding units, the extrusion problem caused by the expansion of the electrode assembly can be improved, but the improvement effect is still poor. For example, a bump structure is provided on the entire surface of the electrode sheet to support the two adjacent winding units. The interface problem of the electrode sheet in the corner part will be improved, but at the same time it will bring new interface problems to the straight part and negative effects such as insufficient electrolyte.

[0046] Based on this, the embodiments of the present application provide an electrode assembly and a battery, which target and locate the bump distribution design for different positions and degrees of wetting problems and electrode interface problems, so as to effectively improve the wetting and interface problems while reducing the negative impact on the normal interface parts.

[0047] As shown in Figure 1, the electrode assembly of an embodiment of the present application includes two electrode sheets 300 of opposite polarity and a separator 50 disposed between the two electrode sheets 300. As shown in Figure 2, a schematic diagram of the front view of one of the electrode sheets 300 in an unfolded state is shown. The electrode sheets 300 have a length direction X, a width direction Y, and a thickness direction Z that are perpendicular to each other. The length direction X, width direction Y, and thickness direction Z of the two electrode sheets 300 of opposite polarity are consistent. The separator 50 is disposed between the two electrode sheets 300 of opposite polarity in the thickness direction Z. One of the two electrode sheets 300 of opposite polarity is a positive electrode sheet 301, and the other is a negative electrode sheet 302. The separator 50 has insulating properties and is used to separate the positive electrode sheet 301 from the negative electrode sheet 302 to prevent the positive electrode sheet 301 and the negative electrode sheet 302 from shorting.

[0048] In the embodiment of the present application, the isolation film 50 and the two pole pieces 300 are wound multiple times along the length direction X of the pole piece 300 to form the electrode body 20. The length direction X of the pole piece is the direction in which the pole piece is wound, and the width direction Y is perpendicular to the length direction X. The electrode body 20 is flat, and each circle of the pole piece 300 includes two straight portions 21 and two corner portions 22. The two straight portions 21 are connected between the two corner portions 22. Among them, the corner portions 22 of two adjacent circles of pole pieces 300 are prone to mutual extrusion, and the straight portions 21 and corner portions 22 of each circle of pole pieces 300 are also squeezed. Therefore, the corner portions 22 are high-incidence areas for extrusion of the electrode body 20. When the corner portions 22 are squeezed, problems such as insufficient electrolyte and poor infiltration are likely to occur, which in turn leads to deterioration of the interface of the pole piece 300 at the corner portion 22, and even cycle failure.

[0049] In the embodiment of the present application, at least one of the two pole pieces 300 has a convex region 310. The pole piece 300 includes a plurality of first convex portions 311 distributed in the convex region 310. The plurality of first convex portions 311 protrude toward the same side of the pole piece 300 in the thickness direction Z of the pole piece 300. In this way, after the two pole pieces 300 and the isolation film 50 are wound multiple times to form the electrode body 20, the first convex portions 311 provide support for the isolation film 50. When the electrode body 20 expands, the first convex portions 311 can still support the isolation film 50. The contact area between the first convex portions 311 and the isolation film 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 film 50 for accommodating electrolyte, thereby preventing abnormal conditions such as insufficient electrolyte and poor wetting between the pole piece 300 and the isolation film 50 due to expansion and squeezing.

[0050] When the two pole pieces 300 and the separator 50 are flattened and stacked along the thickness direction Z of the pole pieces 300, the multiple first protrusions 311 of one pole piece 300 may protrude toward the side where the other pole piece 300 is located. In this way, after the two pole pieces 300 and the separator 50 are wound along the length direction X of the pole piece 300, the first protrusions 311 of the pole piece 300 protrude toward the side where the winding center of the electrode body 20 is located. Alternatively, when the two pole pieces 300 and the separator 50 are flattened and stacked along the thickness direction Z of the pole piece 300, the multiple first protrusions 311 of one pole piece 300 may face the first protrusion 311 on the side away from the other pole piece 300. In this way, after the two pole pieces 300 and the separator 50 are wound along the length direction X of the pole piece 300, the first protrusion 311 of the pole piece 300 protrudes toward the side away from the winding center of the electrode body 20. When both pole pieces 300 have a convex area 310, the first convex portion 311 of either pole piece 300 protrudes toward the side where the other pole piece 300 is located, or the first convex portion 311 of either pole piece 300 protrudes toward the side away from the other pole piece 300. The above is merely an exemplary introduction, and this application does not limit the direction of the first convex portion 311 of each pole piece 300, and the specific direction can be selected according to actual needs.

[0051] The pole piece 300 includes a current collector and an active material layer, the active material layer is arranged on the surface of the current collector, and the surface of the active material layer facing away from the current collector has a convex area 310, wherein the surface of the active material layer with the convex area 310 facing away from the current collector also has a pole ear area 320 and an end space avoidance area 330, and neither the pole ear area 320 nor the end space avoidance area 330 is provided with a first convex portion 311. After the two pole pieces 300 and the isolation film 50 are wound, the surface of the pole piece 300 corresponding to the pole ear area 320 and the end space avoidance area 330 can be spaced apart from the isolation film 50.

[0052] As shown in Figure 2, the end avoidance area 330 is provided at the end of the convex area 310 in the length direction X of the electrode piece 300 and extends to the edge of the electrode piece 300. Correspondingly, after the two electrode pieces 300 and the isolation film 50 are wound, the end avoidance area 330 can be located in the innermost turns of the electrode body 20, which facilitates the winding of the electrode body 20 and helps to improve the structural stability of the central area of ​​the electrode body 20. Alternatively, the end avoidance area 330 can be located in the outermost turns of the electrode body 20. The end avoidance area 330 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 electrode piece 300 corresponding to the end avoidance area 330 can more stably form a constraint on the inner layer structure of the electrode body 20, which helps to improve the packaging stability of the outer layer area of ​​the electrode body 20. In particular, when the electrode body 20 has a tendency to expand, the end avoidance area 330 without the first protrusion 311 is used to tail, which can prevent the tail of the electrode body 20 from slipping due to expansion stress, thereby improving the structural stability of the electrode body 20.

[0053] As shown in FIG2 , the tab region 320 extends to the edge of the pole piece 300 in the width direction Y of the pole piece 300, and the tab assembly 40 is provided in the tab region 320, 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, as well as the stability of the structure surrounding the tab assembly 40, thereby affecting the stability of the interface of the pole piece 300. For example, when the tab assembly 40 is pressed and installed on the pole 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 or have indentations, thereby causing the interface of the pole piece 300 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.

[0054] It is understood that the wider the distribution of the multiple first protrusions 311 provided on the electrode piece 300, the larger the effective support area of ​​the multiple first protrusions 311 for the entire electrode body 20, and the fewer problems caused by extrusion. However, the inventors of this application have discovered that indiscriminately providing the first protrusions 311 in various areas of the electrode piece 300, while it can alleviate the extrusion problem at the corner portion 22, can negatively impact the straight portion 21, such as poor localized electrolyte infiltration and insufficient electrolyte retention. In an embodiment of the present application, a pole ear area 320 and an end avoidance area 330 are provided in combination, wherein the end avoidance area 330 can provide a winding buffer zone for the winding of the electrode body 20, thereby improving the winding stability of the electrode body 20, reducing the winding instability caused by the area with the first protrusion 311 being the winding starting point or winding end point, protecting the straight portion 21, and in this case, combining the pole ear area 320 to prevent the part of the electrode body 20 where the pole ear assembly 40 is installed from expanding and causing 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 pole ear area 320 extends to the edge of the pole piece 300. Because of the presence of the first protrusion 311, the supporting role played by the first protrusion 311 can be extended to the pole ear area 320, making it less likely for squeezing to occur in the pole ear area 320 of the pole piece 300, 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 part 22, but also reduce the negative problems caused by the extrusion of the straight part 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.

[0055] In the embodiment of the present application, the end clearance region 330 includes at least one of a head clearance region 331 and a tail clearance region 332. The head clearance region 331 and the tail clearance region 332 respectively penetrate the electrode 300 in the width direction Y of the electrode 300. In the length direction X of the electrode 300, the head clearance region 331 is provided at one end of the bump region 310, and the tail clearance region 332 is provided at the other end of the bump region 310. The electrode 300 is wound around the head clearance region 331 and the isolation film 50 along the length direction X of the electrode 300 to form a flat electrode body 20. When it is necessary to select either the head clearance region 331 or the tail clearance region 332, the embodiment of the present application preferably includes the tail clearance region 332 in the end clearance region 330, which further helps to improve the winding stability of the electrode body 20. More preferably, the end clearance area 330 includes both a head clearance area 331 and a tail clearance area 332, which can more effectively improve the winding stability of the electrode body 20. Optionally, in the unfolded state of the electrode piece 300, the outer contour of the head clearance area 331 is rectangular, and the outer contour of the tail clearance area 332 is rectangular.

[0056] As shown in Figure 2, along the lengthwise direction X of the electrode sheet 300, the dimension of the tail clearance area 332 is D, where D satisfies the following: 30 mm ≤ D ≤ 1000 mm. For example, D can be 30 mm, 50 mm, 100 mm, 150 mm, 300 mm, 500 mm, 1000 mm, or a range consisting of any two of these. When the dimension D of the tail clearance area 332 is within the range of 30 mm to 1000 mm, the tail clearance area 332 has an appropriate length for the tail, improving the connection stability at the end of the electrode body 20, thereby ensuring good winding stability for the entire electrode assembly. The distribution range of the bumps adjacent to the outer ring is also appropriate, providing support for the winding units located in the outer ring and alleviating the extrusion problem of the outer ring of the electrode body 20. When D is less than the lower limit of 30 mm, the tail clearance area 332 is too small, and the distance from the bumps in the lengthwise direction X of the electrode sheet 300 to the edge of the electrode sheet 300 is too small, making it difficult to improve the packaging stability at the end of the electrode body 20. When D is greater than the upper limit of 1000mm, the tail clearance area 332 is too large and occupies too much area, resulting in insufficient area for the distribution of the protrusions, poor support effect of the first protrusion 311, and difficulty in improving the electrolyte infiltration effect of the outer ring electrode 300. Preferably, D satisfies: 100mm≤D≤500mm.

[0057] In the longitudinal direction X of the electrode 300, the size of the head clearance area 331 is A, where A satisfies the following conditions: 30mm≤A≤1000mm. For example, A can be 30mm, 50mm, 100mm, 200mm, 1000mm, or a range consisting of any two thereof. When the size A of the head clearance area 331 is within the range of 30mm to 1000mm, it is convenient to set the distribution range of the bump area 310 appropriately, so that the first protrusion 311 located in the inner circle can better play a supporting role and improve the electrolyte infiltration effect of the inner circle of the electrode body 20. At the same time, it is convenient to cooperate with the tail clearance area 332, so that the head clearance area 331 and the tail clearance area 332 have an appropriate spacing for setting the bump area 310, so that the bump area 310 distribution range is appropriate, thereby better improving the extrusion problem. When A is less than the lower limit of 30mm, the size of the head clearance area 331 is too short, which is not convenient for aligning the ends of the two electrode pieces 300 and the isolation membrane 50. When A is greater than the upper limit of 1000 mm, the head clearance zone 331 is too long and occupies a large area, resulting in insufficient support for the inner ring of the electrode body 20, which can easily lead to abnormal conditions such as insufficient electrolyte infiltration in the inner ring of the electrode body 20. Preferably, A satisfies the following: 60 mm ≤ A ≤ 500 mm.

[0058] The convex area 310 is spaced apart from the edge of the pole piece 300 in the width direction Y of the pole piece 300. As shown in Figures 3 and 4, in the width direction Y of the pole piece 300, the pole piece 300 has a first area 341 connected to one side of the convex area 310 and a second area 342 connected to the other side of the convex area 310, and 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 apart from the corresponding edges of the pole piece 300.

[0059] The shortest distance between the convex area 310 and the edge of the electrode 300 coated with the active material layer in the width direction Y is T1, and T1 satisfies: 0.5mm≤T1≤30mm. For example, T1 can be 0.5mm, 1mm, 2mm, 10mm, 15mm, 20mm, 30mm, or a range consisting of any two thereof. When T1 is less than the lower limit of 0.5mm, the convex area 310 is too close to the edge of the electrode 300 coated with the active material layer, which will easily cause the first protrusion 311 to be squeezed and deformed. In addition, due to the stress after processing the first protrusion 311, the width of the area reserved at the edge of the convex area 310 where the first protrusion 311 is not provided is too narrow. The electrode 300 in the edge area is prone to abnormal structures such as bending, unevenness, and wavy edges under the action of stress, which affects the accuracy of monitoring and positioning of the electrode 300 during the winding process. When T1 is greater than the upper limit of 30mm, the protrusion area 310 is too far from the edge of the pole piece 300 coated with the active material layer, the distribution area of ​​the first protrusion 311 is too small, and the supporting force is insufficient. Preferably, T1 satisfies: 1mm≤T1≤30mm. More preferably, T1 satisfies: 3mm≤T1≤30mm. A protective adhesive 200 is affixed to the tab area 320. Within the tab area 320, the active material layer is applied to all areas outside the tab 100, and all other areas of the pole piece 300 are coated with the active material layer. The active material layer of the pole piece 300 is disposed on the surface of the current collector and covers the entire surface of the current collector in the thickness direction of the pole piece 300. In other embodiments, the current collector includes a coating portion and a hollow foil portion. The hollow foil portion is connected to the outside of the coating portion in the width direction Y of the pole piece 300. The active material layer covers the entire surface of the coating portion and avoids the surface of the hollow foil portion. This design can better reduce lithium plating, reduce the impact of cold pressing on cell deformation, and improve battery safety.

[0060] Specifically, the pole piece 300 has a first edge 3411 and a second edge 3421 that are oppositely disposed in the width direction Y of the pole piece 300. The convex region 310 has a first boundary 3101 and a second boundary 3102 that are oppositely disposed in the width direction Y of the pole piece 300. The first region 341 is formed between the first edge 3411 and the first boundary 3101, and the second region 342 is formed between the second edge 3421 and the second boundary 3102. In the width direction Y of the pole piece 300, the distance between the first edge 3411 and the first boundary 3101 is the width T11 of the first region 341 in the width direction Y of the pole piece 300, and the distance between the second edge 3421 and the second boundary 3102 is the width T12 of the second region 342 in the width direction Y of the pole piece 300. When the electrode 300 has a first region 341 and a second region 342, the distance T1 between the convex area 310 and the edge of the active material layer in the width direction Y of the electrode 300 includes T11 and T12, T11 satisfies: 0.5mm≤T11≤30mm, T12 satisfies: 0.5mm≤T12≤30mm, wherein 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 △T1, △T1=|T11-T12|, △T1 satisfies: 0mm≤△T1≤29.5mm. When this range is met, the lithium ion migration rate can be made to meet the appropriate range during the high-rate charge and discharge test, thereby improving the high and low temperature cycle performance of the battery.

[0061] In addition, the tab assembly 40 and the convex area 310 are also spaced apart, which facilitates the processing of the first convex portion 311 on the pole piece 300, and also facilitates the installation of the tab assembly 40 in the tab area 320 of the pole piece 300, and provides installation stability of the tab assembly 40 and structural stability of the first convex portion 311.

[0062] As shown in Figures 2 and 4, the spacing between the tab assembly 40 and the bump area 310 is T2. The spacing between the tab assembly 40 and the bump area 310 includes the spacing in the length direction X and the width direction Y of the pole piece 300, and the spacing in both directions is T2. T2 satisfies the following: 0.5mm≤T2≤30mm. For example, T2 can be 0.5mm, 1mm, 2mm, 8mm, 10mm, 15mm, 20mm, 30mm, or any range consisting of two thereof. When T2 is within the range of 0.5mm to 30mm, the spacing between the tab assembly 40 and the bump area 310 is appropriate, meeting the support requirements of the first protrusion 311 for the tab assembly 40 and facilitating processing. When T2 is less than the lower limit of 0.5mm, the spacing is too small, which can easily affect the structural stability of the first protrusion 311 when the tab assembly 40 is installed in the tab area 320 of the pole piece 300, and the processing is difficult. When T2 is greater than the upper limit of 30 mm, the spacing is too large, the tab area 320 occupies a larger space, and the distribution area of ​​the first protrusions 311 is correspondingly reduced, which easily leads to insufficient supporting force of the first protrusions 311 distributed in the bump area 310.

[0063] The tab assembly 40 includes tabs 100, and there are multiple tabs 100, wherein some of the tabs 100 are installed on one of the pole pieces 300, and another portion of the tabs 100 are installed on the other pole piece 300. The tabs 100 installed on the positive pole piece 301 are positive tabs, and the tabs 100 installed on the negative pole piece 302 are negative tabs. When the tabs 100 are provided on a pole piece 300 having a convex area 310, a tab area 320, and an end avoidance area 330, each tab 100 is provided in one of the tab areas 320. Alternatively, when only one of the two pole pieces 300 with opposite polarities has a convex area 310, a tab area 320, and an end avoidance area 330, then some of the tabs 100 are provided corresponding to the tab area 320 of one of the pole pieces 300, and the other portion of the tabs 100 are directly installed in the edge area of ​​the other pole piece 300. Optionally, when two pole pieces 300 of opposite polarity both have a convex point area 310, a tab area 320, and an end avoidance area 330, a portion of the tabs 100 is provided corresponding to the tab area 320 of one of the pole pieces 300, and another portion of the tabs 100 is provided corresponding to the tab area 320 of one of the pole pieces 300. It should be noted that after the isolation film 50 and the two pole pieces 300 are wound to form a flat electrode body 20, the tab 100 installed on one of the pole pieces 300 needs to be spaced apart from the tab 100 installed on the other pole piece 300 to prevent the two pole pieces 300 of opposite polarity from short-circuiting.

[0064] Optionally, as shown in FIG5 , the tab 100 includes a connecting section connected to the pole piece 300 and a docking section extending from the edge of the pole piece 300. A plurality of second protrusions 110 are provided on the surface of the connecting section facing away from the pole piece. The second protrusions 110 provide support for the structure at the tab 100. For example, the second protrusions 110 are in contact with the isolation membrane 50, providing support for the isolation membrane 50 and improving the electrolyte infiltration effect at the tab 100. Furthermore, the boundary of the region where the tab 100 is provided with the plurality of second protrusions 110 is flush with the second boundary 3102 of the convex area 310. The shape, size, and arrangement of the second protrusions 110 and the first protrusions 311 can be set to be the same.

[0065] 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 from the negative electrode tab and preventing lithium deposition around the negative electrode tab.

[0066] Optionally, all protective adhesives 200 are installed on the same pole piece 300. For example, all protective adhesives 200 are installed on the same pole piece 300 having a convex region 310, a tab region 320, and an end avoidance region 330. Alternatively, all protective adhesives 200 are installed on one of the pole pieces 300 that is not provided with a convex region 310, a tab region 320, and an end avoidance region 330. Alternatively, a portion of the protective adhesive 200 is installed on one of the pole pieces 300, and another portion of the protective adhesive 200 is installed on another pole piece 300. When the protective adhesive 200 is installed on a pole piece 300 having a convex region 310, a tab region 320, and an end avoidance region 330, each protective adhesive 200 is installed on one of the tab regions 320.

[0067] In the embodiment of the present application, the number of the tab area 320 can be one or more. As shown in Figures 2 and 3, the number of the tab area 320 is one, and the tab area 320 extends along the length direction X of the pole piece 300 to connect to the end avoidance area 330. Specifically, in the length direction X of the pole piece 300, one end of the tab area 320 is connected to the head avoidance area 331, and the other end is connected to the tail avoidance area 332. In this way, the outer peripheral contour of the convex area 310 is regular, which facilitates the processing of the first convex portion 311 in the convex area 310 of the pole piece 300, and the processing efficiency is high. In addition, the position of the tab assembly 40 installed in the tab area 320 is relatively flexible, which is convenient for adapting to a variety of different installation requirements.

[0068] Optionally, as shown in FIG. 2, in the width direction Y of the electrode tab 300, the electrode tab 300 has a first region 341 connected to one side of the bump region 310 and an ear region 320 connected to the other side of the bump region 310. That is, in this case, the electrode tab 300 does not have a second region 342. At this time, the width T11 of the first region 341 in the width direction Y of the electrode tab 300 is the distance T1 between the bump region 310 and the edge of the electrode tab 300 in the width direction Y. Among them, in the width direction Y of the electrode tab 300, the width of the ear region 320 is W1, and T1 < W1. In this case, the width of the ear region 320 is relatively wide, which is convenient for increasing the contact area of the ear assembly 40 mounted on the electrode tab 300 and improving the mounting stability of the ear assembly 40. Further, W1 satisfies: 2 mm ≤ W1 ≤ 40 mm. For example, W1 can be 2 mm, 6 mm, 10 mm, 15 mm, 28 mm, 30 mm, 40 mm or any range composed of any two of them.

[0069] Optionally, as shown in FIG. 3, in the width direction Y of the electrode tab 300, the electrode tab 300 has a first region 341 connected to one side of the bump region 310 and a second region 342 connected to the other side of the bump region 310, and a partial region of the second region 342 far from the bump forms the ear region 320. The width of the ear region 320 is W1, and W1 < T1, specifically W1 < T12. In this way, the regions on both sides of the bump region 310 are fully utilized for mounting the ear assembly 40, so as to design more regions for setting the first convex portion 311, increase the support area of the first convex portion 311, and further improve the support stability of the first convex portion 311.

[0070] As shown in FIG. 6, the number of tab regions 320 and bump regions 310 is plural. In the length direction X of the electrode tab 300, one tab region 320 is provided between two adjacent bump regions 310. Each tab region 320 penetrates the electrode tab 300 in the width direction Y of the electrode tab 300, facilitating the machining of the first convex portion 311 on the plural bump regions 310 of the electrode tab 300. Correspondingly, the tab assembly provided in the tab region 320 can extend from one edge of the electrode tab 300 to the other edge in the width direction Y of the electrode tab 300, and both ends of the electrode tab can protrude from the edge of the electrode tab 300. Optionally, the edge profile of the tab region 320 can be a quadrilateral such as a rectangle or a square, and the edge profile of the bump region 310 is a quadrilateral such as a rectangle or a square. Among them, in the length direction X of the electrode tab 300, the width of any tab region 320 is W3, and W3 satisfies: 4 mm ≤ W3 ≤ 100 mm. For example, W3 can be 4 mm, 6 mm, 10 mm, 15 mm, 20 mm, 25 mm, 50 mm, 80 mm, 100 mm or the range composed of any two of them. Setting W3 within the range of 4 mm to 100 mm facilitates the distribution of the widths of the tab region 320 and the bump region 310, improves the support stability of the first convex portion 311 of the bump region 310, and further improves the stability of the structure of the electrode main body 20.

[0071] Please refer to FIG. 4 again. The bump region 310 has at least one avoidance opening region. Each avoidance opening region extends along the width direction Y of the electrode tab 300 to the edge of the electrode tab 300 to form a tab region 320, and the plural avoidance opening regions extend toward the same edge of the electrode tab 300 in the width direction Y of the electrode tab 300. For example, they all extend toward the second edge 3421 of the electrode tab. At this time, the electrode tab 300 has a first region 341 and plural second regions 342. Each avoidance opening region extends along the width direction Y of the electrode tab 300 and passes between two adjacent second regions 342, and then continues to extend to the edge of the electrode tab 300 to form a tab region 320. In this embodiment, by making full use of each part region of the electrode tab 300, the designed areas of both the bump region 3'10 and the tab region 320 can be relatively large, which is suitable for the installation of a tab assembly 40 with a relatively large connection area, and the effective support area of the first convex portion 311 of the bump region 310 is larger. Optionally, in this embodiment, the edge profile of the tab region 320 can be a polygon such as a rectangle or a square. Among them, in the width direction Y of the electrode tab 300, the width of the tab region 320 is W1, and T1 < W1. In this case, the width of the tab region 320 is relatively wide, which is convenient for increasing the contact area when the tab assembly 40 is installed on the electrode tab 300.

[0072] As shown in Figure 7, optionally, the pole ear area 320 is provided at the straight part 21, and the convex area 310 is provided at the corner part 22. In the length direction X of the pole piece 300, the size of the corner part 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 at the corner part 22 to provide support. In this case, the first protrusion 311 can provide good support, and has a balanced wetting effect on the straight part 21 and the corner part 22, thereby improving the shortcomings of the battery cell and improving the overall cycle performance of the battery cell.

[0073] As shown in Figure 8, optionally, the ear area 320 is provided in the straight part 21, the convex area 310 is provided in the corner part 22 and extends to the straight part 21, and the two convex areas 310 of the same circle of the electrode 300 are arranged at intervals. In the length direction X of the electrode 300, the size of the corner part 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 electrode 300, solve the problem of insufficient electrolyte and premature failure in some areas due to uneven wetting, and improve the cycle performance. When the electrode assembly is used in the battery, the charge and discharge cycle life of the battery under 3C / 5C can be improved, and the original 300CL cycle number of the battery can be improved to more than 800CL.

[0074] 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.

[0075] As shown in FIG7 , the pole piece 300 can optionally have the same size W6 of all convex areas 310 in the length direction X of the pole piece 300. It can be understood that the circumference of each pole piece 300 gradually increases from the inner circle to the outer circle of the electrode body 20, wherein the size of the corner portion 22 of the outermost pole piece 300 in the length direction X of the pole piece 300 is W. max , W6≥W max 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 part 22, and some of the convex areas 310 can extend to partially cover the straight part 21 while covering the corner part 22.

[0076] Optionally, from the inner circle to the outer circle of the electrode body 20, the size W6 of the convex area 310 in the length direction X of the pole piece 300 gradually increases. At this time, from the inner circle to the outer circle of the electrode body 20, the size W6 of the convex area 310 in the length direction X of the pole piece 300 gradually increases with the increase of the size of the corner part 22 in the length direction X of the pole piece 300. In this case, the size W6 of the convex area 310 in the length direction X of the pole piece 300 may be equal to the size of the corresponding corner part 22 in the length direction X of the pole piece 300, that is, the convex area 310 only covers the corresponding corner part 22; or, the size W6 of the convex area 310 in the length direction X of the pole piece 300 may also be greater than the size of the corresponding corner part 22 in the length direction X of the pole piece 300, that is, the convex area 310 covers the corresponding corner part 22 while also extending to the straight part 21.

[0077] In the embodiment of the present application, the first protrusion 311 has a vertex and a bottom edge. The bottom edge of the first protrusion 311 is connected to the surface of other structures of the electrode 300 (the surface can be a flat surface or a convex arc surface). The first protrusion 311 extends from its bottom edge to protrude from the surface connected thereto. The vertex of the first protrusion 311 is the point of the first protrusion 311 farthest from the bottom edge in the thickness direction of the electrode 300. The thickness of the first protrusion 311 is the dimension from the vertex of the first protrusion 311 to the bottom edge of the first protrusion 311 in the thickness direction of the electrode 300. When the corner portion 22 has the first protrusion 311, the height of the first protrusion 311 provided at the corner portion 22 is h1. When the straight portion 21 has the first protrusion 311, the height of the first protrusion 311 provided at the straight portion 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 portion 21 is h2, and h2 satisfies: 10 μm≤h2≤18 μm.

[0078] It should be noted that, in addition to the solutions in Figures 7 and 8, in the embodiments of the present application, when the straight portion 21 and the corner portion 22 are respectively provided with a first convex portion 311, h2≤h1, 55μm≤h1≤70μm, and 10μm≤h2≤18μm are satisfied.

[0079] In addition, preferably, after the electrode piece 300 is used to be wound multiple times with the isolation membrane 50 along the length direction of the electrode piece 300 to form the electrode body 20, the multiple first protrusions 311 of each circle of the electrode piece 300 are protruded toward the winding center of the electrode body 20 in the thickness direction of the electrode piece 300, which has a better improvement effect on the infiltration of the electrolyte.

[0080] 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 and damaging the isolation membrane 50.

[0081] Optionally, the outer contours of the first convex portions 311 are of equal size. For example, when the outer contour of the first convex portion 311 is circular, the outer contour radii of the first convex portion 311 of each circle are 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.

[0082] 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 8 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 9, 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.

[0083] The pole piece 300 of the embodiment of the present application includes a current collector and an active material layer disposed on the surface of the current collector. 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 formed by rolling. Specifically, a rolling method is applied to a portion of the pole piece 300 on one side of the pole piece 300, causing the current collector and the active material layer in that region to deform and bend together, thereby forming the first protrusion 311.

[0084] The embodiments of the present application have no particular restrictions on the positive electrode sheet 301 , the negative electrode sheet 302 , the separator 50 , the positive electrode tab 100 , and the negative electrode tab 100 . Various components that can be used as electrode assemblies that are well known in the art are applicable to the present application.

[0085] In some exemplary embodiments, the negative electrode sheet 302 may include a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector. For example, 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, in the thickness direction ZZ of the negative electrode sheet, the negative electrode active material layer may be coated only on a portion of the negative electrode current collector. For example, the thickness of the negative electrode active material layer may be 10 μm to 500 μm.

[0086] 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.

[0087] In some exemplary embodiments, the positive electrode sheet 301 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 Z of the positive electrode sheet 301, 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.

[0088] 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.

[0089] In some exemplary embodiments, separator 50 includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid. For example, polyethylene includes 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 a shutdown effect. The thickness of separator 50 ranges from approximately 3 μm to 500 μm.

[0090] 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.

[0091] 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.

[0092] In each embodiment and comparative example of the present application, lithium-ion batteries were prepared and their performance was tested using the following method:

[0093] 1. Preparation method of lithium-ion battery

[0094] (1) Preparation of positive electrode sheet 301

[0095] The positive electrode active material, lithium cobalt oxide (LiCoO2), the conductive agent, conductive carbon black, and the 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 coated on the positive electrode current collector and dried, cold pressed, and cut to obtain a positive electrode sheet. The compacted density of the positive electrode active material layer of the positive electrode sheet 301 was 4.2g / cm 3 .

[0096] In the following embodiments, the positive electrode plate 301 has a convex point area 310 , a tab area 320 and an end free space area 330 .

[0097] (2) Preparation of negative electrode sheet 302

[0098] 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 coated on the negative electrode current collector, dried, cold pressed, and cut to obtain a negative electrode sheet. The compacted density of the negative electrode active material layer of the negative electrode sheet was 1.8g / cm 3 .

[0099] (3) Preparation of isolation film 50

[0100] 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%.

[0101] (4) Preparation of electrolyte

[0102] 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%.

[0103] (5) Assembly of lithium-ion electronics

[0104] The positive tab 100 is installed on one tab area 320 of the positive electrode sheet 301 by rolling, the protective glue 200 is attached to the other tab area 320 of the positive electrode sheet 301, and the negative tab 100 is installed on the edge area of ​​the negative electrode sheet 302 by rolling.

[0105] The positive electrode sheet 301 with the positive electrode tab 100 installed, the separator 50, and the negative electrode sheet 302 with the negative electrode tab 100 installed are stacked in sequence, with the separator 50 positioned between the positive electrode sheet 301 and the negative electrode sheet 302 to provide isolation. The electrodes are then wound to form the electrode body 20. The electrode assembly is placed in an outer packaging aluminum-plastic film, 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.

[0106] 2. Performance test of lithium-ion batteries

[0107] (1) 25℃ cycle test

[0108] In a 25°C environment, perform constant current charging of the electrode assembly at a charging current of 2C / 5C to the full charge voltage (the battery is designed for a maximum voltage of 4.5V). Then, perform constant voltage charging at the maximum voltage until the current reaches 0.02C. Then, perform constant current discharge at a discharge current of 0.5C until the final voltage reaches 3.0V. Record the discharge capacity of the first cycle. Repeat the above steps for charge and discharge cycles, and record the cycle number N at which the cycle capacity retention rate begins to be less than or equal to 80%.

[0109] Cycle capacity retention rate=(discharge capacity at the Nth cycle / discharge capacity at the first cycle)×100%.

[0110] (2) 45℃ cycle test

[0111] In a 45°C environment, perform constant current charging of the electrode assembly at a charging current of 2C / 5C to the full charge voltage (the battery is designed for a maximum voltage of 4.5V). Then, perform constant voltage charging at the maximum voltage until the current reaches 0.02C. Then, perform constant current discharge at a discharge current of 0.5C until the final voltage reaches 3.0V. Record the discharge capacity of the first cycle. Repeat the above steps for charge and discharge cycles, and record the cycle number N when the cycle capacity retention rate is <80%.

[0112] Cycle capacity retention rate=(discharge capacity at the Nth cycle / discharge capacity at the first cycle)×100%.

[0113] (3) Winding quality test

[0114] An electrode body is formed by placing a separator between two electrode sheets 300 (a positive electrode sheet 301 and a negative electrode sheet 302) of opposite polarity on an integrated winding machine. An X-ray device is used to measure the distance M (a value greater than 0.1 mm) between the edge of the negative electrode sheet 302 of the electrode body and the edge of the positive electrode sheet 301 in the width direction of the positive electrode sheet 301. Samples are continuously prepared, and the total number of samples T (a total of 100) and the number of qualified products N are counted.

[0115] Winding rate = N / T × 100%

[0116] (4) Wetting improvement effect test

[0117] After the electrode assembly is placed in the outer packaging aluminum-plastic film injection process, it is left at room temperature (25°C) for 24 hours, disassembled and observed for the wetting of the isolation membrane, and the area size of the wetted part is estimated and compared, and divided into three levels: significant (wetting area is 60% to 100%), moderate (wetting area is 30% to 60%), and no difference (wetting area is 0% to 30%); the non-wetted area is usually an irregular water pattern boundary, and the difference in area size can be directly observed visually.

[0118] (5) Liquid retention test

[0119] The electrolyte retention volume is the amount of electrolyte that is ultimately retained in the lithium-ion battery. To ensure the consumption of electrolyte during the formation of the lithium-ion battery, a certain amount of electrolyte is usually injected, and then the excess electrolyte is withdrawn after formation. It is measured by weighing, with the injection volume m1 and the withdrawal volume m2.

[0120] Liquid retention volume = m1-m2.

[0121] In Table 1, Examples 1-1 to 1-21 use the electrode 300 shown in FIG4 as the positive electrode 300. The relevant parameters of Examples 1-1 to 1-21 are shown in Table I.

[0122] Table I

[0123] The difference between Comparative Examples 1-1 to 1-3, Examples 1-2 to 1-21 and Example 1-1 is that the distance T1 between the convex area 310 and the edge of the electrode, the distance T21 between the tab and the convex area 310, and the distance T22 between the protective glue and the convex area 310 of the lithium-ion battery are different (here, the distance T2 between the tab and the convex area 310 of the lithium-ion battery is recorded as T21, and the distance T2 between the protective glue and the convex area 310 is recorded as T22 for convenience of expression). The parameters and performance test results of the lithium-ion batteries in Comparative Examples 1-1 to 1-3 and Examples 1-1 to 1-21 are shown in Table 1.

[0124] Table 1

[0125] According to Comparative Examples 1-1 to 1-3 and Examples 1-1 to 1-9 in Table 1, it can be seen that the spacing T1 between the convex area 310 and the edge of the pole piece 300 satisfies: 0.5mm≤T1≤30mm, the flatness of the edge of the pole piece 300 is good, the room temperature and high temperature cycle performance of the lithium-ion battery is improved, and the high rate charge and discharge performance is greatly improved. In addition, the winding rate in the actual production process will also be improved. When T1 is less than the lower limit of 0.5mm, since the first protrusion 311 is too close to the edge of the pole piece 300, when the first protrusion 311 is rolled out on the pole piece 300, the edge of the pole piece 300 is prone to wavy curling due to rolling stress, poor flatness, and reduced cycle performance of the lithium-ion battery. When T1 is greater than the upper limit of 30 mm, the area of ​​the convex region 310 is too small, and the effective support area of ​​the first protrusion 311 provided in the convex region 310 is insufficient, resulting in insufficient electrolyte channels for the lithium-ion battery, poor improvement in high-temperature and room-temperature cycle performance, and inability to improve high-current charge and discharge performance, which will also have a negative impact on the winding efficiency.

[0126] As shown in Examples 1-10 to 1-15 in Table 1, when the spacing T21 between the tab 100 and the bump area 310 is between 1 mm and 30 mm, the normal-temperature and high-temperature cycling performance of the lithium-ion battery is improved, and the high-rate charge and discharge performance is significantly enhanced. Furthermore, the winding quality in the actual production process is also improved.

[0127] As shown in Examples 1-16 to 1-21 in Table 1, when the spacing T22 between the protective adhesive and the bump area 310 is between 0.5 mm and 30 mm, the normal-temperature and high-temperature cycling performance of the lithium-ion battery is improved, and the high-rate charge and discharge performance is significantly enhanced. Furthermore, the winding efficiency in the actual production process is also improved.

[0128] In Table 2, Comparative Examples 2-1 to 2-2, Examples 1-4, and Examples 2-1 to 2-12 use the electrode sheet 300 shown in FIG4 as the positive electrode sheet 300. The differences between Examples 2-1 to 2-12 and Example 1-4 are that the dimension W1 of the tab region in the width direction Y of the tab region and the dimension of the tab region in the length direction X of the tab region are different, and the spacing T21 between the tab and the bump region and the spacing T22 between the protective adhesive and the bump region are equal and are both 4 mm. The parameters and performance test results of the lithium-ion batteries in Comparative Examples 2-1 to 2-2, Examples 1-4, and Examples 2-1 to 2-12 are shown in Table 2.

[0129] Table 2

[0130] It can be seen from Comparative Examples 2-1 to 2-2, Examples 1-4, and Examples 2-1 to 2-7 in Table 2 that in the embodiments of the present application, providing the pole piece 300 with a convex point area 310 and an end avoidance area 330 can effectively improve the room temperature cycle and high temperature cycle performance of the lithium-ion battery.

[0131] Among them, according to Example 2-12, Comparative Example 1-1 and Comparative Example 1-2, it can be seen that when the pole piece 300 has a head avoidance area 331 and a tail avoidance area 332, it has basically no effect on the winding excellence. On the contrary, when the head avoidance area 331 and the tail avoidance area 332 are cancelled, the winding excellence will drop significantly.

[0132] As can be seen from Comparative Example 2-1 to Example 2-2, Examples 1-4, and Examples 2-1 to 2-12, by configuring the electrode 300 with a bump region 310, a tab region 320, and an end clearance region 330, the cycling performance of the lithium-ion battery at both room and high temperatures can be improved. This is due to the combined effect of the appropriate design of the tab region 320 and the end clearance region 330. A properly dimensioned W1 of the tab region 320 in the width direction Y of the electrode 300 allows the bump region 310 to avoid the tab and the adhesive tape, preventing the tab and the adhesive tape from damaging the interface. A properly dimensioned W3 of the tab region 320 in the length direction X of the electrode 300 allows the bump region 310 to occupy a sufficiently large area, further significantly improving the cycling performance of the lithium-ion battery. Properly designing both W1 and W3 allows the bump region 310 to occupy a sufficiently large area while avoiding the tab and the adhesive tape, achieving the best improvement in both high-temperature and room-temperature cycling performance.

[0133] According to Examples 1-4, 2-1 to 2-3, 2-9 to 2-12, and Comparative Examples 2-1 to 2-2, it can be seen that the dimension W1 of the tab area 320 in the length direction X of the pole piece 300 satisfies: 2mm≤W1≤40mm, and the cycle performance of the lithium-ion battery can be improved. The improvement of the 2C high-rate charge and discharge cycle is more significant. The main reason is that the reasonable setting of W1 can improve the interface and avoid the tab at the same time, reducing damage to the tab. When W1 is greater than the upper limit of 40mm, although the tab is avoided, the area of ​​the convex area is reduced due to the excessive avoidance spacing, thereby weakening the improvement effect on the poor interface and ultimately causing the cycle performance to decline.

[0134] According to Examples 2-4 to 2-7, Examples 2-10 to 2-12, and Comparative Examples 2-1 to 2-2, it can be seen that the dimension W3 of the tab region 320 in the length direction X of the pole piece 300 satisfies the following conditions: 10 mm ≤ W3 ≤ 50 mm. This improves both the room temperature and high temperature cycling performance of the lithium-ion battery, with the improvement being more significant under 2C high-rate charge and discharge cycling conditions. When W3 is greater than the upper limit of 50 mm, the distance between the bump region and the tab region is too large, resulting in a weakened improvement in the areas on both sides of the tab, which in turn affects the cycling performance.

[0135] In Table 3, Examples 3-1 to 3-12 use the electrode sheet 300 shown in FIG4 as the positive electrode sheet 300. The difference between Examples 3-1 to 3-12 and Example 1-2 lies in the difference in the size A of the head clearance area and the size D of the tail clearance area of ​​the lithium-ion battery. The parameters and performance test results of the lithium-ion batteries in Examples 3-1 to 3-12 are shown in Table 3.

[0136] Table 3

[0137] According to Examples 3-1 to 3-4 and 3-9 to 3-10 in Table 3, the dimension A of the head avoidance zone 331 satisfies the following conditions: 30mm≤A≤1000mm, which has little impact on the winding efficiency and improves both the room temperature cycling performance and the high temperature cycling performance of the battery at high rate current density. When A is less than the lower limit of 30mm, the winding feeding accuracy is affected. When A is greater than the upper limit of 1000mm, the avoidance zone is too large, the area of ​​the bump area is reduced, and the cycling improvement effect is reduced. Preferably, A satisfies the following conditions: 60mm≤A≤500mm.

[0138] According to Examples 3-5 to 3-8 and 3-11 to 3-12 in Table 3, it can be seen that the size D of the tail avoidance area 332 satisfies: 30mm≤D≤1000mm, which has a relatively small effect on the winding efficiency of the lithium-ion battery, while improving both the room temperature cycle performance and the high temperature cycle performance at a current density of 5C. When D is lower than the lower limit of 30mm, it will affect the winding tail accuracy, resulting in insufficient winding efficiency. When D is higher than the upper limit of 1000mm, the cycle performance of the lithium-ion battery will decrease and fall back. This is because when D is too large, a convex point is added to the interface area of ​​the original straight part of the tail, resulting in an excessively large interlayer spacing of the original straight part, an increase in the lithium ion transmission path, and a decrease in efficiency, resulting in insufficient lithium insertion, which ultimately affects the cycle performance.

[0139] In Table 4, Examples 4-1 to 4-8 use the electrode 300 shown in FIG7 as the positive electrode 300, W6 is the size of the bump area in each circle of the electrode, and the size of the bump area in each circle of the electrode is equal. The parameters and performance test results of the lithium-ion batteries in Examples 4-1 to 4-8 and Example 1-4 are shown in Table 4. The size A of the head avoidance area, the size D of the tail avoidance area, and the distance T1 between the bump area and the edge of the electrode in Examples 4-1 to 4-8 are the same as those in Example 1-4.

[0140] Table 4

[0141] In Table 5, Examples 5-1 to 5-9 use the electrode 300 shown in Figure 8 as the positive electrode 300. The size A of the head avoidance area, the size D of the tail avoidance area, and the spacing T1 between the convex area and the edge of the electrode in Examples 5-1 to 5-9 are the same as those in Examples 1-4. The parameters and performance test results of the lithium-ion batteries in Comparative Example 5-1 and Examples 5-1 to 5-9 are shown in Table 5. In Figure 8, the size W6 of the convex area gradually increases from the inner circle to the outer circle. The W6 in Table 5 is the size of the convex area of ​​the electrode in the outermost circle, wherein the size W6(i) of the convex area of ​​the i-th circle from the outside to the inside is calculated according to the following formula: W6(i)=W6-(i*t*π)

[0142] Where i is the number of layers of the electrode assembly from the outside to the inside;

[0143] t is the thickness of the electrode 0.12 mm;

[0144] When W6(i) is less than 0, it means that no bump is set on this layer.

[0145] Table 5

[0146] According to the embodiments in Table 4 and Table 5, it can be seen that when the convex area 310 is provided corresponding to the corner portion 22, and the sizes of the convex areas 310 of the pole piece 300 in the length direction X of the pole piece 300 are equal or approximately equal, the size W6 of the convex area 310 in the length direction X of the pole piece 300 satisfies: 0.5mm≤W6≤100m, and the electrolyte retention and electrolyte infiltration effect of the lithium-ion battery are improved.

[0147] When W6 is too small, the size of the convex area 310 in the length direction X of the electrode 300 is too small, the area ratio of the convex area 310 is greatly reduced, and it cannot effectively support the extrusion of the battery cell. The electrolyte channel is blocked, resulting in a decrease in cycle performance.

[0148] When W6 is greater than the upper limit of 100mm, the size of the convex area 310 in the length direction X of the electrode 300 is too large, almost covering all areas of the electrode. On the one hand, the avoidance is insufficient, and the positions of the electrode ears and the impregnated adhesive tape cannot even be avoided, causing the interface between the electrode ears and the impregnated adhesive tape to deteriorate, and eventually spread to the entire electrode, resulting in a significant weakening of the cycle performance improvement effect. This weakening of the improvement effect is more significant in the test of high-rate batteries.

[0149] 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.

[0150] 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, characterized in that, The pole piece includes a current collector and an active material layer disposed on the surface of the current collector. The surface of the active material layer facing away from the current collector has a tab area, a bump area, and an end clearance area; the pole piece includes a plurality of first protrusions distributed in the bump area, and the plurality of first protrusions protrude toward the same side of the pole piece in the thickness direction of the pole piece; the end clearance area is disposed at the end of the bump area in the length direction of the pole piece and extends to the edge of the pole piece; the tab area extends to the edge of the pole piece in the width direction of the pole piece, and the tab area is used to dispose a tab assembly. In the width direction of the pole piece, the shortest distance between the bump area and the edge of the active material layer is T1, and T1 satisfies: 0.5 mm ≤ T1 ≤ 30 mm; the interval between the tab assembly and the bump area is T2, and T2 satisfies: 0.5 mm ≤ T2 ≤ 30 mm.

2. The pole piece according to claim 1, characterized in that, The end clearance area includes a head clearance area and a tail clearance area. In the length direction of the pole piece, the head clearance area is disposed at one end of the bump area, and the tail clearance area is disposed at the other end of the bump area; the pole piece is used to wind with a separator film along the length direction of the pole piece from the head clearance area to form a flat electrode body.

3. The pole piece according to claim 2, wherein In the length direction of the pole piece, the size of the head clearance area is A, and the size of the tail clearance area is D. A satisfies: 30 mm ≤ A ≤ 1000 mm, and D satisfies: 30 mm ≤ D ≤ 1000 mm.

4. The pole piece according to claim 3, characterized in that, In the length direction of the pole piece, A satisfies: 60 mm ≤ A ≤ 500 mm, and D satisfies: 100 mm ≤ D ≤ 500 mm.

5. The pole piece according to claim 1, characterized in that, T1 satisfies: 1 mm ≤ T1 ≤ 30 mm.

6. The pole piece according to claim 1, wherein T1 satisfies: 3 mm ≤ T1 ≤ 30 mm.

7. The pole piece according to claim 1, wherein T1 satisfies: 3 mm ≤ T1 ≤ 20 mm.

8. The pole piece according to claim 1, characterized in that, In the width direction of the pole piece, the surface of the active material layer facing away from the current collector has a first area connected to one side of the bump area and a second area connected to the other side of the bump area. The first area extends to the edge of the active material layer along the direction away from the second area, and the second area extends to the edge of the active material layer along the direction away from the first area. Let T11 be the width of the first area in the width direction of the pole piece, and T12 be the width of the second area in the width direction of the pole piece. The difference between T11 and T12 is ΔT1, ΔT1 = |T11 - T12|, and ΔT1 satisfies: 0 mm ≤ ΔT1 ≤ 29.5 mm.

9. The pole piece according to claim 1, characterized in that, The tab assembly includes a tab; and / or, the tab assembly includes a protective adhesive.

10. The pole piece according to claim 1, characterized in that, The number of the tab areas is one, and the tab area extends in the length direction of the pole piece to be connected to the end clearance area.

11. The pole piece according to claim 1, characterized in that, In the width direction of the pole piece, the surface of the active material layer facing away from the current collector has a first area connected to one side of the bump area. The first area is located on the side of the bump area facing away from the tab area and extends to the edge of the pole piece. The width of the tab area in the width direction of the pole piece is W1, and W1 satisfies: 2 mm ≤ W1 ≤ 40 mm.

12. The pole piece according to claim 1, characterized in that, The number of the tab areas and the bump areas is plural; in the length direction of the pole piece, one tab area is provided between two adjacent bump areas, and each tab area penetrates the pole piece in the width direction of the pole piece.

13. The pole piece according to claim 1, wherein, The bump area has at least one avoidance opening area, and each avoidance opening area extends to the edge of the pole piece in the width direction of the pole piece to form the tab area, and a plurality of the avoidance opening areas extend toward the same edge of the pole piece in the width direction of the pole piece.

14. The pole piece according to claim 12 or 13, characterized in that, The size of the tab area in the length direction of the pole piece is W3, and W3 satisfies: 10 mm ≤ W3 ≤ 50 mm.

15. The electrode sheet according to claim 1, characterized in that, The pole piece is used to wind multiple turns with the separator along the length direction of the pole piece to form an electrode body; each turn of the pole piece includes a straight part and corner parts provided at both ends of the straight part, and the tab area is provided on the straight part; in the length direction of the pole piece, the size of the corner part is W5, and the size of the bump area is W6; The bump area is provided at the corner part, wherein, W6 = W5; or, The bump area is provided at the corner part and extends to the straight part, and two bump areas of the same turn of the pole piece are arranged at intervals, wherein, W6 > W5.

16. The pole piece according to claim 15, wherein W5 satisfies: 0.5 mm ≤ W5 ≤ 20 mm; and / or, W6 satisfies: 0.5 mm ≤ W6 ≤ 100 mm.

17. The pole piece according to claim 15, wherein The sizes W6 of all the bump areas in the length direction of the pole piece are equal; or, From the inner circle to the outer circle of the electrode body, the size W6 of the bump area in the length direction of the pole piece gradually increases.

18. The electrode tab according to claim 1, wherein The pole piece is used to wind multiple turns with the separator along the length direction of the pole piece to form an electrode body; each turn of the pole piece includes a straight part and corner parts provided at both ends of the straight part, and the tab area is provided on the straight part; The height of the first convex part provided at the corner part is h1, and h1 satisfies: 55 μm ≤ h1 ≤ 70 μm; The height of the first convex part provided on the straight part is h2, and h2 satisfies: 10 μm ≤ h2 ≤ 18 μm.

19. The pole piece according to claim 1, characterized in that, The pole piece is used to wind multiple turns with the separator along the length direction of the pole piece to form an electrode body; a plurality of the first convex parts of each turn of the pole piece protrude toward the winding center of the electrode body in the thickness direction of the pole piece.

20. The pole piece according to claim 1, wherein The outer contour of the first convex part is circular, oval or regular polygon; or, The outer contour sizes of the first convex part are equal; or, In the width direction of the pole piece, the outer contour size of the first convex part gradually decreases from the central area to the edge area of the bump area; or; In the length direction of the pole piece, the outer contour size of the first convex part gradually decreases from the central area to the edge area of the bump area.

21. An electrode assembly, characterized in that, It includes a plurality of tab components, the pole piece according to any one of claims 1-20 above, and a separator provided between two pole pieces, and the separator and the two pole pieces are wound along the length direction of the pole piece to form a flat electrode body.

22. The electrode assembly according to claim 21, wherein, The tab assembly includes tabs, and the tabs are disposed in the tab area of the electrode tab; the tabs include a connecting section connected to the electrode tab and a docking section extending out of the edge of the electrode tab, and a plurality of second protrusions are convexly provided on the surface of the connecting section facing away from the electrode tab.

23. A battery, characterized in that, Comprising: a housing; and the electrode assembly as described in claim 22 above, and the electrode assembly is disposed in the internal space of the housing.

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