Battery

Abstract

The utility model relates to the technical field of batteries, and discloses a battery which comprises a negative plate, a positive plate and a diaphragm, and the negative plate, the positive plate and the diaphragm are wound together to form a roll core; the negative plate comprises: a first current collector comprising a first target surface facing away from a winding center; a first coating layer including an active material; the first coating layer is arranged on the first target surface; the first coating layer comprises a first flat part and a plurality of first convex parts which are formed by protruding the first flat part in the thickness direction towards the direction away from the first target surface, the first convex parts are arranged at intervals in the length direction, and the first convex parts are arranged in the arc area of the roll core. According to the battery provided by the utility model, the first convex part is arranged in the arc area of the roll core, so that the gap between the first coating layer and the diaphragm in the arc area is reduced, the bonding effect of the diaphragm and an active substance in the arc area is enhanced, and the multiplying power and the cycle performance of the battery are further improved.

Description

Technical Field

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

[0002] To boost energy density, lithium-ion batteries are currently using increasingly more layers in their wound structures, leading to increasingly severe lithium deposition issues. This is particularly true in the arc region, where the pressure applied during winding and formation is minimal, resulting in poor adhesion between the separator and the negative electrode. Consequently, separator adhesion issues in this arc region have long been a significant issue affecting lithium-ion battery performance, impacting rate and cycling performance. Improving separator adhesion in lithium-ion batteries has become an important and pressing issue.

[0003] Existing batteries are basically not subjected to stress during hot pressing in the arc area, resulting in poor adhesion of the diaphragm in the arc area, affecting the battery's rate and cycle performance. Utility Model Content

[0004] In view of this, the present invention provides a battery to solve the problem that the existing battery has poor adhesion of the arc area separator, which affects the battery's rate and cycle performance.

[0005] The battery provided by the utility model includes:

[0006] The negative electrode sheet, the positive electrode sheet and the separator are wound together to form a core;

[0007] The negative electrode sheet includes:

[0008] a first current collector including a first target surface facing away from the winding center;

[0009] The first coating layer includes an active material; the first coating layer is arranged on the first target surface; the first coating layer includes a first flat portion and a plurality of first convex portions formed by the first flat portion protruding along the thickness direction toward away from the first target surface, the plurality of first convex portions are arranged at intervals along the length direction, and the first convex portions are arranged in the arc area of ​​the winding core.

[0010] Beneficial effect: The battery provided by the utility model arranges a first coating layer on the first target surface of the first current collector, and the first coating layer protrudes from the first flat portion along the thickness direction toward the direction away from the first target surface to form a plurality of first convex portions. In the process of winding to form a core, the first convex portions are arranged in the arc area of ​​the core to reduce the gap between the first coating layer and the diaphragm in the arc area, thereby enhancing the bonding effect of the diaphragm with the active material in the arc area, thereby improving the rate and cycle performance of the battery.

[0011] In an optional embodiment, the first protrusion includes a platform portion and a transition portion, the transition portion is provided on both sides of the platform portion in the length direction, and the transition portion is connected between the platform portion and the first flat portion.

[0012] Beneficial effect: The setting of the transition portion can reduce the stress concentration in the arc area and reduce the risk of the pole piece being broken due to pressure.

[0013] In an optional embodiment, the dimension of the first protrusion along the length direction is L, and L satisfies 1mm≤L≤15mm.

[0014] Beneficial effects: On the one hand, it can ensure that the first convex portion completely covers the arc area of ​​the winding core, reducing the gap between the diaphragm in the arc area and the first coating layer, thereby enhancing the bonding effect of the diaphragm and the active material in the arc area, thereby improving the battery rate and cycle performance; on the other hand, it can ensure the consistency and uniformity of the thickness of the flat area of ​​the winding core, thereby ensuring the consistency of the battery performance in the charge and discharge cycle, thereby maintaining good power and capacity; on the other hand, it can avoid the excessive capacity of the negative electrode active material, thereby improving the energy density of the battery cell and reducing the overall weight of the battery cell.

[0015] In an optional embodiment, the dimension of the first protrusion along the length direction is the length of the outermost arc of the arc region of the winding core.

[0016] Beneficial effect: The arc area of ​​the battery cell maintains a good CB value, reducing the risk of lithium plating.

[0017] In an optional embodiment, the dimension of the first protrusion along the length direction becomes wider as the length of the arc area of ​​the winding core increases, and L satisfies L=h×π / 2, where h is the thickness of the winding core of the winding layer where the first protrusion is located.

[0018] Beneficial effects: It can ensure that the capacity of the negative electrode active material will not be excessive, reduce the overall weight of the battery cell, and improve the energy density.

[0019] In an optional embodiment, the distance between two adjacent first protrusions along the length direction is D, and D satisfies 15 mm ≤ D ≤ 80 mm.

[0020] Beneficial effects: It not only ensures the consistency and uniformity of the thickness of the flat area of ​​the winding core, thereby ensuring the consistency of the battery's performance during the charge and discharge cycle, and thus maintaining good power and capacity, but also avoids the excessive capacity of the negative electrode active material, thereby increasing the energy density of the battery cell and reducing the overall weight of the battery cell.

[0021] In an optional embodiment, the distance between the starting position of the first coating layer on the first target surface and the first first convex portion along the length direction is S, and S satisfies S≥30 mm;

[0022] And / or, S=a×D, where a is 2, 3, 4 or 5.

[0023] Beneficial effect: The CB value of the inner arc area of ​​the winding core can be kept in a normal state, and the risk of lithium plating is relatively small.

[0024] In an optional embodiment, the distance between the side of the first convex portion away from the first target surface along the thickness direction and the first target surface is P, and the distance between the side of the first flat portion away from the first target surface along the thickness direction and the first target surface is Q, and P and Q satisfy 1.002≤P / Q≤1.03.

[0025] Beneficial effect: By increasing the surface density of the first coating layer in the arc area of ​​the winding core, not only the gap between the negative electrode sheet and the positive electrode sheet is shortened, thereby shortening the transmission path of lithium ions and improving the fast charging performance, but also the CB value of the positive and negative electrodes in the arc area can be increased, reducing the risk of lithium plating.

[0026] In an optional embodiment, the diaphragm is arranged between the negative electrode sheet and the positive electrode sheet; the gap between the diaphragm in the flat area of ​​the winding core and the positive electrode sheet is G1, and the gap between the diaphragm in the arc area of ​​the winding core and the positive electrode sheet is G2, G1≥G2.

[0027] Beneficial effects: It is helpful to reduce the distance between the diaphragm and the positive and negative electrode sheets, thereby shortening the transmission path of lithium ions and improving the fast charging performance.

[0028] In an optional embodiment, the angle between the starting position of the first convex portion in the arc area of ​​the winding core and the extension line direction of the first flat portion is θ, and θ satisfies 0°≤θ≤0.5°.

[0029] Beneficial effects: It can not only reduce the gap between the first coating layer and the diaphragm in the arc area, thereby effectively increasing the adhesion between the diaphragm and the active material, but also effectively avoid stress concentration in the arc area, reduce the risk of the pole piece being broken by pressure, and at the same time increase the overall consistency of the core thickness.

[0030] In an optional embodiment, the positive electrode sheet includes:

[0031] a second current collector including a second target surface oriented toward the center of the winding;

[0032] A second coating layer includes an active material; the second coating layer is disposed on the second target surface; the second coating layer includes a second flat portion and a plurality of second convex portions formed by the second flat portion protruding in a thickness direction away from the second target surface, the plurality of second convex portions being spaced apart in a length direction;

[0033] The second convex portion and the first convex portion are staggered and aligned along the length direction; the first convex portions are spaced apart in pairs along the length direction to form a first groove, and the second convex portion is built into the first groove; the second convex portions are spaced apart in pairs along the length direction to form a second groove, and the first convex portion is built into the second groove.

[0034] Beneficial effects: It is beneficial to the overall combination of the winding structure and increases the energy density and structural stability of the core structure.

[0035] In an optional embodiment, the axially symmetrical center line of the first protrusion coincides with the winding center of the arc region of the winding core; the axially symmetrical center line of the second groove coincides with the winding center of the arc region of the winding core.

[0036] Beneficial effects: reducing the gap between the positive and negative electrodes in the arc area, shortening the transmission path of lithium ions in the arc area; ensuring that the second convex portion and the first groove and the first convex portion and the second groove are completely aligned, thereby improving the consistency of battery capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the specific implementation methods of the utility model or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 A cross-sectional view of a negative electrode sheet of a battery according to an embodiment of the present utility model;

[0039] Figure 2 for Figure 1 a cross-sectional view of the first coating layer shown;

[0040] Figure 3 A cross-sectional view of a positive electrode sheet of a battery according to an embodiment of the present utility model;

[0041] Figure 4 A cross-sectional view of a battery winding core according to an embodiment of the present invention;

[0042] Figure 5 for Figure 4 A local enlarged schematic diagram of point A in the middle.

[0043] Description of reference numerals:

[0044] 10. Negative electrode sheet; 11. First current collector; 111. First target surface; 12. First coating layer; 121. First flat portion; 122. First convex portion; 1221. Platform portion; 1222. Transition portion; 123. First groove;

[0045] 20, positive electrode sheet; 21, second current collector; 211, second target surface; 22, second coating layer; 221, second flat portion; 222, second convex portion; 223, second groove;

[0046] 30. Diaphragm. DETAILED DESCRIPTION

[0047] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts shall fall within the scope of protection of the present invention.

[0048] The battery in the related art is basically not subjected to stress during hot pressing in the arc area, resulting in poor adhesion of the diaphragm in the arc area, affecting the battery's rate and cycle performance.

[0049] In order to solve the problems existing in the above-mentioned related technologies, the present invention provides a battery, which can make the diaphragm have better adhesion at the raised part, and improve the rate and cycle performance of the arc area.

[0050] The following combination Figures 1 to 5 , describing the embodiments of the present utility model.

[0051] According to an embodiment of the present invention, a battery is provided, comprising:

[0052] A negative electrode sheet 10, a positive electrode sheet 20 and a separator 30 are wound together to form a winding core;

[0053] The negative electrode sheet 10 includes:

[0054] First collector 11, see Figure 1 As shown, the first current collector 11 includes a first target surface 111 facing away from the winding center;

[0055] The first coating layer 12 includes an active material; the first coating layer 12 is disposed on the first target surface 111; the first coating layer 12 includes a first flat portion 121 and a plurality of first convex portions 122 formed by the first flat portion 121 protruding in the thickness direction away from the first target surface 111, and the plurality of first convex portions 122 are spaced apart along the length direction. Figure 4 and Figure 5 As shown, the first protrusion 122 is disposed in the arc region of the winding core.

[0056] The battery provided by the present invention is provided with a first coating layer 12 on the first target surface 111 of the first current collector 11. The first coating layer 12 is formed by a first flat portion 121 protruding in the thickness direction toward the direction away from the first target surface 111 to form a plurality of first convex portions 122. During the process of winding to form a core, the first convex portions 122 are provided in the arc region of the core to reduce the gap between the first coating layer 12 and the diaphragm 30 in the arc region, thereby enhancing the bonding effect of the diaphragm 30 with the active material in the arc region, thereby improving the rate and cycle performance of the battery.

[0057] Please note that, see Figure 1 and Figure 3 As shown, the "thickness direction" in this article refers to the vertical direction of the electrode coating layer, the "length direction" in this article refers to the horizontal extension direction of the electrode and / or the direction in which the longest edge of the electrode points, and the "winding direction" in this article refers to the direction of the winding path followed in the process of continuously and spirally winding the negative electrode sheet 10, the positive electrode sheet 20 and the separator 30 into a battery core. Figure 4 As shown, Figure 4 The "flat area" and "arc area" of the battery roll are shown in the figure, where the "flat area" refers to the portion of the negative electrode sheet 10, the positive electrode sheet 20 and the separator 30 that does not bend during the process of winding into the battery roll, and the "arc area" refers to the non-straight portion formed during the process of winding the negative electrode sheet 10, the positive electrode sheet 20 and the separator 30 into the battery roll. The first coating layer 12 mainly includes active materials such as graphite or its modified materials. In addition, the first coating layer 12 also includes a conductive agent and a binder to ensure that the negative electrode sheet 10 has good electrochemical performance and mechanical stability. For the preparation of the negative electrode sheet 10, for example, a variable speed pump coating can be used. During the process, the pump speed can be increased at the corresponding position of the arc area to form the first protrusion 122. Alternatively, a double-layer coating can be used. During the process, the bottom layer can be continuously coated and the surface layer can be intermittently coated to form the first protrusion 122.

[0058] In some embodiments, see Figure 2 As shown, the first convex portion 122 includes a platform portion 1221 and a transition portion 1222 . The transition portions 1222 are provided on both sides of the platform portion 1221 in the length direction. The transition portions 1222 are connected between the platform portion 1221 and the first flat portion 121 .

[0059] In this embodiment, a transition portion 1222 is provided between the platform portion 1221 and the first flat portion 121. During the winding process, the thickness of the first coating layer 12 is gradually thickened from the transition portion 1222 on one side to the maximum thickness along the length direction, and then passes through the platform portion 1221 with a constant maximum thickness, and then gradually decreases from the transition portion 1222 on the other side to the first flat portion 121. The provision of the transition portion 1222 can reduce stress concentration in the arc area and reduce the risk of the pole piece being broken due to pressure.

[0060] In some embodiments, see Figure 1 As shown, the dimension of the first protrusion 122 along the length direction is L, and L satisfies 1mm≤L≤15mm.

[0061] It should be noted that the dimension of the first protrusion 122 along the length direction cannot be too small, otherwise it will easily cause the first protrusion 122 to fail to completely cover the arc area of ​​the winding core, resulting in an increase in the gap between the diaphragm 30 and the first coating layer 12 in the arc area, affecting the adhesion of the diaphragm 30 to the active material in the arc area. Therefore, L must satisfy L≥1mm; if the dimension of the first protrusion 122 along the length direction is too large, it will not only easily affect the consistency and uniformity of the thickness of the flat area of ​​the winding core, but also easily cause the capacity of the negative active material to be excessively exerted, easily reduce the energy density of the battery cell, and increase the overall weight of the battery cell. Therefore, L must also satisfy L≤15mm.

[0062] In this embodiment, the dimension L of the first protrusion 122 along the length direction satisfies 1mm≤L≤15mm. On the one hand, it can ensure that the first protrusion 122 completely covers the arc area of ​​the winding core, reducing the gap between the diaphragm 30 and the first coating layer 12 in the arc area, thereby enhancing the bonding effect of the diaphragm 30 with the active material in the arc area, thereby improving the battery rate and cycle performance. On the other hand, it can ensure the consistency and uniformity of the thickness of the flat area of ​​the winding core, thereby ensuring the consistency of the battery performance in the charge and discharge cycle, thereby maintaining good power and capacity. On the other hand, it can avoid the excessive capacity of the negative electrode active material, thereby improving the energy density of the battery cell and reducing the overall weight of the battery cell.

[0063] Preferably, the value range of L can further be 1mm≤L≤11mm.

[0064] In some embodiments, the length of the first protrusion 122 along the length direction is the length of the outermost arc of the arc region of the winding core.

[0065] It should be noted that when the size of the first protrusion 122 along the length direction needs to be constant, the size of the first protrusion 122 along the length direction can adopt the outermost arc length of the winding core arc area, so that the arc area of ​​the battery cell can maintain a good CB value and reduce the risk of lithium plating. The CB value is an indicator used to measure the capacitance that can be provided per unit area in a specific area of ​​a lithium battery.

[0066] In some embodiments, the length of the first protrusion 122 becomes wider as the length of the arc region of the winding core increases, and L satisfies L=h×π / 2, where h is the thickness of the winding core of the winding layer where the first protrusion 122 is located.

[0067] It should be noted that as the number of winding layers of the core increases, the size of the first protrusion 122 along the length direction becomes wider as the length of the arc area of ​​the core increases. L satisfies L=h×π / 2, where h is the core thickness of the winding layer where the first protrusion 122 is located. This can ensure that the capacity of the negative electrode active material will not be excessive, reduce the overall weight of the battery cell, and improve the energy density.

[0068] In some embodiments, see Figure 1 As shown, the distance between two adjacent first protrusions 122 along the length direction is D, and D satisfies 15 mm ≤ D ≤ 80 mm.

[0069] It should be noted that the first flat portion 121 is located between every two adjacent first protrusions 122 along the length of the first flat portion 121, and the thickness of the first flat portion 121 remains constant. If the distance between two adjacent first protrusions 122 along the length is too small, it can easily cause the first protrusions 122 to deviate from the arc area of ​​the winding core, or even cause the first protrusions 122 to deviate to the flat area of ​​the winding core, affecting the flatness of the electrode sheet and the consistency and uniformity of the thickness of the flat area of ​​the winding core. Therefore, D must satisfy D ≥ 15mm. If the distance between two adjacent first protrusions 122 along the length is too large, it can easily lead to excessive capacity of the negative electrode active material, easily reducing the energy density of the battery cell and increasing the overall weight of the battery cell. Therefore, D must also satisfy D ≤ 80mm.

[0070] In this embodiment, the distance D between two adjacent first protrusions 122 along the length direction satisfies 15mm≤D≤80mm, which not only ensures the consistency and uniformity of the thickness of the flat area of ​​the winding core, thereby ensuring the consistency of the battery performance during the charge and discharge cycle, and thus maintaining good power and capacity, but also avoids excessive capacity of the negative electrode active material, thereby improving the energy density of the battery cell and reducing the overall weight of the battery cell.

[0071] It should be noted that the distance between two adjacent first protrusions 122 can remain constant, while the length of the first protrusion 122 increases as the length of the arc region of the winding core increases. This ensures that the capacity of the negative electrode active material is not excessive, reduces the overall weight of the battery cell, and improves energy density. The distance between two adjacent first protrusions 122 can also gradually increase along the length direction. At the same time, the length of the first protrusion 122 adopts the length of the outermost arc of the arc region of the winding layer where the first protrusion 122 is located, thereby ensuring that the first protrusion 122 is in the arc region of the winding core and improving the flatness of the electrode sheet.

[0072] In some embodiments, see Figure 1 As shown, the distance between the starting position of the first coating layer 12 on the first target surface 111 and the first first convex portion 122 along the length direction is S, and S satisfies S≥30 mm;

[0073] And / or, S=a×D, where a is 2, 3, 4 or 5, wherein D is the distance between two adjacent first protrusions 122 along the length direction, and D satisfies 15 mm ≤ D ≤ 80 mm.

[0074] It should be noted that since the winding radius of the inner arc area of ​​the core (the arc area close to the winding center) is small, the first protrusion 122 can be omitted in the inner arc area of ​​the core, so that the CB value of the inner arc area of ​​the core can be in a normal state, and the risk of lithium plating is relatively small.

[0075] In some embodiments, see Figure 1 As shown, the distance between the side of the first convex portion 122 away from the first target surface 111 along the thickness direction and the first target surface 111 is P, and the distance between the side of the first flat portion 121 away from the first target surface 111 along the thickness direction and the first target surface 111 is Q, and P and Q satisfy 1.002≤P / Q≤1.03.

[0076] By setting it in this way, the surface density of the first coating layer 12 in the arc area of ​​the winding core is increased, which not only shortens the gap between the negative electrode sheet 10 and the positive electrode sheet 20, thereby shortening the transmission path of lithium ions and improving the fast charging performance, but also improves the CB value of the positive and negative electrodes in the arc area and reduces the risk of lithium plating.

[0077] In some embodiments, see Figure 5 As shown, the diaphragm 30 is arranged between the negative electrode sheet 10 and the positive electrode sheet 20; the gap between the diaphragm 30 in the flat area of ​​the winding core and the positive electrode sheet 20 is G1, and the gap between the diaphragm 30 in the arc area of ​​the winding core and the positive electrode sheet 20 is G2, G1 ≥ G2, which is conducive to reducing the distance between the diaphragm 30 and the positive electrode sheet 20 and the negative electrode sheet 10, thereby shortening the transmission path of lithium ions and improving the fast charging performance.

[0078] In some embodiments, see Figure 5 As shown, the angle between the first convex portion 122 at the starting position of the arc region of the winding core and the extension line direction of the first flat portion 121 is θ, and θ satisfies 0°≤θ≤0.5°.

[0079] It should be noted that the smaller the value of θ, the smoother the transition between the first convex portion 122 and the first flat portion 121. By satisfying the condition 0° ≤ θ ≤ 0.5°, θ can reduce the gap between the first coating layer 12 and the diaphragm 30 in the arc region, thereby effectively improving the adhesion between the diaphragm 30 and the active material. It can also effectively avoid stress concentration in the arc region, reducing the risk of electrode breakage due to pressure, while also improving the overall consistency of the winding core thickness.

[0080] In some embodiments, see Figure 3 As shown, the positive electrode sheet 20 includes:

[0081] The second current collector 21 includes a second target surface 211 facing the winding center;

[0082] The second coating layer 22 includes an active material; the second coating layer 22 is disposed on the second target surface 211; the second coating layer 22 includes a second flat portion 221 and a plurality of second protrusions 222 formed by the second flat portion 221 protruding in the thickness direction away from the second target surface 211, and the plurality of second protrusions 222 are spaced apart along the length direction;

[0083] The second protrusions 222 and the first protrusions 122 are staggered and aligned along the length direction; the first protrusions 122 are spaced apart in pairs along the length direction to form first grooves 123, and the second protrusions 222 are embedded in the first grooves 123; the second protrusions 222 are spaced apart in pairs along the length direction to form second grooves 223, and the first protrusions 122 are embedded in the second grooves 223, which is beneficial to the overall combination of the winding structure and increases the energy density and structural stability of the core structure.

[0084] Furthermore, the first protrusion 122 and the second groove 223 have the same size along the length direction, and the second protrusion 222 and the first groove 123 have the same size along the length direction.

[0085] Furthermore, the distance between the starting position of the second coating layer 22 on the second target surface 211 and the first second groove 223 along the length direction is also S. Since the winding radius of the inner arc region of the winding core (the arc region close to the winding center) is relatively small, the second groove 223 can be omitted in the inner arc region of the winding core, so that the CB value of the inner arc region of the winding core is kept normal, and the risk of lithium deposition is relatively small.

[0086] In some embodiments, please combine Figure 1 and Figure 5As shown, the axisymmetric center line W1 of the first protrusion 122 coincides with the winding center O of the arc region of the winding core, thereby reducing the gap between the positive and negative electrodes in the arc region and shortening the transmission path of lithium ions in the arc region; please combine Figure 3 and Figure 5 As shown, the axially symmetrical center line W2 of the second groove 223 coincides with the winding center O of the arc area of ​​the winding core, thereby ensuring that the second protrusion 222 and the first groove 123 and the first protrusion 122 and the second groove 223 are completely aligned, thereby improving the consistency of battery capacity.

[0087] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations shall fall within the scope defined by the appended claims.

Claims

1. A battery, characterized in that: include: A negative electrode sheet (10), a positive electrode sheet (20) and a separator (30), wherein the negative electrode sheet (10), the positive electrode sheet (20) and the separator (30) are wound together to form a winding core; The negative electrode sheet (10) comprises: A first current collector (11) including a first target surface (111) facing away from the winding center; The first coating layer (12) includes an active material; the first coating layer (12) is arranged on the first target surface (111); the first coating layer (12) includes a first flat portion (121) and a plurality of first convex portions (122) formed by the first flat portion (121) protruding in a thickness direction away from the first target surface (111), the plurality of first convex portions (122) are arranged at intervals along a length direction, and the first convex portions (122) are arranged in an arc area of ​​the winding core.

2. The battery according to claim 1, characterized in that The first convex portion (122) includes a platform portion (1221) and a transition portion (1222), wherein the transition portion (1222) is arranged on both sides of the platform portion (1221) in the length direction, and the transition portion (1222) is connected between the platform portion (1221) and the first flat portion (121).

3. The battery according to claim 1, characterized in that The first protrusion (122) has a length L, and L satisfies 1 mm ≤ L ≤ 15 mm.

4. The battery according to claim 3, characterized in that The dimension of the first convex portion (122) along the length direction is the length of the outermost arc of the arc region of the winding core.

5. The battery according to claim 3, characterized in that The dimension of the first convex portion (122) along the length direction becomes wider as the length of the arc region of the winding core increases, and L satisfies L=h×π / 2, where h is the thickness of the winding core of the winding layer where the first convex portion (122) is located.

6. The battery according to claim 1, characterized in that The distance between two adjacent first protrusions (122) along the length direction is D, and D satisfies 15mm≤D≤80mm.

7. The battery according to claim 6, characterized in that The distance between the starting position of the first coating layer (12) on the first target surface (111) and the first first protrusion (122) along the length direction is S, and S satisfies S≥30mm; And / or, S=a×D, where a is 2, 3, 4 or 5.

8. The battery according to any one of claims 1 to 7, characterized in that A distance P between a side of the first convex portion (122) away from the first target surface (111) along the thickness direction and the first target surface (111) is a distance Q between a side of the first flat portion (121) away from the first target surface (111) along the thickness direction and the first target surface (111), and P and Q satisfy 1.002≤P / Q≤1.

03.

9. The battery according to claim 1, characterized in that The diaphragm (30) is arranged between the negative electrode sheet (10) and the positive electrode sheet (20); the gap between the diaphragm (30) at the flat area of ​​the winding core and the positive electrode sheet (20) is G1, and the gap between the diaphragm (30) at the arc area of ​​the winding core and the positive electrode sheet (20) is G2, and G1≥G2.

10. The battery according to claim 1, characterized in that The angle between the first convex portion (122) at the starting position of the arc area of ​​the winding core and the extension line direction of the first flat portion (121) is θ, and θ satisfies 0°≤θ≤0.5°.

11. The battery according to claim 9 or 10, characterized in that The positive electrode sheet (20) comprises: A second current collector (21) including a second target surface (211) facing the winding center; A second coating layer (22) comprising an active material; the second coating layer (22) is disposed on the second target surface (211); the second coating layer (22) comprises a second flat portion (221) and a plurality of second convex portions (222) formed by the second flat portion (221) protruding in a thickness direction away from the second target surface (211), the plurality of second convex portions (222) being spaced apart in a length direction; The second convex portion (222) and the first convex portion (122) are arranged in a staggered and aligned manner along the length direction; the first convex portions (122) are spaced apart in pairs along the length direction to form a first groove (123), and the second convex portions (222) are built into the first groove (123); the second convex portions (222) are spaced apart in pairs along the length direction to form a second groove (223), and the first convex portion (122) is built into the second groove (223).

12. The battery according to claim 11, characterized in that The axial symmetry center line of the first protrusion (122) coincides with the winding center of the circular arc area of ​​the winding core; the axial symmetry center line of the second groove (223) coincides with the winding center of the circular arc area of ​​the winding core.

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