Pole piece, roll core and battery

Abstract

The invention provides a pole piece, a roll core and a battery, relates to the technical field of batteries, and is used for solving the technical problem that an active material layer at a knurling bulge is separated from a current collector due to the fact that the knurling bulge is arranged on the pole piece in the prior art. The pole piece comprises the current collector, a first active material layer and a second active material layer; the current collector has a first surface and a second surface opposite to each other, 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 convex parts are arranged on the first active material layer, and a plurality of concave parts corresponding to the first convex parts are arranged on the second active material layer; the current collector is provided with a bent part and a flat part, the bent part is located between the first protruding part and the concave part, the bent part is provided with a plurality of second protruding parts, and the second protruding parts are arranged on the first surface or the second surface in a protruding mode. The second protruding parts can increase the contact area between the active material layer and the current collector, improve the bonding strength between 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 batteries, and in particular to a pole piece, a winding core and a battery. Background Art

[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 charge and discharge process of lithium-ion batteries, the negative electrode sheet will expand, and the interlayer of the electrode sheet will be squeezed. The interlayer squeezing will lead to insufficient interlayer electrolyte and poor infiltration, affecting the safety of the battery cell.

[0003] In the prior art, embossed protrusions are processed on the positive electrode sheet by using special rollers to increase the micro-spacing between the electrode sheets, so that there is a certain support between the positive electrode, the separator and the negative electrode, solving the problems of insufficient electrolyte between the layers and poor wetting.

[0004] However, when embossing protrusions are provided on the pole piece, there is a risk that the active material layer at the embossing protrusions will be separated from the current collector. Summary of the invention

[0005] In view of the above problems, the embodiments of the present application provide a pole piece, a winding core and a battery to solve the problem in the prior art that the active material layer at the embossed protrusions is separated from the current collector due to the provision of embossed protrusions on the pole piece.

[0006] In order to achieve the above objectives, the present application provides the following technical solutions:

[0007] An embodiment of the present application provides a pole piece, which includes: a current collector, a first active material layer and a second active material layer; the current collector has a first surface and a second surface opposite to each other 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 recessed portions 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 protrusion and the recessed portion, the bending portion has a plurality of second protrusions, and the second protrusions are protruding from the first surface or the second surface.

[0008] A first protrusion and a recessed portion corresponding to the first protrusion are provided on the pole piece. The first protrusion provides support for the contact of the diaphragm and increases the micro-spacing between the pole piece and the diaphragm. These micro-spacings form a space for accommodating electrolyte, so that the electrolyte has sufficient infiltration amount to the pole piece, thereby avoiding the abnormal situation of insufficient electrolyte and poor infiltration between the pole piece and the diaphragm due to interlayer extrusion of the pole piece.

[0009] At the same time, multiple second protrusions are arranged on the bent portion of the current collector between the first protrusion and the recessed portion, which can increase the contact area between the active material layer and the bent portion, thereby improving the bonding strength between the active material layer and the bent portion and preventing the active material layer between the first protrusion and the recessed portion from detaching from the bent portion.

[0010] In one embodiment of the present application, the center interval between the projections of two adjacent first protrusions in the first direction is a first distance L1; there is a straight section between two adjacent first protrusions, and the straight section has a second distance L2 in the second direction; the center interval between the projections of two adjacent second protrusions in the first direction is a third distance L3; there is a first connecting section between two adjacent second protrusions, and along the second direction, the projection of the first connecting section in the first direction has a fourth distance L4; 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 are equivalent to limiting the density of the second protrusions to be greater than the density of the first protrusions; ensuring that each first protrusion on the pole piece has a second protrusion on the current collector, thereby ensuring the bonding strength between the current collector in the pole piece protrusion area and the active material layer, and preventing the active material layer 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 is equivalent to limiting the density of the second protrusions, ensuring that there is a suitable spacing between the multiple second protrusions, 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 one embodiment of the present application, the first protrusion has a first arcuate outer surface, the first arcuate outer surface is located in the first active material layer, and the first arcuate outer surface has a first radius R1; the recessed portion has a first arcuate inner surface, the first arcuate inner surface is located in the second active material layer, and the first arcuate 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 protrusion is equivalent to a sphere, the first radius R1 is the outer surface radius, and the second radius R2 is the inner surface radius. The volume of the first protrusion is limited by limiting the ratio of the first radius R1 to the second radius R2, so that there is a suitable deformation space between the pole sheet layers, thereby better improving the expansion of the negative electrode.

[0016] In an embodiment of the present application, the second protrusion has a second arc-shaped inner surface, 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 protrusion is equivalent to a sphere, the fourth radius R4 is the radius of its inner surface; by limiting the ratio of the fourth radius R4 to the second radius R2, the radius of the second protrusion on the current collector is smaller than the radius of the recessed portion on the second active material layer, so that the second protrusion on the current collector has a suitable volume.

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

[0019] In one embodiment of the present application, the flat portion has a third raised portion; the first raised portion has a first intersection, and the first intersection intersects with the plane where the first active material layer is located; the third raised portion has a second intersection, and the second intersection intersects with the plane where the first surface or the second surface is located; in the first direction, the first intersection and the highest raised point of the first raised portion have a first vertical distance h1, and the second intersection and the highest raised point of the third raised portion have a second vertical distance h2, 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 protrusion. By limiting the height of the first protrusion, a suitable gap can be provided between the pole piece and the diaphragm, which provides support while preventing the pole piece from being too thick. The second vertical distance h2 is the height of the third protrusion. If the third protrusion is too high, the highest protrusion point may be sharp when processing the third protrusion, which may easily cause the current collector to rupture. If the third protrusion is too short, it cannot effectively improve the bonding strength between the active material layer and the current collector.

[0021] ​In one embodiment of the present application, the recessed portion has a third intersection, and the third intersection intersects with the plane where the surface of the second active material layer is located; the first tangent is tangent to the first intersection, and the angle between the first tangent and the plane where the surface of the first active material layer is located is a first angle a1; the second tangent is tangent to the third intersection, and the angle between the second tangent and the plane where the surface of the second active material layer is located is a second angle a2; the first angle a1 and the second angle a2 have the following relationship: a1-a2=0°~40°; or the first angle a1 is 0°~90°, or the second angle a2 is 0°~90°.

[0022] Limiting the first angle a1 and the second angle a2 is equivalent to limiting the height and inclination angle of the first protrusion; when the first angle a1 and the second angle a2 are too large, the first protrusion is prone to breakage at the connection with the straight section; when the first angle a1 and the second angle a2 are too small, the inclination angle of the first protrusion is too large, the height is insufficient, the supporting effect is not obvious, and it is easy to be flattened during the process and cycle.

[0023] Theoretically, the second angle a2 belongs to the compressed side, and the second angle a2 is smaller than the first angle a1, which can avoid fracture at the junction of the recessed portion and the straight section.

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

[0025] Limiting the third angle a3 is equivalent to limiting the height and the inclination angle of the first protrusion, so as to prevent the first protrusion from being too sharp and puncturing the diaphragm to cause a short circuit.

[0026] In one embodiment of the present application, along the second direction and the third direction, the tensile strength of the current collector is the 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 protrusion. The higher the first protrusion is, the greater the compressive stress caused by the first protrusion on the current collector is; the second vertical distance h2 is the height of the third protrusion. The higher the third protrusion is, the greater the tensile force caused to the current collector when preparing the third protrusion is; therefore, by limiting the relationship between the height of the first protrusion and the tensile strength of the current collector, as well as the relationship between the height of the third protrusion and the tensile strength of the current collector, the current collector is prevented from breaking.

[0028] In one embodiment of the present application, the flat portion includes a second connecting segment without the third protruding portion, and the second connecting segment has a second thickness H2 along the first direction; the second vertical distance h2 and the second thickness H2 have the following relationship: h2-H2=0.5μm~10μm.

[0029] The second vertical distance h2 is the height of the third protrusion, and the second thickness H2 is the thickness of the straight area connected to the third protrusion; by limiting the relationship between the second vertical distance h2 and the second thickness H2, the third protrusion has a suitable height; avoiding the situation where the third protrusion is too high, resulting in excessive tensile force on the current collector during the preparation of the third protrusion, and then causing the current collector to break.

[0030] In one embodiment of the present application, the total projection area of ​​the multiple first protrusions in the first direction is the first area S1, and the projection area of ​​the first active material layer in the first direction is the second area S2; the total projection area of ​​the multiple second protrusions in the first direction is the third area S3, and the projection area of ​​the current collector in the first direction is the 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 area of ​​the first protrusion accounts for too large a proportion of the overall area of ​​the single-sided area, the current collector corresponding to the area of ​​the first protrusion on the pole piece will be wrinkled and broken; when the area of ​​the first protrusion accounts for too small a proportion of the overall area, insufficient support space will result.

[0032] When the area of ​​the second protrusion accounts for too large a proportion of the overall area of ​​the single-sided area, the ductility of the current collector will be insufficient, which may easily lead to the current collector rupture; when the area of ​​the second protrusion accounts for too small a proportion of the overall area of ​​the single-sided area, the coating amount cannot be effectively increased, and the improvement in adhesion is not obvious.

[0033] In one embodiment of the present application, a plurality of hole structures are provided on the current collector; the diameter of the hole structure is 1 μm to 20 μm, and / or the spacing between two adjacent hole structures is 20 μm to 300 μm; and / or the projection area of ​​the hole structure 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 to 0.5.

[0034] Providing a pore structure 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 protruding portion and the second protruding portion are both arc edges.

[0036] In an embodiment of the present application, the projection shapes of the first protrusion and the second protrusion in the first direction include circular, semicircular, elliptical, plum blossom or polygonal shapes.

[0037] Prevent edge powder loss when processing the first protrusion and the second protrusion; prevent the first protrusion from piercing the diaphragm and causing safety problems; prevent the second protrusion from piercing the active material layer, prevent the active material layer from cracking and causing powder loss.

[0038] An embodiment of the present application also provides a winding core, which includes the pole piece described above, and the winding core includes a straight area and arc areas located at opposite ends of the straight 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 arc area is provided with multiple grooves.

[0039] Due to the curvature of the arc area, in the arc area, when the positive electrode sheet wraps the negative electrode sheet, the arc circumference of the active material layer of the positive electrode sheet is greater than the arc circumference of the active material layer of the negative electrode sheet, resulting in a decrease in the ratio of the negative electrode surface capacity to the positive electrode surface capacity in this area (CB value decreases), triggering lithium deposition in the arc area. By setting multiple grooves in the active material layer of the positive electrode sheet, the amount of positive electrode lithium removal in this area is reduced, the amount of negative electrode lithium insertion is increased, and the ratio of negative electrode surface capacity to positive electrode surface capacity in this area is increased, thereby improving the risk of lithium deposition in the arc area.

[0040] In one 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 arc area has a first arc circumference N2; along the third direction, any layer of the pole piece in the arc area has a third width M2; the first width N1 and the first arc 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.

[0041] The relationship between the width of the arc zone groove and the width of the pole piece is limited to ensure that the setting of the groove can effectively improve the lithium deposition in the arc zone; if the width of the groove is too large, it will lead to a high loss of battery capacity; if the width of the groove is too small, it will not be able to effectively improve the lithium deposition in the arc zone.

[0042] In an embodiment of the present application, on the cross section where the first direction is located, the cross-sectional shape of the groove includes an arc shape, a cone shape, a V shape, a polygon shape, or the like.

[0043] An embodiment of the present application also provides a battery, which includes the winding core described above.

[0044] The pole piece of the present application forms a plurality of second protrusions on the bending portion 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, so as to reduce the risk of the active material layer at the embossed protrusions falling off the current collector when the pole piece is provided with the embossed protrusions; 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 current collector for the active material layer while ensuring the structural strength of the current collector, thereby facilitating the improvement of the energy density and performance of the battery cell. On the other hand, coating the active material layer on the current collector with the concave-convex structure, and processing the first protrusion and the corresponding concave portion on the active material layer by a special roller can ensure that while improving the bonding strength between the active material layer and the current collector, the electrolyte wettability and liquid storage capacity are further improved, and the expansion of the negative electrode during the cycle is slowed down, thereby improving the cycle performance and safety performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0046] Figure 1 Schematic diagram of the structure of the pole piece provided in the embodiment of the present application Figure 1 ;

[0047] Figure 2 Schematic diagram of the structure of the pole piece provided in the embodiment of the present application Figure 2 ;

[0048] Figure 3 Schematic diagram of the structure of the pole piece provided in the embodiment of the present application Figure 3 ;

[0049] Figure 4 Schematic diagram of the first protrusion of the pole piece provided in the embodiment of the present application Figure 1 ;

[0050] Figure 5 A schematic diagram of a current collector of a pole piece provided in an embodiment of the present application;

[0051] Figure 6 A schematic diagram of a flat portion of a current collector provided in an embodiment of the present application;

[0052] Figure 7 Schematic diagram of the first protrusion of the pole piece provided in the embodiment of the present application Figure 2 ;

[0053] Figure 8 A schematic diagram of the structure of the winding core provided in an embodiment of the present application;

[0054] Fig. 9 Schematic diagram of the structure of the pole piece provided in the embodiment of the present application Figure 4 ;

[0055] Fig.10 Schematic diagram of the structure of the pole piece provided in the embodiment of the present application Figure 5 .

[0056] Reference numerals:

[0057] 100: current collector;

[0058] 101: second raised portion; 102: third raised portion; 110: positive electrode sheet; 120: negative electrode sheet; 130: separator; 140: first center plane; 111: bent portion; 112: flat portion;

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

[0060] 200: first active material layer;

[0061] 201: first protrusion; 202: groove;

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

[0063] 300: second active material layer;

[0064] 301: recessed portion;

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

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

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

[0068] In a wound lithium-ion battery, the electrode assembly is stacked and wound to form a wound structure of the battery cell. The cross-section of the wound structure presents a flat elliptical structure, with arc areas on both sides of the elliptical structure and a flat area in the middle of the elliptical structure. During the charge and discharge process of the lithium-ion battery, the positive and negative electrodes of the battery will expand. The flat area can expand freely upward and downward, but the arc area is constrained from expanding outward due to its structural characteristics and stress accumulation, and eventually the electrode layers are squeezed, resulting in problems such as diaphragm blockage, poor electrolyte infiltration, and lithium precipitation.

[0069] At the same time, the extrusion of the arc area will also be transmitted to the flat area. Since the flat area has undergone extrusion in the hot pressing process during the production process, the flat area will be squeezed very tightly, which will lead to poor electrolyte infiltration in the flat area.

[0070] The winding core provided in the embodiment of the present application is embossed on the positive electrode sheet by a special roller to increase the micro-spacing between the electrode sheets, so that there is a certain support between the positive electrode, the diaphragm and the negative electrode, thereby solving the problem of poor electrolyte infiltration.

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

[0072] Therefore, the pole piece provided in the embodiment of the present application first presses a plurality of third protrusions on the current collector by a special roller, and then coats the active material layer on the upper and lower surfaces of the current collector to obtain the pole piece; then, the pole piece is pressed again by a special roller to obtain a plurality of first protrusions and depressions corresponding to the plurality of first protrusions; the current collector located between the first protrusions and the depressions forms a bending portion under the secondary pressing, and at the same time, the third protrusion on the bending portion forms a second protrusion under the secondary pressing. The second protrusion formed on the bending portion of the current collector after the secondary pressing can increase the roughness between the current collector and the active material layer, improve the adhesion strength between the active material layer and the current collector, and prevent the active material layer and the current collector from detaching.

[0073] Therefore, the electrode provided in the embodiment of the present application solves the problem of poor interlayer electrolyte infiltration by providing embossed protrusions, while preventing the active material layer and the current collector from separating at the embossed protrusions.

[0074] In order to make the above-mentioned purposes, features and advantages of the embodiments of the present application more obvious and understandable, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of this application.

[0075] In the embodiment 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; the third direction is the width direction of the pole piece, that is, the direction perpendicular to the paper surface shown in the figure; the first direction, the second direction and the third direction are perpendicular to each other.

[0076] refer to Figure 1 and Figure 2 The pole piece provided in the embodiment of the present application includes: a current collector 100, a first active material layer 200 and a second active material layer 300. The current collector 100 has a first surface and a second surface relative to each other along a first direction (the 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 may be a positive electrode current collector or a negative electrode current collector. In the embodiment of the present application, the current collector 100 is taken as an example to illustrate the electrode sheet provided in the present application.

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

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

[0080] A first protrusion 201 and a depression 301 are respectively 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, which can increase the micro-spacing between the pole pieces, so that there is a certain support between the positive electrode, the diaphragm and the negative electrode, increase the storage space of the electrolyte, and improve the electrolyte infiltration effect; at the same time, a certain deformation space is provided for the positive electrode piece, which can release the expansion of the negative electrode piece during the cycle process; while improving the battery energy density, 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, the bending portion 111 has a plurality of second protruding portions 101, and the second protruding portions 101 are protruded from the first surface or the second surface; the flat portion 112 has a plurality of third protruding portions 102, and the third protruding portions 102 are protruded from the first surface or the second surface.

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

[0083] At the same time, the second protrusion 101 on the current collector 100 is also beneficial to reducing the contact resistance between the current collector 100 and the active material layer, effectively improving the cycle life of the battery cell.

[0084] Providing the second protrusion 101 on the current collector 100 can also increase the structural strength of the current collector 100 itself and reduce the minimum thickness requirement of the current collector 100. For pole pieces of the same thickness, while ensuring the structural strength of the current collector 100, the pole piece with the second protrusion 101 can effectively increase the capacity for holding active materials and improve the pole piece's ability to store electrolyte, thereby improving the energy density and performance of the battery cell.

[0085] It should be noted that when preparing the pole piece provided in the embodiment of the present application, a plurality of third protrusions 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 pole piece; and then the initial pole piece is pressed for a second time by a special roller to process the first protrusion 201 and the concave portion 301 corresponding to the first protrusion 201 to obtain a pole piece. Under the secondary pressing, the current collector 100 located between the first protrusion 201 and the concave portion 301 will form a bending portion 111, and the third protrusion 102 on the bending portion 111 will be squeezed to form a second protrusion 101, so that the bending portion 111 of the current collector 100 has a second protrusion 101, and the flat portion 112 of the current collector 100 has a third protrusion 102.

[0086] Continue to refer Figure 1In the embodiment of the present application, the first active material layer 200 is disposed on the first surface of the current collector 100 , the second protrusion 101 is protruded from the first surface of the current collector 100 , and the first protrusion 201 is protruded from the first active material layer 200 .

[0087] Continue to refer Figure 2 In the embodiment of the present application, 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 protrusion 101 is protruded from the second surface of the current collector 100, and the first protrusion 201 is protruded from the first active material layer 200; in this embodiment, the second protrusion 101 and the first protrusion 201 protrude in opposite directions.

[0088] Continue to refer Figure 2 In the embodiment of the present application, the center interval of the projections of two adjacent first protrusions 201 in the first direction is a first distance L1; there is a straight section between the two adjacent first protrusions 201, and along the second direction, the straight section has a second distance L2.

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

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

[0091] The limitation of the ratio of the first distance L1 to the second distance L2 is equivalent to limiting the density of the first protrusions 201, ensuring that there is a suitable spacing between the multiple first protrusions 201, so that the first protrusions 201 can be adjusted to a suitable volume, thereby providing sufficient supporting force for the pole piece, so that the pole piece has sufficient deformation space to alleviate expansion.

[0092] The first distance L1 is 2 mm to 10 mm.

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

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

[0095] Preferably, the second distance L2 is 1 mm to 4 mm; 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 pole piece extension cannot meet the density of the first protrusions 201, the first protrusions 201 cannot be adjusted to a suitable volume, and the height of the first protrusions 201 does not meet the requirements, resulting in less deformation space and the pole piece is prone to rupture; 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 supporting area of ​​the first protrusions 201 is insufficient, thereby failing to achieve the electrolyte infiltration effect and improvement effect.

[0097] Similarly, when the second distance L2 is less than 0.5 mm, the first protrusions 201 are too dense, the pole piece extension cannot meet the density of the first protrusions 201, the first protrusions 201 cannot be adjusted to a suitable volume, and the height of the first protrusions 201 does not meet the requirements, resulting in less deformation space and the pole piece is prone to rupture; 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, thereby failing to achieve the electrolyte wetting effect and improvement effect.

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

[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 to the fourth distance L4 is equivalent to limiting the density of the second protrusions 101, ensuring that there is a suitable spacing between the multiple second protrusions 101, so that the second protrusions 101 can be adjusted to a suitable 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 mm to 8 mm.

[0103] Preferably, the third distance L3 is 0.5 mm to 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 too dispersed, making it impossible to ensure that a second protrusion 101 is provided on the current collector 100 between each first protrusion 201 and recessed portion 301, thereby failing to achieve improvement.

[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 too dispersed, making it impossible to ensure that a second protrusion 101 is provided on the current collector 100 between each first protrusion 201 and recessed portion 301, thereby failing to achieve improvement effect.

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

[0109] The fourth distance L4 and the second distance L2 have the following relationship: L4 / L2=0.1-0.5; preferably, L4 / L2=0.2-0.4; 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 ensured that the density of the second protrusions 101 is greater than the density of the first protrusions 201 .

[0111] In the embodiment of the present application, the edges of the second protrusion 101 and the first protrusion 201 are both arc edges. The second protrusion 101 and the first protrusion 201 are prevented from having sharp edges, and the edge of the first protrusion 201 is prevented from piercing the diaphragm, causing a short circuit between the positive and negative electrodes and causing a safety accident of the battery cell; and the edge of the second protrusion 101 is prevented from piercing the active material layer, and cracks in the active material layer are prevented from causing powder loss.

[0112] In the embodiment of the present application, the shapes of the projections of the second protrusion 101 and the first protrusion 201 in the first direction may include a circle, a semicircle, an ellipse, a plum blossom, a polygon, or the like.

[0113] Preferably, the second protrusion 101 and the first protrusion 201 may be quasi-circular without sharp corners, so as to prevent the first protrusion 201 from piercing the diaphragm, causing a short circuit between the positive and negative electrodes and causing a safety accident of the battery cell; and to prevent the second protrusion 101 from piercing the active material layer, so as to prevent cracks in the active material layer and cause powder loss.

[0114] refer to Figure 4 In the embodiment of the present application, the first protrusion 201 and the recessed portion 301 are both formed into a quasi-circular shape, the first protrusion 201 has a first arc-shaped outer surface 2011, the first arc-shaped outer surface 2011 is located in the first active material layer 200, and the first arc-shaped outer surface 2011 has a first radius R1; the recessed portion 301 has a first arc-shaped inner surface 3011, the first arc-shaped inner surface 3011 is located in the second active material layer 300, and the first arc-shaped inner surface 3011 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] The volume of the first protrusion 201 is limited by limiting the ratio of the first radius R1 to the second radius R2, so that there is a suitable deformation space between the electrode layers, thereby better improving the expansion of the negative electrode.

[0117] In the embodiment of the present application, the first radius R1 may be 0.5 mm to 8 mm. Preferably, the first radius R1 may be 2 mm to 5 mm, or the first radius R1 may be 1 mm to 5 mm. Preferably, the first radius R1 may be 3 mm.

[0118] The second radius R2 may be 0.5 mm to 8 mm. Preferably, the second radius R2 may be 2 mm to 5 mm, or the second radius R2 may be 1 mm to 5 mm. Preferably, the second radius R2 may be 3 mm.

[0119] When the first radius R1 or the second radius R2 is less than 0.5 mm, the first protrusion 201 is too small, resulting in insufficient deformation space, and cannot effectively improve the expansion of the negative electrode. In addition, the first protrusion is sharp and can easily damage the diaphragm. When the first radius R1 or the second radius R2 is greater than 8 mm, the first protrusion 201 is too large, and can easily be affected by extrusion force, stretching force and cyclic expansion force during the manufacturing process, thereby causing excessive deformation of the first protrusion 201, causing the first protrusion 201 to collapse and unable to effectively improve the expansion of the negative electrode.

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

[0121] Theoretically, R1=R2+thickness of the pole piece; however, since a special roller is required for pressing when processing the first raised portion 201 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 straight area 401 of the actual pole piece. Therefore, in the embodiment of the present application, R1-R2≤H1.

[0122] Continue to refer 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 of the circle to the first highest raised point 2012 is a third radius R3, which is also the maximum outer surface radius of the first arc-shaped outer surface 2011; theoretically, the third radius R3 is equal to the first radius R1; but in fact, the first raised portion 201 will be appropriately flattened after process extrusion and pole piece extension, and the first raised portion 201 will be deformed, so that the third radius R3 is smaller than the first radius R1.

[0123] refer to Figure 5 In the embodiment of the present application, the second protrusion 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] By the ratio of the second radius R2 to the fourth radius R4, the radius of the second protrusion 101 on the current collector 100 is smaller than the radius of the first protrusion 201 on the active material layer, and the second protrusion 101 on the current collector 100 has a suitable volume.

[0126] The fourth radius R4 may be 0.1 mm to 5 mm; preferably, the fourth radius R4 may be 1 mm to 4 mm; preferably, the fourth radius R4 may be 2 mm.

[0127] When the fourth radius R4 is less than 0.1 mm, the volume of the second protrusion 101 is too small, and the second protrusion 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 protrusion 101 is too large, and the height of the second protrusion 101 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 100; and when the second protrusion 101 is processed on the current collector 100 by a special roller, it is easy to cause the current collector 100 to break.

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

[0129] Figure 6 is a schematic diagram of the third protrusion 102 on the flat portion of the current collector, referring to Figure 6 In the embodiment of the present application, the third protrusion 102 has a second intersection 1023, and the second intersection 1023 intersects with the plane where the first surface or the second surface is located; in the first direction, the second intersection 1023 and the second highest protrusion point 1024 of the third protrusion 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 may be 3 μm to 40 μm; preferably, the first vertical distance h1 may be 5 μm to 30 μm, and preferably, the first vertical distance h1 may be 10 μm or 20 μm.

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

[0133] The first vertical distance h1 is the height of the first protrusion 201 . By limiting the height of the first protrusion 201 , a suitable gap can be provided between the pole piece and the diaphragm, thereby providing support and preventing the pole piece from being too thick.

[0134] When the first vertical distance h1 is less than 3 μm, it means that the first protrusion 201 is too short and the supporting effect is not obvious. The first protrusion 201 is an invalid protrusion and cannot allow sufficient infiltration of the electrolyte. When the first vertical distance h1 is greater than 40 μm, it means that the first protrusion 201 is too high, which will lead to serious stratification between the positive and negative electrode sheets and cause new interface problems.

[0135] It should be noted that the expansion of the negative electrode squeezes the pole piece, and with multiple cycles, the pole piece will have the risk of breaking; the first protrusion 201 has a supporting function and can also improve the problem of pole piece breaking caused by multiple cycles. However, when the first protrusion 201 is too short, the supporting effect is not obvious, and the improvement of cycle breaking is not obvious; the height of the first protrusion 201 of the present application is within the range of 3μm to 40μm, which has sufficient supporting strength and can effectively improve the problem of pole piece breaking caused by multiple cycles.

[0136] The second vertical distance h2 is the height of the third protrusion 102. When the second vertical distance h2 is greater than 20 μm, it means that the third protrusion 102 is too high. When processing the third protrusion 102, it is easy to cause the highest protrusion point to be sharp, which may easily cause the current collector to rupture and cause the flat active material layer to be uneven. When the second vertical distance h2 is less than 1 μm, it means that the third protrusion 102 is too short 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, a suitable gap can be provided between the pole piece and the diaphragm, thereby achieving a supporting effect while avoiding increasing the overall thickness of the pole piece.

[0138] Continue to refer Figure 6 In the embodiment of the present application, the flat portion 112 of the current collector 100 further includes a second connecting segment 402 without the third protruding portion 102 , and the second connecting segment 402 has a second thickness H2 along 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-10 μm.

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

[0141] The second vertical distance h2 is the height of the third protrusion 102, and the second thickness H2 is the thickness of the second connecting section 402 connected to the third protrusion 102; by limiting the relationship between the second vertical distance h2 and the second thickness H2, the third protrusion 102 has a suitable height; avoiding the third protrusion 102 being too high, resulting in excessive tensile force on the collector 100 when preparing the third protrusion 102, and then causing the collector 100 to break.

[0142] When the height difference between the second vertical distance h2 and the second thickness H2 is greater than 10 μm, it means that the height of the third protrusion 102 is higher than the thickness of the current collector 100 itself, and the greater the extrusion stress caused by the third protrusion 102 on the current collector 100 itself, the easier it is for the current collector 100 to break; when the height difference between the second vertical distance h2 and the second thickness H2 is less than 0.5 μm, it means that the height of the third protrusion 102 is relatively small relative to the thickness of the current collector 100 itself, and the coating amount cannot be effectively increased, nor can the adhesion between the active material layer and the current collector 100 be improved.

[0143] In the embodiment 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 protrusion 201. The higher the first protrusion 201 is, the greater the compressive stress caused by the first protrusion 201 on the current collector is. The second vertical distance h2 is the height of the third protrusion 102. The higher the third protrusion 102 is, the greater the tensile force caused to the current collector 100 when preparing the third protrusion 102 is. Therefore, by limiting the relationship between the height of the first protrusion 201 and the tensile strength of the current collector 100, and the relationship between the height of the third protrusion 102 and the tensile strength of the current collector 100, the current collector 100 is prevented from breaking.

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

[0148] refer to Figure 7 In the embodiment of the present application, the recessed portion 301 has a third intersection 3012, and the third intersection 3012 intersects with the plane where the surface of the second active material layer 300 is located; the first tangent line 601 is tangent to the first intersection 2013, and the 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 angle a1; the second tangent line 602 is tangent to the third intersection 3012, and the 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 angle a2.

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

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

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

[0152] Limiting the first angle a1 and the second angle a2 is equivalent to limiting the height and inclination angle of the first protrusion 201; when the first angle a1 and the second angle a2 are greater than 90°, the first protrusion 201 is prone to breakage at the connection with the straight section; when the first angle a1 and the second angle a2 are less than 0°, the inclination angle of the first protrusion 201 is too large, and the height of the first protrusion 201 is insufficient, resulting in insufficient supporting force of the first protrusion 201, which is easily flattened during the process and cycle.

[0153] Theoretically, when processing the first protruding portion 201 , the second angle a2 belongs to the pressure-bearing side, and the second angle a2 is smaller than the first angle a1 to avoid fracture at the junction of the recessed portion 301 and the straight section.

[0154] Continue to refer Figure 7 In the embodiment 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 point 2013, and the angle between the third tangent line 603 and the plane where the surface of the first active material layer 200 is located is a third angle a3.

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

[0156] Limiting the third angle a3 is equivalent to limiting the height and the inclination angle of the first protrusion 201, so as to prevent the first protrusion 201 from being too sharp and puncturing the diaphragm to cause a short circuit.

[0157] In the embodiment of the present application, the total projected area of ​​the plurality of first protrusions 201 in the first direction is a first area S1 , and the projected 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 means that the area of ​​the first protrusion 201 accounts for too large a proportion of the overall area of ​​the single-sided area, which may easily cause the collector 100 corresponding to the area of ​​the electrode having the first protrusion 201 to wrinkle and rupture, causing lithium deposition in 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 means that the area of ​​the first protrusion 201 accounts for too small a proportion of the overall area, which will lead to insufficient support space and unclear improvement effect.

[0160] In the embodiment of the present application, the sum of the projection areas of the plurality of second protrusions 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 means that the area of ​​the second protrusion 101 accounts for too large a proportion of the overall area of ​​the single-sided area, which may easily lead to insufficient ductility and strength of the current collector 100, and further cause the current collector 100 to rupture; when the ratio of the third area S3 to the fourth area S4 is less than 0.1, it means that the area of ​​the second protrusion 101 accounts for too small a proportion of the overall area of ​​the single-sided area, the coating amount cannot be effectively increased, and the improvement in adhesion is not obvious.

[0163] Continue to refer Figure 4 In the embodiment of the present application, the first arcuate outer surface 2011 has a first surface area Q1, and the first arcuate 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 protrusion 201, so that there is a suitable deformation space between the pole sheet layers, thereby better improving the expansion of the negative electrode.

[0165] The projection area of ​​the first arcuate outer surface 2011 in the first direction is the fifth area S5, and the projection area of ​​the first arcuate inner surface 3011 in the first direction is the 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. Therefore, limiting the ratio of the fifth area S5 to the sixth area S6 is equivalent to limiting the ratio of the first radius R1 to the second radius R2, thereby limiting the volume of the first protrusion 201, so that there is a suitable deformation space between the pole sheet layers, thereby better improving the negative electrode expansion.

[0167] In the embodiment of the present application, a plurality of hole structures are provided on the current collector 100. Providing the hole structure on the current collector 100 can further increase the coating amount of the coating layer and the adhesion between the coating layer and the current collector 100.

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

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

[0170] The projection area of ​​the hole structure 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, preferably, S7 / S4=0.2-0.4.

[0171] refer to Figure 8 , Fig. 9 and Fig.10 The embodiment of the present application also provides a winding core, which includes the electrode sheet described above, and the electrode sheet described above can be a positive electrode sheet 110; the winding core also includes 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 the first center plane 140.

[0172] The winding core includes a straight area and arc areas at opposite ends of the straight area. The surface of the first active material layer 200 is away from the first center plane 140, and the surface of the second active material layer 300 is toward the first center plane 140; the surface of the first active material layer 200 and / or the surface of the second active material layer 300 of the pole piece in the arc area is provided with multiple grooves 202.

[0173] Due to the curvature of the arc area, in the arc area, when the positive electrode sheet 110 wraps the negative electrode sheet 120, the arc circumference of the active material layer of the positive electrode sheet 110 is greater than the arc circumference of the active material layer of the negative electrode sheet 120, resulting in a decrease in the ratio of the negative electrode surface capacity to the positive electrode surface capacity in this area, triggering lithium deposition in the arc area.

[0174] In the embodiment of the present application, a plurality of grooves 202 are provided in the active material layer of the positive electrode sheet 110 to reduce the amount of positive electrode lithium desorption in the region, increase the amount of negative electrode lithium migration, and improve the ratio of the negative electrode surface capacity to the positive electrode surface capacity in the region, thereby improving the risk of lithium plating in the arc region.

[0175] In the embodiment of the present application, 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 electrode sheet 110 in the arc area has a first arc circumference N2, and along the third direction, any layer of the positive electrode sheet 110 in the arc area has a third width M2.

[0176] The first width N1 and the first arc 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 circumference N2 is too small, that is, the width of the groove 202 is too small, the effect of improving lithium deposition in the arc area is not obvious; when the ratio of the first width N1 to the first arc circumference N2 is too large, that is, the width of the groove 202 is large, the battery capacity loss is high.

[0178] In the embodiment of the present application, in the cross section in the first direction, the cross-sectional shape of the groove 202 may include an arc shape, a cone shape, a V shape, a polygon shape, or the like.

[0179] An embodiment of the present application also provides a battery, which includes the winding core described above.

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

[0181] Embodiment 1:

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

[0183] 1. Preparation of positive electrode sheet 110:

[0184] The current collector 100 is rolled using a first embossing roller to form a plurality of third protrusions 102 on the current collector 100 .

[0185] Lithium cobalt oxide, conductive agent and PVDF were mixed in a mass ratio of 97.6:1.4:1 and placed in NMP, stirred evenly to prepare a positive electrode slurry; the positive electrode slurry was evenly coated on the front and back 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 was 1.5 μm, and the coating surface density was 0.01704 g / cm 2After drying and rolling, the positive electrode sheet 110 is obtained. The thickness of the positive electrode sheet 110 is the first thickness H1, and the first thickness H1 is 4 μm.

[0186] The positive electrode sheet 110 is rolled using a second embossing roller to form a plurality of first protrusions 201 on the first active material layer 200, and a plurality of recesses 301 arranged opposite to the first protrusions 201 are formed on the second active material layer 300. At the same time, under the secondary pressing, the current collector 100 located between the first protrusions 201 and the recesses 301 forms a bending portion 111, and the third protrusion 102 on the bending portion 111 is squeezed to form a second protrusion 101.

[0187] The center interval of the projections of two adjacent first protrusions 201 on the positive electrode sheet 110 in the first direction is the first distance L1, the length of the straight section between the two adjacent first protrusions 201 in the second direction is the second distance L2, the center interval of the projections of two adjacent second protrusions 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 protrusions 101 in the first direction is the fourth distance L4, wherein L3 / L1=0.25, L4 / L2=0.3, L3 / L4=1.6.

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

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

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

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

[0192] 2. Preparation of negative electrode sheet 120:

[0193] Silicon-containing artificial graphite, conductive carbon black, styrene-butadiene rubber and sodium carboxymethyl cellulose are mixed in deionized water according to a mass ratio of 97.2:0.5:1.3:1, and stirred evenly to obtain a negative electrode slurry; wherein the silicon content in the silicon-containing artificial graphite is 10%.

[0194] The negative electrode slurry is evenly coated on the front and back 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 ear is welded.

[0195] 3. Preparation of diaphragm 130:

[0196] The 9 μm thick diaphragm 130 is manufactured by using a substrate, ceramics, and glue coating.

[0197] 4. Preparation of electrolyte:

[0198] The electrolyte includes lithium salt LiPF6 and a solvent, and the solvent includes ethylene carbonate (EC), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC), wherein the molar ratio of ethylene carbonate (EC), diethyl carbonate (DEC) and ethyl methyl 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 cell, and the cell is then packaged, baked, injected, formed, and sealed to obtain a battery.

[0201] Embodiment 2:

[0202] Example 2 is carried out with reference to Example 1, except that L3 / L1=0.3.

[0203] Embodiment 3:

[0204] Example 3 is carried out with reference to Example 1, except that L3 / L1=0.5.

[0205] Embodiment 4:

[0206] Example 4 is carried out with reference to Example 1, except that L3 / L1=0.05.

[0207] Embodiment 5:

[0208] Example 5 is carried out with reference to Example 1, except that L3 / L1=0.6.

[0209] Embodiment 6:

[0210] Example 6 is carried out with reference to Example 1, except that L3 / L1=0.02.

[0211] Embodiment 7:

[0212] Example 7 is carried out with reference to Example 1, except that L4 / L2=0.4.

[0213] Embodiment 8:

[0214] Example 8 is carried out with reference to Example 1, except that L4 / L2=0.5.

[0215] Embodiment 9:

[0216] Example 9 was carried out with reference to Example 1, with L4 / L2=0.1.

[0217] Embodiment 10:

[0218] Example 10 is carried out with reference to Example 1, except that L4 / L2=0.7.

[0219] Embodiment 11:

[0220] Example 11 was carried out with reference to Example 1, with L4 / L2=0.02.

[0221] Embodiment 12:

[0222] Example 12 is carried out with reference to Example 1, except that L3 / L4=1.7.

[0223] Embodiment 13:

[0224] Example 13 is carried out with reference to Example 1, except that L3 / L4=2.

[0225] Embodiment 14:

[0226] Example 14 is carried out with reference to Example 1, except that L3 / L4=1.2.

[0227] Embodiment 15:

[0228] Example 15 is carried out with reference to Example 1, except that L3 / L4=3.

[0229] Embodiment 16:

[0230] Example 16 is carried out with reference to Example 1, except that L3 / L4=0.5.

[0231] Embodiment 17:

[0232] Example 17 is carried out with reference to Example 1, except that R1 / R2=1.06.

[0233] Embodiment 18:

[0234] Example 18 is carried out with reference to Example 1, except that R1 / R2=1.21.

[0235] Embodiment 19:

[0236] Example 19 is carried out with reference to Example 1, except that R1 / R2=1.01.

[0237] Embodiment 20:

[0238] Example 20 is carried out with reference to Example 1, except that R1 / R2=1.3.

[0239] Embodiment 21:

[0240] Example 21 is carried out with reference to Example 1, except that R1 / R2=0.9.

[0241] Embodiment 22:

[0242] Example 22 is carried out with reference to Example 1, except that R4 / R2=0.25.

[0243] Embodiment 23:

[0244] Example 23 is carried out with reference to Example 1, except that R4 / R2=0.5.

[0245] Embodiment 24:

[0246] Example 24 is carried out with reference to Example 1, except that R4 / R2=0.08.

[0247] Embodiment 25:

[0248] Example 25 is carried out with reference to Example 1, except that R4 / R2=0.6.

[0249] Embodiment 26:

[0250] Example 26 is carried out with reference to Example 1, except that R4 / R2=0.05.

[0251] Embodiment 27:

[0252] Example 27 is carried out with reference to Example 1, except that the first vertical distance h1 is 22 μm.

[0253] Embodiment 28:

[0254] Example 28 is carried out with reference to Example 1, except that the first vertical distance h1 is 40 μm.

[0255] Embodiment 29:

[0256] Example 29 is carried out with reference to Example 1, except that the first vertical distance h1 is 3 μm.

[0257] Embodiment 30:

[0258] Example 30 is carried out with reference to Example 1, except that the first vertical distance h1 is 50 μm.

[0259] Embodiment 31:

[0260] Example 31 is carried out with reference to Example 1, except that the first vertical distance h1 is 1 μm.

[0261] Embodiment 32:

[0262] Example 32 is carried out with reference to Example 1, except that the first vertical distance h2 is 11 μm.

[0263] Embodiment 33:

[0264] Example 33 is carried out with reference to Example 1, except that the first vertical distance h2 is 20 μm.

[0265] Embodiment 34:

[0266] Example 34 is carried out with reference to Example 1, except that the first vertical distance h2 is 1 μm.

[0267] Embodiment 35:

[0268] Example 35 is carried out with reference to Example 1, except that the first vertical distance h2 is 25 μm.

[0269] Embodiment 36:

[0270] Example 36 is carried out with reference to Example 1, except that the first vertical distance h2 is 0.5 μm.

[0271] Embodiment 37:

[0272] Example 37 is carried out with reference to Example 1, except that h1 / M=0.13 μm.

[0273] Embodiment 38:

[0274] Example 38 is carried out with reference to Example 1, except that h1 / M=0.2μm.

[0275] Embodiment 39:

[0276] Example 39 is carried out with reference to Example 1, except that h1 / M=0.05μm.

[0277] Embodiment 40:

[0278] Example 40 is carried out with reference to Example 1, except that h1 / M=0.5 μm.

[0279] Embodiment 41:

[0280] Example 41 is carried out with reference to Example 1, except that h1 / M=0.01 μm.

[0281] Embodiment 42:

[0282] Example 42 is carried out with reference to Example 1, except that h2 / M=0.08μm.

[0283] Embodiment 43:

[0284] Example 43 is carried out with reference to Example 1, except that h2 / M=0.15μm.

[0285] Embodiment 44:

[0286] Example 44 is carried out with reference to Example 1, except that h2 / M=0.01μm.

[0287] Embodiment 45:

[0288] Example 45 is carried out with reference to Example 1, except that h2 / M=0.3μm.

[0289] Embodiment 46:

[0290] Example 46 is carried out with reference to Example 1, except that h2 / M=0.001μm.

[0291] Embodiment 47:

[0292] Example 47 is carried out with reference to Example 1, except that h2-H2=4.

[0293] Embodiment 48:

[0294] Example 48 is carried out with reference to Example 1, except that h2-H2=10.

[0295] Embodiment 49:

[0296] Example 49 is carried out with reference to Example 1, except that h2-H2=0.5.

[0297] Embodiment 50:

[0298] Example 50: proceed as in Example 1, except that h2-H2=12.

[0299] Embodiment 51:

[0300] Example 51 is carried out with reference to Example 1, except that h2-H2=0.1.

[0301] Embodiment 52:

[0302] Example 52 is carried out with reference to Example 1, except that the first angle a1=45°; a1-a2=7°.

[0303] Embodiment 53:

[0304] Example 53 is carried out with reference to Example 1, except that the first angle a1=89°; a1-a2=51°.

[0305] Embodiment 54:

[0306] Example 54 is carried out with reference to Example 1, except that the first angle a1=1°; a1-a2=-37°.

[0307] Embodiment 55:

[0308] Example 55 is carried out with reference to Example 1, except that the first angle a1=100°; a1-a2=62°.

[0309] Embodiment 56:

[0310] Example 56 is carried out with reference to Example 1, except that the first angle a1 = -10°; a1-a2 = -48°.

[0311] Embodiment 57:

[0312] Example 57 is carried out with reference to Example 1, except that the second angle a2 = 45°; a1-a2 = 8°.

[0313] Embodiment 58:

[0314] Example 58 is carried out with reference to Example 1, except that the second angle a2 = 89°; a1-a2 = -36°.

[0315] Embodiment 59:

[0316] Example 59 is carried out with reference to Example 1, except that the second angle a2 = 1°; a1-a2 = 52°.

[0317] Embodiment 60:

[0318] Example 60 is carried out with reference to Example 1, except that the second angle a2 = 100°; a1-a2 = -47°.

[0319] Example 61:

[0320] Example 61 is carried out with reference to Example 1, except that the second angle a2 = -10°; a1-a2 = 63°.

[0321] Embodiment 62:

[0322] Example 62 is carried out with reference to Example 1, except that the first angle a1 = 60°; the second angle a2 = 30°; a1-a2 = 30°.

[0323] Embodiment 63:

[0324] Example 63 is carried out with reference to Example 1, except that the first angle a1 = 80°; the second angle a2 = 40°; a1-a2 = 40°.

[0325] Embodiment 64:

[0326] Example 64 is carried out with reference to Example 1, except that the first angle a1 = 45°; the second angle a2 = 45°; and a1-a2 = 0°.

[0327] Embodiment 65:

[0328] Example 65 is carried out with reference to Example 1, except that the first angle a1 = 80°; the second angle a2 = 30°; and a1-a2 = 50°.

[0329] Embodiment 66:

[0330] Example 66 is carried out with reference to Example 1, except that the first angle a1 = 40°; the second angle a2 = 50°; a1-a2 = -10°.

[0331] Embodiment 67:

[0332] Example 67 is carried out with reference to Example 1, except that the third angle a3 = 40°.

[0333] Embodiment 68:

[0334] Example 68 is carried out with reference to Example 1, except that the third angle a3 = 80°.

[0335] Embodiment 69:

[0336] Example 69 is carried out with reference to Example 1, except that the third angle a3 = 1°.

[0337] Embodiment 70:

[0338] Example 70 is carried out with reference to Example 1, except that the third angle a3 = 89°.

[0339] Embodiment 71:

[0340] Example 71 is carried out with reference to Example 1, except that the third angle a3 = -10°.

[0341] Comparative Example 1:

[0342] Comparative Example 1 is carried out with reference to Example 1, except that the second protrusion 101 is not provided on the current collector in Comparative Example 1.

[0343] Comparative Example 2:

[0344] Comparative Example 2 is carried out with reference to Example 1, except that in Comparative Example 2, no second protrusion 101 is provided on the current collector, and no first protrusion 201 is provided on the active material layer.

[0345] Comparative Example 3:

[0346] Comparative Example 3 is carried out with reference to Example 1, except that in Comparative Example 3, the current collector is provided with the second protrusion 101 , but the active material layer is not provided with the first protrusion 201 .

[0347] Table 1:

[0348]

[0349]

[0350]

[0351] Table 2:

[0352]

[0353]

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

[0355] 1. Liquid retention test

[0356] The retention volume is the amount of electrolyte that is ultimately retained in the lithium-ion battery. In order to ensure the consumption of electrolyte during the formation of the lithium-ion battery, a certain amount of electrolyte is usually injected, and then the excess electrolyte is extracted after the formation. It is measured by weighing, the injection volume is m1, the electrolyte volume extracted is m2, and the retention volume is m3.

[0357] =m1-m2.

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

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

[0360] 3. Current collector tensile strength test

[0361] A vertical tensile testing machine was used for testing. The current collectors obtained in the above embodiments and comparative examples were fixed on the clamps at both ends of the tensile testing machine. The two ends of the clamps were aligned. The tensile equipment button was started. The equipment moved at a speed of 10 mm / s until the current collector broke, and the tensile data was read out.

[0362] 4. Lithium deposition on negative electrode

[0363] After the battery obtained in the above embodiment and the comparative example was subjected to the cell expansion rate test, the battery obtained in the above embodiment and the comparative example was fully charged, and the battery was disassembled in a dry room environment to observe whether lithium deposition occurred on the negative electrode sheet and the degree of lithium deposition. The degree of lithium deposition is divided into slight lithium deposition and severe lithium deposition. Slight lithium deposition refers to the occurrence of lithium deposition at the interface when the color of the lithium deposition is gray or gray-black. In severe lithium deposition, the interface appears silvery white, and the amount of lithium deposition is relatively large.

[0364] 5. Test of bonding strength between active material layer and current collector

[0365] A vertical tensile testing machine was used for testing. The positive electrode sheets obtained in the above embodiments and comparative examples were fixed on the clamps at both ends of the tensile testing machine. The two ends of the clamps were aligned. The tensile equipment button was started. The equipment moved at a speed of 10 mm / s until the active material layer was separated from the current collector, and the tensile data was read.

[0366] 6. Wetting improvement effect test

[0367] The battery was left at room temperature (25°C) for 24 hours, and the wetting of the diaphragm was observed after disassembly. The area of ​​the wetted part was estimated and compared, and divided into three levels: significant (wetting area of ​​60% to 100%), moderate (wetting area of ​​30% to 60%), and slight (wetting area of ​​0% to 30%). The non-wetted area is usually an irregular water pattern boundary, and the difference in area size can be directly observed visually.

[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 Example 2 and Comparative Example 3, and the wetting effect is obvious, indicating that the first protrusion 201 can increase the electrode spacing, 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 the adhesion between the active material layer and the current collector in Comparative Example 1 and Comparative Example 2, indicating that the second protrusion 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 the adhesion between the active material layer and the current collector in Comparative Example 3, indicating that the simultaneous provision of the first protrusion 201 and the second protrusion 101 can improve the wetting effect while increasing the adhesion between the active material layer and the current collector, thereby preventing the active material layer from falling off.

[0374] It can be seen from Examples 2 to 6 that when the ratio of the third distance L3 to the first distance L1 is greater than 0.5, the second protrusions 101 are relatively sparse relative to the first protrusions 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 protrusions 101 are relatively dense relative to the first protrusions 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 rupture.

[0375] It can be seen from Examples 7 to 11 that when the ratio of the fourth distance L4 to the second distance L2 is greater than 0.5, the density of the second protrusions 101 is relatively sparse relative to the density of the first protrusions 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 protrusions 101 is relatively dense relative to the density of the first protrusions 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 rupture.

[0376] It can be seen from Examples 12 to 16 that when the ratio of the third distance L3 to the fourth distance L4 is greater than 2, the spacing between the second protrusions 101 is small, the second protrusions 101 are denser, the adhesion between the active material layer and the current collector is large, but the current collector 100 is easily broken; when the ratio of the third distance L3 to the fourth distance L4 is less than 1.2, the spacing between the second protrusions 101 is large, the second protrusions 101 are too sparse, and the adhesion between the active material layer and the current collector is weak.

[0377] From Example 17 to Example 21, it can be seen that when the ratio of the first radius R1 to the second radius R2 is greater than 1.21, the pole piece is easily damaged, the negative electrode will have slight lithium deposition, and the liquid retention is low, and the wetting effect is poor; the reason is that the volume of the first protrusion 201 is too large, and there is a crack at the highest point of the first protrusion 201; while the volume of the recessed portion 301 is too small, the structure composed of the first protrusion 201 and the recessed portion 301 is easy to collapse, resulting in a small deformation space for the structure composed of the first protrusion 201 and the recessed portion 301, and insufficient electrolyte accommodation space. On the contrary, when the ratio of the first radius R1 to the second radius R2 is less than 1.01, it means that the volume of the first protrusion 201 is too small, and the volume of the recessed portion 301 is too large, the structure composed of the first protrusion 201 and the recessed portion 301 is easy to collapse, the deformation space of the structure composed of the first protrusion 201 and the recessed portion 301 is small, and the electrolyte accommodation space is insufficient, resulting in a low liquid retention.

[0378] It can be seen from Examples 22 to 26 that when the ratio of the fourth radius R4 to the second radius R2 is greater than 0.5, the volume of the second protrusion 101 is large and the current collector 100 is easily broken; when the ratio of the fourth radius R4 to the second radius R2 is less than 0.08, the volume of the second protrusion 101 is small and the adhesion between the active material layer and the current collector is low.

[0379] It can be seen from Examples 27 to 31 that when the first vertical distance h1 is greater than 40, the electrode is easily damaged and slight lithium deposition will occur at the negative electrode; the reason is that the first protrusion 201 is too high and has a crack at its highest point, resulting in damage to the electrode; when the first vertical distance h1 is less than 3, the liquid retention amount is low and the wetting effect is poor; the reason is that the first protrusion 201 is too short and the supporting effect is not obvious. The first protrusion 201 is an invalid protrusion and cannot allow sufficient infiltration of the electrolyte.

[0380] It can be seen from Examples 32 to 36 that when the second vertical distance h2 is greater than 20, the current collector 100 is broken; the reason is that the second protrusion 101 is too high, and the highest protrusion point is easily sharp when processing the second protrusion 101. When the second vertical distance h2 is less than 1, the adhesion between the active material layer and the current collector is low, because the second protrusion 101 is too short to effectively improve the adhesion strength between the active material layer and the current collector 100, and the adhesion is low.

[0381] It can be seen from Examples 37 to 41 that 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 easy to rupture. The reason is that the first protrusion 201 is too high and the tensile strength of the current collector is insufficient, and the first protrusion 201 causes a large extrusion stress on the current collector. 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 means that the second protrusion 101 is too short and the supporting effect is not obvious. The first protrusion 201 is an invalid protrusion and cannot allow sufficient infiltration of the electrolyte.

[0382] It can be seen from Examples 42 to 46 that 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 easy to break. The reason is that the second protrusion 101 is too high and the tensile strength of the current collector is insufficient, resulting in excessive tensile force on the current collector 100 when preparing the second protrusion 101, which in turn causes the current collector to break; 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 means that the second protrusion 101 is too short and cannot effectively improve the bonding strength between the active material layer and the current collector 100, and the bonding force is low.

[0383] It can be seen from Examples 47 to 51 that when the relationship h2-H2 between the second vertical distance h2 and the thickness H2 of the current collector 100 itself is greater than 10, the current collector 100 is prone to rupture. The reason is that the second protrusion 101 is too high, resulting in excessive tensile force on the current collector when preparing the second protrusion 101, which in turn causes the current collector 100 to break; when the relationship h2-H2 between the second vertical distance h2 and the thickness H2 of the current collector 100 itself is less than 0.5, it means that the second protrusion 101 is too short and cannot effectively improve the bonding strength between the active material layer and the current collector 100, and the bonding force is low.

[0384] It can be seen from Example 52 to Example 56 that when the first angle a1 is greater than 90 degrees, and the relationship a1-a2 between the first angle a1 and the second angle a2 is greater than 40 degrees, the electrode is damaged, the liquid retention is low, and the infiltration effect is poor; the reason is that the inclination angle at the connection between the first protrusion 201 and the straight section is too large, causing excessive bending, resulting in damage to the electrode; at the same time, the inclination angle of the first protrusion 201 relative to the recessed portion 301 is too large, and the structure composed of the first protrusion 201 and the recessed portion 301 is unstable, and it is easy to collapse when subjected to extrusion stress, and the electrolyte cannot be sufficiently infiltrated. When the first angle a1 is less than 0 degrees, and the relationship a1-a2 between the first angle a1 and the second angle a2 is less than 0 degrees, it means that the first protrusion 201 is short, the first protrusion 201 is an invalid protrusion, the support effect is poor, and the electrolyte cannot be sufficiently infiltrated, resulting in a low liquid retention amount.

[0385] It can be seen from Examples 57 to 61 that when the second angle a2 is greater than 90 degrees, and the relationship a1-a2 between the first angle a1 and the second angle a2 is less than 0 degrees, the pole piece is damaged; the reason is that the inclination angle at the connection between the recessed portion 301 and the straight section is too large, causing excessive bending, resulting in damage to the pole piece; at the same time, the inclination angle of the recessed portion 301 relative to the first protruding portion 201 is too large, and the structure composed of the first protruding portion 201 and the recessed portion 301 is unstable and easily collapses when subjected to extrusion stress. When the second angle a2 is less than 0 degrees, and the relationship a1-a2 between the first angle a1 and the second angle a2 is greater than 40 degrees, the inclination angle of the recessed portion 301 relative to the first protruding portion 201 is too small, and the depth of the recessed portion 301 is shallow, which cannot allow the electrolyte to be sufficiently infiltrated, resulting in a low liquid retention amount.

[0386] It can be seen from Example 62 to Example 66 that the first angle a1 and the second angle a2 are both in the range of 0 degrees to 90 degrees, but when a1-a2 is greater than 40 degrees, it means that the inclination angle of the connection between the first protrusion 201 and the straight section is too large, and the highest protrusion point of the first protrusion 201 is easily broken, causing damage to the pole piece; but when a1-a2 is less than 0 degrees, it means that the inclination angle of the connection between the recessed portion 301 and the straight section is too large, causing excessive bending, resulting in damage to the pole piece.

[0387] It can be seen from Examples 67 to 71 that when the third angle a3 is greater than 80 degrees, the first protrusion 201 is too sharp, and the highest protrusion point of the first protrusion 201 is easily broken, causing damage to the electrode; when the third angle a3 is less than 0 degrees, it means that the first protrusion 201 is concave, the first protrusion 201 is an invalid protrusion, and the electrolyte cannot be sufficiently infiltrated.

[0388] In this specification, each embodiment or example is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referenced to each other.

[0389] It should be noted that the phrases "one embodiment", "an embodiment", "an exemplary embodiment", "some embodiments", etc. mentioned in the specification indicate that the described embodiments may include certain features, structures or characteristics, but not every embodiment may include the certain features, structures or characteristics. In addition, such phrases do not necessarily refer to the same embodiment. In addition, when describing certain features, structures or characteristics in conjunction with an embodiment, it is within the knowledge of those skilled in the art to implement such features, structures or characteristics in conjunction with other embodiments, whether explicitly or not explicitly described.

[0390] In general, terms should be understood, at least in part, by the context in which they are used. For example, the term "one or more" as used herein may be used to describe any feature, structure, or characteristic in a singular sense, or may be used to describe a combination of features, structures, or characteristics in a plural sense, depending, at least in part, on the context. Similarly, terms such as "a," "an," or "the" may also be understood to convey singular usage or to convey plural usage, depending, at least in part, on the context.

[0391] It should be easily understood that “on,” “above,” and “over” in the present disclosure should be interpreted in the broadest manner, so that “on” not only means “directly on something,” but also includes the meaning of “on something” with intervening features or layers therebetween, and “above” or “over” not only includes the meaning of “above” or “over,” but also may include the meaning of “above” or “over something” with no intervening features or layers therebetween (i.e., directly on something).

[0392] In addition, spatially relative terms, such as "below," "below," "beneath," "above," "above," etc., may be used herein for ease of description to describe the relationship of one element or feature relative to other elements or features as shown in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation shown in the figures. The device may have other orientations (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein may likewise be interpreted accordingly.

[0393] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these 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 in that: include: a current collector, a first active material layer and a second active material layer; The current collector has a first surface and a second surface opposite to each other 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; The first active material layer is provided with a plurality of first protrusions, and the second active material layer is provided with a plurality of recesses corresponding to the first protrusions; The current collector has a bending portion and a flat portion, the bending portion is located between the first convex portion and the concave portion, the bending portion has a plurality of second convex portions, and the second convex portions are convexly arranged on the first surface or the second surface.

2. The pole piece according to claim 1, characterized in that: The center distance between projections of two adjacent first protrusions in the first direction is a first distance L1; There is a straight section between two adjacent first protrusions, and the straight section has a second distance L2 in the second direction; The center distance between 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, and along the second direction, a projection of the first connecting section in the first direction has a fourth distance L4; 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; The second direction is perpendicular to the first direction.

3. The pole piece according to claim 2, characterized in that: The third distance L3 and the fourth distance L4 have the following relationship: L3 / L4=1.2~2.

4. The pole piece according to claim 1, characterized in that: The first protrusion has 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 recessed portion has 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.

5. The pole piece according to claim 1, characterized in that: 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 have the following relationship: R4 / R2=0.08-0.

5.

6. The pole piece according to claim 1, characterized in that: The flat portion has a third convex portion; The first protrusion has a first intersection, and the first intersection intersects with a plane where the surface of the first active material layer is located; The third protrusion has a second intersection point, and the second intersection point intersects with the plane where the first surface or the second surface is located; In the first direction, the first intersection and the highest protrusion point of the first protrusion have a first vertical distance h1, the second intersection and the highest protrusion point of the third protrusion have a second vertical distance h2, and the first vertical distance h1 is 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 according to claim 6, characterized in that: The recessed portion has a third intersection, and the third intersection intersects with the plane where the surface of the second active material layer is located; The first tangent line is tangent to the first intersection point, and the angle between the first tangent line and the plane where the surface of the first active material layer is located is a first angle a1; The second tangent line is tangent to the third intersection point, and the angle between the second tangent line and the horizontal plane where the surface of the second active material layer is located is a second angle a2; The first angle a1 and the second angle a2 have the following relationship: a1-a2=0°-40°; or The first angle a1 is 0° to 90°; or The second angle a2 is between 0° and 90°.

8. The pole piece according to claim 7, characterized in that: A third tangent line is tangent to any point on the first arc-shaped outer surface excluding the first intersection point, and an angle between the third tangent line and the plane where the surface of the first active material layer is located is a third angle a3; The third angle a3 is between 0° and 80°.

9. The pole piece according to claim 6, characterized in that: Along the second direction and the third direction, the tensile strength of the current collector is the 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.

10. The pole piece according to claim 6, characterized in that: The flat portion includes a second connecting segment without the third protruding portion, and the second connecting segment has a second thickness H2 along the first direction; The second vertical distance h2 and the second thickness H2 have the following relationship: h2-H2=0.5 μm-10 μm.

11. The pole piece according to claim 1, characterized in that: The sum of the projection areas of the plurality of first protrusions 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 sum of the projection areas of the plurality of second protrusions 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.

12. The pole piece according to claim 11, characterized in that: The current collector is provided with a plurality of hole structures; The diameter of the pore structure is 1 μm to 20 μm; and / or The distance between two adjacent hole structures is 20 μm to 300 μm; and / or The projection area of ​​the hole structure 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.

13. The pole piece according to claim 1, characterized in that: The edges of the first protruding portion and the second protruding portion are both arc edges.

14. The pole piece according to claim 1, characterized in that: The projections of the first protrusion and the second protrusion in the first direction may have shapes including a circle, a semicircle, an ellipse, a plum blossom, a polygon, or the like.

15. A winding core, characterized in that: A pole piece comprising any one of claims 1 to 14; The winding core includes a straight area and arc areas located at opposite ends of the straight area, and a plurality of grooves are provided on the surface of the first active material layer and / or the surface of the second active material layer of the pole piece in the arc area.

16. The winding core according to claim 15, characterized in that: 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 arc region has a first arc circumference N2; Along the third direction, any layer of the pole piece in the arc region has a third width M2; The first width N1 and the first arc 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 winding core according to claim 15, characterized in that In the cross section in the first direction, the cross-sectional shape of the groove includes arc, cone, V-shape or polygon.

18. A battery, characterized in that: The winding core comprises the winding core as claimed in any one of claims 15 to 17.

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