Pole piece, roll core and battery

Abstract

The application provides an electrode sheet, a roll core and a battery, and relates to the technical field of batteries, and aims to solve the technical problem of the separation of the active material layer and the current collector at the embossed protrusion of the electrode sheet in the prior art. The electrode sheet comprises a current collector, a first active material layer and a second active material layer. The current collector has opposite first and second surfaces. The first active material layer is arranged on the first surface, and the second active material layer is arranged on the second surface. A plurality of first protruding portions are arranged on the first active material layer, and a plurality of recessed portions corresponding to the first protruding portions are arranged on the second active material layer. The current collector has a bending portion and a flat portion. The bending portion is located between the first protruding portions and the recessed portions. The bending portion has a plurality of second protruding portions. The second protruding portions protrude from the first surface or the second surface. The second protruding portions can increase the contact area between the active material layer and the current collector, improve the bonding strength of the active material layer and the current collector, and prevent the active material layer from falling off.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium electronic battery, and particularly relates to a pole piece, a roll core and a battery. BACKGROUND

[0002] With the rapid development of lithium ion battery technology, people have higher requirements for the energy density, cycle life and safety performance of lithium ion batteries. During the charging and discharging process of the lithium ion battery, the negative pole piece will swell, and the layers of the pole piece will be extruded, which will cause insufficient electrolyte and poor wetting between the layers, affecting the safety of the battery cell.

[0003] In the prior art, embossed protrusions are processed on the positive pole piece by a special roller to increase the micro gap between the pole pieces, so that the positive pole, the separator and the negative pole have a certain support, solving the problems of insufficient electrolyte and poor wetting between the layers.

[0004] However, when the embossed protrusions are arranged on the pole piece, the active material layer at the embossed protrusion position has the risk of being separated from the current collector. SUMMARY

[0005] In view of the above problems, the embodiments of the present application provide a pole piece, a roll core and a battery to solve the problem of separation of the active material layer at the embossed protrusion position from the current collector caused by arranging embossed protrusions on the pole piece in the prior art.

[0006] To achieve the above-mentioned purpose, the embodiments of the present application provide the following technical solutions:

[0007] The embodiments of the present application provide a pole piece, which comprises a current collector, a first active material layer and a second active material layer; the current collector has opposite first and second surfaces along a first direction, the first active material layer is arranged on the first surface, and the second active material layer is arranged on the second surface; a plurality of first protrusions are arranged on the first active material layer, and a plurality of recesses corresponding to the first protrusions are arranged on the second active material layer; the current collector has a bending portion and a flat portion, the bending portion is located between the first protrusions and the recesses, and the bending portion has a plurality of second protrusions, which protrude from the first surface or the second surface.

[0008] The first protrusions and the recesses corresponding to the first protrusions are arranged on the pole piece, the first protrusions provide support for the contact of the separator, increase the micro gap between the pole piece and the separator, and these micro gaps form spaces that can accommodate electrolyte, so that the electrolyte has sufficient wetting amount for the pole piece, avoiding the abnormal situation of insufficient electrolyte and poor wetting between the pole piece and the separator caused by the extrusion of the layers of the pole piece.

[0009] Meanwhile, the second protrusions are arranged on the bending part of the current collector between the first protrusions and the recesses, so that the contact area between the active material layer and the bending part is increased, and the bonding strength between the active material layer and the bending part is improved, and the active material layer between the first protrusions and the recesses is prevented from being separated from the bending part.

[0010] In an embodiment of the present application, the center distance between the projections of two adjacent first protrusions in the first direction is a first distance L1; the two adjacent first protrusions have a straight section, and the straight section has a second distance L2 in the second direction; the center distance between the projections of two adjacent second protrusions in the first direction is a third distance L3; the two adjacent second protrusions have a first connecting section, and the projection of the first connecting section in the first direction has a fourth distance L4 in the second direction; the first distance L1 and the third distance L3 have the following relationship: L3 / L1=0.05-0.5; and / or the second distance L2 and the fourth distance L4 have the following relationship: L4 / L2=0.1-0.5; wherein the second direction is perpendicular to the first direction.

[0011] The limitation of the ratio of the third distance L3 to the first distance L1 and the limitation of the ratio of the fourth distance L4 to the second distance L2 correspond to the limitation of the density of the second protrusions being greater than the density of the first protrusions; it is ensured that each first protrusion on the pole piece has a second protrusion on the current collector, and the bonding strength between the current collector and the active material layer in the protrusion area of the pole piece is improved, and the active material layer is prevented from falling off.

[0012] In an embodiment of the present application, the third distance L3 and the fourth distance L4 have the following relationship: L3 / L4=1.2-2.

[0013] The limitation of the ratio of the third distance L3 to the fourth distance L4 corresponds to the limitation of the density of the second protrusions, and it is ensured that the second protrusions have a suitable spacing, so that the second protrusions can be adjusted to a suitable volume, thereby improving the bonding performance between the current collector and the active material layer and reducing the risk of the active material layer falling off.

[0014] In an embodiment of the present application, the first protrusions have a first arc-shaped outer surface, the first arc-shaped outer surface is located in the first active material layer, and the first arc-shaped outer surface has a first radius R1; the recesses have a first arc-shaped inner surface, the first arc-shaped inner surface is located in the second active material layer, and the first arc-shaped inner surface has a second radius R2; the first radius R1 and the second radius R2 have the following relationship: R1 / R2=1.01-1.21.

[0015] When the first protruding part is equivalent to a spherical shape, the first radius R1 is the outer surface radius, the second radius R2 is the inner surface radius, and the volume of the first protruding part is defined by limiting the ratio of the first radius R1 and the second radius R2, so that the interlayer of the pole piece has a suitable deformation space, thereby better improving the negative electrode expansion.

[0016] In an embodiment of the present application, the second protruding part has a second arc-shaped inner surface, and the second arc-shaped inner surface has a fourth radius R4, and the fourth radius R4 and the second radius R2 have the following relationship: R4 / R2 = 0.08-0.5.

[0017] When the second protruding part is equivalent to a spherical shape, the fourth radius R4 is the inner surface radius thereof; and by limiting the ratio of the fourth radius R4 and the second radius R2, the radius of the second protruding part on the current collector is smaller than the radius of the recess on the second active material layer, so that the second protruding part on the current collector has a suitable volume.

[0018] If the radius of the second protruding part on the current collector is large, the height of the second protruding part is too high, which will cause the surface of the active material layer to be uneven when the active material layer is coated on the surface of the current collector; and the current collector is easily crushed in the process of rolling the second protruding part. If the radius of the second protruding part on the current collector is small, the volume of the second protruding part is too small, and the adhesion strength between the active material layer and the current collector cannot be effectively improved.

[0019] In an embodiment of the present application, the flat part has a third protruding part; the first protruding part has a first intersection point, and the first intersection point intersects with the plane on which the first active material layer is located; the third protruding part has a second intersection point, and the second intersection point intersects with the plane on which the first surface or the second surface is located; in the first direction, the first intersection point has a first vertical distance h1 from the highest protruding point of the first protruding part, and the second intersection point has a second vertical distance h2 from the highest protruding point of the third protruding part, and the first vertical distance h1 and the second vertical distance h2 have the following relationship: h2

[0020] The first vertical distance h1 is the height of the first protruding part, and by limiting the height of the first protruding part, the pole piece and the diaphragm have a suitable gap, which has a supporting effect while avoiding the pole piece being too thick; the second vertical distance h2 is the height of the third protruding part, and if the third protruding part is too high, the highest protruding point is easily sharp during the processing of the third protruding part, which easily causes the current collector to be crushed; and if the third protruding part is too low, the adhesion strength between the active material layer and the current collector cannot be effectively improved.

[0021] In an embodiment of the present application, the recess has a third intersection point intersecting a plane in which the surface of the second active material layer is located; a first tangent is tangent to the first intersection point, and an included angle between the first tangent and the plane in which the surface of the first active material layer is located is a first included angle a1; a second tangent is tangent to the third intersection point, and an included angle between the second tangent and the plane in which the surface of the second active material layer is located is a second included angle a2; the first included angle a1 and the second included angle a2 have the following relationship: a1-a2=0°-40°; or the first included angle a1 is 0°-90°, or the second included angle a2 is 0°-90°.

[0022] Defining the first included angle a1 and the second included angle a2 is equivalent to defining the height and the inclination angle of the first protrusion; when the first included angle a1 and the second included angle a2 are too large, the first protrusion is prone to be broken at the connection between the flat section and the protrusion; when the first included angle a1 and the second included angle a2 are too small, the inclination angle of the first protrusion is too large and the height is insufficient, the supporting effect is not obvious, and the first protrusion is prone to be flattened in the process and the cycle.

[0023] In theory, the second included angle a2 belongs to the side under pressure, the second included angle a2 is smaller than the first included angle a1, and the breakage of the connection between the recess and the flat section can be avoided.

[0024] In an embodiment of the present application, a third tangent is tangent to any point on the first arc-shaped outer surface except the first intersection point, and an included angle between the third tangent and the plane in which the surface of the first active material layer is located is a third included angle a3; the third included angle a3 is 0°-80°.

[0025] Defining the third included angle a3 is equivalent to defining the height and the inclination angle of the first protrusion, so as to avoid the first protrusion being too sharp to pierce the diaphragm and cause short circuit.

[0026] In an embodiment of the present application, the tensile strength of the current collector along the second direction and the third direction is a first tensile strength M; the first vertical distance h1 and the first tensile strength M have the following relationship: 0.05≤h1 / M≤0.2; and / or the second vertical distance h2 and the first tensile strength M have the following relationship: 0.01≤h2 / M≤0.15; wherein the third direction, the second direction and the first direction are perpendicular to each other.

[0027] The first vertical distance h1 is the height of the first protruding part, the higher the first protruding part, the greater the extrusion stress of the current collector caused by the first protruding part; the second vertical distance h2 is the height of the third protruding part, the higher the third protruding part, the greater the tensile force of the current collector caused by the third protruding part during preparation of the third protruding part; therefore, by limiting the relationship between the height of the first protruding part and the tensile strength of the current collector, and the relationship between the height of the third protruding part and the tensile strength of the current collector, the current collector is prevented from being broken.

[0028] In an embodiment of the present application, the flat part includes a second connecting section where the third protruding part is not arranged, and the second connecting section has a second thickness H2 in the first direction; the second vertical distance h2 and the second thickness H2 have the following relationship: h2-H2=0.5-10 μm.

[0029] The second vertical distance h2 is the height of the third protruding part, and the second thickness H2 is the thickness of the flat area connected with the third protruding part; by limiting the relationship between the second vertical distance h2 and the second thickness H2, the third protruding part has a suitable height; the third protruding part is prevented from being too high to cause excessive tensile force of the current collector during preparation of the third protruding part, thereby preventing the current collector from being broken.

[0030] In an embodiment of the present application, the total sum of the projection areas of the plurality of first protruding parts in the first direction is a first area S1, and the projection area of the first active material layer in the first direction is a second area S2; the total sum of the projection areas of the plurality of second protruding parts in the first direction is a third area S3, and the projection area of the current collector in the first direction is a fourth area S4; the ratio of the first area S1 to the second area S2 is S1 / S2=0.05-0.7, and / or the ratio of the third area S3 to the fourth area S4 is S3 / S4=0.1-0.6.

[0031] When the proportion of the area of the first protruding part to the overall area of the single-sided area is too large, the current collector corresponding to the area with the first protruding part on the pole piece will be wrinkled and broken; when the proportion of the area of the first protruding part to the overall area is too small, the support space will be insufficient.

[0032] When the proportion of the area of the second protruding part to the overall area of the single-sided area is too large, the ductility of the current collector will be insufficient, which will easily cause the current collector to be broken; when the proportion of the area of the second protruding part to the overall area of the single-sided area is too small, the coating amount cannot be effectively improved, and the improvement of the adhesion force is not obvious.

[0033] In an embodiment of the present application, the current collector is provided with a plurality of hole structures; the hole structures have a diameter of 1-20 μm, and / or the distance between two adjacent hole structures is 20-300 μm; and / or the projection area of the hole structures in the first direction is a seventh area S7, and the ratio of the seventh area S7 to the fourth area S4 is S7 / S4 = 0.1-0.5.

[0034] The hole structures provided on the current collector can further increase the coating amount of the active material layer, thereby improving the bonding strength between the active material layer and the current collector.

[0035] In an embodiment of the present application, the edges of the first and second protruding portions are circular arc edges.

[0036] In an embodiment of the present application, the shape of the projection of the first and second protruding portions in the first direction includes a circle, a semicircle, an ellipse, a plum blossom shape or a polygon, etc.

[0037] The edge powdering during the processing of the first and second protruding portions is prevented; the safety problem caused by the first protruding portion piercing the diaphragm is avoided; and the problem of the active material layer cracking caused by the second protruding portion piercing the active material layer is prevented.

[0038] The present application also provides a core, which comprises the pole piece described above, and the core comprises a flat area and a circular arc area at opposite ends of the flat area, and the surface of the first active material layer and / or the surface of the second active material layer of the pole piece in the circular arc area is provided with a plurality of grooves.

[0039] Due to the curvature of the circular arc area, when the positive pole piece wraps the negative pole piece, the circular arc length of the active material layer of the positive pole piece is greater than that of the negative pole piece, which leads to the decrease of the ratio of the negative surface capacity to the positive surface capacity (CB value) in this area, and causes the lithium precipitation in the circular arc area. By providing a plurality of grooves on the active material layer of the positive pole piece, the amount of lithium removed from the positive pole piece in this area is reduced, the amount of lithium inserted into the negative pole piece is increased, the ratio of the negative surface capacity to the positive surface capacity in this area is improved, and the risk of lithium precipitation in the circular arc area is improved.

[0040] In an embodiment of the present application, along the second direction, the groove has a first width N1; along the third direction, the groove has a second width M1; any layer of the pole piece in the circular arc area has a first arc-shaped circumference N2; along the third direction, any layer of the pole piece in the circular arc area has a third width M2; the first width N1 and the first arc-shaped circumference N2 have the following relationship: N1 / N2 = 0.6-1.2; and the second width M1 and the third width M2 have the following relationship: M1≤M2.

[0041] The relationship between the width of the circular-arc area groove and the width of the pole piece is defined to ensure that the setting of the groove can effectively improve the lithium precipitation in the circular-arc area; if the width of the groove is larger, the battery capacity loss will be high; if the width of the groove is too small, the lithium precipitation in the circular-arc area cannot be effectively improved.

[0042] In an embodiment of the present application, the cross-sectional shape of the groove in the cross section in the first direction includes a circular arc, a cone, a V shape, or a polygon, etc.

[0043] The present application also provides a battery comprising the winding core described above.

[0044] The pole piece of the present application forms a plurality of second protrusions on the bending part of the current collector to increase the roughness between the current collector and the active material layer, thereby improving the bonding strength between the active material layer and the current collector, and reducing the risk of the active material layer at the embossed protrusion falling off the current collector caused by the setting of the embossed protrusion. In addition, the second protrusions can also increase the structural strength of the current collector itself, reduce the minimum thickness requirement of the current collector, and effectively increase the capacity of the active material layer while ensuring the structural strength of the current collector, thereby improving the energy density and use performance of the battery monomer. On the other hand, the active material layer is coated on the current collector with the concave-convex structure, and the first protrusions and corresponding recesses are processed on the active material layer by a special roller, which can ensure that the bonding strength between the active material layer and the current collector is improved while further improving the electrolyte wettability and liquid storage capacity, slowing down the swelling of the negative electrode in the cycle process, and thereby improving the cycle performance and safety performance of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0046] Figure 1 Structure diagram of the pole piece provided by the embodiment of the present application Figure One ;

[0047] Figure 2 Structure diagram of the pole piece provided by the embodiment of the present application Figure Two ;

[0048] Figure 3 Structure diagram of the pole piece provided by the embodiment of the present application Figure Three ;

[0049] Figure 4 Schematic view of the first protruding part of the pole piece provided for an embodiment of the present application Figure One ;

[0050] Figure 5 Schematic view of the current collector of the pole piece provided for an embodiment of the present application

[0051] Figure 6 Schematic view of the flat part of the current collector provided for an embodiment of the present application

[0052] Figure 7 Schematic view of the first protruding part of the pole piece provided for an embodiment of the present application Figure Two ;

[0053] Figure 8 Structural schematic view of the roll core provided for an embodiment of the present application

[0054] Figure 9 Structural schematic view of the pole piece provided for an embodiment of the present application Figure Four ;

[0055] Figure 10 Structural schematic view of the pole piece provided for an embodiment of the present application Figure Five .

[0056] Reference signs:

[0057] 100: current collector

[0058] 101: second protruding part; 102: third protruding part; 110: positive pole piece; 120: negative pole piece; 130: separator; 140: first central plane; 111: bending part; 112: flat part

[0059] 1011: second arc-shaped outer surface; 1012: second arc-shaped inner surface; 1023: second intersection point; 1024: second highest protruding point

[0060] 200: first active material layer

[0061] 201: first protruding part; 202: groove

[0062] 2011: first arc-shaped outer surface; 2012: first highest protruding point; 2013: first intersection point

[0063] 300: second active material layer

[0064] 301: recessed part

[0065] 3011: first arc-shaped inner surface; 3012: third intersection point

[0066] 401: first flat area; 402: second connecting section

[0067] 601: first tangent line; 602: second tangent line; 603: third tangent line. DETAILED DESCRIPTION

[0068] The winding type lithium ion battery is characterized in that: an electrode assembly is subjected to laminating winding to form a winding structure of a battery cell, a cross section of the winding structure presents a flat elliptical structure, two sides of the elliptical structure are circular arc regions, and a middle of the elliptical structure is a planar region; during charging and discharging of the lithium ion battery, positive and negative electrode sheets will swell, the planar region can freely swell upward and downward, but the circular arc regions are restrained from swelling outward due to structural characteristics and stress accumulation, and finally, interlayer extrusion of the electrode sheets occurs, resulting in problems such as blocking of a diaphragm, poor electrolyte immersion, and lithium precipitation.

[0069] Meanwhile, the extrusion of the circular arc regions is also transmitted to the planar region, and the planar region is extruded very tightly due to the extrusion of the hot-pressing process in the production process, thereby causing the planar region to also have a poor electrolyte immersion condition.

[0070] The winding core provided by the embodiment of the application solves the problem of poor electrolyte immersion by processing embossing on the positive electrode sheet through a special roller to increase the micro gap between the electrode sheets, so that the positive electrode, the diaphragm and the negative electrode have a certain support.

[0071] However, if the embossing is processed on the electrode sheet alone, there is a risk that the active material layer on the electrode sheet is separated from the current collector.

[0072] Therefore, the electrode sheet provided by the embodiment of the application first extrudes a plurality of third protruding portions on the current collector through a special roller, then coats an active material layer on the upper surface and the lower surface of the current collector to obtain the electrode sheet, and then extrudes a plurality of first protruding portions and a plurality of recessed portions corresponding to the plurality of first protruding portions on the electrode sheet through the special roller again; the current collector between the first protruding portions and the recessed portions forms a bending portion under the second extrusion, and the third protruding portions on the bending portion form second protruding portions under the second extrusion. The second protruding portions formed on the bending portion of the current collector after the second extrusion can increase the roughness between the current collector and the active material layer, improve the adhesion strength of the active material layer and the current collector, and prevent the active material layer and the current collector from being separated.

[0073] Therefore, the electrode sheet provided by the embodiment of the application solves the problem of poor electrolyte immersion between layers by setting the embossing protrusions, and can avoid separation of the active material layer and the current collector at the embossing protrusions.

[0074] In order to make the above objectives, characteristics and advantages of the embodiments of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0075] In the embodiments of the present application, the first direction is the thickness direction of the pole piece, that is, the z-axis shown in the figure; the second direction is the length direction of the pole piece, that is, the x-axis shown in the figure; and the third direction is the width direction of the pole piece, that is, the direction perpendicular to the paper plane shown in the figure; the first direction, the second direction and the third direction are perpendicular to each other.

[0076] With reference to Figure 1 and Figure 2 The pole piece provided in the embodiments of the present application comprises a current collector 100, a first active material layer 200 and a second active material layer 300. The current collector 100 has opposite first and second surfaces along a first direction (z-axis shown in the figure), the first active material layer 200 is arranged on the first surface, and the second active material layer 300 is arranged on the second surface.

[0077] The current collector 100 can be a positive electrode current collector or a negative electrode current collector. The pole piece provided in the present application is described by taking the current collector 100 as a positive electrode current collector as an example.

[0078] The first active material layer 200 is provided with a plurality of first protruding parts 201, and the second active material layer 300 is provided with a plurality of recessed parts 301 corresponding to the first protruding parts 201.

[0079] The first protruding part 201 corresponds to the recessed part 301, that is, the projection of the first protruding part 201 along the first direction covers the projection of the recessed part 301 along the first direction.

[0080] The first protruding part 201 and the recessed part 301 are arranged on the first active material layer 200 and the second active material layer 300 coated on the two surfaces of the current collector 100, respectively, which can increase the micro-gap between the pole pieces, so that there is a certain support between the positive electrode, the separator and the negative electrode, increase the liquid storage space of the electrolyte, and improve the electrolyte infiltration effect; at the same time, a certain deformation space is provided for the positive pole piece, which can release the expansion amount of the negative pole piece in the cycle process; while improving the energy density of the battery, the cycle performance and safety performance of the battery are ensured.

[0081] The current collector 100 has a bending portion 111 and a flat portion 112. The bending portion 111 is located between the first protruding portion 201 and the recessed portion 301, and has a plurality of second protruding portions 101 protruding from the first surface or the second surface. The flat portion 112 has a plurality of third protruding portions 102 protruding from the first surface or the second surface.

[0082] The second protruding portions 101 on the current collector 100 can increase the contact area between the active material layer and the current collector 100 between the first protruding portion 201 and the recessed portion 301, thereby increasing the roughness between the current collector 100 and the active material layer, improving the bonding strength of the active material layer and the current collector 100, and reducing the risk of active material layer falling off during use. Similarly, the third protruding portions 102 on the current collector 100 can also increase the contact area between the flat portion 112 of the current collector 100 and the active material layer, reducing the risk of active material layer falling off on the flat portion 112.

[0083] At the same time, the second protruding portions 101 on the current collector 100 also help to reduce the contact resistance between the current collector 100 and the active material layer, effectively improving the cycle life of the battery cell.

[0084] The second protruding portions 101 on the current collector 100 can also increase the structural strength of the current collector 100 itself, reduce the minimum thickness requirement of the current collector 100, and for the same thickness of the tab, while ensuring the structural strength of the current collector 100, the tab with the second protruding portions 101 can effectively increase the capacity of the active material, and can improve the preservation ability of the tab to the electrolyte, thereby improving the energy density and use performance of the battery cell.

[0085] It should be noted that when preparing the tab provided in the embodiments of the present application, a plurality of third protruding portions 102 are first pressed on the current collector 100 by a special roller, and then the first active material layer 200 is coated on the first surface and the second active material layer 300 is coated on the second surface to obtain an initial tab. Then, the first protruding portion 201 and the recessed portion 301 corresponding to the first protruding portion 201 are processed on the initial tab by a special roller to obtain the tab. Under the secondary pressing, the current collector 100 between the first protruding portion 201 and the recessed portion 301 will form a bending portion 111, and the third protruding portions 102 on the bending portion 111 will form second protruding portions 101, so that the bending portion 111 of the current collector 100 has second protruding portions 101, and the flat portion 112 of the current collector 100 has third protruding portions 102.

[0086] Continuing to refer to Figure 1In the embodiment, the first active material layer 200 is arranged on the first surface of the current collector 100, the second protruding part 101 protrudes from the first surface of the current collector 100, and the first protruding part 201 protrudes from the first active material layer 200.

[0087] With reference to the foregoing Figure 2 In the embodiment, the first active material layer 200 is arranged on the first surface of the current collector 100, the second active material layer 300 is arranged on the second surface of the current collector 100, the second protruding part 101 protrudes from the second surface of the current collector 100, and the first protruding part 201 protrudes from the first active material layer 200. In this embodiment, the directions in which the second protruding part 101 and the first protruding part 201 protrude are opposite.

[0088] With reference to the foregoing Figure 2 In the embodiment, the center distance between the projections of two adjacent first protruding parts 201 in the first direction is a first distance L1. There is a flat section between the two adjacent first protruding parts 201, and the flat section has a second distance L2 in the second direction.

[0089] The first distance L1 and the second distance L2 satisfy the following relationship: L1 / L2 = 1.05-3.

[0090] Preferably, L1 / L2 = 1.1-2; and preferably, L1 / L2 = 1.3.

[0091] The limitation of the ratio of the first distance L1 to the second distance L2 corresponds to the limitation of the density of the first protruding part 201, and ensures that the plurality of first protruding parts 201 have a suitable spacing, so that the first protruding part 201 can be adjusted to a suitable volume, thereby providing sufficient support for the pole piece and allowing the pole piece to have sufficient deformation space to relieve swelling.

[0092] Preferably, the first distance L1 is 3-8 mm; and preferably, the first distance L1 is 3 mm or 5 mm.

[0093] Preferably, the first distance L1 is 3-8 mm; and preferably, the first distance L1 is 3 mm or 5 mm.

[0094] The second distance L2 is 0.5-8 mm.

[0095] Preferably, the second distance L2 is 1-4 mm; and preferably, the second distance L2 is 2 mm or 3 mm.

[0096] When the first distance L1 is less than 2 mm, the first protrusions 201 are too dense, the extension of the pole piece cannot meet the density of the first protrusions 201, the first protrusions 201 cannot be regulated to a proper volume, the height of the first protrusions 201 cannot meet the requirement, the deformation space is small, and the pole piece is prone to breakage; when the first distance L1 is greater than 10 mm, the first protrusions 201 are too sparse, the first protrusions 201 are too dispersed, and the support area of the first protrusions 201 is insufficient, so that the electrolyte infiltration effect and the improvement effect cannot be achieved.

[0097] Similarly, when the second distance L2 is less than 0.5 mm, the first protrusions 201 are too dense, the extension of the pole piece cannot meet the density of the first protrusions 201, the first protrusions 201 cannot be regulated to a proper volume, the height of the first protrusions 201 cannot meet the requirement, the deformation space is small, and the pole piece is prone to breakage; when the second distance L2 is greater than 8 mm, the first protrusions 201 are too sparse, the first protrusions 201 are too dispersed, and the support area of the first protrusions 201 is insufficient, so that the electrolyte infiltration effect and the improvement effect cannot be achieved.

[0098] Reference Figure 3 In the embodiment of the present application, the center interval of the projections of the two adjacent second protrusions 101 in the first direction is a third distance L3; the first connecting section between the two adjacent second protrusions 101 has a fourth distance L4 in the projection of the first connecting section in the first direction.

[0099] The third distance L3 and the fourth distance L4 have the following relationship: L3 / L4 = 1.2-2.

[0100] Preferably, L3 / L4 = 1.4-1.8; preferably, L3 / L4 = 1.5.

[0101] The limitation of the ratio of the third distance L3 and the fourth distance L4 corresponds to the limitation of the density of the second protrusions 101, which ensures that the multiple second protrusions 101 have a proper interval, so that the second protrusions 101 can be regulated to a proper volume, thereby improving the bonding performance between the current collector 100 and the active material layer and reducing the risk of the active material layer falling off.

[0102] The third distance L3 is 0.2-8 mm.

[0103] Preferably, the third distance L3 is 0.5-5 mm; preferably, the third distance L3 is 2 mm or 4 mm.

[0104] When the third distance L3 is less than 0.2 mm, the second protrusions 101 are too dense, and the current collector 100 is prone to rupture; when the third distance L3 is greater than 8 mm, the second protrusions 101 are too sparse, and the second protrusions 101 are too dispersed, so that it cannot be guaranteed that the second protrusions 101 are arranged on the current collector 100 between each first protrusion 201 and the recess 301, and thus the improvement effect cannot be achieved.

[0105] The fourth distance L4 is 0.2 mm to 8 mm.

[0106] Preferably, the fourth distance L4 is 0.5 mm to 5 mm; preferably, the fourth distance L4 is 2 mm or 4 mm.

[0107] When the fourth distance L4 is less than 0.2 mm, the second protrusions 101 are too dense, and the current collector 100 is prone to rupture; when the fourth distance L4 is greater than 8 mm, the second protrusions 101 are too sparse, and the second protrusions 101 are too dispersed, so that it cannot be guaranteed that the second protrusions 101 are arranged on the current collector 100 between each first protrusion 201 and the recess 301, and thus the improvement effect cannot be achieved.

[0108] In the embodiments of the present application, the third distance L3 and the first distance L1 have the following relationship: L3 / L1 = 0.05 to 0.5; preferably, L3 / L1 = 0.1 to 0.4; preferably, L3 / L1 = 0.2 or 0.3.

[0109] The fourth distance L4 and the second distance L2 have the following relationship: L4 / L2 = 0.1 to 0.5; preferably, L4 / L2 = 0.2 to 0.4; preferably, L4 / L2 = 0.3 or 0.35.

[0110] By limiting the ratio of the third distance L3 to the first distance L1 and the ratio of the fourth distance L4 to the second distance L2, it can be guaranteed that the density of the second protrusions 101 is greater than the density of the first protrusions 201.

[0111] In the embodiments of the present application, the edges of the second protrusions 101 and the first protrusions 201 are all circular arc edges. Avoiding the second protrusions 101 and the first protrusions 201 having sharp edges prevents the edges of the first protrusions 201 from piercing the separator, causing positive and negative short circuits and triggering safety accidents of the battery cell; and avoiding the edges of the second protrusions 101 from piercing the active material layer prevents the active material layer from cracking and triggering the problem of powder falling.

[0112] In the embodiments of the present application, the shapes of the projections of the second protrusions 101 and the first protrusions 201 in the first direction can include a circle, a semicircle, an ellipse, a plum blossom shape, or a polygon, etc.

[0113] Preferably, the shapes of the second protrusion 101 and the first protrusion 201 can be round shapes without sharp corners. The first protrusion 201 is prevented from piercing the diaphragm to cause positive and negative short circuits and trigger safety accidents of the battery cell; and the second protrusion 101 is prevented from piercing the active material layer to prevent cracks in the active material layer and trigger the problem of powder falling.

[0114] With reference to Figure 4 In the embodiments of the present application, the first protrusion 201 and the recess 301 are both formed into round shapes. The first protrusion 201 has a first arc-shaped outer surface 2011, and the first arc-shaped outer surface 2011 is located in the first active material layer 200 and has a first radius R1. The recess 301 has a first arc-shaped inner surface 3011, and the first arc-shaped inner surface 3011 is located in the second active material layer 300 and has a second radius R2.

[0115] The first radius R1 and the second radius R2 have the following relationship: R1>R2, R1 / R2=1.01-1.21; preferably, R1 / R2=1.01-1.1; preferably, R1 / R2=1.02.

[0116] By limiting the ratio of the first radius R1 and the second radius R2 to limit the volume of the first protrusion 201, the interlayer of the pole piece has a suitable deformation space, thereby better improving the negative electrode expansion.

[0117] In the embodiments of the present application, the first radius R1 can be 0.5mm-8mm, preferably, the first radius R1 can be 2mm-5mm, or the first radius R1 can be 1mm-5mm; preferably, the first radius R1 can be 3mm.

[0118] The second radius R2 can be 0.5mm-8mm, preferably, the second radius R2 can be 2mm-5mm, or the second radius R2 can be 1mm-5mm; preferably, the second radius R2 can be 3mm.

[0119] When the first radius R1 or the second radius R2 is less than 0.5mm, the volume of the first protrusion 201 is too small, resulting in insufficient deformation space and being unable to effectively improve the negative electrode expansion, and the first protrusion is too sharp, which can easily damage the diaphragm. When the first radius R1 or the second radius R2 is greater than 8mm, the volume of the first protrusion 201 is too large, and the first protrusion 201 is easily subjected to extrusion force, extension force and cyclic expansion force during the process, thereby causing excessive deformation of the first protrusion 201, so that the first protrusion 201 collapses and cannot effectively improve the negative electrode expansion.

[0120] It should be noted that the pole piece includes a raised area and a first flat area 401, the raised area refers to the area where the first raised portion 201 and the recessed portion 301 are arranged, and the first flat area 401 refers to the area where the first raised portion 201 and the recessed portion 301 are not arranged, and the first flat area 401 has a first thickness H1 along the first direction.

[0121] In theory, R1=R2+the thickness of the pole piece; but because a special roller is needed for pressing when the first raised portion 201 is processed on the pole piece, the thickness of the raised area of the actual pole piece is less than or equal to the thickness of the first flat area 401 of the actual pole piece, so R1-R2≤H1 in the embodiments of the present application.

[0122] Continuing to refer to Figure 4 , it should be noted that the first raised portion 201 has a first highest raised point 2012, and the radius from the center to the first highest raised point 2012 is a third radius R3, and the third radius R3 is also the maximum outer surface radius of the first arc-shaped outer surface 2011; in theory, the third radius R3 is equal to the first radius R1; but in fact, the first raised portion 201 will be flattened after process extrusion and pole piece extension, and the first raised portion 201 will be deformed, so that the third radius R3 is less than the first radius R1.

[0123] Referring to Figure 5 , in the embodiments of the present application, the second raised portion 101 has a second arc-shaped outer surface 1011 and a second arc-shaped inner surface 1012, and the second arc-shaped inner surface 1012 has a fourth radius R4.

[0124] The second radius R2 and the fourth radius R4 have the following relationship: R4 / R2=0.08-0.5; preferably, R4 / R2=0.1-0.4; preferably, R4 / R2=0.2.

[0125] Through the ratio of the second radius R2 and the fourth radius R4, the radius of the second raised portion 101 on the current collector 100 is smaller than the radius of the first raised portion 201 on the active material layer, and the second raised portion 101 on the current collector 100 has a suitable volume.

[0126] Among them, the fourth radius R4 can be 0.1mm-5mm; preferably, the fourth radius R4 can be 1mm-4mm; preferably, the fourth radius R4 can be 2mm.

[0127] When the fourth radius R4 is less than 0.1 mm, the volume of the second protruding part 101 is too small, and the second protruding part 101 cannot effectively improve the bonding strength between the active material layer and the current collector; when the fourth radius R4 is greater than 5 mm, the volume of the second protruding part 101 is too large, the height of the second protruding part 101 is too high, and when the active material layer is coated on the surface of the current collector 100, it will cause the surface of the active material layer to be uneven; and the current collector 100 is easily broken when the second protruding part 101 is processed on the current collector 100 by a special roller.

[0128] With reference to Figure 4 In the embodiment of the present application, the first protruding part 201 has a first intersection point 2013, which intersects with the plane on which the surface of the first active material layer 200 is located; in the first direction, the first intersection point 2013 and the first highest protruding point 2012 of the first protruding part 201 have a first vertical distance h1.

[0129] Figure 6 is a schematic view of the third protruding part 102 on the flat part of the current collector, with reference to Figure 6 In the embodiment of the present application, the third protruding part 102 has a second intersection point 1023, which intersects with the plane on which the first surface or the second surface is located; in the first direction, the second intersection point 1023 and the second highest protruding point 1024 of the third protruding part 102 have a second vertical distance h2.

[0130] The first vertical distance h1 is greater than the second vertical distance h2.

[0131] The first vertical distance h1 can be 3 μm to 40 μm; preferably, the first vertical distance h1 can be 5 μm to 30 μm, preferably, the first vertical distance h1 can be 10 μm or 20 μm.

[0132] The second vertical distance h2 can be 1 μm to 20 μm; preferably, the second vertical distance h2 can be 2 μm to 10 μm, preferably, the second vertical distance h2 can be 5 μm or 8 μm.

[0133] The first vertical distance h1 is the height of the first protruding part 201, by limiting the height of the first protruding part 201, the pole piece and the diaphragm have a suitable gap, which has a supporting effect while avoiding excessive thickness of the pole piece.

[0134] When the first vertical distance h1 is less than 3 μm, it means that the first protruding part 201 is too low, and the supporting effect is not obvious, the first protruding part 201 is an invalid protrusion, and the electrolyte cannot be sufficiently infiltrated; when the first vertical distance h1 is greater than 40 μm, it means that the first protruding part 201 is too high, which will cause serious delamination between the positive and negative pole pieces, causing new interface problems.

[0135] It should be noted that the negative electrode expansion causes extrusion to the pole piece, and the pole piece has a risk of fracture with multiple cycles; the first protruding part 201 has a supporting effect and can also improve the pole piece fracture problem caused by multiple cycles. However, when the first protruding part 201 is too low, the supporting effect is not obvious, and the improvement of the cycle fracture is also not obvious; the height of the first protruding part 201 in the present application is in the range of 3 μm to 40 μm, which has sufficient supporting strength and can effectively improve the pole piece fracture problem caused by multiple cycles.

[0136] The second vertical distance h2 is the height of the third protruding part 102; when the second vertical distance h2 is greater than 20 μm, it means that the third protruding part 102 is too high, which easily causes the highest protruding point to be relatively sharp during processing of the third protruding part 102, and easily causes the current collector to break, and also causes the flat active material layer to be uneven; when the second vertical distance h2 is less than 1 μm, it means that the third protruding part 102 is too low, and cannot effectively improve the bonding strength between the active material layer and the current collector 100.

[0137] By limiting the first vertical distance h1 to be greater than the second vertical distance h2, the pole piece and the diaphragm have a suitable gap, which realizes the supporting effect while avoiding increasing the overall thickness of the pole piece.

[0138] With reference to Figure 6 In the embodiment of the present application, the flat part 112 of the current collector 100 also includes a second connecting section 402 which is not provided with the third protruding part 102; the second connecting section 402 has a second thickness H2 in the first direction, and the second thickness H2 is also the thickness of the current collector 100 itself.

[0139] The second vertical distance h2 and the second thickness H2 have the following relationship: h2-H2=0.5 μm to 10 μm.

[0140] Preferably, h2-H2=1 μm to 9 μm; preferably, h2-H2=2 μm or 5 μm.

[0141] The second vertical distance h2 is the height of the third protruding part 102, and the second thickness H2 is the thickness of the second connecting section 402 connected with the third protruding part 102; by limiting the relationship between the second vertical distance h2 and the second thickness H2, the third protruding part 102 has a suitable height; avoiding the third protruding part 102 being too high to cause the tensile force on the current collector 100 to be too large during preparation of the third protruding part 102, and thus causing the current collector 100 to break.

[0142] When the difference between the second vertical distance h2 and the height of the second thickness H2 is greater than 10 μm, it indicates that the height of the third protruding part 102 is relatively high with respect to the thickness of the current collector 100 itself, the extrusion stress caused by the third protruding part 102 to the current collector 100 itself is greater, and the current collector 100 is prone to breakage; when the difference between the second vertical distance h2 and the height of the second thickness H2 is less than 0.5 μm, it indicates that the height of the third protruding part 102 is relatively small with respect to the thickness of the current collector 100 itself, and the coating amount cannot be effectively improved, nor can the adhesion between the active material layer and the current collector 100 be improved.

[0143] In the embodiments of the present application, the tensile strength of the current collector 100 along the second direction and the third direction is the first tensile strength M.

[0144] The first vertical distance h1 and the first tensile strength M have the following relationship: 0.05≤h1 / M≤0.2; preferably, h1 / M=0.15.

[0145] The second vertical distance h2 and the first tensile strength M have the following relationship: 0.01≤h2 / M≤0.15; preferably, h2 / M=0.08.

[0146] The first vertical distance h1 is the height of the first protruding part 201, and the higher the first protruding part 201, the greater the extrusion stress caused by the first protruding part 201 to the current collector; the second vertical distance h2 is the height of the third protruding part 102, and the higher the third protruding part 102, the greater the tensile force caused by the third protruding part 102 to the current collector 100 during preparation; therefore, by limiting the relationship between the height of the first protruding part 201 and the tensile strength of the current collector 100, and the relationship between the height of the third protruding part 102 and the tensile strength of the current collector 100, the current collector 100 is prevented from breaking.

[0147] The first tensile strength M≥100 MPa, so as to prevent the current collector 100 from breaking.

[0148] Reference Figure 7 In the embodiments of the present application, the recess part 301 has a third intersection point 3012, which intersects with the plane where the surface of the second active material layer 300 is located; a first tangent line 601 is tangent to the first intersection point 2013, and the included angle between the first tangent line 601 and the plane where the surface of the first active material layer 200 is located is a first included angle a1; a second tangent line 602 is tangent to the third intersection point 3012, and the included angle between the second tangent line 602 and the plane where the surface of the second active material layer 300 is located is a second included angle a2.

[0149] The first included angle a1 and the second included angle a2 have the following relationship: a1-a2=0°-40°; preferably, a1-a2=5°-25°; preferably, a1-a2=10°.

[0150] The first included angle a1 is 0°-90°; preferably, the first included angle a1 is 25°-80°; preferably, the first included angle a1 is 45°.

[0151] The second included angle a2 is 0°-90°; preferably, the second included angle a2 is 5°-55°; preferably, the second included angle a2 is 35°.

[0152] Limiting the first included angle a1 and the second included angle a2 is equivalent to limiting the height and the inclination angle of the first protruding part 201; when the first included angle a1 and the second included angle a2 are greater than 90°, the first protruding part 201 is prone to breaking at the connection between the flat section and the first protruding part 201; when the first included angle a1 and the second included angle a2 are less than 0°, the inclination angle of the first protruding part 201 is too large, the height of the first protruding part 201 is insufficient, and the supporting force of the first protruding part 201 is insufficient, which is prone to being flattened during the process and the circulation process.

[0153] In theory, during the processing of the first protruding part 201, the second included angle a2 is the side under pressure, and the second included angle a2 is less than the first included angle a1, so as to avoid breaking at the intersection between the concave part 301 and the flat section.

[0154] Continuing to refer to Figure 7 In the embodiments of the present application, the third tangent line 603 is tangent to any point on the first arc-shaped outer surface 2011 excluding the first intersection 2013, and the included angle between the third tangent line 603 and the plane in which the surface of the first active material layer 200 is located is the third included angle a3.

[0155] The third included angle a3 is 0°-80°; preferably, the third included angle a3 is 30° or 40°.

[0156] Limiting the third included angle a3 is equivalent to limiting the height and the inclination angle of the first protruding part 201, so as to avoid the first protruding part 201 being too sharp and piercing the diaphragm to cause short circuit.

[0157] In the embodiments of the present application, the total projection area of the plurality of first protruding parts 201 in the first direction is a first area S1, and the projection area of the first active material layer 200 in the first direction is a second area S2.

[0158] The ratio of the first area S1 to the second area S2 is: S1 / S2=0.05-0.7, preferably, S1 / S2=0.2-0.5; preferably, S1 / S2=0.3.

[0159] When the ratio of the first area S1 to the second area S2 is greater than 0.7, it indicates that the proportion of the area of the first protruding part 201 in the overall area of the single-face region is too large, which is likely to cause the current collector 100 corresponding to the region with the first protruding part 201 on the pole piece to be wrinkled and broken, resulting in lithium precipitation of the battery cell and affecting the safety performance of the battery; when the ratio of the first area S1 to the second area S2 is less than 0.05, it indicates that the proportion of the area of the first protruding part 201 in the overall area is too small, which will result in insufficient support space and unobvious improvement effect.

[0160] In the embodiments of the present application, the total projection area of the plurality of second protruding parts 101 in the first direction is a third area S3, and the projection area of the current collector 100 in the first direction is a fourth area S4.

[0161] The ratio of the third area S3 to the fourth area S4 is S3 / S4 = 0.1-0.6, preferably S3 / S4 = 0.2-0.4; preferably S3 / S4 = 0.3.

[0162] When the ratio of the third area S3 to the fourth area S4 is greater than 0.6, it indicates that the proportion of the area of the second protruding part 101 in the overall area of the single-face region is too large, which is likely to cause insufficient ductility and strength of the current collector 100, and further cause the current collector 100 to be broken; when the ratio of the third area S3 to the fourth area S4 is less than 0.1, it indicates that the proportion of the area of the second protruding part 101 in the overall area of the single-face region is too small, which cannot effectively improve the coating amount and unobviously improve the adhesion.

[0163] Continuing to refer to Figure 4 In the embodiments of the present application, the first arc-shaped outer surface 2011 has a first surface area Q1, and the first arc-shaped inner surface 3011 has a second surface area Q2; the ratio of the first surface area Q1 to the second surface area Q2 is Q1 / Q2 = 1.02-1.21; preferably Q1 / Q2 = 1.1-1.2.

[0164] The first surface area Q1 can be calculated by the first radius R1, and the second surface area Q2 can be calculated by the second radius R2. Therefore, limiting the ratio of the first surface area Q1 to the second surface area Q2 is equivalent to limiting the ratio of the first radius R1 to the second radius R2, thereby limiting the volume of the first protruding part 201, so that the pole piece layer has a suitable deformation space, thereby better improving the negative electrode expansion.

[0165] The projection area of the first arc-shaped outer surface 2011 in the first direction is a fifth area S5, and the projection area of the first arc-shaped inner surface 3011 in the first direction is a sixth area S6; the ratio of the fifth area S5 to the sixth area S6 is S5 / S6 = 1.02-1.21; preferably S5 / S6 = 1.1-1.2.

[0166] The fifth area S5 can be calculated by the first radius R1, and the sixth area S6 can be calculated by the second radius R2, thus, the ratio of the fifth area S5 and the sixth area S6 is equivalent to the ratio of the first radius R1 and the second radius R2, thereby limiting the volume of the first protruding part 201, so that the electrode sheet layer has a suitable deformation space, thereby better improving the negative electrode expansion.

[0167] In the embodiment of the present application, the current collector 100 is provided with a plurality of hole structures. The hole structure provided on the current collector 100 can further improve the coating amount of the coating layer and the adhesion of the coating layer and the current collector 100.

[0168] The diameter of the hole structure can be 1 μm to 20 μm, preferably, the diameter of the hole structure can be 5 μm to 15 μm; preferably, the diameter of the hole structure can be 10 μm.

[0169] The distance between the adjacent two hole structures is 20 μm to 300 μm; preferably, the distance between the adjacent two hole structures is 50 μm to 280 μm; preferably, the distance between the adjacent two hole structures is 100 μm.

[0170] The projection area of the hole structure in the first direction is the seventh area S7, and the ratio of the seventh area S7 and the fourth area S4 is: S7 / S4 = 0.1 to 0.5, preferably, S7 / S4 = 0.2 to 0.4.

[0171] Reference Figure 8 , Figure 9 and Figure 10 , the present application further provides a roll core, which comprises the above-mentioned electrode sheet, and the above-mentioned electrode sheet can be the positive electrode sheet 110; the roll core further comprises a negative electrode sheet 120 and a separator 130 arranged between the positive electrode sheet 110 and the negative electrode sheet 120, and the positive electrode sheet 110, the negative electrode sheet 120 and the separator 130 are wound around a first center surface 140.

[0172] The roll core comprises a flat area and a circular arc area located at opposite ends of the flat area, the surface of the first active material layer 200 of the electrode sheet is away from the first center surface 140, and the surface of the second active material layer 300 of the electrode sheet faces the first center surface 140; the surface of the first active material layer 200 and / or the surface of the second active material layer 300 of the electrode sheet in the circular arc area are provided with a plurality of grooves 202.

[0173] Due to the curvature of the circular arc area, when the positive electrode sheet 110 wraps the negative electrode sheet 120 in the circular arc area, the circular arc length of the active material layer of the positive electrode sheet 110 is greater than the circular arc length of the active material layer of the negative electrode sheet 120, which leads to the decrease of the ratio of the negative electrode surface capacity to the positive electrode surface capacity in this area, thereby causing lithium precipitation in the circular arc area.

[0174] The application embodiment sets multiple grooves 202 in the active material layer of the positive plate 110 to reduce the positive plate lithium ion amount in this area, increase the negative plate lithium migration amount, improve the ratio of the negative plate surface capacity to the positive plate surface capacity in this area, and further improve the lithium precipitation risk of the arc area.

[0175] In the application embodiment, along the second direction, the groove 202 has a first width N1, and along the third direction, the groove 202 has a second width M1; any layer of the positive plate 110 in the arc area has a first arc-shaped circumference N2, and along the third direction, any layer of the positive plate 110 in the arc area has a third width M2.

[0176] The first width N1 and the first arc-shaped circumference N2 have the following relationship: N1 / N2 = 0.6-1.2; the second width M1 and the third width M2 have the following relationship: M1≤M2.

[0177] When the ratio of the first width N1 to the first arc-shaped circumference N2 is too small, that is, the groove 202 width is too small, the effect of improving the lithium precipitation in the arc area is not obvious; when the ratio of the first width N1 to the first arc-shaped circumference N2 is too large, that is, the groove 202 width is large, the battery capacity loss is high.

[0178] In the application embodiment, on the cross section in the first direction, the cross-sectional shape of the groove 202 can include a circular arc shape, a conical shape, a V-shaped type or a polygonal shape, etc.

[0179] The application embodiment also provides a battery comprising the above-mentioned winding core.

[0180] The above winding core provided by the application is described in detail through specific embodiments below, and the specific differences of different embodiments are shown in Table 1 and Table 2.

[0181] Embodiment 1:

[0182] The battery preparation of the embodiment includes the following steps:

[0183] 1. Preparation of the positive plate 110:

[0184] The first embossing roller is used to roll the current collector 100 to form multiple third protruding parts 102 on the current collector 100.

[0185] Lithium cobaltate, a conductive agent and PVDF are mixed in a mass ratio of 97.6:1.4:1, and then placed in NMP and stirred uniformly to prepare a positive electrode slurry; the positive electrode slurry is uniformly coated on the positive and negative surfaces of the current collector 100 to form a first active material layer 200 and a second active material layer 300 on the current collector 100; the thickness of the current collector 100 is 1.5 μm, and the coating surface density is 0.01704 g / cm 2; sequentially dried, rolled, to obtain the positive plate 110, the thickness of the positive plate 110 is the first thickness H1, the first thickness H1 is 4 μm.

[0186] The positive plate 110 is rolled using the second embossing roller, a plurality of first protruding parts 201 are formed on the first active material layer 200, and a plurality of recessed parts 301 are formed on the second active material layer 300, which are oppositely arranged with the first protruding parts 201. At the same time, under the secondary pressing, the current collector 100 located between the first protruding part 201 and the recessed part 301 forms a bending part 111, and the third protruding part 102 on the bending part 111 is extruded to form a second protruding part 101.

[0187] The center interval of the projection of the two adjacent first protruding parts 201 on the positive plate 110 in the first direction is the first distance L1, the length of the flat section between the two adjacent first protruding parts 201 in the second direction is the second distance L2, the center interval of the projection of the two adjacent second protruding parts 101 in the first direction is the third distance L3, and the length of the projection of the first connecting section between the two adjacent second protruding parts 101 in the first direction is the fourth distance L4, wherein L3 / L1=0.25, L4 / L2=0.3, and L3 / L4=1.6.

[0188] The radius of the arc-shaped outer surface of the first protruding part 201 is the first radius R1, the radius of the arc-shaped inner surface of the recessed part 301 is the second radius R2, and the radius of the arc-shaped inner surface of the second protruding part 101 is the fourth radius R4; wherein R1 / R2=1.05, and R4 / R2=0.3.

[0189] The height of the first protruding part 201 is the first vertical distance h1, which is 18 μm; the height of the third protruding part 102 is the second vertical distance h2, which is 6 μm; the thickness of the current collector 100 itself is the second thickness H2, and h2-H2=5.

[0190] The tensile strength of the current collector 100 is the first tensile strength M, h1 / M=0.15, and h2 / M=0.07.

[0191] The first included angle a1 of the first protruding part 201 is 53°, the second included angle a2 of the first protruding part 201 is 38°, the third included angle a3 of the first protruding part 201 is 35°, and the relationship between the first included angle a1 of the first protruding part 201 and the second included angle a2 of the recessed part 301 is a1-a2=15°.

[0192] 2. Preparation of the negative plate 120:

[0193] The silicon-containing artificial graphite, conductive carbon black, butadiene styrene rubber, and sodium carboxymethyl cellulose are mixed in deionized water in a mass ratio of 97.2:0.5:1.3:1, and a negative electrode slurry is prepared after uniform stirring. In the silicon-containing artificial graphite, the content of silicon is 10%.

[0194] The negative electrode slurry is uniformly coated on the positive and negative surfaces of the negative electrode current collector, and after baking and rolling, a negative electrode sheet 120 with a thickness of 220 μm is obtained, and the negative electrode tab is welded.

[0195] 3. Preparation of the separator 130:

[0196] The substrate, ceramic, and glue are used to prepare a 9 μm thick separator 130.

[0197] 4. Preparation of the electrolyte:

[0198] The electrolyte includes lithium salt LiPF6 and a solvent, and the solvent includes ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC), wherein the molar ratio of ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) is DEC:EC:EMC=1:1:1.

[0199] 5. Assembly:

[0200] The positive electrode sheet 110, the separator 130, and the negative electrode sheet 120 are wound to obtain a battery cell, and the battery cell is subjected to packaging, baking, liquid injection, formation, and double sealing to obtain a battery.

[0201] Example 2:

[0202] Example 2 is performed according to Example 1, except that L3 / L1=0.3.

[0203] Example 3:

[0204] Example 3 is performed according to Example 1, except that L3 / L1=0.5.

[0205] Example 4:

[0206] Example 4 is performed according to Example 1, except that L3 / L1=0.05.

[0207] Example 5:

[0208] Example 5 is performed according to Example 1, except that L3 / L1=0.6.

[0209] Example 6:

[0210] Example 6 is performed according to Example 1, except that L3 / L1=0.02.

[0211] Example 7:

[0212] Example 7 was conducted as in Example 1 except that L4 / L2 = 0.4.

[0213] Example 8:

[0214] Example 8 was conducted as in Example 1 except that L4 / L2 = 0.5.

[0215] Example 9:

[0216] Example 9 was conducted as in Example 1 except that L4 / L2 = 0.1.

[0217] Example 10:

[0218] Example 10 was conducted as in Example 1 except that L4 / L2 = 0.7.

[0219] Example 11:

[0220] Example 11 was conducted as in Example 1 except that L4 / L2 = 0.02.

[0221] Example 12:

[0222] Example 12 was conducted as in Example 1 except that L3 / L4 = 1.7.

[0223] Example 13:

[0224] Example 13 was conducted as in Example 1 except that L3 / L4 = 2.

[0225] Example 14:

[0226] Example 14 was conducted as in Example 1 except that L3 / L4 = 1.2.

[0227] Example 15:

[0228] Example 15 was conducted as in Example 1 except that L3 / L4 = 3.

[0229] Example 16:

[0230] Example 16 was conducted as in Example 1 except that L3 / L4 = 0.5.

[0231] Example 17:

[0232] Example 17 was conducted as in Example 1 except that R1 / R2 = 1.06.

[0233] Example 18:

[0234] Example 18 was performed according to Example 1 except that R1 / R2 = 1.21.

[0235] Example 19:

[0236] Example 19 was performed according to Example 1 except that R1 / R2 = 1.01.

[0237] Example 20:

[0238] Example 20 was performed according to Example 1 except that R1 / R2 = 1.3.

[0239] Example 21:

[0240] Example 21 was performed according to Example 1 except that R1 / R2 = 0.9.

[0241] Example 22:

[0242] Example 22 was performed according to Example 1 except that R4 / R2 = 0.25.

[0243] Example 23:

[0244] Example 23 was performed according to Example 1 except that R4 / R2 = 0.5.

[0245] Example 24:

[0246] Example 24 was performed according to Example 1 except that R4 / R2 = 0.08.

[0247] Example 25:

[0248] Example 25 was performed according to Example 1 except that R4 / R2 = 0.6.

[0249] Example 26:

[0250] Example 26 was performed according to Example 1 except that R4 / R2 = 0.05.

[0251] Example 27:

[0252] Example 27 was performed according to Example 1 except that the first vertical distance hi was 22 μm.

[0253] Example 28:

[0254] Example 28 was performed according to Example 1 except that the first vertical distance hi was 40 μm.

[0255] Example 29:

[0256] Example 29 was performed as in Example 1 except that the first vertical distance hi was 3 μm.

[0257] Example 30:

[0258] Example 30 was performed as in Example 1 except that the first vertical distance hi was 50 μm.

[0259] Example 31:

[0260] Example 31 was performed as in Example 1 except that the first vertical distance hi was 1 μm.

[0261] Example 32:

[0262] Example 32 was performed as in Example 1 except that the first vertical distance h2 was 11 μm.

[0263] Example 33:

[0264] Example 33 was performed as in Example 1 except that the first vertical distance h2 was 20 μm.

[0265] Example 34:

[0266] Example 34 was performed as in Example 1 except that the first vertical distance h2 was 1 μm.

[0267] Example 35:

[0268] Example 35 was performed as in Example 1 except that the first vertical distance h2 was 25 μm.

[0269] Example 36:

[0270] Example 36 was performed as in Example 1 except that the first vertical distance h2 was 0.5 μm.

[0271] Example 37:

[0272] Example 37 was performed as in Example 1 except that hi / M = 0.13 μm.

[0273] Example 38:

[0274] Example 38 was performed as in Example 1 except that hi / M = 0.2 μm.

[0275] Example 39:

[0276] Example 39 was performed as in Example 1 except that hi / M = 0.05 μm.

[0277] Example 40:

[0278] Example 40 was performed as in Example 1 except that hi / M = 0.5 μm.

[0279] Example 41:

[0280] Example 41 was performed as in Example 1 except that hi / M = 0.01 μm.

[0281] Example 42:

[0282] Example 42 was performed as in Example 1 except that h2 / M = 0.08 μm.

[0283] Example 43:

[0284] Example 43 was performed as in Example 1 except that h2 / M = 0.15 μm.

[0285] Example 44:

[0286] Example 44 was performed as in Example 1 except that h2 / M = 0.01 μm.

[0287] Example 45:

[0288] Example 45 was performed as in Example 1 except that h2 / M = 0.3 μm.

[0289] Example 46:

[0290] Example 46 was performed as in Example 1 except that h2 / M = 0.001 μm.

[0291] Example 47:

[0292] Example 47 was performed as in Example 1 except that h2-h2= 4.

[0293] Example 48:

[0294] Example 48 was performed as in Example 1 except that h2-h2= 10.

[0295] Example 49:

[0296] Example 49 was performed as in Example 1 except that h2-h2= 0.5.

[0297] Example 50:

[0298] Example 50 was performed as in Example 1 except that h2-h2= 12.

[0299] Example 51:

[0300] Example 51 was performed as in Example 1 except that h2-H2= 0.1.

[0301] Example 52:

[0302] Example 52 was performed as in Example 1 except that the first angle a1 = 45°; a1-a2 = 7°.

[0303] Example 53:

[0304] Example 53 was performed as in Example 1 except that the first angle a1 = 89°; a1-a2 = 51°.

[0305] Example 54:

[0306] Example 54 was performed as in Example 1 except that the first angle a1 = 1°; a1-a2 = -37°.

[0307] Example 55:

[0308] Example 55 was performed as in Example 1 except that the first angle a1 = 100°; a1-a2 = 62°.

[0309] Example 56:

[0310] Example 56 was performed as in Example 1 except that the first angle a1 = -10°; a1-a2 = -48°.

[0311] Example 57:

[0312] Example 57 was performed as in Example 1 except that the second angle a2 = 45°; a1-a2 = 8°.

[0313] Example 58:

[0314] Example 58 was performed as in Example 1 except that the second angle a2 = 89°; a1-a2 = -36°.

[0315] Example 59:

[0316] Example 59 was performed as in Example 1 except that the second angle a2 = 1°; a1-a2 = 52°.

[0317] Example 60:

[0318] Example 60 was performed as in Example 1 except that the second angle a2 = 100°; a1-a2 = -47°.

[0319] Example 61:

[0320] Example 61 was performed as in Example 1 except that the second included angle a2 = -10°; a1-a2 = 63°.

[0321] Example 62:

[0322] Example 62 was performed as in Example 1 except that the first included angle a1 = 60°; the second included angle a2 = 30°; a1-a2 = 30°.

[0323] Example 63:

[0324] Example 63 was performed as in Example 1 except that the first included angle a1 = 80°; the second included angle a2 = 40°; a1-a2 = 40°.

[0325] Example 64:

[0326] Example 64 was performed as in Example 1 except that the first included angle a1 = 45°; the second included angle a2 = 45°; a1-a2 = 0°.

[0327] Example 65:

[0328] Example 65 was performed as in Example 1 except that the first included angle a1 = 80°; the second included angle a2 = 30°; a1-a2 = 50°.

[0329] Example 66:

[0330] Example 66 was performed as in Example 1 except that the first included angle a1 = 40°; the second included angle a2 = 50°; a1-a2 = -10°.

[0331] Example 67:

[0332] Example 67 was performed as in Example 1 except that the third included angle a3 = 40°.

[0333] Example 68:

[0334] Example 68 was performed as in Example 1 except that the third included angle a3 = 80°.

[0335] Example 69:

[0336] Example 69 was performed as in Example 1 except that the third included angle a3 = 1°.

[0337] Example 70:

[0338] Example 70 was performed as in Example 1 except that the third included angle a3 = 89°.

[0339] Example 71:

[0340] Example 71 was performed according to Example 1, except that the third included angle a3 = -10°.

[0341] Comparative Example 1:

[0342] Comparative Example 1 was performed according to Example 1, except that no second protrusion 101 was provided on the current collector in Comparative Example 1.

[0343] Comparative Example 2:

[0344] Comparative Example 2 was performed according to Example 1, except that no second protrusion 101 was provided on the current collector in Comparative Example 2, and no first protrusion 201 was provided on the active material layer.

[0345] Comparative Example 3:

[0346] Comparative Example 3 was performed according to Example 1, except that a second protrusion 101 was provided on the current collector in Comparative Example 3, but no first protrusion 201 was provided on the active material layer.

[0347] Table 1:

[0348]

[0349]

[0350]

[0351] Table 2:

[0352]

[0353]

[0354] The relevant performances of the batteries in the above examples and comparative examples were tested, and the test results are recorded in Table 3, and the test methods are as follows:

[0355] 1. Electrolyte retention amount test

[0356] The electrolyte retention amount is the amount of electrolyte finally retained in the lithium ion battery. In order to ensure the consumption of electrolyte in the formation of lithium ion batteries, a certain amount of electrolyte is usually injected, and the excess electrolyte is extracted after formation. The injection amount m1, the extracted electrolyte amount m2, and the electrolyte retention amount

[0357] = m1-m2.

[0358] 2. Appearance state of the current collector 100, the separator 130, and the positive electrode sheet 110:

[0359] The shape of the second protrusion 101 and the first protrusion 201 was observed using a 3D microscope, and the damage of the current collector 100, the separator 130, and the positive electrode sheet 110 was observed using a 3D microscope.

[0360] 3. Current collector tensile strength test

[0361] Using a vertical tensile testing machine, the current collector obtained in the above examples and comparative examples was fixed on the clamps at both ends of the tensile testing machine, the clamps at both ends were aligned, the tensile testing machine button was started, and the machine was moved at a speed of 10 mm / s until the current collector was broken, and the tensile data was read out.

[0362] 4. Lithium precipitation of negative electrode sheet

[0363] After the battery obtained in the above examples and comparative examples was subjected to the cell expansion rate test, the battery obtained in the above examples and comparative examples was fully charged, and the battery was disassembled in a dry room environment, the lithium precipitation of the negative electrode sheet was observed, and the degree of lithium precipitation was observed. The degree of lithium precipitation is divided into slight lithium precipitation and severe lithium precipitation. When lithium precipitation occurs at the interface, the lithium precipitation color is gray or gray-black. When the interface is silver-white, the amount of lithium precipitation is large.

[0364] 5. Active material layer and current collector adhesion strength test

[0365] Using a vertical tensile testing machine, the positive electrode sheet obtained in the above examples and comparative examples was fixed on the clamps at both ends of the tensile testing machine, the clamps at both ends were aligned, the tensile testing machine button was started, and the machine was moved at a speed of 10 mm / s until the active material layer and the current collector were separated, and the tensile data was read out.

[0366] 6. Wettability improvement effect test

[0367] The battery was left at room temperature (25°C) for 24 h, and the wettability of the separator was observed by disassembly. The wetted area size was estimated and compared, and was divided into three levels: significant (wetting area 60%-100%), moderate (wetting area 30%-60%), and slight (wetting area 0%-30%). The unwetted area usually has an irregular water streak boundary, and the size difference can be directly observed.

[0368] Table 3:

[0369]

[0370]

[0371]

[0372] As shown in Table 2, the liquid retention amount of Comparative Example 1 is higher than that of Comparative Examples 2 and 3, and the wetting effect is obvious, which indicates that the first protruding part 201 can increase the pole piece distance, increase the electrolyte storage space, and improve the electrolyte wetting effect; the adhesion between the active material layer and the current collector in Comparative Example 3 is greater than that in Comparative Examples 1 and 2, which indicates that the second protruding part 101 can improve the adhesion between the active material layer and the current collector.

[0373] The liquid retention amount of Example 1 is higher than that of Comparative Example 1, and the adhesion between the active material layer and the current collector in Example 1 is greater than that in Comparative Example 3, which indicates that the simultaneous arrangement of the first protruding part 201 and the second protruding part 101 can improve the wetting effect while improving the adhesion between the active material layer and the current collector, thereby avoiding the active material layer from falling off.

[0374] From Example 2 to Example 6, it can be seen that when the ratio of the third distance L3 to the first distance L1 is greater than 0.5, the second protruding part 101 is relatively sparse relative to the first protruding part 201, and the adhesion between the active material layer and the current collector is low; when the ratio of the third distance L3 to the first distance L1 is less than 0.05, the second protruding part 101 is relatively dense relative to the first protruding part 201, and the adhesion between the active material layer and the current collector is large, but it is easy to cause the current collector 100 to break.

[0375] From Example 7 to Example 11, it can be seen that when the ratio of the fourth distance L4 to the second distance L2 is greater than 0.5, the density of the second protruding part 101 is relatively sparse relative to the density of the first protruding part 201, and the adhesion between the active material layer and the current collector is low; when the ratio of the fourth distance L4 to the second distance L2 is less than 0.1, the density of the second protruding part 101 is relatively dense relative to the density of the first protruding part 201, and the adhesion between the active material layer and the current collector is large, but it is easy to cause the current collector 100 to break.

[0376] From Example 12 to Example 16, it can be seen that when the ratio of the third distance L3 to the fourth distance L4 is greater than 2, the second protruding part 101 is relatively dense, the adhesion between the active material layer and the current collector is large, but the current collector 100 is easy to break; when the ratio of the third distance L3 to the fourth distance L4 is less than 1.2, the second protruding part 101 is too sparse, and the adhesion between the active material layer and the current collector is slight.

[0377] As can be seen from Example 17 to Example 21, when the ratio of the first radius R1 and the second radius R2 is greater than 1.21, the pole piece is prone to damage, the negative electrode will have slight lithium precipitation, and the liquid retention amount is low and the infiltration effect is poor; the reason is that the volume of the first protruding part 201 is too large, the highest point of the first protruding part 201 has cracks; and the volume of the recessed part 301 is too small, the structure composed of the first protruding part 201 and the recessed part 301 is prone to collapse, resulting in that the deformation space of the structure composed of the first protruding part 201 and the recessed part 301 is small, and the electrolyte containing space is insufficient. On the contrary, when the ratio of the first radius R1 and the second radius R2 is less than 1.01, it means that the volume of the first protruding part 201 is too small, and the volume of the recessed part 301 is too large, the structure composed of the first protruding part 201 and the recessed part 301 is prone to collapse, the deformation space of the structure composed of the first protruding part 201 and the recessed part 301 is small, and the electrolyte containing space is insufficient, thereby resulting in low liquid retention amount.

[0378] As can be seen from Example 22 to Example 26, when the ratio of the fourth radius R4 and the second radius R2 is greater than 0.5, the volume of the second protruding part 101 is large, and the current collector 100 is prone to breakage; when the ratio of the fourth radius R4 and the second radius R2 is less than 0.08, the volume of the second protruding part 101 is small, and the adhesion between the active material layer and the current collector is low.

[0379] As can be seen from Example 27 to Example 31, when the first vertical distance h1 is greater than 40, the pole piece is prone to damage, and the negative electrode will have slight lithium precipitation; the reason is that the first protruding part 201 is too high, and the highest point thereof has cracks, resulting in damage to the pole piece; when the first vertical distance h1 is less than 3, the liquid retention amount is low and the infiltration effect is poor; the reason is that the first protruding part 201 is too low, and the supporting effect is not obvious, the first protruding part 201 is an invalid protrusion, and the electrolyte cannot be sufficiently infiltrated.

[0380] As can be seen from Example 32 to Example 36, when the second vertical distance h2 is greater than 20, the current collector 100 is broken; the reason is that the second protruding part 101 is too high, and the highest protruding point thereof is prone to be sharp when the second protruding part 101 is processed. When the second vertical distance h2 is less than 1, the adhesion between the active material layer and the current collector is low; the reason is that the second protruding part 101 is too low, and cannot effectively improve the adhesion strength between the active material layer and the current collector 100, and the adhesion is low.

[0381] As can be seen from Examples 37 to 41, when the ratio h1 / M between the first vertical distance h1 and the tensile strength M of the current collector is greater than 0.2, the current collector 100 is prone to rupture, because the first protruding portion 201 is too high and the tensile strength of the current collector is insufficient, and the extrusion stress caused by the first protruding portion 201 to the current collector is too large; when the ratio h1 / M between the first vertical distance h1 and the tensile strength M of the current collector is less than 0.05, it indicates that the second protruding portion 101 is too low, and the supporting effect is not obvious, the first protruding portion 201 is an invalid protruding portion, and the electrolyte cannot be sufficiently infiltrated.

[0382] As can be seen from Examples 42 to 46, when the ratio h2 / M between the second vertical distance h2 and the tensile strength M of the current collector is greater than 0.15, the current collector 100 is prone to rupture, because the second protruding portion 101 is too high and the tensile strength of the current collector is insufficient, and the tensile force caused to the current collector 100 during preparation of the second protruding portion 101 is too large, thereby causing the current collector to rupture; when the ratio h2 / M between the second vertical distance h2 and the tensile strength M of the current collector is less than 0.01, it indicates that the second protruding portion 101 is too low, and cannot effectively improve the bonding strength between the active material layer and the current collector 100, and the bonding force is low.

[0383] As can be seen from Examples 47 to 51, when the relationship h2-H2 between the second vertical distance h2 and the thickness H2 of the current collector 100 is greater than 10, the current collector 100 is prone to rupture, because the second protruding portion 101 is too high, and the tensile force caused to the current collector during preparation of the second protruding portion 101 is too large, thereby causing the current collector 100 to rupture; when the relationship h2-H2 between the second vertical distance h2 and the thickness H2 of the current collector 100 is less than 0.5, it indicates that the second protruding portion 101 is too low, and cannot effectively improve the bonding strength between the active material layer and the current collector 100, and the bonding force is low.

[0384] As can be seen from Examples 52 to 56, when the first included angle a1 is greater than 90 degrees, and the relationship a1-a2 between the first included angle a1 and the second included angle a2 is greater than 40 degrees, the pole piece is damaged, and the liquid retention amount is low, and the infiltration effect is poor; because the inclination angle at the connection between the first protruding portion 201 and the flat section is too large, causing excessive bending and damage to the pole piece; at the same time, the inclination angle of the first protruding portion 201 relative to the recessed portion 301 is too large, and the structure composed of the first protruding portion 201 and the recessed portion 301 is unstable and prone to collapse under extrusion stress, and the electrolyte cannot be sufficiently infiltrated. When the first included angle a1 is less than 0 degrees, and the relationship a1-a2 between the first included angle a1 and the second included angle a2 is less than 0 degrees, it indicates that the first protruding portion 201 is too low, the first protruding portion 201 is an invalid protruding portion, the supporting effect is poor, and the electrolyte cannot be sufficiently infiltrated, thereby causing the liquid retention amount to be low.

[0385] As can be seen from Embodiment 57 to Embodiment 61, when the second included angle a2 is greater than 90 degrees, and the relationship a1-a2 between the first included angle a1 and the second included angle a2 is less than 0 degrees, the pole piece is damaged; the reason is that the inclined angle of the connection between the recess 301 and the flat section is too large, causing excessive bending, resulting in damage to the pole piece; at the same time, the inclined angle of the recess 301 relative to the first protruding part 201 is too large, and the structure composed of the first protruding part 201 and the recess 301 is unstable, and is easy to collapse under extrusion stress. When the second included angle a2 is less than 0 degrees, and the relationship a1-a2 between the first included angle a1 and the second included angle a2 is greater than 40 degrees, the inclined angle of the recess 301 relative to the first protruding part 201 is too small, and the depth of the recess 301 is shallow, which cannot make the electrolyte have sufficient infiltration, thereby resulting in low liquid retention.

[0386] As can be seen from Embodiment 62 to Embodiment 66, when the first included angle a1 and the second included angle a2 are both in the range of 0 degrees-90 degrees, but a1-a2 is greater than 40 degrees, it indicates that the inclined angle of the connection between the first protruding part 201 and the flat section is too large, and the highest protruding point of the first protruding part 201 is easy to break, causing damage to the pole piece; but a1-a2 is less than 0 degrees, which indicates that the inclined angle of the connection between the recess 301 and the flat section is too large, causing excessive bending, resulting in damage to the pole piece.

[0387] As can be seen from Embodiment 67 to Embodiment 71, when the third included angle a3 is greater than 80 degrees, the first protruding part 201 is too sharp, and the highest protruding point of the first protruding part 201 is easy to break, causing damage to the pole piece; when the third included angle a3 is less than 0 degrees, it indicates that the first protruding part 201 is recessed, and the first protruding part 201 is an invalid protrusion, which also cannot make the electrolyte have sufficient infiltration.

[0388] The embodiments in the specification or the embodiments are described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts between the embodiments can be referred to each other.

[0389] It should be noted that the phrases "one embodiment", "an embodiment", "exemplary embodiment", "some embodiments" and the like in the specification indicate that the described embodiment can include a particular feature, structure or characteristic, but not necessarily every embodiment. In addition, such phrases do not necessarily refer to the same embodiment. In addition, when a specific feature, structure or characteristic is described in combination with an embodiment, it is within the knowledge of those skilled in the art to realize such feature, structure or characteristic in combination with other embodiments that are explicitly or implicitly described.

[0390] In general, terminology can be understood at least in part from usage in context. For example, terms, such as "one or more" as used herein, can be taken to describe any feature, structure, or characteristic in the singular or can be taken to describe a combination of features, structures or characteristics in the plural sense. Similarly, terms, such as "a" or "an," as used herein can be taken to convey a singular usage or a plural usage, depending at least in part on context.

[0391] It will be readily understood that the terms "on," "above," and "over," in the present disclosure, are to be interpreted in the broadest context possible so that "on" means not only "directly on" but also includes the meaning of "on" with intervening features or layers therebetween, and "above" or "over" includes not only the meaning of "above" or "over" but also can include the meaning of "above" or "over" without intervening features or layers therebetween (i.e., directly on).

[0392] In addition, spatially relative terms, such as "beneath", "below", "lower", "above", "upper", and the like, can be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientations depicted in the figures. The devices can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0393] Finally, it should be noted that the above-described embodiments are merely intended to illustrate the technical solutions of the present application, but not to limit the same; even though the present application has been described in detail with reference to the above-described embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the above-described embodiments, or equivalently replace some or all of the technical features thereof; and such modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A pole piece characterized by, Comprising: a current collector, a first active material layer, and a second active material layer; the current collector has opposite first and second surfaces in a first direction, the first active material layer is disposed on the first surface, and the second active material layer is disposed on the second surface; a plurality of first protrusions are provided on the first active material layer, and a plurality of recesses corresponding to the first protrusions are provided on the second active material layer, the first protrusions and the recesses being formed by secondary pressing of the current collector after coating the active material layer; the current collector has a bending portion and a flat portion, the bending portion is located between the first protrusions and the recesses, the bending portion has a plurality of second protrusions protruding from the first surface or the second surface, and the second protrusions are formed by the plurality of third protrusions formed by primary pressing of the current collector before coating the active material layer during the secondary pressing.

2. The pole piece of claim 1, wherein: the center distance between the projections of two adjacent first protrusions in the first direction is a first distance L1; a flat section is provided between two adjacent first protrusions, the flat section has a second distance L2 in a second direction; the center distance between the projections of two adjacent second protrusions in the first direction is a third distance L3; a first connecting section is provided between two adjacent second protrusions, the projection of the first connecting section in the first direction has a fourth distance L4 in the second direction; the first distance L1 and the third distance L3 satisfy the relationship L3 / L1 = 0.05-0.5; and / or the second distance L2 and the fourth distance L4 satisfy the relationship L4 / L2 = 0.1-0.5; wherein the second direction is perpendicular to the first direction.

3. The pole piece of claim 2, wherein: the third distance L3 and the fourth distance L4 satisfy the relationship L3 / L4 = 1.2-2.

4. The pole piece of claim 2, wherein: the first protrusion has a first arc-shaped outer surface, the first arc-shaped outer surface is located on the first active material layer, and the first arc-shaped outer surface has a first radius R1; the recess has a first arc-shaped inner surface, the first arc-shaped inner surface is located on the second active material layer, and the first arc-shaped inner surface has a second radius R2; the first radius R1 and the second radius R2 satisfy the relationship R1 / R2 = 1.01-1.

21.

5. The pole piece of claim 4, wherein: the second protrusion has a second arc-shaped inner surface, and the second arc-shaped inner surface has a fourth radius R4; the fourth radius R4 and the second radius R2 satisfy the relationship R4 / R2 = 0.08-0.

5.

6. The pole piece of claim 4, wherein: the flat portion has a third protrusion; the first protrusion has a first intersection point, and the first intersection point intersects a plane on which the surface of the first active material layer is located. The third protruding part has a second intersection point intersecting with the plane on which the first surface or the second surface lies; In the first direction, the first intersection point has a first vertical distance h1 from the highest protruding point of the first protruding part, and the second intersection point has a second vertical distance h2 from the highest protruding point of the third protruding part, the first vertical distance h1 being greater than the second vertical distance h2; The first vertical distance h1 is 3 μm to 40 μm; and / or The second vertical distance h2 is 1 μm to 20 μm.

7. The pole piece of claim 6, wherein, The recessed part has a third intersection point intersecting with the plane on which the surface of the second active material layer lies; A first tangent line is tangent to the first intersection point, and an included angle between the first tangent line and the plane on which the surface of the first active material layer lies is a first included angle a1; A second tangent line is tangent to the third intersection point, and an included angle between the second tangent line and the horizontal plane on which the surface of the second active material layer lies is a second included angle a2; The first included angle a1 and the second included angle a2 have the following relationship: a1-a2=0° to 40°; or The first included angle a1 is 0° to 90°; or The second included angle a2 is 0° to 90°.

8. The pole piece of claim 7, wherein, A third tangent line is tangent to any point on the first arc-shaped outer surface excluding the first intersection point, and an included angle between the third tangent line and the plane on which the surface of the first active material layer lies is a third included angle a3; The third included angle a3 is 0° to 80°.

9. The pole piece of claim 6, wherein, In the second direction and the third direction, the tensile strength of the current collector is a first tensile strength M; The first vertical distance h1 and the first tensile strength M have the following relationship: 0.05≤h1 / M≤0.2; and / or The second vertical distance h2 and the first tensile strength M have the following relationship: 0.01≤h2 / M≤0.15; The third direction, the second direction and the first direction are perpendicular to each other.

10. The pole piece of claim 6, wherein, The flat part includes a second connecting section on which the third protruding part is not arranged, and the second connecting section has a second thickness H2 in the first direction; The second vertical distance h2 and the second thickness H2 have the following relationship: h2-H2=0.5 μm to 10 μm.

11. The pole piece of claim 1, wherein, The total sum of the projection areas of the plurality of first protruding parts in the first direction is a first area S1, and the projection area of the first active material layer in the first direction is a second area S2; The total sum of the projection areas of the plurality of second protruding parts in the first direction is a third area S3, and the projection area of the current collector in the first direction is a fourth area S4; The ratio of the first area S1 to the second area S2 is: S1 / S2=0.05 to 0.7; and / or The ratio of the third area S3 to the fourth area S4 is S3 / S4=0.1-0.

6.

12. The pole piece of claim 11, wherein, a plurality of hole structures are arranged on the current collector; a diameter of the hole structure is 1-20 μm; and / or a distance between two adjacent hole structures is 20-300 μm; and / or a projection area of the hole structure in the first direction is a seventh area S7, and a ratio of the seventh area S7 to the fourth area S4 is S7 / S4=0.1-0.

5.

13. The pole piece of claim 1, wherein, an edge of the first protruding part and the second protruding part is a circular arc edge.

14. The pole piece of claim 1, wherein, a shape of a projection of the first protruding part and the second protruding part in the first direction comprises a circle, a semi-circle, an ellipse, a plum blossom shape, or a polygon.

15. A core, characterized in that The pole piece of any one of claims 1-14; the core comprises a flat area and a circular arc area at opposite ends of the flat area, and a surface of the first active material layer and / or a surface of the second active material layer of the pole piece in the circular arc area is provided with a plurality of grooves.

16. The core of claim 15, wherein, in a second direction, the groove has a first width N1; in a third direction, the groove has a second width M1; any layer of the pole piece in the circular arc area has a first arc-shaped circumference N2; in the third direction, any layer of the pole piece in the circular arc area has a third width M2; the first direction is a thickness direction of the pole piece, the second direction is a length direction of the pole piece, and the third direction is a width direction of the pole piece; the first width N1 and the first arc-shaped circumference N2 have the following relationship: N1 / N2=0.6-1.2; the second width M1 and the third width M2 have the following relationship: M1≤M2.

17. The core of claim 15, wherein, in a cross section in the first direction, a cross-sectional shape of the groove comprises a circular arc shape, a conical shape, or a polygonal shape.

18. A battery, characterized by The core of any one of claims 15-17.

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