Positive plate, battery cell and battery

Abstract

The invention provides a positive plate, a battery cell and a battery. The positive plate comprises a current collector; the current collector comprises a first surface and a second surface which are opposite in the thickness direction; the coating comprises a safety coating and an active substance layer, the safety coating is located on the surface of the current collector, and the active substance layer is located on the surface, away from the current collector, of the safety coating; the positive plate is provided with a first area, and the first surface and the second surface of a current collector in the first area are provided with a safety coating and an active material layer; a plurality of first protrusions and first recesses corresponding to the first protrusions are arranged in the first area, and the first protrusions are formed by protruding the safety coating and the active material layer on the first surface towards the second surface. The safety coating forms a convex part and a concave part which are matched with the first bulge and the first recess; the safety coating further comprises a straight part located outside the protruding part, and the thickness of the vertex area of the protruding part of the safety coating is smaller than that of the straight part of the safety coating. According to the positive plate, impedance can be reduced, and polarization can be weakened.

Description

Technical Field

[0001] The present invention relates to the field of batteries, and in particular to a positive electrode sheet, a battery cell and a battery. Background Art

[0002] Lithium-ion batteries have been widely used in energy storage systems such as hydropower, thermal power, wind power and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles and other fields. As lithium-ion batteries have made great progress, higher requirements have been put forward for their energy density, cycle performance and safety performance.

[0003] When traditional lithium-ion batteries are damaged by external forces, such as needle puncture, the positive electrode current collector debris is usually aluminum. The positive electrode current collector debris directly contacts the negative electrode active material layer, generating intense heat and causing the battery to catch fire and explode. By coating a layer of safety coating on the surface of the positive electrode current collector, it can be prevented from directly contacting the negative electrode active material, significantly improving the safety performance of the battery when damaged by external forces.

[0004] However, compared with the positive electrode active layer, the safety coating has poor conductivity. After using the safety coating, the impedance and polarization on the positive electrode side increase, affecting the rate performance of the battery cell. Summary of the invention

[0005] In view of the above problems, the present invention provides a positive electrode sheet, a battery cell and a battery, which can improve the wetting ability of the electrolyte, reduce the impedance in the battery cell, and improve the rate performance of the battery cell.

[0006] In the first aspect, the present invention provides a positive electrode sheet, comprising: a current collector; the current collector comprising a first surface and a second surface opposite to each other along the thickness direction; a coating, comprising: a safety coating and an active material layer, wherein the safety coating is located on the surface of the current collector, and the active material layer is located on the surface of the safety coating away from the current collector; the positive electrode sheet is provided with a first area, and the first surface and the second surface of the current collector in the first area are both provided with a safety coating and an active material layer; a plurality of first protrusions and first depressions corresponding to the first protrusions are provided in the first area, and the first protrusions are formed by the safety coating and the active material layer on the first surface protruding toward the second surface; the safety coating forms a convex portion and a concave portion matching the first protrusion and the first concave portion; the safety coating also includes a straight portion located outside the convex portion, and the thickness of the safety coating located in the vertex area of ​​the convex portion is less than the thickness of the safety coating located in the straight portion.

[0007] The first protrusion formed on the positive electrode sheet of the present invention can provide support for the contact of the diaphragm, so that there is a certain support between the positive electrode, the diaphragm and the negative electrode, and the micro-spacing between the electrode sheet and the diaphragm is increased. 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 shortage of electrolyte between the electrode sheet and the diaphragm due to the interlayer extrusion of the electrode sheet, poor infiltration and even abnormal lithium deposition on the negative electrode sheet.

[0008] Moreover, the safety coating and the active material layer both form protrusions corresponding to the first protrusions, which can shorten the transmission path of lithium ions in the area, improve the transmission efficiency of lithium ions, and help reduce the concentration difference of lithium ions on the two side surfaces of the electrode, thereby weakening the polarization phenomenon.

[0009] The first depression on the other side of the positive electrode sheet can form a liquid storage tank for accommodating electrolyte, which can not only increase the electrolyte capacity and improve the electrolyte infiltration ability; moreover, compared with the position where no depression is formed in the prior art, the liquid storage tank formed at this position greatly reduces the transmission impedance of lithium ions (because the transmission impedance of lithium ions in the electrolyte is much smaller than the transmission impedance in the active layer), and the higher the electrolyte content at this position, the lower the transmission impedance of lithium ions. It is also beneficial to reduce the polarization caused by electrolyte loss during the long-term cycle of the battery, and has the effect of improving the battery rate performance.

[0010] In addition, the thickness of the vertex area of ​​the convex part of the safety coating is smaller than the thickness of the straight part. On the one hand, it can further reduce the lithium ion transmission path between the positive electrode sheet and the negative electrode sheet in the convex area. At the same time, the thinning of the safety coating means thinning the part with poor conductivity, thereby reducing the overall transmission impedance of electrons and improving the overall conductivity of the electrode sheet.

[0011] In some embodiments, the current collector, the safety coating layer, and the active material layer all form convex portions and concave portions that match the first convex portions and the first concave portions.

[0012] In some embodiments, the current collector includes a first surface and a second surface opposite to each other along the thickness direction, and the first surface and the second surface are both provided with the coating, wherein the surface of the active material layer on the first surface away from the current collector constitutes the first surface, and the surface of the active material layer on the second surface away from the current collector constitutes the second surface.

[0013] In some embodiments, the projection of the first protrusion in the reference plane has a shape of any one of a circle, an ellipse, a line, a wave, a polygon, and a capsule, and the reference plane is parallel to the first surface.

[0014] According to some embodiments of the present invention, the coating on the first surface is a first coating layer, and the coating on the second surface is a second coating layer. Along the length direction of the positive electrode sheet, the length of the first coating layer is greater than the length of the second coating layer, the positive electrode sheet area of ​​the first coating layer exceeding the second coating layer constitutes a single-sided coating area, and there is a spacing distance between the first area and the single-sided coating area; and / or, The positive electrode sheet comprises a tab connection area, the tab connection area exposes the current collector, the positive electrode sheet is further provided with a tab, the tab is connected to the current collector in the tab connection area, there is a spacing distance between the first region and the tab connection area, and / or, The positive electrode sheet includes a first edge and a second edge located on both sides of the first region along the width direction of the positive electrode sheet, and a third edge located on one side of the first region along the length direction of the positive electrode sheet. A spacing distance is provided between the first area and the first edge and / or the second edge; and / or, A spacing distance is set between the first area and the third edge.

[0015] According to some embodiments of the present invention, along the width direction of the positive electrode sheet, the width of the gap between the tab connection area and the first region is: 0<w1≤10mm; and / or, Along the width direction of the positive electrode sheet, the distance between the first region and the first edge and / or the second edge is: 2mm≤w2≤20mm; and / or, Along the length direction of the positive electrode sheet, the distance between the first region and the third edge is: 0<A≤20mm.

[0016] According to some embodiments of the present invention, a thickness h4 of the safety coating at the vertex region of the convex portion and a thickness h3 of the safety coating at the straight portion satisfy: h4 / 2<h3.

[0017] In some embodiments, the active material layer includes active material particles, and at least a portion of the active material particles located in the protrusions of the active material layer are embedded in the safety coating layer.

[0018] According to some embodiments of the present invention, a plurality of texture structures are disposed on the current collector, and the texture structures include a second protrusion located on a first surface of the current collector and a second groove located on a second surface of the current collector.

[0019] According to some embodiments of the present invention, the distribution density x of the second protrusions and the distribution density y of the first protrusions satisfy: 1.2≤x / y≤10.

[0020] According to some embodiments of the present invention, a height h1 of the second protrusion and a thickness h2 of the current collector satisfy: 0.08≤h1 / h2≤0.8.

[0021] According to some embodiments of the present invention, the depth h5 of the second groove and the thickness h3 of the straight portion satisfy: 0.45≤h3 / h5≤6.

[0022] According to some embodiments of the present invention, the ratio of the depth h5 of the second groove to the particle size of the safety coating is in the range of 20-5000.

[0023] In some embodiments, the safety coating includes at least one of lithium iron phosphate, aluminum oxide, boehmite, lithium vanadium phosphate, magnesium oxide, silicon oxide, and calcium oxide.

[0024] In a second aspect, the present invention provides a battery cell, comprising: a negative electrode sheet; a separator; and a positive electrode sheet as described in any one of the above items, wherein the positive electrode sheet, the separator and the negative electrode sheet are stacked and then wound to form a wound battery cell.

[0025] The battery cell of the present invention, by using the above-mentioned positive electrode sheet, can improve the infiltration ability of the electrolyte while taking into account the safety of use, reduce the impedance of the battery cell, and improve the rate performance of the battery cell.

[0026] In a third aspect, the present invention provides a battery comprising the above-mentioned battery cell.

[0027] The battery of the present invention, because of using the above-mentioned battery core, has a higher rate performance and a faster battery charging rate, which is beneficial to improving user satisfaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] 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.

[0029] Figure 1 This is one of the structural schematic diagrams of the positive electrode sheet according to an embodiment of the present invention; Figure 2 This is the second structural schematic diagram of the positive electrode sheet of an embodiment of the present invention; Figure 3 A cross-sectional view of a first protrusion and a first depression of a positive electrode sheet according to an embodiment of the present invention; Figure 4 Schematic diagram of the structure of a battery cell according to an embodiment of the present invention.

[0030] Description of reference numerals: 100- positive electrode; 110 - current collector; 110a - first surface; 110b - second surface; 111 - single-sided coating area; 112 - pole ear connection area; 113a - first edge; 113b - second edge; 113c - third edge; 115 - texture structure; 120 - coating layer; 120a - first coating layer; 120b - second coating layer; 121 - safety coating layer; 121a - raised portion; 121b - straight portion; 122 - active material layer; 131 - first depression; 132 - first protrusion; 140-1st area; 200-battery cells; 210-negative electrode sheet; 220-diaphragm. DETAILED DESCRIPTION

[0031] 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.

[0032] Traditional lithium-ion batteries have the problem of poor heat resistance of the positive electrode, which reduces the high-temperature cycle performance of the battery. By applying a layer of safety coating between the positive electrode active layer and the current collector, the safety performance of the battery when damaged by external forces can be significantly improved, such as needle puncture safety, to prevent safety problems caused by fire and explosion of the battery cell.

[0033] However, compared with the positive electrode active layer, the safety coating has poor electrical and ion conductivity. After using the safety coating, the impedance and polarization on the positive electrode side increase, affecting the rate performance of the battery cell.

[0034] In view of this, the present invention provides a positive electrode sheet, a battery cell and a battery, which can improve the wetting ability of the electrolyte, reduce the impedance in the battery cell, and improve the rate performance of the battery cell.

[0035] refer to Figures 1 to 4 In a first aspect, an embodiment of the present invention provides a positive electrode sheet 100 , and the positive electrode sheet 100 may include: a current collector 110 and a coating 120 .

[0036] The current collector 110 has good conductivity to ensure that electrons are effectively transferred to the external circuit. Optionally, the positive electrode sheet 100 can be used as a positive electrode sheet. In this case, the current collector 110 can be a positive electrode current collector, the coating 120 is a positive electrode coating, and the current collector 110 can include a first surface 110a and a second surface 110b opposite to each other along the thickness direction.

[0037] In this embodiment, aluminum foil is generally used as the current collector 110 , which has good conductivity and low cost. The current collector 110 provides physical support and an attachment surface for the coating 120 .

[0038] The coating 120 may include: a safety coating 121 and an active material layer 122. The safety coating 121 has the effect of enhancing the safety performance of the battery. The active material layer 122 may include materials such as lithium cobalt oxide (LiCoO2), lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide (NCA) and lithium iron phosphate (LiFePO4). The active layer realizes the charging and discharging process of the battery by embedding and de-embedding lithium ions. During charging, lithium ions are de-embedded from the positive electrode active material layer (i.e., the above-mentioned active material layer 122) and move to the negative electrode active material layer through the electrolyte; during discharge, lithium ions return from the negative electrode active material layer to the positive electrode. Among them, the safety coating 121 is coated on the surface of the current collector 110, and the active material layer 122 is located on the surface of the safety coating 121 away from the current collector 110. Exemplarily, the coating 120 on the positive electrode sheet 100 can be arranged in such a manner that: a safety coating 121 is coated on one side (one of the first surface 110a and the second surface 110b) of the current collector 110 along the thickness direction, and the active material layer 122 is coated on the safety coating 121; or, both sides (the first surface 110a and the second surface 110b) of the current collector 110 along the thickness direction are coated with the safety coating 121, and the active material layer 122 is coated on the safety coating 121.

[0039] The positive electrode sheet is provided with a first area 140, and the first surface 110a and the second surface 110b of the current collector 110 in the first area 140 are both provided with a safety coating 121 and an active material layer 122; a plurality of first protrusions 132 and first recesses 131 corresponding to the first protrusions 132 are provided in the first area 140, and the first protrusions 132 are formed by the safety coating 121 and the active material layer 122 on the first surface 110a protruding toward the second surface 110b.

[0040] By providing the first region 140, the bonding force between the coating 120 and the current collector 110 in the first region 140 can be improved, thereby reducing the risk of the coating 120 falling off and increasing the cycle stability of the battery. At the same time, the first protrusion 132 and the first depression 131 are limited to be in a specific first region 140 on the positive electrode sheet 100, which simplifies the complexity of the manufacturing process, helps to reduce the processing steps, and thus improves production efficiency.

[0041] It can be understood that when the first depression 131 and the first protrusion 132 are formed, the corresponding positions on the safety coating are formed with convex parts and concave parts matching the first protrusion 132 and the first depression 131. This makes the safety coating 121 have a good bonding effect with the positive electrode sheet 100. Furthermore, the safety coating and the active material layer are convex toward the second surface 110b, that is, the safety coating and the active material layer are bent, thereby changing the overall geometric shape of the positive electrode sheet, increasing the contact area between the active material layer and the electrolyte, and then reducing the interface impedance during the lithium ion transmission process, forming a more favorable lithium ion conduction path, and reducing the migration resistance of lithium ions in the active material layer.

[0042] The safety coating may include a straight portion 121b located outside the convex portion, the convex portion 121a corresponds to the convex portion on the safety coating 121, the straight portion 121b corresponds to the outer portion of the convex portion of the safety coating 121, and the thickness of the vertex region of the convex portion 121a is less than the thickness of the safety coating located at the straight portion 121b. In other words, on the one hand, the transmission path between the positive electrode sheet and the negative electrode sheet in the convex region can be further reduced, and at the same time, the thinning of the safety coating means the thinning of the portion with poor conductivity, thereby reducing the overall transmission impedance of the electrons and improving the overall conductivity of the electrode sheet.

[0043] The positive electrode sheet 100 of the present invention is provided with a safety coating 121 between the current collector 110 and the active material layer 122. When the battery using the positive electrode sheet 100 is damaged by external force such as needle puncture, causing the current collector 110 to contact the negative electrode sheet 210, the safety coating 121 can prevent heat conduction between the positive and negative electrode sheets and inhibit electrical conduction, thereby improving safety.

[0044] The first protrusion 132 on one side of the positive electrode sheet 100 can provide support for the contact of the diaphragm 220, so that there is a certain support between the positive electrode sheet 100-diaphragm 220-negative electrode sheet 210, and the micro-spacing between the positive electrode sheet 100 and the diaphragm 220 is increased. These micro-spacings form a space that can accommodate the electrolyte, so that the electrolyte has sufficient infiltration amount for the positive electrode sheet 100, avoiding the insufficient electrolyte between the electrode sheet and the diaphragm 220 due to the interlayer extrusion of the electrode sheet, poor infiltration and even abnormal lithium deposition of the negative electrode sheet 210.

[0045] Moreover, the safety coating 121 and the active material layer 122 both form a convex portion corresponding to the first convex portion 132, which can shorten the distance between the convex region and the negative electrode sheet, that is, shorten the transmission path of lithium ions in the thickness direction, improve the transmission efficiency of lithium ions, and help reduce the concentration difference of lithium ions on the two side surfaces of the electrode sheet, thereby weakening the polarization phenomenon and improving the dynamics on the positive electrode side.

[0046] The first depression 131 on the other side of the positive electrode sheet 100 can form a liquid storage tank for accommodating electrolyte, which can not only increase the electrolyte capacity and improve the electrolyte infiltration ability; moreover, compared with the position where no depression is formed in the prior art, the liquid storage tank formed at this position greatly reduces the transmission impedance of lithium ions (because the transmission impedance of lithium ions in the electrolyte is much smaller than the transmission impedance in the active layer), and the higher the electrolyte content at this position, the lower the transmission impedance of lithium ions. It is also beneficial to reduce the polarization caused by electrolyte loss during the long-term cycle of the battery, and has the effect of improving the battery rate performance.

[0047] In addition, the thickness of the vertex area of ​​the raised portion of the safety coating 121 is smaller than the thickness of the straight portion. On the one hand, it can further reduce the lithium ion transmission path between the positive electrode sheet and the negative electrode sheet in the raised portion area. At the same time, the thinning of the safety coating means thinning the part with poor conductivity, thereby reducing the overall transmission impedance of electrons and improving the overall conductivity of the electrode sheet.

[0048] refer to Figure 3 In some embodiments, the current collector 110, the safety coating 121 and the active material layer 122 all form convex and concave parts that match the first convexity 132 and the first concave 131. That is, when the first convexity 132 and the first concave 131 are processed on the positive electrode sheet 100, the current collector 110, the safety coating 121 and the active material layer 122 are deformed synchronously, and the convexity and concave parts that match the first convexity 132 and the first concave 131 are formed. In this way, the integrity of the positive electrode sheet 100 is good, and the overall deformation ability of the positive electrode sheet is stronger, which means that its tensile and deformation resistance are improved; the current collector 110, the safety coating 121 and the active material layer 122 can maintain a stable fit to shorten the lithium ion transmission path as much as possible, improve the transmission efficiency, and thus improve the battery performance.

[0049] In some embodiments, the projection of the first protrusion 132 in the reference plane is in the shape of any one of a circle, an ellipse, a line, a wave, a polygon, and a capsule, wherein the reference plane is parallel to the first surface 110a. For example, the first protrusion 132 may be a circle, or an ellipse, or a line, or a wave, or a polygon (such as a triangle, a prism, or a trapezoid, etc.), or the first protrusion 132 may also be a capsule. Of course, the present invention is not limited to this, and the shape of the first protrusion 132 may be reasonably selected within the above range as needed. The shape of the first depression 131 is adapted to the shape of the first protrusion 132. In this way, by selecting a suitable shape of the first protrusion 132, it is beneficial to increase the contact area between the active material layer 122 and the electrolyte, thereby improving the electrochemical performance of the battery. On the other hand, it is also convenient for processing, which is beneficial to reducing processing costs.

[0050] Optionally, the first depression 131 and the first protrusion 132 of the present embodiment may be formed by pressing by a processing device, the processing device may include a workbench and a pressing part, the pressing part is provided with a template of one of the above shapes at one end facing the workbench, the positive electrode sheet 100 coated with the coating 120 is placed on the workbench, the pressing part moves toward the workbench, and the first depression 131 and the first protrusion 132 are pressed on the positive electrode sheet 100. Of course, the first depression 131 and the first protrusion 132 may also be formed by roll pressing.

[0051] refer to Figures 1 to 3 According to some embodiments of the present invention, the coating 120 on the first surface 110a is the first coating layer 120a, and the coating 120 on the second surface 110b is the second coating layer 120b. Along the length direction of the positive electrode sheet 100, the length of the first coating layer 120a is greater than the length of the second coating layer 120b. The area of ​​the positive electrode sheet 100 where the first coating layer 120a exceeds the second coating layer 120b constitutes a single-sided coating area 111, and the first area 140 is spaced apart from the single-sided coating area 111, i.e., they are staggered.

[0052] It can be understood that when the positive electrode sheet 100 of the present embodiment is used for a wound battery cell, the winding starting end or the winding end of the positive electrode sheet 100 will usually constitute the innermost circle or the outermost circle of the wound battery cell. At this time, the portion of the positive electrode sheet 100 that constitutes the innermost circle or the outermost circle of the wound battery cell has only one side opposite to the other positive electrode sheet of opposite polarity. In order to improve the utilization rate of the internal space of the battery, only one side of the positive electrode sheet 100 that is opposite to the other positive electrode sheet is the single-sided coating area 111. In other words, the single-sided coating area 111 of the present embodiment can serve as the winding starting end or the winding end of the positive electrode sheet 100 in the winding process.

[0053] The single-sided coating area 111 is provided with an active material layer 122 only on one side of the current collector 110. Processing the first depression 131 and the first protrusion 132 on the single-sided coating area 111 easily leads to uneven force on both sides of the current collector 110, thereby causing the single-sided coating area 111 to fall off or a fracture at the junction of the single-sided coating area 111 and the area where both sides of the positive electrode current collector 110 have the positive electrode coating 120. There is a spacing distance between the first area 140 and the single-sided coating area 111, thereby improving the use safety of the positive electrode sheet 100.

[0054] The positive electrode sheet 100 may include a tab connection area 112, and the tab connection area 112 exposes the current collector, that is, the coating 120 is not provided in the tab connection area 112. The positive electrode sheet 100 may also be provided with a tab, and the tab is connected to the current collector 110 in the tab connection area. Exemplarily, the tab and the current collector 110 may be connected by welding.

[0055] It can be understood that when the positive electrode sheet 100 has only one pole lug, only one pole lug connection area 112 can be set; when the positive electrode sheet 100 is provided with multiple pole lugs, multiple pole lug connection areas 112 corresponding to the pole lugs can be provided. In this case, the multiple pole lug connection areas 112 can be distributed at intervals from each other, or only one pole lug connection area 112 can be provided. In this case, the pole lug connection area 112 extends along the edge of the current collector 110 so that multiple pole lugs can be arranged in the pole lug connection area 112.

[0056] Since the tab connection area 112 needs to be connected to the tab by welding, the tab connection area 112 is not coated with the coating 120 to ensure the connection stability between the positive electrode sheet 100 and the tab. In this way, in order to prevent the tab from fracturing the current collector in the tab connection area after the tab connection area 112 is compressed, the first area 140 is set at a distance from the tab connection area 112, that is, staggered, that is, the first recess 131 and the first protrusion 132 are not processed in the tab connection area 112, thereby improving the structural stability of the positive electrode sheet 100.

[0057] refer to Figure 2 , the positive electrode sheet 100 may also include a first edge 113a and a second edge 113b located on both sides of the first region 140 along the width direction of the positive electrode sheet 100, and a third edge 113c located on one side of the first region along the length direction of the positive electrode sheet, and a spacing distance is set between the first region 140 and the first edge 113a and the second edge 113b. In another embodiment, a spacing distance is also set between the first region 140 and the third edge 113c. The first region 140 is located in the region near the middle of the positive electrode sheet 100, and the first depression 131 and the first protrusion 132 are processed away from the edge of the positive electrode sheet 100. In this way, on the one hand, it is conducive to improving the bonding force between the coating 120 and the current collector 110, and on the other hand, it is avoided that the edge of the positive electrode sheet 100 is compressed to cause the coating 120 at the edge to fall off, resulting in the risk of reduced capacity of the battery cell 200 and dust piercing the diaphragm for short circuit.

[0058] refer to Figure 2, according to some embodiments of the present invention, the width of the gap between the tab connection area 112 and the first area 140 is: 0<w1≤10mm; for example, w1 can be 0.1mm, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 5mm, 5.5mm, d6mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm or 10mm, so that the first area 140 is kept away from the tab connection area 112, so as to avoid damage to the tab connection area 112 caused by processing the first recess 131 and the first protrusion 132 in the tab connection area 112. Of course, w1 can also be other values, which can be selected by those skilled in the art according to needs, and this embodiment does not limit this.

[0059] Along the width direction of the positive electrode sheet 100, the distance between the first region 140 and the first edge 113a and the second edge 113b is: 2mm≤w2≤20mm; for example, w2 can be 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm or 20mm. Of course, w2 can also be other values, and those skilled in the art can choose according to needs, and this embodiment does not limit this. On the one hand, it is prevented that the width of the first edge 113a and the second edge 113b is too small (such as less than 2mm), so that the range of the first region 140 is too large, resulting in powder falling off the edge of the positive electrode sheet 100. On the other hand, it is prevented that the range of the second edge 113b is too large (such as more than 20mm), so that the range of the first region 140 is too small, resulting in the first depression 131. The effect of increasing the infiltration ability of the electrolyte is reduced.

[0060] Along the length direction of the positive electrode sheet 100, the distance between the first region 140 and the third edge 113c is: 0<A≤20mm; for example, the value of A can be 0.1mm, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm or 20mm. Of course, A can also be other values, and those skilled in the art can choose according to needs, and this embodiment is not limited to this. In this way, on the one hand, it is avoided that the first region 140 extends to the edge of the positive electrode sheet 100 and causes powder to fall off. On the other hand, the distance between the first region 140 and the third edge 113c is too large (such as more than 20mm), which makes the range of the first region 140 too small, resulting in the first depression 131. The effect of increasing the wetting ability of the electrolyte is reduced.

[0061] refer to Figure 3 According to some embodiments of the present invention, the thickness h4 of the safety coating at the vertex area of ​​the convex part and the thickness h3 of the safety coating at the straight part 121b satisfy: h4 / 2<h3. In this way, on the one hand, it is beneficial to increase the difference between the thickness of the convex part 121a and the thickness of the straight part 121b, which is beneficial to thinning the thickness of the safety coating 121 at the convex part 121a, further reducing the lithium ion transmission path between the positive electrode sheet and the negative electrode sheet in the convex area, and at the same time, the thinning of the safety coating means thinning the part with poor conductivity, thereby reducing the overall transmission impedance of electrons and improving the overall conductivity of the electrode sheet.

[0062] In some embodiments, the active material layer 122 includes active material particles, and at least part of the active material particles located at the protrusion of the active material layer 122 are embedded in the safety coating 121. It can be understood that in the embossing process of processing the first protrusion 132, under the extrusion of the embossing die, the number of active material particles at the protrusion of the active material layer 122 embedded in the safety coating 121 will increase, and the depth of embedding in the safety coating 121 will be further deepened, forming a co-embedded area of ​​the active material layer 122 and the safety coating 121.

[0063] In the co-embedded region, the active material particles have a stronger conductivity than the particles of the safety coating 121, which is beneficial to improving the ion conductivity of the co-embedded region, reducing impedance, and thus improving the rate performance of the battery. On the other hand, by forming a co-embedded region, the thickness of the region of the pure safety coating becomes thinner, further reducing the impact of the low conductivity of the safety coating on lithium ion transmission, which is also beneficial to improving the rate performance of the battery.

[0064] refer to Figure 3According to some embodiments of the present invention, a plurality of texture structures 115 are provided on the current collector 110. Exemplarily, the texture structure 115 can be formed by embossing the current collector 110. The texture structure 115 includes a second protrusion located on the first surface 110a of the current collector 110 and a second groove located on the second surface 110b of the current collector 110. The first protrusion 132 of the positive electrode sheet 100 of the present invention can be formed by extrusion of a processing device after the positive electrode coating 120 is coated on the positive electrode current collector 110. The texture structure 115 can be formed by processing the current collector 110 before coating the coating 120. The texture structure 115 on the current collector 110 is conducive to increasing the surface roughness of the current collector 110, thereby increasing the bonding force between the safety coating 121 and the current collector 110, preventing the coating 120 from falling off the current collector 110, and thus improving the structural stability of the positive electrode sheet 100. At the same time, processing the texture structure 115 on the current collector 110 can also improve the flexibility and ductility of the current collector 110, avoid stress concentration, improve the structural strength of the current collector 110, and avoid the current collector 110 from being broken when processing the first recess 131 and the first protrusion 132 on the positive electrode sheet 100.

[0065] Optionally, the coverage area of ​​the texture structure 115 on the current collector 110 at least exceeds the first area 140 to ensure the adhesion effect of the coating 120 on the positive electrode sheet 100 on the current collector 110 .

[0066] It can be understood that in order to avoid the texture structure 115 on the current collector 110 from being compressed and deformed when processing the first depression 131 and the first protrusion 132, resulting in a gap between the coating 120 and the protrusion of the texture structure 115, the first protrusion 132 of the positive electrode sheet 100 can correspond to the protrusion on the current collector 110. In other words, in the process of forming the texture structure 115 on the current collector 110 and processing the first depression 131 and the first protrusion 132 on the positive electrode sheet 100, the direction of the force applied to the current collector 110 is the same. In addition, the shape of the texture structure 115 can also match the shape of the first depression 131 and the first protrusion 132 to improve the adhesion between the coating 120 and the current collector 110.

[0067] According to some embodiments of the present invention, the distribution density x of the second protrusions and the distribution density y of the first protrusions 132 satisfy: 1.2≤x / y≤10. For example, the value of x / y may be 1.2, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5 or 10. Of course, x / y may also be other values, and those skilled in the art may select them according to their needs, and this embodiment does not limit this. In this way, in order to ensure that the distribution density of the second protrusions exceeds the distribution density of the first protrusions 132, the surface roughness of the current collector 110 is increased, thereby increasing the bonding force between the safety coating 121 and the current collector 110, preventing the coating 120 from falling off the current collector 110, and improving the structural stability of the positive electrode sheet 100.

[0068] refer to Figure 1 and Figure 3 According to some embodiments of the present invention, the height h1 of the second protrusion and the thickness h2 of the current collector 110 satisfy: 0.08≤h1 / h2≤0.8. For example, h1 / h2 can be 0.08, 0.1, 0.15, 0.2, 0.25, 0.3, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75 or 0.8. Of course, h1 / h2 can also be other values, and those skilled in the art can choose according to needs, and this embodiment does not limit this. In this way, on the one hand, it is avoided that the height of the second protrusion of the texture structure 115 is too low, which cannot increase the surface roughness of the current collector 110 and improve the flexibility of the current collector 110. On the other hand, in order to prevent the height of the second protrusion of the texture structure 115 from being too high, when processing the first depression 131 and the first protrusion 132 on the positive electrode sheet 100, due to the need to perform secondary embossing on the current collector, if the height of the texture structure is too high, the tensile strength of the current collector 110 will be reduced. When the first depression and the first protrusion are formed, the stress on the current collector will be too great, which may cause the current collector 110 to break.

[0069] refer to Figure 3According to some embodiments of the present invention, the depth h5 of the second groove and the thickness h3 of the straight portion 121b satisfy: 0.45≤h3 / h5≤6. For example, the value of h3 / h5 can be 0.45, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5 or 6. Of course, h3 / h5 can also be other values, and those skilled in the art can select them according to needs, and this embodiment does not limit this. In this way, the depth of the second groove of the texture structure 115 of the current collector 110 has a suitable size. In the process of processing the first depression 131 and the first protrusion 132 of the positive electrode sheet 100, it is beneficial to make the current collector 110, the safety coating 121 and the active material layer 122 deform synchronously to avoid destroying the integrity of the positive electrode sheet 100. If the ratio is too large, it means that the depth of the groove formed by the bending of the current collector is too large, and the safety coating on the surface is prone to cracking and powdering, thereby making the safety coating ineffective and reducing the safety performance of the battery cell.

[0070] Optionally, the second groove depth h5 may be equal to the second protrusion height h1 , which simplifies the processing of the texture structure 115 and facilitates forming the texture structure 115 on the current collector 110 by one extrusion.

[0071] According to some embodiments of the present invention, the ratio of the depth h5 of the second groove to the particle size of the safety coating 121 ranges from 20 to 5000. For example, the ratio of the depth h5 of the second groove to the particle size of the safety coating 121 may be 20, 100, 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500 or 5000. Of course, the ratio of the depth h5 of the second groove to the particle size of the safety coating 121 may also be other values, and those skilled in the art may select them according to needs, and this embodiment does not limit this.

[0072] The greater the depth of the second groove, the higher the protrusion height of the protrusion point of the second protrusion. When the particle size of the safety coating 121 is larger, it means that the specific surface area of ​​the safety coating is smaller. Then, when the convex portion of the safety coating increases with the height of the second protrusion, the greater the possibility that the current collector 110 will be exposed after the particles of the safety coating 121 crack. The smaller the particle size, the greater the specific surface area of ​​the particle size of the safety coating 121, and the smaller the possibility that the current collector 110 will be exposed after the particles of the safety coating 121 crack. By limiting the ratio of the depth h5 of the second groove to the particle size of the safety coating 121 to a value range of 20-5000, it is ensured that the cracks between the particles of the safety coating 121 will not expose the current collector 110, thereby improving the safety of the battery.

[0073] Optionally, the particle size of the material of the safety coating 121 may be 20 nm-1000 nm, and the depth h5 of the second groove may be 1 μm-5 μm. In this way, it is convenient to select materials for production.

[0074] In some embodiments, the safety coating 121 includes at least one of lithium iron phosphate, aluminum oxide, boehmite, lithium vanadium phosphate, magnesium oxide, silicon oxide, and calcium oxide. For example, the material of the safety coating 121 may include one of the above materials, or the safety coating 121 may also include a combination of any of the above materials.

[0075] Among them, lithium iron phosphate is a stable battery material with good thermal stability and chemical stability. Lithium iron phosphate can improve the safety of the battery and reduce the risk of thermal runaway. Aluminum oxide has excellent thermal stability and chemical corrosion resistance, can prevent the battery from overheating, and provide a certain mechanical strength for the battery. Boehmite is a hydrated aluminum oxide that can enhance the stability of the safety coating 121 and provide additional mechanical support for the positive electrode sheet 100 at high temperatures. Lithium vanadium phosphate has high conductivity and good cycle stability, can improve the electrochemical performance of the battery, and enhance the safety of the positive electrode sheet 100 to a certain extent. Magnesium oxide has good thermal stability and insulation properties, and can be used as a fireproof material to help suppress thermal runaway inside the battery. Silicon oxide can improve the chemical resistance and mechanical strength of the safety coating 121 and prevent electrolyte leakage. Calcium oxide is stable at high temperatures and can provide additional thermal protection for the positive electrode sheet 100.

[0076] Thus, by using the above materials to form the safety coating 121, the safety coating 121 has good thermal stability, can maintain structural integrity under high temperature conditions, and avoid thermal runaway of the battery. At the same time, even in the case of needle puncture, the safety coating 121 can provide support and protection for the positive electrode sheet 100, reduce the explosion and combustion of the battery due to external stimulation, and improve the safety of the battery.

[0077] refer to Figure 4 In the second aspect, an embodiment of the present invention provides a battery cell 200, comprising: a negative electrode sheet 210, a separator 220 and the above-mentioned positive electrode sheet 100, wherein the above-mentioned positive electrode sheet is used as a positive electrode sheet, and the positive electrode sheet, the separator 220 and the negative electrode sheet 210 are stacked and wound to form a wound battery cell.

[0078] The battery cell 200 of the present invention can be arranged with the positive electrode sheet 100 and the negative electrode sheet 210 staggered in the length direction during winding. The positive electrode sheet and the negative electrode sheet 210 are separated by the separator 220. The starting end of the winding is located at the negative electrode sheet 210. The negative electrode sheet 210 is wound to form the innermost circle of the battery cell 200, and then the positive electrode sheet, the separator 220 and the negative electrode sheet 210 are wound together. In this way, the single-sided coated area of ​​the positive electrode sheet constitutes the outermost circle of the battery cell 200, and the winding end of the positive electrode sheet is an empty foil area, which is fixed to the outermost circle of the battery cell 200 by fixing glue.

[0079] The battery cell 200 of the present invention uses the above-mentioned positive electrode sheet 100 , which not only takes into account the safety of use, but also improves the infiltration ability of the electrolyte, reduces the impedance of the battery cell 200 , and improves the rate performance of the battery cell 200 .

[0080] In the third aspect, the embodiment of the present invention provides a battery, which can be a primary battery or a secondary battery. A primary battery refers to a battery that cannot be recharged and reused after the battery is discharged, and a secondary battery refers to a battery that can be recharged to activate the active material and continue to be used after the battery is discharged. According to the classification of the electrochemical composition in the battery, the battery can be a lithium-ion battery, a sodium-ion battery, a sodium-lithium-ion battery, a lithium metal battery, a sodium metal battery, a lithium-sulfur battery, a magnesium-ion battery, a nickel-cadmium battery, etc.; according to the classification of the battery shape, the battery can be a square shell battery, a cylindrical battery, etc.; according to the classification of the battery shell, the battery can be a steel shell battery, a soft pack battery, etc., and the embodiment of the present application does not limit this.

[0081] The battery may include a housing and the above-mentioned battery cell 200. A receiving cavity may be provided inside the housing, and the battery cell 200 may be provided in the receiving cavity.

[0082] The battery of the present invention uses the battery core 200, so the battery has a higher rate performance and a faster battery charging rate, which is beneficial to improving user satisfaction.

[0083] In a fourth aspect, an embodiment of the present invention further provides an electrical device, comprising the above-mentioned battery and a device body. The device body may include a battery compartment, in which the battery is disposed and electrically connected to the device body, for example, a power supply interface may be provided in the battery compartment, and the battery may be connected to the power supply interface.

[0084] It can be understood that the electrical device of the present application can be mobile electronic devices, power tools, smart home devices, electric vehicles and electric bicycles, drones, medical equipment, photographic equipment, outdoor equipment, wireless headphones and Bluetooth speakers, energy storage systems and other equipment, using the above-mentioned batteries as a power source to power the electrical devices.

[0085] The electrical equipment of the present invention uses the above-mentioned battery, so the battery has a higher rate performance, which is beneficial to improving the working efficiency of the electrical equipment.

[0086] Below, multiple embodiments are provided to illustrate the battery made of the positive electrode sheet 100 of the present invention.

[0087] Embodiment 1: Step 1: Roll emboss the current collector 110 with a thickness h2 of 8 μm to form a texture structure 115 on the current collector 110. The height h1 of the second protrusion of the texture structure 115 is 3 μm. A portion of the positive electrode current collector 110 is observed under a 3D profile microscope, and the distribution density x of the second protrusion is 100. Step 2: prepare a slurry of the safety coating 121 , and coat the slurry on the positive electrode current collector 110 by gravure coating, and obtain the positive electrode current collector 110 with the safety coating 121 after drying.

[0088] The preparation method of the safety coating 121 provided in this embodiment is as follows: a primer material with a particle size of 100 nm is mixed evenly with an organic polymer styrene-butadiene rubber (SBR), a conductive agent carbon black and carbon nanotubes, and then a certain amount of adhesive polyimide copolymer glue and NMP are added and stirred evenly to obtain a positive electrode protective layer slurry. Among them, the mass fraction of SBR is 88%, the mass fraction of polyacrylic acid copolymer is 6%, the mass fraction of the conductive agent is 6%, and the thickness of the safety coating 121 is 5 μm.

[0089] Step 3: Preparation of positive electrode sheet 100: Mix (lithium cobalt oxide + Li2NiO2), SP, and PVDF in a mass ratio of 97.6 (the weight of Li2NiO2 accounts for 1% of the weight of LCO): 1.4:1, add NMP, stir evenly, and prepare a positive electrode active material slurry; apply the positive electrode active material slurry on both surfaces of the positive electrode collector 110 with a safety coating 121, and after baking and rolling, obtain a positive electrode sheet 100 with a thickness of 85μm.

[0090] The positive electrode sheet 100 is embossed with a roller, and the shape of the obtained first protrusion 132 is circular. A part of the positive electrode sheet 100 is cut off, and the distribution density y of the first protrusion 132 is recorded under a 3D profile microscope as 50, the thickness h4 of the protruding portion 121a of the safety coating 121 is 8μm, and the thickness h3 of the straight portion 121b is 10μm; the range of the first area A=2mm, the width of the single-sided coating area is 108mm, w1=2mm, w2=8mm.

[0091] Step 4: The silicon-carbon-doped negative electrode active material is mixed with SP, CMC-Li, and PAA in a mass ratio of 97 (the weight of silicon and carbon accounts for 5% of the weight of graphite): 0.4:0.1:2.5, and deionized water is added to prepare a negative electrode active material slurry; the negative electrode active material slurry is coated on the front and back surfaces of the carbon-coated copper foil, and after baking and rolling, a negative electrode sheet 210 with a thickness of 90 μm is obtained. A certain position of the negative electrode sheet 210 has a groove of fixed size, and the copper-plated nickel tab is welded in this groove by laser or ultrasonic welding.

[0092] Step 5: After being cut and sliced, the positive electrode sheet 100 and the negative electrode sheet 210 are wound with the separator 220 to obtain a winding core.

[0093] Step 6: After packaging, baking, liquid injection, formation, secondary sealing, sorting and OCV, the lithium-ion battery is obtained.

[0094] The electrolyte is a commercially available conventional electrolyte, and the lithium salt therein is LiFP6.

[0095] Comparative Example 1 is different from Example 1 in that it does not have a safety coating; Embodiment 2 is different from Embodiment 1 in that the particle size of the safety coating is 20 nm, and the height of the second protrusion of the texture structure is 3 μm.

[0096] Example 3 is different from Example 1 in that the particle size of the safety coating is 20 nm and it has no texture structure, and is set as Comparative Example 2.

[0097] Embodiment 4 is different from Embodiment 1 in that the particle size of the safety coating is 1000 nm, and the height of the second protrusion of the texture structure is 5 μm.

[0098] Example 5 is different from Example 1 in that the particle size of the safety coating is 1000 nm, and the height of the second protrusion of the texture structure is 6 μm.

[0099] Embodiment 6 is different from Embodiment 1 in that the height of the second protrusion in the texture area is 6 μm, and the thickness of the positive electrode current collector is 6 μm.

[0100] Embodiment 7 is different from Embodiment 1 in that the height of the second protrusion in the textured area is 6 μm, the thickness of the straight portion is 2 μm, and the thickness of the protrusion is 1.5 μm.

[0101] Embodiment 8 is different from Embodiment 1 in that the height of the second protrusions in the textured area is 1 μm, and the thickness of the straight portion is 7 μm.

[0102] Embodiment 9 is different from Embodiment 1 in that the distribution density of the second protrusions is 50.

[0103] Embodiment 10 is different from Embodiment 1 in that the distribution density of the second protrusions is 200, and the distribution density of the first protrusions is 20.

[0104] Example 11, which differs from Example 1 in that it does not have the first depression and the first protrusion, is used as Comparative Example 3.

[0105] Among them, the test methods of various parameters include: Distribution density of the first protrusions: After discharging the fresh battery to 0% SOC, disassemble and take out the positive electrode sheet, cut off part of the positive electrode sheet 100, cut off the part with coating 120 on both sides of the positive electrode sheet 100, the cutting length is 50 cm, the cutting width is 40 cm, record the number of first protrusions under a 3D profile microscope, and then calculate the distribution density y of the first protrusions, then soak this part of the positive electrode sheet 100 in NMP solvent for 12 hours, and then use non-woven fabric to gently wipe off the surface positive electrode coating 120, record the number of texture structures under a 3D profile microscope, and calculate the distribution density x of the second protrusions; Height of the second protrusion of the texture structure: Use CP or cross-section or glue molding to detect the height of the second protrusion of the texture structure.

[0106] 5C rate discharge retention rate: keep in a 25℃ constant temperature room or thermostat for 2H, use 0.2C constant current and constant voltage to the upper limit voltage, cut off current 0.02C, let it stand for 5min and then discharge at 0.2C to 3.0V, cycle 3T, take the maximum capacity of 3 discharges as the initial capacity C0 of the battery, then use 0.2C constant current and constant voltage to the upper limit voltage, cut off current 0.02C, let it stand for 5min and then discharge at 5C constant current to 3.0V, record the discharge capacity C1, where C1 / C0 is the 5C rate discharge retention rate of the battery; Needle puncture pass rate: before needling, perform 5 normal temperature cycles (charge to the upper limit voltage with 0.5C, cut off with 0.02C, discharge to 3.0V with 0.5C), and complete the needling test within 2 days after the cycle. The battery cell is fully charged with 0.5C, CV 0.02C, and the test is carried out within 24 hours; use a long conical angle steel needle with a diameter of 4mm, a cone length of 15mm, a taper of 15 degrees, and a total length of 100mm to pass through the left, center and right positions of the battery cell (the coding side faces down and the deep pit side faces up). The left and right needling positions are 7.5mm±2.5mm away from the edge, the needle speed is 30mm / s, and the nail is left in the battery. When the temperature drops to 20% of the peak temperature, remove the steel nail and stop the test. Test 5pcs of battery cells at each position, and the battery cell is judged to pass if it does not catch fire or explode.

[0107] Table 1. Parameters of positive electrode sheets of various embodiments and comparative examples

[0108] Table 2. Battery performance test results of various embodiments and comparative examples

[0109] Combining Examples 1, 2, 3, 4 and Comparative Example 1, it can be seen that the safety coating can increase the needle penetration rate of the battery and improve the safety of the battery. The height of the second protrusion of the texture structure reflects the surface roughness of the safety coating. The surface roughness of the safety coating should match the particle size of the safety coating to avoid the product of the particle size of the safety coating and the height of the second protrusion being too large or too small, causing the safety coating particles to fall off or the safety coating to crack, resulting in reduced safety performance of the battery.

[0110] In combination with Examples 1, 2, and 3, if the height of the second protrusions of the texture structure is small, the surface roughness of the current collector will be small, which may easily cause the adhesion between the safety coating and the active material layer to fall off.

[0111] In combination with Examples 1, 4, and 5, if the height of the second protrusion of the texture structure is too large, the surface roughness of the safety coating will be too large. When used in combination with safety coating particles having a larger particle size, the safety coating will be prone to cracking, resulting in the current collector being exposed.

[0112] In combination with Examples 1 and 6, if the height of the second protrusion of the texture structure is too large and the thickness of the positive electrode current collector is small, it will cause uneven force on the current collector and the current collector is at risk of breaking.

[0113] In combination with Examples 1 and 7, if the thickness of the safety coating is insufficient, the positive electrode impedance can be reduced to a certain extent and the battery rate performance can be improved, but the safety of the battery is reduced.

[0114] In combination with Examples 1 and 8, if the height of the second protrusion of the texture structure is too low, the surface roughness of the safety coating may be reduced, which may easily cause the adhesion between the safety coating and the active material layer to fall off, thereby reducing the safety of the battery.

[0115] In combination with Examples 1, 2, 9, 10 and 11, the presence or absence of a texture structure is an important indicator for measuring battery safety, but the correlation between the texture structure and the rate performance of the battery is relatively small. The distribution density of the first protrusions and the first depressions has little effect on the rate performance of the battery, but the presence or absence of the first protrusions and the first depressions has an important influence on the rate performance of the battery.

[0116] It should be noted that the embodiments represented by "one embodiment", "an embodiment", "an exemplary embodiment", "some embodiments", etc. mentioned in the specification may include specific features, structures or characteristics, but not every embodiment may include the specific features, structures or characteristics. In addition, such phrases do not necessarily refer to the same embodiment. In addition, when describing specific 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 that are explicitly or not explicitly described.

[0117] 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" or "" may also be understood to convey singular usage or to convey plural usage, depending, at least in part, on the context.

[0118] 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).

[0119] 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.

[0120] 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 positive electrode sheet, characterized in that: include: a current collector, the current collector comprising a first surface and a second surface opposite to each other in a thickness direction; A coating, comprising: a safety coating and an active material layer, wherein the safety coating is located on the surface of the current collector, and the active material layer is located on the surface of the safety coating away from the current collector; The positive electrode sheet is provided with a first region, and the first surface and the second surface of the current collector in the first region are both provided with a safety coating and an active material layer; A plurality of first protrusions and first depressions corresponding to the first protrusions are provided in the first region, wherein the first protrusions are formed by the safety coating and the active material layer on the first surface protruding toward the second surface; The safety coating forms a convex portion and a concave portion matching the first convex portion and the first concave portion; The safety coating further comprises a straight portion located outside the convex portion, and the thickness of the safety coating at the vertex region of the convex portion is smaller than the thickness of the safety coating at the straight portion.

2. The positive electrode sheet according to claim 1, characterized in that: The current collector, the safety coating layer, and the active material layer all form convex portions and concave portions that match the first convex portions and the first concave portions.

3. The positive electrode sheet according to claim 1, characterized in that: The projection of the first protrusion on the reference surface is in any one of a circular, elliptical, linear, wavy, polygonal, and capsule shape. The reference surface is parallel to the first surface.

4. The positive electrode sheet according to claim 3, characterized in that: The coating on the first surface is a first coating layer, and the coating on the second surface is a second coating layer, Along the length direction of the positive electrode sheet, the length of the first coating layer is greater than the length of the second coating layer, the positive electrode sheet area of ​​the first coating layer exceeding the second coating layer constitutes a single-sided coating area, and there is a spacing distance between the first area and the single-sided coating area; and / or, The positive electrode sheet comprises a tab connection area, the tab connection area exposes the current collector, the positive electrode sheet is further provided with a tab, the tab is connected to the current collector in the tab connection area, there is a spacing distance between the first region and the tab connection area, and / or, The positive electrode sheet includes a first edge and a second edge located on both sides of the first region along the width direction of the positive electrode sheet, and a third edge located on one side of the first region along the length direction of the positive electrode sheet. A spacing distance is provided between the first area and the first edge and / or the second edge; and / or, A spacing distance is set between the first area and the third edge.

5. The positive electrode sheet according to claim 4, characterized in that: Along the width direction of the positive electrode sheet, the width of the gap between the tab connection area and the first region is: 0<w1≤10mm; and / or, Along the width direction of the positive electrode sheet, the distance between the first region and the first edge and / or the second edge is: 2mm≤w2≤20mm; and / or, Along the length direction of the positive electrode sheet, the distance between the first region and the third edge is: 0<A≤20mm.

6. The positive electrode sheet according to claim 1, characterized in that: The thickness h4 of the safety coating at the vertex area of ​​the convex portion and the thickness h3 of the safety coating at the straight portion satisfy: h4 / 2<h3.

7. The positive electrode sheet according to claim 1, characterized in that: The active material layer includes active material particles, and at least a portion of the active material particles located at the protrusions of the active material layer are embedded in the safety coating layer.

8. The positive electrode sheet according to any one of claims 1 to 7, characterized in that: The current collector is provided with a plurality of texture structures, wherein the texture structures include a second protrusion located on a first surface of the current collector and a second groove located on a second surface of the current collector.

9. The positive electrode sheet according to claim 8, characterized in that: The distribution density x of the second protrusions and the distribution density y of the first protrusions satisfy: 1.2≤x / y≤10.

10. The positive electrode sheet according to claim 8, characterized in that: A height h1 of the second protrusion and a thickness h2 of the current collector satisfy: 0.08≤h1 / h2≤0.

8.

11. The positive electrode sheet according to claim 8, characterized in that: The depth h5 of the second groove and the thickness h3 of the straight portion satisfy: 0.45≤h3 / h5≤6.

12. The positive electrode sheet according to claim 8, characterized in that: The ratio of the depth h5 of the second groove to the particle size of the safety coating is in the range of 20-5000.

13. The positive electrode sheet according to any one of claims 1 to 7, characterized in that: The safety coating includes at least one of lithium iron phosphate, aluminum oxide, boehmite, lithium vanadium phosphate, magnesium oxide, silicon oxide and calcium oxide.

14. A battery cell, characterized in that: include: Negative electrode; Diaphragm; The positive electrode sheet according to any one of claims 1 to 13, wherein the positive electrode sheet, the separator and the negative electrode sheet are stacked and then wound to form a wound battery cell.

15. A battery, characterized in that: Comprising the battery cell as claimed in claim 14.

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