Pole piece, battery cell and battery module

Abstract

The utility model belongs to the technical field of batteries, and discloses a pole piece, a battery cell and a battery module, the pole piece comprises a pole piece body and N tabs, and the pole piece body has a length direction and a width direction which are perpendicular to each other; the N tabs are arranged at intervals along the length direction of the pole piece body, the bottom widths of the N tabs are sequentially decreased progressively and then increased progressively along the length direction of the pole piece body, and the N tabs are overlapped after the pole piece body is wound; n is a positive integer greater than or equal to 3. According to the technical scheme, the tab with the small bottom width can fall in the area of the tab with the large bottom width, even if some deviation exists, the edges of the two sides of the tab with the small bottom width cannot exceed the edge of the tab with the large bottom width, and the tab dislocation phenomenon caused by the size precision of the winding needle and the thickness precision of the pole piece can be counteracted. The N tabs are not in the trend of decreasing in sequence, so that the bottom width value of the tab with the narrowest bottom width is not too narrow, the width of the tabs meets the ultrasonic welding requirement, the welding firmness and the overcurrent capability of the N tabs are ensured, and the yield of the battery is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, and in particular to a pole piece, a battery core and a battery module. Background Art

[0002] The method of winding pole pieces to make batteries is conducive to increasing production speed and reducing production costs. In order to increase battery energy density, multi-pole tab pole pieces are often used for winding. In the winding process of multi-pole tab pole pieces, due to the error in the winding needle processing size accuracy and the error in the thickness of the pole piece incoming material, the pole tabs are misaligned after winding. Severe misalignment will affect the ultrasonic welding of the pole tabs and the adapters in the later stage and the assembly of the battery cell, increase defects in the production process, and affect product performance.

[0003] In the multi-electrode winding battery cell disclosed in the prior art, the width of the multiple pole ears gradually decreases from the starting end to the ending end of the winding. The pole ears with reduced width layer by layer after winding can avoid the influence of pole ear misalignment and make the alignment degree of multiple pole ears higher.

[0004] However, the above scheme has the following defects: due to the decreasing width of the pole lugs, when the number of pole lugs is large, one or more pole lugs at the end are narrower. After the pole piece is wound, the overlapping pole lugs need to be ultrasonically welded, and the ultrasonic weld marks formed on the pole lugs must meet certain size requirements to ensure the welding firmness and current carrying capacity of the pole lug position. In the above scheme, the width of the pole lug at the end may be less than the length of the designed weld mark, resulting in poor welding and seriously affecting the performance of the battery.

[0005] Therefore, there is an urgent need for a pole piece, a battery cell and a battery module to solve the above problems. Utility Model Content

[0006] The purpose of the utility model is to provide a pole piece, a battery cell and a battery module, which can not only solve the problem of misalignment between pole ears after winding of a multi-ear pole piece, but also ensure that the width of the pole ear meets the requirements of ultrasonic welding, thereby improving the yield rate of the battery.

[0007] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0008] In a first aspect, a pole piece is provided, comprising:

[0009] The pole piece body has a length direction and a width direction that are perpendicular to each other;

[0010] N pole tabs are arranged at intervals along the length direction of the pole piece body, the bottom widths of the N pole tabs decrease and then increase in sequence along the length direction of the pole piece body, and the N pole tabs overlap after the pole piece body is wound;

[0011] N is a positive integer greater than or equal to 3.

[0012] As a preferred solution of the pole piece provided by the utility model, the N pole ears include a middle pole ear and two end pole ears located at both ends;

[0013] If N is an odd number, the (N+1) / 2th pole lug is the middle pole lug;

[0014] If N is an even number, the N / 2th pole lug and the (N / 2)+1th pole lug are the middle pole lugs;

[0015] Among the N pole tabs, the bottom width of the middle pole tab is the narrowest, and the bottom widths of the two end pole tabs are consistent.

[0016] As a preferred solution of the pole piece provided by the utility model, the bottom width of the end pole ear is a, the bottom width of the middle pole ear is b, and b<a;

[0017] If N is an odd number, the difference in bottom width between two adjacent tabs is Δw=2(ab) / (N-1);

[0018] If N is an even number, the bottom width difference between the two middle pole ears Δw=0; the bottom width difference between the non-middle pole ears, and the bottom width difference between the middle pole ear and the non-middle pole ear are both Δw=2(ab) / (N-2); the non-middle pole ear is the pole ear other than the middle pole ear.

[0019] As a preferred solution of the pole piece provided by the utility model, the bottom width a of the end pole lug and the bottom width b of the middle pole lug satisfy: b≥a / 2.

[0020] As a preferred solution of the pole piece provided by the utility model, the difference Δw between the bottom widths of two adjacent pole ears ranges from 0 to 4 mm.

[0021] As a preferred solution of the pole piece provided by the utility model, ultrasonic welding marks are provided on the N pole ears, and the N pole ears are fixedly connected at the ultrasonic welding marks. The dimension of the ultrasonic welding marks along the length direction of the pole piece body is L, and the bottom width of the pole ear with the narrowest bottom width is 0.8mm to 2mm larger than L.

[0022] As a preferred solution of the pole piece provided by the utility model, the heights of the N pole ears are consistent;

[0023] Alternatively, the heights of the N pole ears gradually increase along the length direction of the pole piece body.

[0024] As a preferred solution of the pole piece provided by the utility model, the center distance between two adjacent pole ears gradually increases along the length direction of the pole piece body.

[0025] As a preferred solution of the pole piece provided by the utility model, the pole lug is trapezoidal, and the lower bottom edge of the pole lug is connected to the pole piece body.

[0026] In a second aspect, a battery cell is provided, comprising a shell and a winding core assembly arranged in the shell, the winding core assembly comprising a first diaphragm, a positive electrode sheet, a second diaphragm and a negative electrode sheet stacked in sequence, and the positive electrode sheet and the negative electrode sheet both adopt the electrode sheets as described above.

[0027] In a third aspect, a battery module is provided, comprising a plurality of battery cells as described above.

[0028] Beneficial effects of the utility model:

[0029] The utility model provides a pole piece, a battery cell and a battery module, wherein the pole piece comprises a pole piece body and N pole ears arranged on the pole piece body, one end of the pole piece body is fixed, and the other end is wound to form a winding core, and the N pole ears overlap after winding. The bottom widths of the N pole ears decrease and then increase in sequence along the length direction of the pole piece body. Among the N overlapping pole ears, the two adjacent pole ears have different bottom widths, so the pole ear with a smaller bottom width will fall in the area of ​​the pole ear with a larger bottom width. Even if there is a slight deviation, the edges on both sides of the pole ear with a smaller bottom width will not exceed the edges of the pole ear with a larger bottom width. The design of the width difference between adjacent pole ears can offset the pole ear misalignment phenomenon caused by the winding needle size accuracy and the pole piece thickness accuracy. In addition, since the bottom widths of the N pole ears decrease and then increase in sequence along the length direction of the pole piece body, rather than showing a decreasing trend, the bottom width value of the pole ear with the narrowest bottom width will not be too narrow, so that the width of the pole ear meets the ultrasonic welding requirements, ensures the welding firmness and current capacity of the N pole ears, and improves the battery yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural schematic diagram of the first pole piece provided by the specific implementation mode of the utility model;

[0031] Figure 2 It is a structural schematic diagram of a second pole piece provided by a specific embodiment of the utility model;

[0032] Figure 3 It is a schematic diagram of a pole piece wound into a winding core assembly provided by a specific embodiment of the utility model;

[0033] Figure 4 It is a schematic diagram of a plurality of pole ears after the first pole piece is wound provided by a specific embodiment of the utility model;

[0034] Figure 5 It is a schematic diagram of a plurality of pole ears after the second pole piece is wound according to a specific embodiment of the utility model.

[0035] In the figure:

[0036] 1. Pole body; 2. Pole ear;

[0037] 100. Core assembly. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only the parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0039] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] In the present utility model, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0041] In the description of this embodiment, the terms "upper", "lower", "left", "right" and other directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplified operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0042] like Figure 1 and Figure 2 As shown, this embodiment provides a pole piece, in particular a multi-ear pole piece, comprising a pole piece body 1 and N pole ears 2. The pole piece can not only solve the problem of misalignment between the pole ears 2 after the multi-ear pole piece is wound, but also ensure that the bottom width of the pole ear 2 meets the requirements of ultrasonic welding, thereby improving the yield rate of the battery.

[0043] The pole piece body 1 has a length direction and a width direction that are perpendicular to each other. Figure 1 and Figure 2 In the figure, the left-right direction is the length direction of the pole piece body 1 , and the up-down direction is the width direction of the pole piece body 1 .

[0044] N pole tabs 2 are arranged at intervals along the length direction of the pole piece body 1, and the bottom widths of the N pole tabs 2 decrease and then increase along the length direction of the pole piece body 1, and the N pole tabs 2 overlap after the pole piece body 1 is wound; N is a positive integer greater than or equal to 3, such as N is 5, 6, 7, 8, etc., which is selected according to the design requirements of the battery.

[0045] When the pole piece is wound, one end of the pole piece body 1 is fixed, and the other end is wound to form a winding core. After winding, N pole ears 2 overlap, such as Figure 3 , Figure 4 as well as Figure 5 As shown. The N pole tabs 2 after overlapping are welded together by ultrasonic welding process, and then electrically connected to the pole column on the battery cover plate through the adapter. In this embodiment, the bottom width of the N pole tabs 2 decreases and then increases along the length direction of the pole piece body 1. Among the N overlapping pole tabs 2, the two adjacent pole tabs 2 have different bottom widths. Therefore, the pole tab 2 with a smaller bottom width will fall in the area of ​​the pole tab 2 with a larger bottom width. Even if there is a slight deviation, the edges of the two sides of the pole tab 2 with a smaller bottom width will not exceed the edges of the pole tab 2 with a larger bottom width. The design of the width difference between adjacent pole tabs 2 can offset the misalignment of the pole tab 2 caused by the winding needle size accuracy and the pole piece thickness accuracy. In addition, since the bottom width of the N pole tabs 2 decreases and then increases along the length direction of the pole piece body 1, rather than showing a decreasing trend, the bottom width value of the pole tab 2 with the narrowest bottom width is not too narrow, so that the width of the pole tab 2 meets the ultrasonic welding requirements, ensures the welding firmness and current capacity of the N pole tabs 2, and improves the yield rate of the battery.

[0046] like Figure 1 and Figure 2 As shown, the original pole piece is cut by a cutting device to form a plurality of pole ears 2, and the pole piece body 1 has N pole ears 2 on both sides along the width direction, and the N pole ears 2 on both sides are arranged one by one opposite to each other. Figure 1 and Figure 2 The pole piece shown is cut along the center line in the length direction to form two upper and lower pole pieces, both of which can be used for winding. Furthermore, the bottom widths of the two pole ears 2 facing each other in the width direction are completely consistent, which improves the cutting efficiency.

[0047] The N pole tabs 2 include a middle pole tab and two end pole tabs located at both ends. After the pole piece body 1 is wound, the two end pole tabs are located at the outermost sides.

[0048] If N is an odd number, the (N+1) / 2th pole lug 2 is the middle pole lug, that is, the middlemost pole lug 2 is the middle pole lug. Figure 1 , N is 5, then the third pole lug 2 is the middle pole lug, that is, the pole lug 2 at position A3 is the middle pole lug, and the number of pole lugs 2 on both sides of the middle pole lug is the same. If N is 7, then the fourth pole lug 2 is the middle pole lug, and so on, which will not be listed here one by one.

[0049] If N is an even number, the N / 2th pole lug 2 and the (N / 2)+1th pole lug 2 are middle pole lugs, that is, the two middle pole lugs 2 are middle pole lugs. Figure 2 , N is 6, then the third and fourth pole lugs 2 are middle pole lugs, that is, the pole lugs 2 at positions B3 and B4 are middle pole lugs, and the number of pole lugs 2 on both sides of the two middle pole lugs is the same. If N is 8, then the fourth and fifth pole lugs 2 are middle pole lugs, and so on, which are not listed here one by one.

[0050] Among the N tabs 2 of this embodiment, the bottom width of the middle tab is the narrowest. Figure 1 The bottom width of the middle tab at position A3 is the narrowest. Among the tabs 2 on both sides, the bottom width of the tab 2 at position A1 is greater than the bottom width of the tab 2 at position A2, and the bottom width of the tab 2 at position A5 is greater than the bottom width of the tab 2 at position A4. Figure 2 The bottom width of the middle tabs at positions B3 and B4 is the narrowest. Among the tabs 2 on both sides, the bottom width of the tab 2 at position B1 is greater than the bottom width of the tab 2 at position B2, and the bottom width of the tab 2 at position B6 is greater than the bottom width of the tab 2 at position B5. Since the bottom width of the middle tab is the narrowest, the bottom widths of the tabs 2 on both sides increase from the middle to both ends. While compensating for the misalignment of the tabs 2, the bottom width of the narrowest tab 2 can be guaranteed to the maximum extent, so that it will not be too narrow to affect the subsequent ultrasonic welding.

[0051] Figure 1 The overlapping schematic diagram of the five pole ears 2 after the pole piece body 1 is wound is shown in FIG. Figure 4 As shown, the narrowest middle pole lug is located in the middle of the five pole lugs 2 . Figure 2 The overlapping schematic diagram of the six pole ears 2 after the pole piece body 1 is wound is shown in FIG. Figure 5 As shown, the two narrowest middle pole lugs are located in the middle of the six pole lugs 2 .

[0052] Furthermore, the bottom widths of the two end tabs are consistent. Figure 1 The bottom width of the tabs 2 at positions A1 and A5 is the same. Figure 2 The bottom widths of the tabs 2 at positions B1 and B6 are the same. Figure 4 and Figure 5As shown, the two end tabs are located at the innermost and outermost sides, and the edges of the remaining tabs 2 do not exceed the edges of the two end tabs, thereby ensuring the uniformity of the multiple tabs 2 after overlapping.

[0053] Optionally, except for the two adjacent middle tabs, the bottom width difference between the other two adjacent tabs 2 is the same. Specifically, the bottom width of the end tab is a, the bottom width of the middle tab is b, and b>a. If N is an odd number, the bottom width difference between the two adjacent tabs 2 is Δw=2(ab) / (N-1).

[0054] See also Figure 1 , the bottom width of the pole lug 2 at position A3 is b, the bottom width of the pole lug 2 at positions A1 and A5 is a, the bottom widths of the two pole lugs 2 at positions A2 and A4 are the same, N is 5, the bottom width difference between two adjacent pole lugs 2 Δw=(ab) / 2, the bottom width difference between the two pole lugs 2 at positions A5 and A4 is equal to the bottom width difference between the two pole lugs 2 at positions A4 and A3, and the bottom width difference between the two pole lugs 2 at positions A1 and A2 is equal to the bottom width difference between the two pole lugs 2 at positions A2 and A3. If N is an even number, for the two middle pole lugs in the middle, their bottom width difference Δw=0; except for the two middle pole lugs, the remaining pole lugs are defined as non-middle pole lugs, and the bottom width difference between the non-middle pole lugs, and the bottom width difference between the middle pole lugs and the non-middle pole lugs are all Δw=2(ab) / (N-2). See Figure 2 , the bottom width of the tab 2 at positions B3 and B4 is b, the bottom width of the tab 2 at positions B1 and B6 is a, the bottom widths of the two tabs 2 at positions B2 and B5 are the same, N is 6, the bottom width difference between two adjacent tabs 2 is Δw = (ab) / 2, the bottom width difference between the two tabs 2 at positions B6 and B5 is equal to the bottom width difference between the two tabs 2 at positions B5 and B4, and the bottom width difference between the two tabs 2 at positions B1 and B2 is equal to the bottom width difference between the two tabs 2 at positions B2 and B3. (ab) is the total width difference between the widest tab 2 and the narrowest tab 2. In this embodiment, the total width difference is evenly distributed to the two adjacent tabs 2, so that each adjacent tab 2 has an anti-misalignment effect.

[0055] Optionally, the bottom width a of the end tab and the bottom width b of the middle tab satisfy: b ≥ a / 2. This dimension design ensures that the total difference in width between the widest tab 2 and the narrowest tab 2 is not too large, ensures that the width of the narrowest tab 2 is not too narrow, and saves material. Exemplarily, the bottom width b of the middle tab is a / 2; or the bottom width b of the middle tab is a / 3. For example, the bottom width a of the end tab is 6 mm, and the bottom width b of the middle tab is 3 mm.

[0056] Optionally, the bottom width difference Δw between two adjacent pole ears 2 ranges from 0 to 4 mm. Specifically, only when N is an even number does Δw=0 exist, and the bottom width difference Δw=0 specifically refers to the bottom width difference between the two middle pole ears. For the bottom width difference of the pole ears when N is an odd number, the bottom width difference between the non-middle pole ears when N is an even number, and the bottom width difference Δw between the middle pole ears and the non-middle pole ears when N is an even number, the range of values ​​is 0.1mm to 4mm. Exemplarily, the bottom width difference Δw is 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, and so on. In this embodiment, it can be 2mm, 3mm, or 4mm to ensure that there is sufficient misalignment tolerance between the two adjacent pole ears 2, and that more pole ear 2 materials are not wasted.

[0057] See also Figure 3 , in the adjacent two pole ears 2 whose bottom width difference is not zero, the misalignment amount on the left and right sides of the narrower pole ear 2 is defined as the misalignment redundant space Q, Q = Δw / 2, that is, the allowable misalignment displacement amount of the left and right edges of the narrower pole ear 2 is Δw / 2, when the center lines of the two adjacent pole ears 2 coincide, the distance between the edge of the narrower pole ear 2 and the edge of the wider pole ear 2 is exactly Δw / 2. The value range of the misalignment redundant space Q is 0.05mm to 2mm. For example, the misalignment redundant space Q is 0.5mm, 1mm, 1.5mm, 2mm, etc., to ensure that there is a sufficient misalignment allowable value between the adjacent two pole ears 2, and effectively offset the misalignment phenomenon of the pole ear 2 caused by the winding needle size accuracy and the pole piece thickness accuracy.

[0058] The N pole tabs 2 are subsequently connected together using an ultrasonic welding process. After the ultrasonic welding head is stamped, ultrasonic weld marks are formed on the N pole tabs 2, and the N pole tabs 2 are fixedly connected at the ultrasonic weld marks. For the ultrasonic weld marks of the battery cell pole tabs 2, it is necessary to specify their size range during design to ensure the stability after ultrasonic connection and the current carrying capacity of the pole tabs 2. In this embodiment, the size of the ultrasonic weld mark along the length direction of the pole piece body 1 is L, and the bottom width of the pole tab 2 with the narrowest bottom width is 0.8mm to 2mm larger than L. That is, Figure 1 and Figure 2 The bottom width b of the middle pole ear is 0.8mm to 2mm larger than the design length L of the ultrasonic weld mark, for example, 0.8mm, 1mm, 1.2mm, 1.4mm, 1.6mm, 1.8mm, 2mm, etc., to ensure that each pole ear 2 has a complete ultrasonic weld mark, to ensure the connection strength of the pole ear 2 after ultrasonic welding and the current capacity after assembly into a battery cell, thereby improving the performance of the battery product.

[0059] Exemplarily, the bottom width b of the middle pole ear is 1 mm larger than the designed length L of the ultrasonic weld mark, which can reduce the material usage as much as possible while ensuring that each pole ear 2 has a complete ultrasonic weld mark.

[0060] In some embodiments, see Figure 1 and Figure 2 , the heights of the N pole tabs 2 are consistent, so that the top edges of the N pole tabs 2 after winding are as flat as possible.

[0061] In some embodiments, the heights of the N pole tabs 2 may gradually increase along the length direction of the pole piece body 1. After the pole piece body 1 is wound, the top portions of the N pole tabs 2 may be cut off to make the tops of the overlapping N pole tabs 2 more flush.

[0062] In this embodiment, the center distance between two adjacent pole tabs 2 gradually increases along the length direction of the pole piece body 1, so that N pole tabs 2 can be overlapped during the winding process. One end of the pole piece body 1 is the winding insertion end (the end is fixed), and the other end is the winding end section. From the winding insertion end to the winding end section, the center distance between two adjacent pole tabs 2 gradually increases to ensure that N pole tabs 2 overlap after winding. That is, the end with a smaller center distance is used as the winding insertion end for winding.

[0063] See also Figure 1 and Figure 2 , the pole lug 2 is trapezoidal, and its lower bottom edge is connected to the pole piece body 1, which can improve the strength of the root of the pole lug 2 and prevent the pole lug 2 from breaking due to pulling. Exemplarily, the pole lug 2 is an isosceles trapezoid, which ensures that the strength of the roots on both sides of the pole lug 2 is uniform, and ensures the quality of multiple pole lugs 2 after winding and overlapping, thereby improving the current capacity at the pole lug 2.

[0064] This embodiment also provides a battery cell, including a shell and a winding core assembly 100 disposed in the shell, the winding core assembly 100 includes a first diaphragm, a positive electrode sheet, a second diaphragm and a negative electrode sheet stacked in sequence, and the positive electrode sheet and the negative electrode sheet are both the electrodes described above. Optionally, a third diaphragm and a packaging film are stacked on the side of the negative electrode sheet facing away from the second diaphragm, and the winding core assembly 100 is formed after being wound together. Figure 3 As shown, it is a cross-sectional view of the winding core assembly 100. Among the multiple overlapping pole tabs 2 on the left side and the multiple overlapping pole tabs 2 on the right side, one is formed by winding the positive pole sheet, and the other is formed by winding the negative pole sheet. The winding core assembly 100 can eliminate the misalignment of the pole tabs 2, ensure that the N pole tabs 2 of the positive pole sheet and the N pole tabs 2 of the negative pole sheet can meet the subsequent ultrasonic welding requirements, and improve the performance of the battery cell.

[0065] The shell of the battery cell includes a containing shell and a cover plate, on which a positive electrode column and a negative electrode column are arranged, and N overlapping pole tabs 2 are welded and connected to corresponding pole columns through adapter sheets.

[0066] This embodiment also provides a battery module, including a plurality of battery cells as described above. The battery module also includes a CCS component for collecting voltage signals and temperature signals of the battery cells. The battery module with the battery cells as described above is assembled smoothly and has excellent performance.

[0067] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the implementation methods of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the scope of protection of the present invention. It is not necessary and impossible to list all implementation methods here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the scope of protection of the claims of the present invention.

Claims

1. A pole piece, characterized in that: include: The pole piece body (1) has a length direction and a width direction that are perpendicular to each other; N pole ears (2) are arranged at intervals along the length direction of the pole piece body (1), the bottom widths of the N pole ears (2) decrease and then increase in sequence along the length direction of the pole piece body (1), and the N pole ears (2) overlap after the pole piece body (1) is wound; N is a positive integer greater than or equal to 3.

2. The pole piece according to claim 1, characterized in that: The N pole ears (2) include a middle pole ear and two end pole ears located at both ends; If N is an odd number, the (N+1) / 2th pole lug (2) is the middle pole lug; If N is an even number, the N / 2th pole lug (2) and the (N / 2)+1th pole lug (2) are the middle pole lugs; Among the N pole tabs (2), the bottom width of the middle pole tab is the narrowest, and the bottom widths of the two end pole tabs are consistent.

3. The pole piece according to claim 2, characterized in that: The bottom width of the end tab is a, the bottom width of the middle tab is b, and b<a; If N is an odd number, the difference in bottom width between two adjacent tabs (2) is Δw=2(ab) / (N-1); If N is an even number, the bottom width difference between the two middle pole ears Δw=0; the bottom width difference between the non-middle pole ears, and the bottom width difference between the middle pole ear and the non-middle pole ear are both Δw=2(ab) / (N-2); the non-middle pole ear is the pole ear other than the middle pole ear.

4. The pole piece according to claim 3, characterized in that: The bottom width a of the end tab and the bottom width b of the middle tab satisfy: b≥a / 2.

5. The pole piece according to claim 1, characterized in that: The value range of the bottom width difference Δw between two adjacent pole tabs (2) is 0 to 4 mm.

6. The pole piece according to any one of claims 1 to 5, characterized in that: Ultrasonic welding marks are arranged on the N pole tabs (2), and the N pole tabs (2) are fixedly connected at the ultrasonic welding marks. The dimension of the ultrasonic welding marks along the length direction of the pole piece body (1) is L, and the bottom width of the pole tab (2) with the narrowest bottom width is 0.8 mm to 2 mm larger than L.

7. The pole piece according to any one of claims 1 to 5, characterized in that: The heights of the N tabs (2) are consistent; Alternatively, the heights of the N pole tabs (2) gradually increase along the length direction of the pole piece body (1).

8. The pole piece according to any one of claims 1 to 5, characterized in that: The center distance between two adjacent pole ears (2) gradually increases along the length direction of the pole piece body (1).

9. The pole piece according to any one of claims 1 to 5, characterized in that: The pole lug (2) is trapezoidal, and the lower bottom edge of the pole lug (2) is connected to the pole piece body (1).

10. A battery cell, characterized in that: The invention comprises a shell and a winding core assembly (100) arranged in the shell, wherein the winding core assembly (100) comprises a first diaphragm, a positive electrode sheet, a second diaphragm and a negative electrode sheet stacked in sequence, and the positive electrode sheet and the negative electrode sheet are both the electrode sheet as described in any one of claims 1 to 9.

11. A battery module, characterized in that: The invention comprises a plurality of battery cells as claimed in claim 10.

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