Roll core and battery

Abstract

The invention provides a roll core and a battery, relates to the technical field of batteries, and is used for solving the technical problem of insufficient interlayer electrolyte caused by interlayer extrusion of pole pieces of the roll core in the related art. The roll core comprises a negative pole piece and a positive pole piece which are opposite in polarity, and the negative pole piece comprises a negative current collector; the negative current collector is provided with a first surface and a second surface along the first direction, the first surface is provided with a first paste layer, and the second surface is provided with a second paste layer; a plurality of grooves are formed in the first pasting layer, and the centers of every two adjacent grooves are spaced by a first distance; a plurality of convex parts and concave parts corresponding to the convex parts are arranged on the positive plate, and the surfaces of the convex parts of the positive plate are opposite to the surfaces of the grooves of the negative plate; the projection size of the convex part on the negative plate is greater than the first distance along the width direction of the groove. The positive plate is provided with the convex part and the concave part opposite to the convex part, and the negative plate is provided with the groove opposite to the convex part, so that the pole plates are supported, the fine spacing between the pole plates is increased, and sufficient infiltration of electrolyte is ensured.

Description

Technical Field

[0001] The present application relates to the technical field of lithium electronic batteries, and in particular to a winding core and a battery. Background Art

[0002] With the rapid development of lithium-ion battery technology, people have higher requirements on the energy density, cycle life and safety performance of lithium-ion batteries.

[0003] During the charge and discharge process of lithium-ion batteries, the negative electrode sheets will expand, and there will be extrusion between the layers of the electrode sheets. In particular, the arc area of ​​the wound lithium-ion battery formed by winding has a large stress accumulation, and there is extrusion between the electrode sheets in the arc area itself. In addition, during the charge and discharge process, the negative electrode sheets will expand, and the extrusion between the electrode sheets will be aggravated. At the same time, this extrusion will also be transmitted from the arc area to the flat area. This interlayer extrusion will eventually lead to insufficient electrolyte and poor wetting between the layers, resulting in interface deterioration, and even lithium deposition on the negative electrode sheets, affecting the safety of the battery cell. Summary of the invention

[0004] In view of the above problems, the embodiments of the present application provide a winding core and a battery to solve the problems of insufficient electrolyte and poor electrolyte infiltration caused by extrusion between the layers of the pole pieces of the winding core in the related art.

[0005] In order to achieve the above objectives, the embodiments of the present application provide the following technical solutions: An embodiment of the present application provides a winding core, which includes: a negative electrode sheet and a positive electrode sheet which are stacked; the positive electrode sheet is provided with a plurality of protrusions and concave portions which are arranged opposite to the protrusions.

[0006] A convex portion and a concave portion corresponding to the convex portion are provided on the positive electrode sheet. The convex portion provides support for the contact of the diaphragm and increases the micro-spacing between the electrode sheet and the diaphragm. These micro-spacings form a space for accommodating the electrolyte, so that the electrolyte has sufficient infiltration amount to the electrode sheet, thereby avoiding the abnormal situation of insufficient electrolyte between the electrode sheet and the diaphragm, poor infiltration and even lithium deposition on the negative electrode sheet due to interlayer extrusion of the electrode sheet.

[0007] The negative electrode sheet includes a negative electrode current collector, which has a first surface and a second surface opposite to each other along a first direction, the first surface is provided with a first paste layer, and the second surface is provided with a second paste layer; a plurality of grooves are provided on the first paste layer, and the surface where the convex part of the positive electrode sheet is located and the surface where the grooves of the negative electrode sheet are located are arranged opposite to each other.

[0008] A groove is provided on the negative electrode sheet opposite to the convex part, and the groove provided on the negative electrode sheet can effectively enhance the infiltration of the electrolyte into the negative electrode sheet; in addition, the surface where the convex part of the positive electrode sheet is located and the surface where the groove of the negative electrode sheet is located are arranged relative to each other; an expansion space is provided for the expansion of the negative electrode sheet, thereby alleviating the extrusion deformation of the positive electrode convex part or the deformation of the negative electrode groove caused by the expansion of the negative electrode sheet during hot pressing or battery charging and discharging, ensuring the structural strength of the convexity and the groove and the interface bonding strength between the electrode sheet and the diaphragm, which stably plays a supporting role for the diaphragm. At the same time, sufficient expansion space can also prevent the negative electrode sheet from squeezing the diaphragm during the expansion process, causing deformation of the diaphragm.

[0009] The centers of two adjacent grooves are spaced apart by a first distance, and along the width direction of the grooves, the projection size of the protrusion on the negative electrode sheet is greater than the first distance.

[0010] While the positive electrode protrusion and the negative electrode groove are arranged relatively to each other, the projection size of the positive electrode protrusion on the negative electrode sheet is larger than the center spacing of the negative electrode grooves, which prevents the positive electrode protrusion from being embedded in the negative electrode grooves. This is beneficial to the formation of SEI film on the protruding part of the positive electrode, thereby effectively protecting the protruding part of the positive electrode and preventing the active particles on the protruding part of the positive electrode from breaking or even cobalt precipitation, which leads to reduced structural stability of the positive electrode active material and accelerated battery capacity decay.

[0011] In one embodiment of the present application, the first surface and the second surface of the negative electrode sheet are respectively provided with a plurality of the grooves; the convex portion and the grooves are arranged opposite to each other; and the concave portion and the grooves are arranged opposite to each other.

[0012] Grooves are arranged on both sides of the negative electrode sheet, so that the positive electrode convex portion and the negative electrode groove are arranged opposite to each other, and the positive electrode concave portion is also arranged opposite to the negative electrode groove; the relative arrangement of the positive electrode concave portion and the negative electrode groove can increase the space between the positive electrode sheet and the negative electrode sheet, provide a larger infiltration space for the electrolyte, thereby increasing the amount of stored electrolyte.

[0013] In an embodiment of the present application, along the width direction of the groove, the size of the projection of the protrusion in the thickness direction of the negative electrode sheet is R1, the first distance is S, and R1 / S=1.02~8.

[0014] Within the above ratio range, the extrusion deformation of the positive electrode protrusion or the deformation of the negative electrode groove caused by the expansion of the negative electrode sheet during hot pressing or battery charging and discharging can be alleviated. If it is lower than the above ratio range, it means that the groove width of the first distance is large. When the negative electrode sheet expands and causes the interlayer compression of the electrode sheet, the positive electrode protrusion is easily embedded in the negative electrode groove, which is easy to cause damage to the SEI film of the positive electrode protrusion and make the positive electrode protrusion lack protection; if it is higher than the above ratio range, it means that the groove width of the first distance is small, and the setting of the first distance will be meaningless. The groove cannot provide expansion space for the expansion of the negative electrode sheet. At the same time, during hot pressing or battery charging and discharging, as the negative electrode sheet expands, the positive electrode protrusion is easily squeezed and deformed or the negative electrode groove is deformed.

[0015] In one embodiment of the present application, along the width direction of the groove, the size of the projection of the protrusion in the thickness direction of the negative electrode sheet is R1, the groove width of the groove is M, and R1 / M=8~50.

[0016] Within the above ratio range, the extrusion deformation of the positive electrode convex part or the deformation of the negative electrode groove caused by the expansion of the negative electrode sheet during hot pressing or battery charging and discharging can be alleviated. If it is lower than the above ratio range, it means that the groove width of the groove is large. When the negative electrode sheet expands and causes the interlayer compression of the electrode sheet, the positive electrode convex part is easy to be embedded in the negative electrode groove, which is easy to cause damage to the SEI film of the positive electrode convex part and make the positive electrode convex part lack protection; if it is higher than the above ratio range, it means that the groove width of the groove is small, and the setting of the groove will be meaningless. The groove is difficult to store enough electrolyte, and it is impossible to provide expansion space for the expansion of the negative electrode sheet, and it is impossible to alleviate the extrusion deformation of the positive electrode convex part or the deformation of the negative electrode groove caused by the expansion of the negative electrode sheet during hot pressing or battery charging and discharging.

[0017] In one embodiment of the present application, the first paste layer and / or the second paste layer comprises a silicon-carbon composite material and / or a silicon-oxygen composite material, and the mass proportion of the silicon-carbon composite material and / or the silicon-oxygen composite material in the first paste layer and / or the second paste layer is less than or equal to 50wt%.

[0018] In one embodiment of the present application, the positive electrode sheet includes a positive electrode collector, the positive electrode collector has a third surface and a fourth surface relative to each other along the first direction, the third surface is provided with a third paste layer, and the fourth surface is provided with a fourth paste layer; the negative electrode sheet and the positive electrode sheet are wound around a first center plane, the surface of the positive electrode collector facing the first center plane is the third surface, and the surface of the positive electrode collector away from the first center plane is the fourth surface; the third surface and the first surface are arranged opposite to each other, and the fourth surface and the second surface are arranged opposite to each other; the winding core includes a straight area and corner areas located at opposite ends of the straight area; the convex portion protrudes from the third paste layer to the fourth paste layer.

[0019] Due to the curvature of the corner area, the first surface of the silicon-doped negative electrode sheet is subjected to a greater extrusion pressure than the second surface of the silicon-doped negative electrode sheet. When the silicon-doped negative electrode sheet expands as a whole, the expansion degree of the second surface is greater than that of the first surface, which easily leads to cracks on the second surface of the negative electrode sheet; the first surface and the groove of the negative electrode are arranged relative to the third surface of the positive electrode, that is, the depression of the second surface of the negative electrode and the third surface of the positive electrode are arranged relative to each other. When the second surface of the negative electrode expands severely, part of the coating on the second surface can enter the concave part of the positive electrode to release the stress of the expansion of the negative electrode, thereby not affecting the depth of the convex part of the positive electrode, and ensuring the normal supporting function of the convex part of the positive electrode; In addition, due to the curvature of the corner area, when the arc on the outside of the positive electrode sheet wraps the negative electrode sheet, the arc circumference of the third paste layer on the third surface of the inner side of the positive electrode sheet is greater than the circumference of the first surface of the negative electrode sheet in the corner area, resulting in a decrease in the ratio of the negative electrode surface capacity to the positive electrode surface capacity in this area, and there is a risk of lithium precipitation. In the embodiment of the present application, the convex portion protrudes from the third paste layer to the fourth paste layer, and the depression on the first surface of the negative electrode and the concave portion on the third surface of the positive electrode are relatively arranged, the migration path of the positive electrode active material in the concave portion is longer, and the migration path of the positive electrode active material in other parts is shorter, thereby reducing the positive electrode active material participating in the charge and discharge reaction in the concave portion, so that the negative electrode paste layer on the third surface has sufficient sites for deintercalation of lithium ions, thereby increasing the CB value (negative electrode surface capacity / positive electrode surface capacity) of the area, and reducing the probability of lithium precipitation in the area.

[0020] In one embodiment of the present application, the total projected area of ​​the plurality of protrusions on the negative electrode sheet is 60% to 90% of the area of ​​the fourth paste layer; the winding core also includes an electrolyte doped with a 1,4-dicyano-2-butene additive, and the content of the 1,4-dicyano-2-butene additive in the electrolyte is 0.05% to 3%.

[0021] Limiting the proportion of the positive electrode convex area on the paste layer can ensure the supporting effect of the positive electrode convex; at the same time, the electrolyte infiltrated between the positive and negative electrode sheets is also doped with a certain amount of 1,4-dicyano-2-butene additive, which can protect the edge of the positive electrode convex part and strengthen the edge of the convex part; prevent the active particles of the positive electrode convex part from breaking or even cobalt precipitation, which leads to reduced structural stability of the positive electrode active material and accelerated battery capacity decay.

[0022] In one embodiment of the present application, the projection shape of the convex portion on the negative electrode sheet includes a circular shape, a semicircular shape, an elliptical shape, a plum blossom shape, a polygonal shape, a diamond shape, a capsule shape or an island shape.

[0023] In one embodiment of the present application, the positive electrode sheet includes an upper surface and a lower surface that are relatively arranged, and the protrusion is formed by protruding outward from the upper surface of the positive electrode sheet; the protrusion includes a protrusion portion and a root connecting the protrusion portion and the upper surface; the protrusion is an arc-shaped surface, and / or the protrusion is connected to the upper surface through an arc-shaped edge surface, and the edge of the protrusion in a polygonal, rhombus or island shape is an arc edge.

[0024] Avoid having sharp edges on the protrusions to prevent powder falling from the edges when processing the protrusions; at the same time, avoid the edges or tops of the protrusions from piercing the positive electrode paste to prevent cracks in the paste and cause powder falling. The powder particles can easily fall onto the negative electrode sheet, causing short circuits and fire risks. It can also prevent the tops of the protrusions from piercing the diaphragm and contacting the negative electrode sheet to cause a short circuit.

[0025] In one embodiment of the present application, a line connecting the root and the vertex of the raised portion is a first line, an angle between the first line and the upper surface is a first angle, and the first angle is 3°~45°.

[0026] By limiting the angle between the first connecting line and the upper surface, it is ensured that the positive convex portion has a suitable slope, so that the positive convex portion can play a supporting role between the positive and negative electrode sheets, and at the same time, it can prevent the positive convex portion from being too sharp and piercing the diaphragm. When the first angle is less than 3°, the convex portion is too small and cannot play a supporting role between the positive and negative electrode sheets; when the first angle is greater than 45°, the convex portion has too high a slope, which will cause a protruding tip problem, which is easy to pierce the diaphragm and cause safety problems.

[0027] In an embodiment of the present application, the corner area has a first thickness H1, the straight area has a second thickness H2, and the first thickness H1 and the second thickness H2 have the following relationship: H1 / (H2 / 2)=1.05~1.5.

[0028] Due to the structural characteristics of the corner area and the accumulation of stress, the outward expansion of the corner area is restrained, which eventually leads to the problem of lithium deposition caused by the compression between the electrode layers. The embodiment of the present application achieves the above-mentioned thickness relationship by providing a convex portion and a concave portion opposite to the convex portion on the positive electrode sheet, and providing a groove opposite to the convex portion on the negative electrode sheet. The setting of the above-mentioned thickness relationship can effectively improve the lithium deposition problem in the corner area. At the same time, it ensures that the convex portion and the groove in the corner area and the straight area have matching thickness, so that the interaction force between the layers of the battery cell is appropriate, and ensures that the convexity of the positive electrode sheet and the depression of the negative electrode will not be deformed during the charging and discharging process.

[0029] In one embodiment of the present application, along the width direction of the groove, the size of the projection of the protrusion on the negative electrode sheet is R1=0.3 mm~8mm; and / or the center distance between the projections of two adjacent protrusions on the negative electrode sheet is D1, D1=1 mm~6mm; and / or in the first direction, the root and the vertex of the protrusion have a vertical distance, and the vertical distance is H3=3um~80um.

[0030] Ensure that the size of the projection of the convex part on the negative electrode sheet is within the above range to avoid the tip effect caused by the convex part being too small and to prevent the diaphragm from being punctured; avoid the convex part having a large span due to the convex part being too large, which will affect the convex support effect. Ensure that the center spacing of the convex parts is within the above range to avoid the convex part overlapping or the convex part being too dense due to the convex part center spacing being too small. When forming the convex parts, the rolling pressure is too large and the convex parts are too dense. During the charging and discharging process, the interlayer stress of the battery cell is difficult to release, which may easily cause the electrode sheet to lose powder; avoid the convex part having a large span due to the convex part center spacing being too large, which may affect the convex support effect. Ensure that the height of the convex part is within the above range to avoid the poor support effect due to the convex part being too small and the inability to provide sufficient infiltration space for the electrolyte; avoid the serious stratification between the positive and negative electrode sheets due to the large convex parts, which may cause new interface problems.

[0031] In one embodiment of the present application, in a corner area, the vertical distance from the apex of the convexity of the innermost circle of the winding core to the root of the convexity is a first vertical distance, and the vertical distance from the apex of the convexity of the outermost circle of the winding core to the root of the convexity is a second vertical distance, and the first vertical distance is greater than the second vertical distance.

[0032] The extrusion in the corner area mainly occurs in the layers close to the inner circle of the core. The closer to the outer circle, the smaller the extrusion pressure, the smaller the electrolyte shortage, and the lower the risk of lithium deposition. The vertical distance of the convex part of the innermost circle of the core is greater than the vertical distance of the convex part of the outermost circle of the core, which can increase the electrolyte retention in the innermost circle of the core and ensure that lithium deposition will not occur in the inner circle of the battery cell. Moreover, the convex part of the corner area of ​​the inner circle is reduced, which can reduce the width of the corner area, thereby improving the problem of excessive width of the battery cell and improving the energy density of the battery cell.

[0033] In an embodiment of the present application, the groove width is M=30um~170um; and / or in the first direction, the groove has a groove depth, and the groove depth is T=10um~60um; and / or the first distance is S=0.5mm~3mm.

[0034] Ensure that the groove width is within the above range to avoid the situation where the groove is too small and cannot provide expansion space for the expansion of the negative electrode sheet, and cannot slow down the extrusion deformation of the positive electrode protrusion or deformation of the negative electrode groove caused by the expansion of the negative electrode sheet during hot pressing or battery charging and discharging; at the same time, avoid the problem that the positive electrode protrusion is easily embedded in the negative electrode groove when the negative electrode sheet expands due to excessive groove width, resulting in extrusion between the electrode sheets. Ensure that the groove depth is within the above range to avoid the situation where the groove depth is too small and cannot slow down the deformation of the protrusion caused by the expansion of the electrode sheet during charging and discharging. A too small groove depth will also reduce the storage capacity of the electrolyte; at the same time, avoid the problem that the negative electrode sheet is easy to break in the groove area due to excessive groove depth. Ensure that the center spacing of the grooves is within the above range, so that the grooves on the negative electrode sheet have a suitable density.

[0035] In one embodiment of the present application, the projection of each of the protrusions on the negative electrode sheet has a center point, and some of the center points are distributed on the second connecting line; the projection of the groove on the negative electrode current collector is a rectangular surface, and the second connecting line is parallel to or intersects with the rectangular surface; when the second connecting line intersects with the rectangular surface, the angle between the second connecting line and the rectangular surface is 0°~45°.

[0036] When the second connecting line and the rectangular surface are parallel, the multiple protrusions on the second connecting line can be arranged opposite to a groove, making the processing of the protrusions and the grooves more convenient; when the second connecting line and the rectangular surface intersect, the multiple protrusions on the second connecting line are respectively opposite to different grooves, and at the same time, the angle between the second connecting line and the rectangular surface is limited to the above range, ensuring that each protrusion on the second connecting line can be arranged opposite to the groove.

[0037] An embodiment of the present application also provides a battery, which includes the winding core described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] 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.

[0039] Figure 1 It is a structural schematic diagram of a winding core provided in the related art; Figure 2 A schematic diagram of the structure of the negative electrode sheet and the positive electrode sheet of the winding core provided in an embodiment of the present application; Figure 3 Schematic diagram of the structure of the negative electrode sheet of the winding core provided in the embodiment of the present application Figure 1 ; Figure 4 Schematic diagram of the structure of the negative electrode sheet of the winding core provided in the embodiment of the present application Figure 2 ; Figure 5 A schematic diagram of the top view of the negative electrode sheet of the winding core provided in an embodiment of the present application; Figure 6 A schematic diagram of the structure of the positive electrode sheet of the winding core provided in an embodiment of the present application; Figure 7 A schematic diagram of the structure of the stacked arrangement of positive and negative electrode sheets in the corner area of ​​the winding core provided in an embodiment of the present application; Figure 8 A schematic diagram of the top view of the positive electrode sheet of the winding core provided in the embodiment of the present application Figure 1 ; Fig. 9 A schematic diagram of the top view of the positive electrode sheet of the winding core provided in the embodiment of the present application Figure 2 ; Fig.10 A schematic structural diagram of a convex portion of a positive electrode sheet of a winding core provided in an embodiment of the present application; Fig.11 A schematic diagram of the slope of the convex portion provided in an embodiment of the present application; Fig.12 Schematic diagram of the intersection of the convex portion and the concave portion provided in the embodiment of the present application Figure 1 ; Fig.13 Schematic diagram of the intersection of the convex portion and the concave portion provided in the embodiment of the present application Figure 2 ; Fig.14 Thickness data of the straight area and corner area of ​​10 types of winding cores provided in the embodiments of the present application; Fig.15 Specific values ​​of the first width and the first distance of the 10 types of winding cores provided in the embodiments of the present application; Fig.16 The vertical distance between each coil layer in the winding core provided in the embodiment of the present application; Fig.17 These are specific values ​​of the first width and slot width of the 10 types of winding cores provided in the embodiments of the present application.

[0040] Reference numerals: 100: negative electrode; 101: negative electrode current collector; 102: first paste layer; 103: second paste layer; 110: groove; 1011: first surface; 1012: second surface; 200: positive electrode; 201: positive electrode current collector; 202: third paste layer; 203: fourth paste layer; 210: convex portion; 2011: third surface; 2012: fourth surface; 301: first connecting line; 302: first horizontal plane; 401: rectangular surface; 402: second connecting line. DETAILED DESCRIPTION

[0041] The winding core structure of the wound lithium-ion battery in the related art is as follows Figure 1 As shown, the electrode assembly is stacked and wound to form a winding structure of the battery cell. The cross-section of the winding structure presents a flat elliptical structure, with arc areas on both sides of the elliptical structure and a plane area in the middle of the elliptical structure. The area surrounded by the dotted box in the arc area in the figure is the stress concentration area, and the direction indicated by the arrow is the expansion direction of the positive and negative electrodes when they expand. The positive and negative electrodes of the lithium-ion battery will expand during the charging and discharging process. The plane area can expand freely upward and downward, but the arc area is constrained from expanding outward due to its structural characteristics and stress accumulation.

[0042] 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.

[0043] Finally, the extrusion between the electrode layers leads to poor infiltration of the electrolyte, resulting in too low a liquid retention capacity of the electrolyte between the electrode layers, which means that the area has lost the lithium ion transmission channel, making it impossible for the lithium ions of the positive electrode to escape, and the number of lithium ions embedded in the corresponding position of the negative electrode is insufficient, resulting in the appearance of purple spots. Finally, the lithium ions of the negative electrode cannot return to the positive electrode, and are finally deposited on the surface of the negative electrode, i.e., lithium deposition. In addition, during the cycle, due to the large expansion of the negative electrode, it is easy to squeeze the diaphragms on both sides in contact with the negative electrode, resulting in deformation of the diaphragm and clogging of the pores of the diaphragm, further increasing the risk of lithium deposition in this area.

[0044] The winding core provided in the embodiment of the present application is provided with a convex portion and a concave portion corresponding to the convex portion on the positive electrode sheet. The convex portion provides support for the contact of the diaphragm and increases the micro-spacing between the electrode sheet and the diaphragm. These micro-spacings form a space that can accommodate the electrolyte, so that the electrolyte has sufficient infiltration amount to the electrode sheet, avoiding the abnormal situation of insufficient electrolyte between the electrode sheet and the diaphragm due to interlayer extrusion of the electrode sheet, poor infiltration and even lithium deposition on the negative electrode sheet.

[0045] At the same time, a groove is provided on the negative electrode sheet opposite to the convex part, and the groove provided on the negative electrode sheet can effectively enhance the infiltration of the electrolyte into the negative electrode sheet; in addition, the surface where the convex part of the positive electrode sheet is located and the surface where the groove of the negative electrode sheet is located are arranged relatively to each other; an expansion space is provided for the expansion of the negative electrode sheet, thereby alleviating the extrusion deformation of the positive electrode convex part or the deformation of the negative electrode groove caused by the expansion of the negative electrode sheet during hot pressing or battery charging and discharging, ensuring the structural strength of the convexity and the groove and the interface bonding strength between the electrode sheet and the diaphragm, which stably plays a supporting role for the diaphragm. At the same time, sufficient expansion space can also prevent the negative electrode sheet from squeezing the diaphragm during the expansion process, causing deformation of the diaphragm.

[0046] Furthermore, the size of the vertical projection of the protrusion in the thickness direction of the negative electrode sheet is limited to be larger than the center distance between two adjacent grooves, so as to prevent the positive electrode protrusion from being embedded in the negative electrode groove, which is conducive to the formation of SEI film on the protruding part of the positive electrode, thereby effectively protecting the protruding part of the positive electrode and preventing the active particles in the protruding part of the positive electrode from being broken or even cobalt precipitation, which may lead to reduced structural stability of the positive electrode active material and accelerated battery capacity decay.

[0047] 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.

[0048] refer to Figure 2 The winding core provided in the embodiment of the present application includes: a negative electrode sheet 100 and a positive electrode sheet 200, the negative electrode sheet 100 and the positive electrode sheet 200 are stacked, and the polarities of the negative electrode sheet 100 and the positive electrode sheet 200 are opposite.

[0049] refer to Figure 3 and Figure 5 The negative electrode sheet 100 includes a negative electrode current collector 101, which has a first surface 1011 and a second surface 1012 relative to each other along a first direction (z-axis shown in the figure), the first surface 1011 is provided with a first paste layer 102, and the second surface 1012 is provided with a second paste layer 103; similarly, the positive electrode sheet 200 includes a positive electrode current collector 201, the positive electrode current collector 201 has a third surface 2011 and a fourth surface 2012 relative to each other along the first direction (z-axis shown in the figure), the third surface 2011 is provided with a third paste layer 202, and the fourth surface 2012 is provided with a fourth paste layer 203.

[0050] The first paste layer 102 is provided with a plurality of grooves 110 extending along the second direction (the y-axis shown in the figure), and the plurality of grooves 110 are arranged at the same distance along the third direction (the x-axis shown in the figure); that is, the grooves 110 extend along the width direction of the negative electrode sheet 100, and the plurality of grooves 110 are arranged at intervals along the length direction of the negative electrode sheet 100.

[0051] refer to Figure 8-Figure 10 The positive electrode sheet 200 has a plurality of convex portions 210 arranged in an array, and a plurality of concave portions arranged in an array, and the convex portions 210 and the concave portions are arranged opposite to each other; the convex portions 210 may be protrusions located on the upper surface of the positive electrode sheet 200, and the concave portions may be depressions located on the lower surface of the positive electrode sheet 200.

[0052] When the negative electrode sheet 100 and the positive electrode sheet 200 are stacked, in a first direction (z-axis shown in the figure), the first paste layer 102 is opposite to the fourth paste layer 203; at the same time, the groove 110 on the first paste layer 102 and the protrusion 210 on the fourth paste layer 203 are arranged opposite to each other along the first direction (z-axis shown in the figure).

[0053] The surface where the convex portion of the positive electrode sheet is located and the surface where the concave portion of the negative electrode sheet is located are arranged relative to each other, which means that the projection of the convex portion 210 along the first direction and the projection of the concave portion 110 along the first direction (z-axis shown in the figure) at least partially overlap, or the projection of the convex portion 210 along the first direction and the projection of the concave portion 110 along the first direction completely overlap.

[0054] The winding core provided in the embodiment of the present application increases the micro-spacing between the negative electrode sheet 100, the diaphragm and the positive electrode sheet 200 by providing a protrusion 210 and a recessed portion arranged opposite to the protrusion 210 on the positive electrode sheet 200. The protrusion provides support for the contact of the diaphragm, so that there is a certain support between the negative electrode sheet 100 and the positive electrode sheet 200. These micro-spacings form a space for accommodating electrolyte, so that the electrolyte has sufficient infiltration amount to the electrode sheet, avoiding insufficient electrolyte between the electrode sheet and the diaphragm due to interlayer extrusion of the electrode sheet, poor infiltration and even abnormal lithium deposition on the negative electrode sheet, and ensuring that the electrolyte has sufficient infiltration amount.

[0055] The winding core provided in the embodiment of the present application is provided with a groove 110 on the negative electrode sheet 100 which is opposite to the protrusion 210, providing expansion space for the expansion of the negative electrode sheet, thereby alleviating the extrusion deformation of the positive electrode protrusion or the deformation of the negative electrode groove caused by the expansion of the negative electrode sheet during hot pressing or battery charging and discharging, ensuring the structural strength of the protrusion and the groove and the interface bonding strength between the electrode sheet and the diaphragm, and stably playing a supporting role for the diaphragm. At the same time, sufficient expansion space can also prevent the negative electrode sheet from squeezing the diaphragm during the expansion process, causing deformation of the diaphragm.

[0056] Continue to refer Figure 3In the embodiment of the present application, the centers of two adjacent grooves 110 are spaced apart by a first distance S; the size of the vertical projection of the protrusion 210 in the thickness direction of the pole piece is a first width R1, and the first width R1 is greater than the first distance S.

[0057] When the protrusion 210 faces the groove 110, the protrusion 210 is prevented from being embedded in the groove 110 of the negative electrode, which is beneficial to the formation of an SEI film on the protruding part of the positive electrode, thereby effectively protecting the protrusion 210 of the positive electrode and preventing the active particles of the protrusion 210 of the positive electrode from being broken or even cobalt from precipitating, which would lead to reduced structural stability of the positive electrode active material and accelerated battery capacity decay.

[0058] In the embodiment of the present application, the ratio between the first width R1 and the first distance S is: R1 / S=1.02~8.

[0059] Within the above ratio range, the compression deformation of the positive electrode protrusion 210 or the deformation of the negative electrode groove 110 caused by the expansion of the negative electrode sheet 100 during hot pressing or battery charging and discharging can be alleviated.

[0060] If the ratio of the first width R1 to the first distance S is less than 1.02, it means that the groove width of the first distance S is relatively large. When the negative electrode sheet 100 expands and causes compression between the electrode sheets, the protrusion 210 of the positive electrode is easily embedded in the groove 110 of the negative electrode, which can easily cause damage to the SEI film of the positive electrode protrusion and make the positive electrode protrusion lack protection; if the ratio of the first width R1 to the first distance S is greater than 8, it means that the groove width of the first distance S is relatively small, and the setting of the first distance S will be meaningless. The first distance S cannot provide expansion space for the expansion of the negative electrode sheet, nor can it slow down the extrusion deformation of the positive electrode protrusion or the deformation of the negative electrode groove caused by the expansion of the negative electrode sheet during hot pressing or battery charging and discharging.

[0061] refer to Fig.15 , 10 kinds of winding cores (winding cores 1-10) are provided, and the above ratio relationship is explained through 10 embodiments. Among them, the 10 kinds of winding cores have different first widths R1 and first distances S, and the first width R1 and first distance S of each winding core have the above ratio relationship.

[0062] The 10 types of winding cores with the above ratio relationship can prevent the protrusion 210 from being embedded in the groove 110 when the positive and negative electrode sheets of the winding core expand and cause interlayer compression of the electrode sheets, especially when the interlayer compression in the corner area intensifies, thereby preventing the protrusion 210 from being deformed or the groove 110 from being deformed.

[0063] Preferably, the ratio between the first width R1 and the first distance S is: R1 / S=1.05-4.

[0064] In the embodiment of the present application, the first width R1=0.3 mm~8 mm.

[0065] When the first width R1 is less than 0.3 mm, it is easy to cause a tip effect, that is, the highest point of the protrusion 210 forms a sharp protrusion, which will cause damage to the diaphragm; when the first width R1 is greater than 8 mm, the protrusion surface span of the protrusion 210 is large, which is not conducive to playing a supporting role between the positive and negative electrode sheets.

[0066] Preferably, the first width R1=1mm~3mm.

[0067] It should be noted that, when the projection of the protrusion 210 on the pole piece is fitted into a circle, the first width R1 of the projection of the protrusion 210 on the pole piece may be the diameter of the circle.

[0068] In the embodiment of the present application, the center distance between the projections of two adjacent protrusions 210 on the negative electrode sheet 100 is D1, where D1=1 mm to 6 mm.

[0069] When the center distance D1 is less than 1mm, it is easy to cause the protrusions 210 to overlap or the density of the protrusions is too high. When the protrusions are formed, the rolling pressure is too large and the protrusions are too dense. During the charging and discharging process, the interlayer stress of the battery cell is difficult to release, which can easily cause the electrode to lose powder. When the center distance D1 is greater than 6mm, the raised surface span of the two protrusions 210 is large and cannot play a supporting role.

[0070] Preferably, the center distance is D1=1.5mm~4mm.

[0071] In the embodiment of the present application, the groove 110 has a groove width M in the third direction (x axis shown in the figure), the first width R1 is greater than the groove width M, and the ratio between the first width R1 and the groove width M can be: R1 / M=8~50.

[0072] Within the above ratio range, the compression deformation of the positive electrode protrusion 210 or the deformation of the negative electrode groove 110 caused by the expansion of the negative electrode sheet during hot pressing or battery charging and discharging can be alleviated.

[0073] If the ratio of the first width R1 to the groove width M is less than 8, it means that the groove width of the groove 110 is relatively large. When the negative electrode sheet expands and causes inter-layer squeezing of the electrode sheet, especially when the inter-layer squeezing in the corner area intensifies, it is easy for the protrusion 210 to be embedded in the groove 110, which can easily cause damage to the SEI film of the positive electrode protrusion and make the positive electrode protrusion lack protection; if the ratio of the first width R1 to the groove width M is greater than 50, it means that the groove width of the groove 110 is relatively small, and the setting of the groove 110 will be meaningless. The groove is difficult to store enough electrolyte, and the groove 110 cannot provide expansion space for the expansion of the negative electrode sheet, nor can it slow down the deformation of the protrusion 210 or the groove 110 caused by the expansion of the negative electrode sheet during hot pressing or charging and discharging.

[0074] refer to Fig.17 , 10 kinds of winding cores (winding cores 1-10) are provided, and the above ratio relationship is explained through 10 embodiments. Among them, the 10 kinds of winding cores have different first widths R1 and slot widths M, and the first width R1 and slot width M of each winding core have the above ratio relationship.

[0075] The 10 types of winding cores with the above ratio relationship can prevent the protrusion 210 from being embedded in the groove 110 when the positive and negative electrode sheets of the winding core expand and cause interlayer compression of the electrode sheets, especially when the interlayer compression in the corner area intensifies, thereby preventing the protrusion 210 from being deformed or the groove 110 from being deformed.

[0076] Preferably, the ratio between the first width R1 and the groove width M may be: R1 / M=16-40.

[0077] In the embodiment of the present application, the groove 110 has a groove width M in the third direction (the x-axis shown in the figure), and the groove width M=30um~170um; ensure that the groove width M of the groove 110 is within the above range. When the groove width M is less than 30um, the groove width M is too small, and the setting of the groove 110 will be meaningless, resulting in the groove 110 being unable to provide expansion space for the expansion of the negative electrode sheet, and unable to alleviate the compression deformation of the positive electrode protrusion 210 or the deformation of the negative electrode groove 110 caused by the expansion of the negative electrode sheet during hot pressing or battery charging and discharging; when the groove width M is greater than 170um, the negative electrode sheet 100 expands and causes compression between the electrode sheets, and the positive electrode protrusion 210 is easily embedded in the negative electrode groove 110.

[0078] Preferably, the groove width M=60um~120um.

[0079] The groove 110 has a groove depth T in the first direction (z-axis shown in the figure), and the groove depth T=10um~60um; when the groove depth T is less than 10um, it will not be able to slow down the deformation of the protrusion 210 caused by the expansion of the electrode during the charge and discharge process, and will also affect the increase in the amount of stored electrolyte; when the groove depth T is greater than 60um, it will affect the thickness of the negative electrode sheet, and the area where the groove 110 is set is prone to breakage.

[0080] Preferably, the groove depth T=12um~30um.

[0081] The plurality of grooves 110 are spaced at the same distance in the second direction (the y-axis shown in the figure), and the centers of two adjacent grooves 110 are spaced at a first distance S, and the first distance S=0.5mm~3mm. When the first distance S is less than 0.5mm, the setting of the grooves 110 will be meaningless, and the expansion of the pole piece during the charge and discharge process will easily cause the protrusion 210 or the groove 110 to deform; when the first distance S is greater than 3mm, it means that the first width R1 of the protrusion 210 opposite thereto also needs to be increased. When the first width R1 is too large, the convex surface span of the protrusion 210 is large, which is not conducive to playing a supporting role between the positive and negative pole pieces.

[0082] Continue to refer Figure 3 In the cross section along the first direction (z axis shown in the figure), the cross-sectional shape of the groove 110 may be V-shaped.

[0083] Continue to refer Figure 4 The first surface 1011 and the second surface 1012 of the negative electrode current collector 101 are respectively provided with a plurality of grooves 110 ; the convex portion 210 and the grooves 110 are arranged opposite to each other; and the concave portion and the grooves 110 are arranged opposite to each other.

[0084] That is to say, grooves are arranged on both sides of the negative electrode sheet 100, so that the convex portion 210 of the positive electrode and the groove 110 of the negative electrode are arranged opposite to each other, and the concave portion of the positive electrode is also arranged opposite to the groove 110 of the negative electrode; the relative arrangement of the concave portion of the positive electrode and the groove 110 of the negative electrode can increase the space between the positive electrode sheet 200 and the negative electrode sheet 100, provide a larger infiltration space for the electrolyte, thereby increasing the amount of stored electrolyte.

[0085] In the embodiment of the present application, the winding core includes a straight area and corner areas located at opposite ends of the straight area, the corner area has a first thickness H1, and the straight area has a second thickness H2. The first thickness H1 and the second thickness H2 have the following relationship: H1 / (H2 / 2)=1.05~1.5.

[0086] It should be noted that the second thickness H2 of the straight area refers to Figure 1 The thickness in the vertical direction shown in , the corner area is formed into an arc, and the first thickness H1 of the corner area is the radius of the arc. In one embodiment, the thickness of the straight area can also refer to the thickness of all straight areas of the battery cell, that is, the thickness of the battery cell, and correspondingly, the thickness of the corner area is the thickness of all corner areas connected to the two ends of the innermost corner area in the width direction.

[0087] refer to Fig.14 , 10 kinds of winding cores (winding cores 1-10) are provided, and the above thickness relationship is explained through 10 embodiments. Among them, the 10 kinds of winding cores have different straight area thicknesses and corner area thicknesses, and the straight area thickness and corner area thickness of each winding core have the above thickness relationship.

[0088] Due to the structural characteristics of the corner area and the accumulation of stress, the outward expansion of the corner area is restrained, which eventually leads to the problem of lithium deposition caused by the compression between the electrode layers. The 10 kinds of winding cores provided in the embodiments of the present application are achieved by providing a convex portion 210 and a concave portion opposite to the convex portion 210 on the positive electrode sheet 200 of each winding core, and providing a groove 110 opposite to the convex portion 210 on the negative electrode sheet 100, so as to achieve the above-mentioned thickness relationship. The setting of the above-mentioned thickness relationship can effectively improve the lithium deposition problem in the corner area. At the same time, it ensures that the convex portion and the groove in the corner area and the straight area have matching thickness, so that the interaction force between the layers of the battery cell is appropriate, and it is ensured that the convexity of the positive electrode sheet and the depression of the negative electrode will not be deformed during the charging and discharging process.

[0089] Preferably, the first thickness H1 and the second thickness H2 have the following relationship: H1 / (H2 / 2)=1.08~1.3.

[0090] refer to Fig. 9 In the embodiment of the present application, the positive electrode sheet 200 includes an upper surface and a lower surface that are arranged opposite to each other, and the protrusion is formed by protruding outward from the upper surface of the positive electrode sheet 200; the protrusion 210 includes a protruding portion and a root connecting the protruding portion and the upper surface.

[0091] In the first direction (z axis shown in the figure), the root of the protrusion 210 intersects with the surface of the positive electrode sheet 200, and there is a vertical distance between the root of the protrusion 210 and the vertex of the protrusion 210, and the vertical distance is H3 = 3um~80um.

[0092] When the vertical distance H3 is less than 3um, it means that the protrusion 210 is too small and cannot support the positive and negative electrodes. The protrusion 210 is an invalid protrusion and cannot allow the electrolyte to be sufficiently infiltrated. When the vertical distance H3 is greater than 80um, it means that the protrusion 210 is too large, which will cause serious stratification between the positive and negative electrodes and cause new interface problems.

[0093] Among them, the extrusion of the corner area mainly occurs in the layers close to the inner circle of the core. The closer to the outer circle, the smaller the extrusion pressure, the smaller the electrolyte shortage, and the lower the risk of lithium deposition. Therefore, the vertical distance of the convex part of the innermost circle of the core is greater than the vertical distance of the convex part of the outermost circle of the core, which can increase the electrolyte retention amount in the innermost circle of the core and ensure that lithium deposition will not occur in the inner circle of the battery cell. Moreover, the convex part of the corner area of ​​the inner circle is reduced, which can reduce the width of the corner area, thereby improving the problem of excessive width of the battery cell and improving the energy density of the battery cell.

[0094] refer to Fig.16 , a vertical distance H3 of all the coils in a winding core is provided to illustrate the above relationship.

[0095] The innermost circle of the winding core refers to the circle layer where the winding starting section of the pole piece is located, and the outermost circle of the winding core refers to the circle layer where the winding ending section of the pole piece is located. There are also multiple layers of intermediate circles between the innermost circle of the winding core and the outermost circle of the winding core.

[0096] The first middle circle is adjacent to the innermost circle of the winding core, and the first middle circle surrounds the innermost circle of the winding core, the second middle circle is adjacent to the first middle circle, and the second middle circle surrounds the first middle circle, and so on, until the outermost circle of the winding core.

[0097] When the vertical distance H3 of the protrusion 210 of the innermost circle of the winding core is 80um, the vertical distance H3 of the protrusion 210 of the first middle circle can be 75um; the vertical distance H3 of the protrusion 210 of the second middle circle can be 70um; the vertical distance H3 of the protrusion 210 of the third middle circle can be 65um; the vertical distance H3 of the protrusion 210 of the outermost circle of the winding core can be 3um.

[0098] Continue to refer Fig.11 In the embodiment of the present application, the convex portion 210 is formed by protruding outward from the upper surface of the positive electrode sheet 200; the convex portion 210 includes a convex portion and a root portion connecting the convex portion and the upper surface. The root portion of the convex portion 210 intersects with the upper surface of the positive electrode sheet 200, and the line connecting the root portion of the convex portion 210 and the vertex of the convex portion 210 is a first connecting line 301. The angle between the first connecting line 301 and the first horizontal plane 302 is a first angle, and the first angle is 3° to 45°.

[0099] When the first angle is less than 3°, the protrusion 210 is too small and cannot support the positive and negative electrodes. When the first angle is greater than 45°, the protrusion 210 has too high a slope, which may cause a protruding tip problem and easily pierce the diaphragm, causing safety problems.

[0100] Preferably, the first angle may be 5°~25°.

[0101] In the embodiment of the present application, the shape of the protrusion 210 may include a circle, a semicircle, an ellipse, a plum blossom, a polygon, a diamond, a capsule or an island.

[0102] In the embodiment of the present application, the positive electrode sheet 200 includes an upper surface and a lower surface that are arranged opposite to each other, and the protrusion is formed by protruding outward from the upper surface of the positive electrode sheet 200; the protrusion 210 includes a protrusion portion and a root portion connecting the protrusion portion and the upper surface.

[0103] The raised portion is an arc-shaped surface, and / or the raised portion is connected to the upper surface through the arc-shaped edge surface, and the edge of the polygonal, rhombus or island-shaped raised portion is an arc edge.

[0104] That is to say, when the shape of the protrusion 210 is a polygon or rhombus with corners, the corners of the protrusion 210 are all provided with arc corners; or when the shape of the protrusion 210 is a polygon or rhombus with obvious sharp edges, the edge of the protrusion 210 is an arc edge.

[0105] Avoid having sharp edges on the protrusions to prevent powder falling from the edges when processing the protrusions; at the same time, avoid the edges or tops of the protrusions from piercing the positive electrode paste to prevent cracks in the paste and cause powder falling. The powder particles can easily fall onto the negative electrode sheet, causing short circuits and fire risks. It can also prevent the tops of the protrusions from piercing the diaphragm and contacting the negative electrode sheet to cause a short circuit.

[0106] Preferably, the shape of the protrusion 210 may be circular without sharp corners.

[0107] It should be noted that when a 3D profilometer is used to test the state of the positive electrode sheet 200 , it can be clearly detected that the edge of the protrusion 210 is quasi-circular.

[0108] Continue to refer Figure 2 and Figure 7 In the embodiment of the present application, the negative electrode sheet 100 and the positive electrode sheet 200 are wound around the first center plane, the surface of the positive electrode collector 201 facing the first center plane is the third surface 2011, and the surface of the positive electrode collector 201 away from the first center plane is the fourth surface 2012. The third surface 2011 is provided with a third paste layer 202, and the fourth surface 2012 is provided with a fourth paste layer 203. The protrusion 210 protrudes from the third paste layer 202 to the fourth paste layer 203.

[0109] The first center plane refers to Figure 1 The center is the horizontal plane perpendicular to the paper surface at the innermost circle of the winding core.

[0110] Due to the curvature of the corner area, the first surface of the silicon-doped negative electrode sheet is subjected to a greater extrusion pressure than the second surface of the silicon-doped negative electrode sheet. When the silicon-doped negative electrode sheet expands as a whole, the expansion degree of the second surface is greater than that of the first surface, which can easily lead to cracks on the second surface of the negative electrode sheet; the first surface and the groove of the negative electrode and the third surface of the positive electrode are arranged relative to each other, that is, the depression of the second surface of the negative electrode and the third surface of the positive electrode are arranged relative to each other. When the second surface of the negative electrode expands severely, part of the coating on the second surface can enter the recess of the positive electrode to release the stress of the expansion of the negative electrode, thereby not affecting the depth of the convex part of the positive electrode and ensuring the normal supporting function of the convex part of the positive electrode.

[0111] Due to the curvature of the corner area, when the arc formed by the third coating layer 202 wraps the negative electrode sheet 100, the circumference of the arc of the third coating layer 202 will be greater than the circumference of the negative electrode sheet 100 in the corner area, which causes the amount of positive electrode active material in this area to be greater than the amount of positive electrode active material in this area when designed, that is, the ratio of the negative electrode surface capacity to the positive electrode surface capacity in this area is reduced, resulting in the risk of lithium plating.

[0112] In the embodiment where the above-mentioned facts cannot be changed, in the embodiment of the present application, the convex portion protrudes from the third paste layer to the fourth paste layer, and the depression on the first surface of the negative electrode and the concave portion on the third surface of the positive electrode are arranged relatively to each other, so that the migration path of the positive electrode active material in the concave portion is longer, and the migration path of the positive electrode active material in other parts is shorter, thereby reducing the positive electrode active material in the concave portion participating in the charge and discharge reaction, so that the negative electrode paste layer on the third surface has sufficient sites for deintercalating and extracting lithium ions, thereby increasing the CB value (negative electrode surface capacity / positive electrode surface capacity) of the region and reducing the probability of lithium plating in the region.

[0113] Continue to refer Figure 6 and Figure 7 In the embodiment of the present application, the total projection area of ​​the plurality of protrusions 210 on the negative electrode sheet 100 is 60% to 90% of the area of ​​the fourth paste layer 203, ensuring the support effect of the protrusions 210; if it is less than 60%, it will affect the support effect of the protrusions 210; if it is higher than 90%, it will affect the normal operation of the paste.

[0114] At the same time, the core also includes an electrolyte doped with 1,4-dicyano-2-butene additive, and the content of 1,4-dicyano-2-butene additive in the electrolyte accounts for 3%~60%.

[0115] The electrolyte soaked between the positive and negative electrode sheets is also doped with a certain amount of 1,4-dicyano-2-butene additive, so that the electrolyte can play a film-forming protective role on the positive electrode protrusion 210; prevent the active particles of the positive electrode protrusion 210 from breaking or even cobalt precipitation, which leads to reduced structural stability of the positive electrode active material and accelerated battery capacity decay.

[0116] When the content of the 1,4-dicyano-2-butene additive is lower than the range, it cannot protect the edge of the protrusion 210; when the content of the 1,4-dicyano-2-butene additive is higher than the range, it will affect the normal use of the electrolyte.

[0117] refer to Fig.10In the embodiment of the present application, the projection of each convex portion 210 on the first horizontal plane (the horizontal plane where the y-axis is located) has a center point, and some of the center points are distributed on the second connecting line 402, and the second connecting line 402 is parallel to the second direction (the y-axis shown in the figure); the projection of the groove 110 on the first horizontal plane is a rectangular surface 401, and the second connecting line 402 is parallel to the rectangular surface 401.

[0118] When the second connecting line is parallel to the rectangular surface, a plurality of convex portions located on the second connecting line can be arranged opposite to a concave groove, so that the processing of the convex portions and the concave groove is more convenient.

[0119] refer to Fig.11 In another embodiment of the present application, the projection of each convex portion 210 on the first horizontal plane (the horizontal plane where the y-axis is located) has a center point, and some of the center points are distributed on the second line 402, and the second line 402 is parallel to the second direction (the y-axis shown in the figure); the projection of the groove 110 on the first horizontal plane is a rectangular surface 401, and the second line 402 and the rectangular surface 401 intersect; when the second line 402 and the rectangular surface 401 intersect, the angle between the second line 402 and the rectangular surface 401 is 0°~45°.

[0120] When the second connecting line intersects the rectangular surface, the multiple convex portions on the second connecting line are respectively opposite to different grooves, and the angle between the second connecting line and the rectangular surface is limited within the above range to ensure that each convex portion on the second connecting line can be arranged opposite to the groove.

[0121] refer to Figure 7 In the embodiment of the present application, the first paste layer 102 and / or the second paste layer 103 include a silicon-carbon composite material and / or a silicon-oxygen composite material, and the mass proportion of the silicon-carbon composite material and / or the silicon-oxygen composite material in the first paste layer 102 and / or the second paste layer 103 is less than or equal to 50wt%.

[0122] The silicon-carbon composite material includes a porous carbon matrix, silicon grains in the pores of the porous carbon matrix, and a carbon layer on the surface of the porous carbon matrix. The present invention can arrange silicon grains in the pores of the porous carbon matrix by deposition, by arranging silicon grains in the pores, and by forming a carbon layer on the surface of the porous carbon matrix, and the carbon layer can be shaped carbon or amorphous carbon. When the silicon grains expand, the interior of the porous carbon matrix can provide sufficient expansion space to prevent the overall structure of the silicon-carbon composite material from deforming, and the carbon layer can constrain the outward expansion force of the porous carbon matrix during the silicon expansion process, ensure the structural strength of the silicon-carbon material, thereby avoiding the problems of cracking, pulverization, and shedding of the negative electrode active layer, and improving the cycle performance and rate performance of the battery.

[0123] In a specific embodiment, the carbon layer includes openings arranged corresponding to the pores of the porous carbon matrix. When the carbon layer is provided with openings, the wettability of the electrolyte to the negative electrode sheet can be improved, and the expansion performance of the silicon-based material can be reduced, thereby reducing the impedance of the battery and improving the cycle performance and rate performance of the battery.

[0124] In a specific embodiment, the specific surface area of ​​the silicon-carbon composite material and / or the silicon-oxygen composite material is 0.5-10 m 2 / g, for example 0.5m 2 / g, 1m 2 / g, 2m 2 / g, 3m 2 / g, 4m 2 / g, 5m 2 / g, 6m 2 / g, 7m 2 / g, 8m 2 / g, 9m 2 / g or 10m 2 When the specific surface area of ​​the silicon-carbon composite material and / or the silicon-oxygen composite material is within the above range, the SEI film formed on the surface of the negative electrode active layer during the charge and discharge process is suitable, which can reduce the impedance of the battery and improve the cycle performance and rate performance of the battery.

[0125] In a specific embodiment, the particle size Dv50 of the silicon-carbon composite material and / or the silicon-oxygen composite material is 6-15 μm, for example, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm. When the particle size Dv50 of the silicon-carbon composite material and / or the silicon-oxygen composite material is within the above range, the particle size Dv50 of the silicon-carbon composite material is appropriate, which can avoid the situation where the particle size is too small, which easily leads to an increase in the specific surface area of ​​the silicon particles and an increase in side reactions, and can also avoid the situation where the particle size is too large, which easily leads to excessive expansion of the silicon particles, resulting in blocking of the pores of the porous carbon matrix and affecting the infiltration of the electrolyte, thereby improving the cycle performance and rate performance of the battery.

[0126] In a specific embodiment, the powder resistivity of the silicon-carbon composite material and / or the silicon-oxygen composite material is 0.1-1000 Ω·cm, for example, 0.1Ω·cm, 0.5Ω·cm, 1Ω·cm, 5Ω·cm, 10Ω·cm, 50Ω·cm, 100Ω·cm, 200Ω·cm, 300Ω·cm, 400Ω·cm, 500Ω·cm, 600Ω·cm, 700Ω·cm, 800Ω·cm, 900Ω·cm or 1000Ω·cm. When the powder resistivity of the silicon-carbon composite material and / or the silicon-oxygen composite material is within the above range, the conductivity of the silicon-carbon composite material and / or the silicon-oxygen composite material is high, which can improve the conductivity of the negative electrode active layer, thereby improving the cycle performance and rate performance of the battery.

[0127] In a specific embodiment, the silicon content in the silicon-carbon composite material and / or the silicon-oxygen composite material is 30-75%, for example, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or 75%, etc. When the silicon content in the silicon-carbon composite material is within the above range, it is possible to avoid excessive silicon content in the silicon-carbon composite material, which leads to excessive expansion of the silicon-carbon composite material and deformation of the overall structure of the silicon-carbon composite material, thereby avoiding cracking and pulverization of the negative electrode active layer, ensuring the energy of the silicon-carbon composite material, and improving the cycle performance and rate performance of the battery.

[0128] The third surface 2011 of the positive current collector 201 is the inner surface of the positive electrode, and the corresponding first surface 1011 of the negative current collector 101 is the outer surface of the negative electrode. Since the outer surface of the negative electrode in the arc area expands greatly, and the silicon-carbon composite material of the negative electrode itself expands greatly, on this basis, the groove 110 on the outer surface of the negative electrode corresponds to the concave portion of the inner surface of the positive electrode, which can provide space for the negative electrode silicon-doped active layer on the outer surface of the negative electrode to fully expand, and the concave portion on the inner surface of the positive electrode provides avoidance for the expansion of the outer surface of the negative electrode, thereby not affecting the depth of the convex portion 210 of the positive electrode, thereby ensuring the normal supporting function of the convex portion 210 of the positive electrode.

[0129] An embodiment of the present application also provides a battery, which includes the winding core described above.

[0130] In summary, the embodiment of the present application provides a winding core and a battery, the winding core includes a negative electrode sheet 100 and a positive electrode sheet 200 which are stacked, the polarities of the negative electrode sheet 100 and the positive electrode sheet 200 are opposite; the negative electrode sheet 100 includes a negative electrode current collector 101, the negative electrode current collector 101 has a first surface 1011 and a second surface 1012 which are opposite to each other along a first direction (the z-axis shown in the figure), the first surface 1011 is provided with a first paste layer 102, and the second surface 1012 is provided with a second paste layer 103; the first paste layer 102 is provided with a plurality of grooves 110 extending along a second direction (the y-axis shown in the figure), and the centers of two adjacent grooves 110 are arranged at a first distance S along a third direction; the positive electrode sheet 200 has a plurality of protrusions 210 and concave portions arranged opposite to the protrusions 210, and the grooves 110 are arranged opposite to the protrusions 210; the size of the projection of the protrusion 210 on the electrode sheet is a first width R1, and the first width R1 is greater than the first distance S.

[0131] The winding core provided in the embodiment of the present application increases the micro-spacing between the negative electrode sheet 100, the diaphragm and the positive electrode sheet 200 by providing a protrusion 210 and a recessed portion arranged opposite to the protrusion 210 on the positive electrode sheet 200. The protrusion provides support for the contact of the diaphragm, so that there is a certain support between the negative electrode sheet 100 and the positive electrode sheet 200. These micro-spacings form a space for accommodating electrolyte, so that the electrolyte has sufficient infiltration amount to the electrode sheet, avoiding insufficient electrolyte between the electrode sheet and the diaphragm due to interlayer extrusion of the electrode sheet, poor infiltration and even abnormal lithium deposition on the negative electrode sheet, and ensuring that the electrolyte has sufficient infiltration amount.

[0132] At the same time, a groove 110 is provided on the negative electrode sheet 100 facing the protrusion 210 to provide expansion space for the expansion of the negative electrode sheet, thereby alleviating the extrusion deformation of the positive electrode protrusion or the deformation of the negative electrode groove caused by the expansion of the negative electrode sheet during hot pressing or battery charging and discharging, ensuring the structural strength of the protrusion and the groove and the interface bonding strength between the electrode sheet and the diaphragm, which stably supports the diaphragm. At the same time, sufficient expansion space can also prevent the negative electrode sheet from squeezing the diaphragm during the expansion process, causing deformation of the diaphragm.

[0133] Furthermore, when the protrusion 210 is facing the groove 110, the protrusion 210 is prevented from being embedded in the groove 110 of the negative electrode, which is beneficial to the formation of an SEI film on the raised part of the positive electrode, thereby effectively protecting the protrusion 210 of the positive electrode and preventing the active particles of the protrusion 210 of the positive electrode from being broken or even cobalt from precipitating, which would lead to reduced structural stability of the positive electrode active material and accelerated battery capacity decay.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] 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).

[0138] 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.

[0139] 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 winding core, characterized in that: include: A negative electrode sheet and a positive electrode sheet are stacked; The negative electrode sheet comprises a negative electrode current collector, wherein the negative electrode current collector has a first surface and a second surface opposite to each other along a first direction, wherein the first surface is provided with a first paste layer, and the second surface is provided with a second paste layer; The first paste layer is provided with a plurality of grooves, and the centers of two adjacent grooves are spaced a first distance apart; The positive electrode sheet is provided with a plurality of convex portions and concave portions corresponding to the convex portions, and the surface where the convex portions of the positive electrode sheet are located and the surface where the concave portions of the negative electrode sheet are located are arranged opposite to each other; Along the width direction of the groove, a vertical projection size of the protrusion in the thickness direction of the negative electrode sheet is greater than the first distance.

2. The winding core according to claim 1, characterized in that: The first surface and the second surface of the negative electrode sheet are respectively provided with a plurality of grooves; The convex part and the concave part are arranged opposite to each other; the concave part and the concave part are arranged opposite to each other.

3. The winding core according to claim 1, characterized in that: Along the width direction of the groove, the projection size of the protrusion in the thickness direction of the negative electrode sheet is R1, the first distance is S, and R1 / S=1.02~8.

4. The winding core according to claim 1, characterized in that: Along the width direction of the groove, the projection size of the protrusion in the thickness direction of the negative electrode sheet is R1, and the groove width of the groove is M, R1 / M=8~50.

5. The winding core according to claim 1, characterized in that: The first paste layer and / or the second paste layer comprises a silicon-carbon composite material and / or a silicon-oxygen composite material, and the mass proportion of the silicon-carbon composite material and / or the silicon-oxygen composite material in the first paste layer and / or the second paste layer is less than or equal to 50wt%.

6. The winding core according to claim 1, characterized in that: The positive electrode sheet comprises a positive electrode current collector, the positive electrode current collector has a third surface and a fourth surface opposite to each other along the first direction, the third surface is provided with a third paste layer, and the fourth surface is provided with a fourth paste layer; The negative electrode sheet and the positive electrode sheet are wound around a first central plane, the surface of the positive electrode current collector facing the first central plane is the third surface, and the surface of the positive electrode current collector away from the first central plane is the fourth surface; the third surface is arranged opposite to the first surface, and the fourth surface is arranged opposite to the second surface; The winding core includes a straight area and corner areas located at opposite ends of the straight area. The convex portion protrudes from the third paste layer toward the fourth paste layer.

7. The winding core according to claim 6, characterized in that: The total projection area of ​​the plurality of protrusions on the negative electrode sheet is 60% to 90% of the area of ​​the fourth paste layer; The winding core also includes an electrolyte doped with 1,4-dicyano-2-butene, and the content of the 1,4-dicyano-2-butene additive in the electrolyte is 0.05% to 3%.

8. The winding core according to claim 6, characterized in that: The projection shape of the convex portion on the negative electrode sheet includes a circle, a semicircle, an ellipse, a plum blossom, a polygon, a rhombus, a capsule or an island.

9. The winding core according to claim 8, characterized in that: The positive electrode sheet comprises an upper surface and a lower surface which are arranged opposite to each other, and the convex portion is formed by protruding outward from the upper surface of the positive electrode sheet; The convex portion includes a protruding portion and a root portion connecting the protruding portion and the upper surface; The raised portion is an arc-shaped surface, and / or The protrusion is connected to the upper surface via an arc-shaped edge surface.

10. The winding core according to claim 9, characterized in that: A line connecting the root and the vertex of the raised portion is a first line, an angle between the first line and the upper surface is a first angle, and the first angle is 3° to 45°.

11. The winding core according to claim 6, characterized in that: The winding core has a first thickness H1 in the corner area, and the winding core has a second thickness H2 in the straight area. The first thickness H1 and the second thickness H2 have the following relationship: H1 / (H2 / 2)=1.05~1.

5.

12. The winding core according to claim 9, characterized in that: Along the width direction of the groove, the vertical projection size of the protrusion in the thickness direction of the negative electrode sheet is R1=0.3 mm~8 mm; and / or The center distance between the vertical projections of two adjacent protrusions in the thickness direction of the negative electrode sheet is D1=1 mm~6 mm; and / or In the first direction, the root portion and the vertex of the protrusion portion have a vertical distance, and the vertical distance is H3=3um~80um.

13. The winding core according to claim 12, characterized in that: In the corner area, the vertical distance from the apex of the convexity of the innermost circle of the winding core to the root of the convexity is a first vertical distance, and the vertical distance from the apex of the convexity of the outermost circle of the winding core to the root of the convexity is a second vertical distance, and the first vertical distance is greater than the second vertical distance.

14. The winding core according to claim 4, characterized in that: The groove width is M=30um~170um; and / or In the first direction, the groove has a groove depth, and the groove depth is T=10um~60um; and / or The first distance is S=0.5mm~3mm.

15. The winding core according to claim 4, characterized in that: The projection of each of the protrusions on the negative electrode sheet has a center point, and some of the center points are distributed on the second connecting line; The projection of the groove on the negative electrode current collector is a rectangular surface, and the first connecting line is parallel to or intersects with the rectangular surface; When the first connecting line intersects the rectangular surface, the angle between the first connecting line and the rectangular surface is 0°~45°.

16. A battery, characterized in that: The winding core comprises the winding core according to any one of claims 1 to 15.

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