Positive electrode sheet, battery cell, and battery

Abstract

The application provides a positive electrode sheet, a battery cell and a battery. The positive electrode sheet comprises: a current collector; the current collector comprises a first surface and a second surface opposite to each other in the thickness direction; a coating layer, comprising: a safety coating layer and an active material layer, wherein the safety coating layer is located on the surface of the current collector, and the active material layer is located on the surface of the safety coating layer 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 the safety coating layer and the active material layer; a plurality of first protrusions and first recesses corresponding to the first protrusions are arranged in the first region, and the first protrusions are formed by the safety coating layer and the active material layer on the first surface protruding towards the second surface; the safety coating layer forms protruding parts and recessed parts matched with the first protrusions and the first recesses; and the safety coating layer further comprises a flat part outside the protruding parts, and the thickness of the vertex region of the protruding parts of the safety coating layer is smaller than the thickness of the flat part of the safety coating layer. The positive electrode sheet can reduce impedance and weaken polarization.

Description

[0001] This application is a divisional application. The original application, application number 202411732188.9, was filed on November 29, 2024. The entire contents of the original application are incorporated herein by reference. Technical Field

[0002] This invention relates to the field of batteries, and more particularly to a positive electrode, a battery cell, and a battery. Background Technology

[0003] Lithium-ion batteries have been widely used in energy storage systems for hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, and electric vehicles. Due to the significant advancements in lithium-ion battery technology, higher requirements have been placed on their energy density, cycle performance, and safety performance.

[0004] When traditional lithium-ion batteries are damaged by external forces, such as being punctured by a needle, the debris from the positive electrode current collector is usually made of aluminum. This debris comes into direct contact with the negative electrode active material layer, generating intense heat and causing the battery to catch fire and explode. By coating the surface of the positive electrode current collector with a safety coating, direct contact between it and the negative electrode active material can be prevented, significantly improving the battery's safety performance when damaged by external forces.

[0005] However, compared to the positive electrode active layer, the safety coating material has poor conductivity. After using the safety coating, the positive electrode side impedance increases and polarization increases, which affects the rate performance of the cell. Summary of the Invention

[0006] In view of the above problems, the present invention provides a positive electrode, a battery cell, and a battery, which can improve the wetting ability of the electrolyte, reduce the impedance within the battery cell, and improve the rate performance of the battery cell.

[0007] In a first aspect, the present invention provides a positive electrode sheet, comprising: a current collector; the current collector including a first surface and a second surface opposite to each other along the thickness direction; a coating including: 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 opposite to the current collector; the positive electrode sheet is provided with a first region, wherein the first surface and the second surface of the current collector in the first region are both provided with the safety coating and the active material layer; the first region is provided with a plurality of first protrusions and first recesses corresponding to the first protrusions, the first protrusions being formed by the safety coating and the active material layer on the first surface protruding toward the second surface; the safety coating forming convex portions and recesses matching the first protrusions and the first recesses; the safety coating further includes a flat portion located outside the convex portion, the thickness of the safety coating at the apex region of the convex portion being less than the thickness of the safety coating at the flat portion.

[0008] The positive electrode of the present invention has a first protrusion that provides support for the contact with the separator, so that there is a certain support between the positive electrode, the separator and the negative electrode, increasing the micro-spacing between the electrode and the separator. These micro-spacings form a space that can accommodate the electrolyte, so that the electrolyte has sufficient wetting amount on the electrode, avoiding the occurrence of insufficient electrolyte between the electrode and the separator, poor wetting or even abnormal lithium plating on the negative electrode caused by interlayer compression of the electrode.

[0009] Furthermore, both the safety coating and the active material layer form protrusions corresponding to the first protrusion, which can shorten the lithium ion transport path in this region, improve the lithium ion transport efficiency, and help reduce the concentration difference of lithium ions on both sides of the electrode, thereby weakening the polarization phenomenon.

[0010] The first recess on the other side of the positive electrode can form a reservoir for electrolyte, which not only increases the electrolyte capacity and improves the electrolyte wetting ability, but also significantly reduces the lithium-ion transport impedance compared to the location without a recess in the prior art (because the lithium-ion transport impedance in the electrolyte is much lower than that in the active layer). The higher the electrolyte content at this location, the lower the lithium-ion transport impedance. It also helps reduce polarization caused by electrolyte loss during long-term battery cycling, thus improving the battery's rate performance.

[0011] In addition, the thickness of the apex region of the convex part of the safety coating is less than that of the flat part. On the one hand, this can further reduce the lithium-ion transport path between the positive and negative electrodes in the convex region. On the other hand, the thinning of the safety coating means thinning of the part with poor conductivity, thereby reducing the overall electron transport impedance and improving the overall conductivity of the electrode.

[0012] In some embodiments, the current collector, the safety coating, and the active material layer are all formed with protrusions and recesses adapted to the first protrusion and the first recess.

[0013] In some embodiments, the current collector includes a first surface and a second surface opposite to each other along the thickness direction, both the first surface and the second surface being provided with the coating, wherein the side of the active material layer of the first surface away from the current collector constitutes the first surface, and the side of the active material layer of the second surface away from the current collector constitutes the second surface.

[0014] In some embodiments, the shape of the projection of the first protrusion onto the reference surface is any one of a circle, an ellipse, a line, a wave, a polygon, or a capsule, and the reference surface is parallel to the first surface.

[0015] 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.

[0016] Along the length of the positive electrode sheet, the length of the first coating layer is greater than the length of the second coating layer, and the region of the first coating layer extending beyond the second coating layer on the positive electrode sheet constitutes a single-sided coating area, with a gap between the first region and the single-sided coating area; and / or,

[0017] The positive electrode includes a tab connection region that exposes the current collector. The positive electrode also has a tab connected to the current collector in the tab connection region. There is a gap between the first region and the tab connection region, and / or...

[0018] The positive electrode includes a first edge and a second edge located on both sides of the first region along the width direction of the positive electrode, and a third edge located on one side of the first region along the length direction of the positive electrode.

[0019] A spacing distance is provided between the first region and the first edge and / or the second edge; and / or,

[0020] A gap is provided between the first region and the third edge.

[0021] 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 ≤ 10 mm; and / or,

[0022] 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,

[0023] Along the length of the positive electrode sheet, the distance between the first region and the third edge is: 0 < A ≤ 20 mm.

[0024] In some embodiments, the active material layer includes active material particles, and at least a portion of the active material particles located on the protrusions of the active material layer are embedded in the safety coating.

[0025] According to some embodiments of the present invention, the current collector is provided with a plurality of texture structures, the texture structures including 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.

[0026] According to some embodiments of the present invention, the distribution density x of the second protrusion and the distribution density y of the first protrusion satisfy: 1.2≤x / y≤10.

[0027] According to some embodiments of the present invention, the height h1 of the second protrusion and the thickness h2 of the current collector satisfy: 0.08≤h1 / h2≤0.8.

[0028] 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.

[0029] 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 ranges from 20 to 5000.

[0030] In some embodiments, the safety coating comprises at least one of lithium iron phosphate, alumina, boehmite, lithium vanadium phosphate, magnesium oxide, silicon oxide, and calcium oxide.

[0031] 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 embodiments, wherein the positive electrode sheet, the separator, and the negative electrode sheet are stacked and arranged in a stacked manner and then wound to form a wound battery cell.

[0032] The battery cell of the present invention, by using the above-mentioned positive electrode, not only ensures safety in use, but also improves the wetting ability of the electrolyte, reduces the impedance of the battery cell, and enhances the rate performance of the battery cell.

[0033] Thirdly, the present invention provides a battery comprising the aforementioned battery cell.

[0034] The battery of the present invention, due to the use of the above-mentioned battery cell, has higher rate performance and faster charging speed, which is beneficial to improving user satisfaction. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is one of the structural schematic diagrams of the positive electrode sheet according to an embodiment of the present invention;

[0037] Figure 2 This is a second schematic diagram of the positive electrode sheet according to an embodiment of the present invention;

[0038] Figure 3 This is a cross-sectional view of the first protrusion and the first recess of the positive electrode sheet according to an embodiment of the present invention;

[0039] Figure 4This is a schematic diagram of the battery cell structure according to an embodiment of the present invention.

[0040] Explanation of reference numerals in the attached figures:

[0041] 100-Positive electrode plate;

[0042] 110 - Current collector; 110a - First surface; 110b - Second surface; 111 - Single-sided coating area; 112 - Tab connection area; 113a - First edge; 113b - Second edge; 113c - Third edge; 115 - Texture structure;

[0043] 120 - Coating; 120a - First coating layer; 120b - Second coating layer; 121 - Safety coating; 121a - Raised portion; 121b - Flat portion; 122 - Active material layer;

[0044] 131 - First depression; 132 - First protrusion;

[0045] 140 - First Zone;

[0046] 200-cell;

[0047] 210 - Negative electrode; 220 - Separator. Detailed Implementation

[0048] To make the above-mentioned objectives, features, and advantages of the embodiments of this application more apparent and understandable, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0049] Traditional lithium-ion batteries suffer from poor heat resistance of the positive electrode, which reduces the battery's high-temperature cycle performance. However, by coating a safety coating between the positive electrode active layer and the current collector, the battery's safety performance when subjected to external forces can be significantly improved, such as its resistance to puncture, thus preventing the cell from catching fire or exploding and causing safety issues.

[0050] However, compared to the positive electrode active layer, the safety coating has poor conductivity and ion conduction capabilities. After using the safety coating, the impedance on the positive electrode side increases and the polarization increases, which affects the rate performance of the battery cell.

[0051] In view of this, the present invention provides a positive electrode, a battery cell, and a battery that can improve the wetting ability of the electrolyte, reduce the impedance within the battery cell, and improve the rate performance of the battery cell.

[0052] refer to Figures 1 to 4In a first aspect, embodiments of the present invention provide a positive electrode 100, which may include a current collector 110 and a coating 120.

[0053] The current collector 110 has good conductivity to ensure that electrons are effectively transferred to the external circuit. Optionally, the positive electrode 100 can be used as the positive electrode, in which case the current collector 110 can be the positive current collector, and the coating 120 is the positive electrode coating. The current collector 110 may include a first surface 110a and a second surface 110b that are opposite each other along the thickness direction.

[0054] In this embodiment, aluminum foil is typically used as the current collector 110, which offers good conductivity at a low cost. The current collector 110 provides physical support and an adhesion surface for the coating 120.

[0055] The coating 120 may include a safety coating 121 and an active material layer 122. The safety coating 121 enhances the battery's safety performance, and the active material layer 122 may include lithium cobalt oxide (…). Lithium nickel cobalt manganese oxide () Lithium nickel cobalt aluminum oxide () ) and lithium iron phosphate ( The battery uses materials such as lithium ions (122) to perform charging and discharging processes through the insertion and extraction of lithium ions. During charging, lithium ions are extracted from the positive electrode active material layer (i.e., the active material layer 122 mentioned above) and move to the negative electrode active material layer through the electrolyte; during discharging, lithium ions return from the negative electrode active material layer to the positive electrode. A 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 facing away from the current collector 110. For example, the coating 120 on the positive electrode sheet 100 can be configured such that: the safety coating 121 is coated on one side of the current collector 110 along the thickness direction (one of the first surface 110a and the second surface 110b), and the active material layer 122 is coated on the safety coating 121; or, the safety coating 121 is coated on both sides of the current collector 110 along the thickness direction (the first surface 110a and the second surface 110b), and the active material layer 122 is coated on the safety coating 121.

[0056] The positive electrode is provided with a first region 140. The first surface 110a and the second surface 110b of the current collector 110 of the first region 140 are both provided with a safety coating 121 and an active material layer 122. The first region 140 is provided with a plurality of first protrusions 132 and first recesses 131 corresponding to the first protrusions 132. The first protrusions 132 are formed by the safety coating 121 and the active material layer 122 of the first surface 110a protruding toward the second surface 110b.

[0057] By setting the first region 140, the adhesion between the coating 120 and the current collector 110 within the first region 140 can be improved, thereby reducing the risk of coating 120 peeling off and increasing the cycle stability of the battery. At the same time, defining the first protrusion 132 and the first recess 131 on the positive electrode 100 in the specific first region 140 simplifies the complexity of the manufacturing process, helps to reduce processing steps, and thus improves production efficiency.

[0058] Understandably, when forming the first recess 131 and the first protrusion 132, corresponding protrusions and recesses matching the first protrusion 132 and the first recess 131 are formed on the safety coating. This ensures good adhesion between the safety coating 121 and the positive electrode 100. Furthermore, the safety coating and the active material layer protrude towards the second surface 110b, i.e., the safety coating and the active material layer are bent, thereby changing the overall geometry of the positive electrode, increasing the contact area between the active material layer and the electrolyte, and thus reducing the interfacial resistance during lithium-ion transport, forming a more favorable lithium-ion conduction path, and reducing the migration resistance of lithium ions in the active material layer.

[0059] The safety coating may include a flat portion 121b located outside the protrusion, a protrusion 121a corresponding to the protrusion on the safety coating 121, and a flat portion 121b corresponding to the outer portion of the protrusion on the safety coating 121. The thickness of the vertex region of the protrusion 121a is less than the thickness of the safety coating located in the flat portion 121b. In other words, on the one hand, the transmission path between the positive and negative electrodes in the protrusion region can be further reduced; on the other hand, the thinning of the safety coating means thinning of the less conductive portion, thereby reducing the overall electron transport impedance and improving the overall conductivity of the electrode.

[0060] The positive electrode 100 of the present invention has a safety coating 121 between the current collector 110 and the active material layer 122. When the battery using the positive electrode 100 is damaged by external force such as a needle puncture, causing the current collector 110 to come into contact with the negative electrode 210, the safety coating 121 can prevent heat conduction between the positive and negative electrodes and suppress conductivity, thereby improving safety.

[0061] The first protrusion 132 on one side of the positive electrode 100 can provide support for the contact of the separator 220, so that there is a certain support between the positive electrode 100, the separator 220 and the negative electrode 210, increasing the micro-spacing between the positive electrode 100 and the separator 220. These micro-spacings form a space that can accommodate the electrolyte, so that the electrolyte has sufficient wetting amount on the positive electrode 100, avoiding the occurrence of insufficient electrolyte between the electrode and the separator 220, poor wetting or even abnormal lithium plating on the negative electrode 210 due to interlayer compression of the electrode.

[0062] Furthermore, both the safety coating 121 and the active material layer 122 form protrusions corresponding to the first protrusion 132, which can shorten the distance between the protrusion area and the negative electrode, that is, shorten the lithium ion transport path in the thickness direction, improve the lithium ion transport efficiency, and help reduce the concentration difference of lithium ions on both sides of the electrode, thereby weakening the polarization phenomenon and improving the dynamics on the positive electrode side.

[0063] The first recess 131 on the other side of the positive electrode 100 can form a reservoir for containing electrolyte. This not only increases the electrolyte capacity and improves the electrolyte wetting ability, but also, compared to the location where no recess is formed in the prior art, the reservoir formed at this location significantly reduces the lithium-ion transport impedance (because the lithium-ion transport impedance in the electrolyte is much lower than that in the active layer). The higher the electrolyte content at this location, the lower the lithium-ion transport impedance. It also helps to reduce polarization caused by electrolyte loss during long-term battery cycling, thus improving the battery's rate performance.

[0064] In addition, the thickness of the apex region of the protrusion of the safety coating 121 is less than the thickness of the flat region. On the one hand, this can further reduce the lithium-ion transport path between the positive and negative electrodes in the protrusion region. On the other hand, the thinning of the safety coating means thinning of the part with poor conductivity, thereby reducing the overall electron transport impedance and improving the overall conductivity of the electrode.

[0065] refer to Figure 3 In some embodiments, the current collector 110, the safety coating 121, and the active material layer 122 all form protrusions and recesses adapted to the first protrusion 132 and the first recess 131. That is, when the first protrusion 132 and the first recess 131 are processed on the positive electrode sheet 100, the current collector 110, the safety coating 121, and the active material layer 122 deform synchronously, forming protrusions and recesses adapted to the first protrusion 132 and the first recess 131. This results in better overall integrity of the positive electrode sheet 100 and stronger overall deformation capability, meaning improved tensile and deformation resistance; the current collector 110, the safety coating 121, and the active material layer 122 can maintain stable adhesion to shorten the lithium-ion transport path as much as possible, improve transport efficiency, and thus improve battery performance.

[0066] In some embodiments, the projection of the first protrusion 132 onto the reference plane can be any one of a circle, ellipse, line, wave, polygon, or capsule shape, wherein the reference plane is parallel to the first surface 110a. For example, the first protrusion 132 can be circular, or elliptical, or line-shaped, or wave-shaped, or polygonal (such as triangle, rhombus, or trapezoid), or the first protrusion 132 can be capsule-shaped. Of course, the present invention does not limit this, and the shape of the first protrusion 132 can be reasonably selected within the above range as needed. The shape of the first recess 131 is adapted to the shape of the first protrusion 132. Thus, by selecting a suitable shape for 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 also facilitates processing and helps to reduce processing costs.

[0067] Optionally, the first recess 131 and the first protrusion 132 in this embodiment can be formed by pressing with a processing device. The processing device may include a worktable and a pressing section. One end of the pressing section facing the worktable is provided with a template of one of the above-mentioned shapes. The positive electrode sheet 100 after coating 120 is placed on the worktable, and the pressing section moves toward the worktable to press the first recess 131 and the first protrusion 132 onto the positive electrode sheet 100. Of course, the first recess 131 and the first protrusion 132 can also be formed by roll forming.

[0068] refer to Figures 1 to 3 According to some embodiments of the present invention, the coating 120 on the first surface 110a is a first coating layer 120a, and the coating 120 on the second surface 110b is a second coating layer 120b. Along the length direction of the positive electrode 100, the length of the first coating layer 120a is greater than the length of the second coating layer 120b. The positive electrode 100 region of the first coating layer 120a that extends beyond the second coating layer 120b constitutes a single-sided coating region 111. The first region 140 and the single-sided coating region 111 are spaced apart, i.e., staggered.

[0069] Understandably, when the positive electrode 100 in this embodiment is used for a wound cell, the starting end or ending end of the winding of the positive electrode 100 usually constitutes the innermost or outermost ring of the wound cell. At this time, the part of the positive electrode 100 that constitutes the innermost or outermost ring of the wound cell has only one side facing the positive electrode with the opposite polarity. In order to improve the utilization rate of the internal space of the battery, the part of the positive electrode 100 with only one side facing the other positive electrode is a single-sided coating area 111. In other words, the single-sided coating area 111 in this embodiment can be used as the starting end or ending end of the winding of the positive electrode 100 in the winding process.

[0070] The single-sided coating area 111 has an active material layer 122 only on one side of the current collector 110. Processing the first recess 131 and the first protrusion 132 in the single-sided coating area 111 can easily lead to uneven stress on both sides of the current collector 110, resulting in powder shedding from the single-sided coating area 111 or breakage at the boundary between 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. This creates a gap between the first region 140 and the single-sided coating area 111, thereby improving the safety of the positive electrode sheet 100 in use.

[0071] The positive electrode 100 may include a tab connection region 112, which exposes the current collector, i.e., the tab connection region 112 is not coated with a coating 120. The positive electrode 100 may also have a tab connected to the current collector 110 in the tab connection region. For example, the tab and the current collector 110 may be connected by welding.

[0072] Understandably, when the positive electrode 100 has only one tab, only one tab connection area 112 can be provided; when the positive electrode 100 has multiple tabs, multiple tab connection areas 112 corresponding to each tab can be provided. In this case, the multiple tab connection areas 112 can be distributed at intervals, or only one tab connection area 112 can be provided. In this case, the tab connection area 112 extends along the edge of the current collector 110 so that multiple tabs can be arranged in the tab connection area 112.

[0073] Since the tab connection area 112 needs to be welded to the tab, the tab connection area 112 is not coated with the coating 120 to ensure the connection stability between the positive electrode 100 and the tab. Thus, to prevent the tab from cracking the current collector within the tab connection area 112 under pressure, the first region 140 and the tab connection area 112 are spaced apart, i.e., staggered. This means that 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 100.

[0074] refer to Figure 2The positive electrode 100 may further 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 100, and a third edge 113c located on one side of the first region along the length direction of the positive electrode 100. A spacing distance is provided between the first region 140 and the first edge 113a and the second edge 113b. In another embodiment, a spacing distance is also provided between the first region 140 and the third edge 113c. This ensures that the first region 140 is located in the region near the center of the positive electrode 100, avoiding the processing of the first recess 131 and the first protrusion 132 at the edge of the positive electrode 100. This, on the one hand, helps to improve the bonding force between the coating 120 and the current collector 110; on the other hand, it avoids the risk of powder shedding from the coating 120 at the edge of the positive electrode 100 due to pressure, which could lead to a reduction in the capacity of the cell 200 and a short circuit caused by dust puncturing the separator.

[0075] 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 region 140 is: 0 < w1 ≤ 10 mm; for example, w1 can be 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, or 10 mm, so that the first region 140 and the tab connection area 112 maintain a distance, avoiding damage to the tab connection area 112 caused by processing the first recess 131 and the first protrusion 132. Of course, w1 can also be other values, and those skilled in the art can select according to their needs. This embodiment does not limit this.

[0076] Along the width direction of the positive electrode 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 their needs. This embodiment does not limit this. On the one hand, it avoids the width of the first edge 113a and the second edge 113b being too small (e.g., less than 2mm), which would make the first region 140 too large, resulting in powder shedding at the edge of the positive electrode 100. On the other hand, it avoids the second edge 113b being too large (e.g., exceeding 20mm), which would make the first region 140 too small, reducing the effect of the first recess 131 in increasing the wetting ability of the electrolyte.

[0077] Along the length of the positive electrode 100, the distance between the first region 140 and the third edge 113c is: 0 < A ≤ 20 mm; for example, the value of A can be 0.1 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, or 20 mm. Of course, A can also be other values, and those skilled in the art can choose according to their needs. This embodiment does not limit this. In this way, on the one hand, the first region 140 is prevented from extending to the edge of the positive electrode 100, which would cause powder shedding. On the other hand, if the distance between the first region 140 and the third edge 113c is too large (e.g., exceeding 20 mm), the area of ​​the first region 140 becomes too small, resulting in a reduction in the effect of the first recess 131 in increasing the wetting ability of the electrolyte.

[0078] refer to Figure 3 According to some embodiments of the present invention, the thickness h4 of the safety coating at the apex region of the protrusion and the thickness h3 of the safety coating at the flat region 121b satisfy: h4 / 2 < h3. This, on the one hand, helps to increase the difference between the thickness of the protrusion 121a and the thickness of the flat region 121b, which facilitates a reduction in the thickness of the safety coating 121 at the protrusion 121a, further reducing the lithium-ion transport path between the positive and negative electrodes in the protrusion region. Simultaneously, the thinning of the safety coating means thinning the portion with poor conductivity, thereby reducing the overall electron transport impedance and improving the overall conductivity of the electrode.

[0079] In some embodiments, the active material layer 122 includes active material particles, and at least a portion of the active material particles located on the protrusions of the active material layer 122 are embedded in the safety coating 121. Understandably, during the embossing process of processing the first protrusion 132, under the pressure of the embossing die, the number of active material particles on the protrusions of the active material layer 122 embedded in the safety coating 121 increases, and the depth of embedding in the safety coating 121 further increases, forming a co-embedded region of the active material layer 122 and the safety coating 121.

[0080] Within the co-intercalation region, the active material particles exhibit stronger conductivity compared to the safety coating 121 particles, which enhances the ion conduction capability of the co-intercalation region, reduces impedance, and thus improves the battery's rate performance. Furthermore, by forming the co-intercalation region, the thickness of the pure safety coating becomes thinner, further reducing the impact of the safety coating's low conductivity on lithium-ion transport, which also contributes to improving the battery's rate performance.

[0081] refer to Figure 3According to some embodiments of the present invention, the current collector 110 is provided with a plurality of textured structures 115. Exemplarily, the textured structures 115 can be formed by embossing the current collector 110. The textured 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 using a processing device after coating the positive electrode coating 120 onto the positive electrode current collector 110. The textured structure 115 can be formed by processing the current collector 110 before coating the coating 120. The textured structure 115 on the current collector 110 helps to increase the surface roughness of the current collector 110, thereby increasing the adhesion 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. Meanwhile, processing the textured 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 prevent the current collector 110 from breaking when processing the first depression 131 and the first protrusion 132 on the positive electrode 100.

[0082] Optionally, the coverage area of ​​the textured structure 115 on the current collector 110 extends at least beyond the first region 140 to ensure the adhesion of the coating 120 on the positive electrode 100 to the current collector 110.

[0083] Understandably, to avoid deformation of the textured structure 115 on the current collector 110 during the processing of the first recess 131 and the first protrusion 132, which could lead to gaps between the coating 120 and the protrusions of the textured structure 115, the first protrusion 132 of the positive electrode 100 can correspond to the protrusion on the current collector 110. In other words, the direction of the force applied to the current collector 110 is the same during the formation of the textured structure 115 on the current collector 110 and the processing of the first recess 131 and the first protrusion 132 on the positive electrode 100. Furthermore, the shape of the textured structure 115 can also match the shape of the first recess 131 and the first protrusion 132 to improve the adhesion between the coating 120 and the current collector 110.

[0084] According to some embodiments of the present invention, the distribution density x of the second protrusion and the distribution density y of the first protrusion 132 satisfy: 1.2 ≤ x / y ≤ 10. For example, the value of x / y can 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 can also be other values, and those skilled in the art can select them according to their needs; this embodiment does not limit this. In this way, the distribution density of the second protrusion exceeds the distribution density of the first protrusion 132, increasing the surface roughness of the current collector 110, thereby increasing the adhesion 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 100.

[0085] 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 the condition: 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 select them according to their needs; this embodiment does not limit this. In this way, on the one hand, the height of the second protrusion of the textured structure 115 is avoided from being too low, so as to avoid failing to increase the surface roughness of the current collector 110 and improve the flexibility of the current collector 110. On the other hand, to avoid the second protrusion of the textured structure 115 being too high, when processing the first depression 131 and the first protrusion 132 in the positive electrode 100, due to the need for secondary embossing of the current collector, if the height of the textured structure is too high, the tensile strength of the current collector 110 will decrease. At that time, 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.

[0086] 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 the condition: 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, which can be selected by those skilled in the art according to their 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. During the processing of the first recess 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, so as to avoid damaging the integrity of the positive electrode sheet 100. If the ratio is too large, it means that the groove depth formed by the bending of the current collector is too large, and the surface safety coating is prone to cracking and powdering, thereby causing the safety coating to fail and reducing the safety performance of the cell.

[0087] Optionally, the depth h5 of the second groove can be equal to the height h1 of the second protrusion, which simplifies the processing of the texture structure 115 and facilitates the formation of the texture structure 115 on the current collector 110 by a single extrusion.

[0088] 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 can 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 can also be other values, and those skilled in the art can select them according to their needs. This embodiment does not limit this.

[0089] The greater the depth of the second groove, the higher the height of the second protrusion's starting point. When the particle size of the safety coating 121 is larger, the specific surface area of ​​the safety coating is smaller. Therefore, as the height of the second protrusion increases, the likelihood of the current collector 110 being exposed after the particles of the safety coating 121 break apart. Conversely, the smaller the particle size, the larger the specific surface area of ​​the safety coating 121, and the lower the likelihood of the current collector 110 being exposed after the particles of the safety coating 121 break apart. By limiting the ratio of the depth h5 of the second groove to the particle size of the safety coating 121 to a range of 20-5000, it is ensured that the current collector 110 will not be exposed even if the particles of the safety coating 121 break apart, thus improving battery safety.

[0090] Optionally, the particle size of the safety coating 121 can be 20nm-1000nm, and the depth h5 of the second groove can be 1μm-5μm. This facilitates material selection for production.

[0091] In some embodiments, the safety coating 121 includes at least one selected from lithium iron phosphate, alumina, 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.

[0092] Lithium iron phosphate (LFP) is a stable battery material with good thermal and chemical stability. LFP can improve battery safety and reduce the risk of thermal runaway. Alumina has excellent thermal stability and chemical corrosion resistance, preventing battery overheating and providing a certain degree of mechanical strength. Boehmite, a hydrated alumina, can enhance the stability of the safety coating 121 and provide additional mechanical support for the positive electrode 100 at high temperatures. Lithium vanadium phosphate has high conductivity and good cycle stability, improving the electrochemical performance of the battery and enhancing the safety of the positive electrode 100 to some extent. Magnesium oxide has good thermal stability and insulation properties, serving as a fire-retardant material and helping to suppress internal thermal runaway. 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 100.

[0093] Thus, by using the aforementioned materials to form the safety coating 121, the safety coating 121 possesses excellent thermal stability, maintaining structural integrity under high-temperature conditions and preventing thermal runaway of the battery. Simultaneously, even under conditions such as needle penetration, the safety coating 121 provides support and protection for the positive electrode 100, reducing the likelihood of the battery exploding or burning due to external stimuli, thereby improving the safety of battery use.

[0094] refer to Figure 4 Secondly, embodiments of the present invention provide a battery cell 200, comprising: a negative electrode 210, a separator 220 and the aforementioned positive electrode 100, wherein the aforementioned positive electrode serves as the positive electrode, and the positive electrode, separator 220 and negative electrode 210 are stacked and arranged and then wound to form a wound battery cell.

[0095] When the battery cell 200 of the present invention is wound, the positive electrode 100 and the negative electrode 210 can be arranged staggered along the length direction. The positive electrode 100 and the negative electrode 210 are separated by a separator 220. The winding start end is located at the negative electrode 210. The negative electrode 210 is wound to form the innermost ring of the battery cell 200. Then the positive electrode 100, the separator 220 and the negative electrode 210 are wound together. In this way, the single-sided coating area of ​​the positive electrode 100 constitutes the outermost ring of the battery cell 200. The winding end of the positive electrode 100 is an empty foil area. The empty foil area is fixed to the outermost ring of the battery cell 200 by a fixing adhesive.

[0096] The battery cell 200 of the present invention, by using the above-mentioned positive electrode 100, not only ensures safety in use, but also improves the wetting ability of the electrolyte, reduces the impedance of the battery cell 200, and enhances the rate performance of the battery cell 200.

[0097] Thirdly, embodiments of the present invention provide a battery, which can be a primary battery or a secondary battery. A primary battery is a battery that cannot be recharged and reused after discharge, while a secondary battery is a battery that can be recharged to activate the active materials and continue to be used after discharge. According to the electrochemical composition, the battery can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-cadmium battery, etc.; according to the battery shape, the battery can be a prismatic battery, cylindrical battery, etc.; according to the battery casing, the battery can be a steel-cased battery, pouch battery, etc., but the embodiments of this application are not limited in this respect.

[0098] The battery may include a casing and the aforementioned battery cell 200. The casing may have an inner cavity, and the battery cell 200 may be disposed within the cavity.

[0099] The battery of the present invention, due to the use of the aforementioned cell 200, has higher rate performance and faster charging speed, which is beneficial to improving user satisfaction.

[0100] Fourthly, embodiments of the present invention also provide an electrical device, including the aforementioned battery and 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, the battery compartment may be provided with a power supply interface, and the battery may be connected to the power supply interface.

[0101] Understandably, the electrical device of this application may be a mobile electronic device, power tool, smart home device, electric vehicle and electric bicycle, drone, medical device, photography equipment, outdoor equipment, wireless headphones and Bluetooth speaker, and energy storage system, etc., which uses the aforementioned battery as a power source to power the electrical device.

[0102] The electrical equipment of the present invention, due to the use of the aforementioned battery, has a higher rate capability, which is beneficial to improving the working efficiency of the electrical equipment.

[0103] The following provides several embodiments illustrating a battery made from the positive electrode 100 of the present invention.

[0104] Example 1:

[0105] Step 1: The current collector 110 with a thickness h2 of 8μm is embossed by a roller to form a texture structure 115 on the current collector 110. The height h1 of the second protrusion of the texture structure 115 is 3μm. A portion of the positive current collector 110 is cut off and observed under a 3D contour microscope. The distribution density x of the second protrusion is 100.

[0106] Step 2: Prepare the slurry for the safety coating 121, and coat the slurry onto the positive current collector 110 by gravure printing. After drying, the positive current collector 110 with the safety coating 121 is obtained.

[0107] The preparation method of the safety coating 121 provided in this embodiment is as follows: A safety coating material with a particle size of 100 nm is mixed uniformly with the organic polymer styrene-butadiene rubber (SBR), the conductive agent carbon black, and carbon nanotubes. Then, a certain amount of the binder polyimide copolymer solution and NMP are added and stirred uniformly to obtain the positive electrode protective layer slurry. 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.

[0108] Step 3: Preparation of positive electrode 100: Mix (lithium cobalt oxide + Li2NiO2), SP, and PVDF at a mass ratio of 97.6 (Li2NiO2 accounts for 1% of the weight of LCO): 1.4:1, add NMP, stir evenly, and prepare a positive electrode active material slurry; coat the positive electrode active material slurry on the two surfaces of the positive electrode current collector 110 with a safety coating 121, and after baking and rolling, obtain a positive electrode 100 with a thickness of 85μm.

[0109] The positive electrode sheet 100 is embossed by a roller, and the resulting first protrusion 132 is circular. A portion of the positive electrode sheet 100 is cut off, and the distribution density y of the first protrusion 132 is recorded as 50 under a 3D contour microscope. The thickness h4 of the protrusion 121a of the safety coating 121 is 4μm, and the thickness h3 of the flat part 121b is 5μm. The range of the first region A is 2mm, the width of the single-sided coating area is 108mm, w1=2mm, and w2=8mm.

[0110] Step 4: Mix the silicon-carbon-doped negative electrode active material with SP, CMC-Li, and PAA at a mass ratio of 97 (silicon-carbon weight accounts for 5% of graphite weight): 0.4:0.1:2.5, and add deionized water to prepare a negative electrode active material slurry. Coat the negative electrode active material slurry onto both sides of the carbon-coated copper foil. After baking and rolling, a negative electrode sheet 210 with a thickness of 90μm is obtained. The negative electrode sheet 210 has a groove of a fixed size at a certain position. Copper-plated nickel tabs are welded into this groove by laser or ultrasonic welding.

[0111] Step 5: After the positive electrode 100 and negative electrode 210 are slit and formed, they are wound with the separator 220 to obtain the core.

[0112] Step 6: The lithium-ion battery is obtained through packaging, baking, electrolyte injection, formation, secondary sealing, sorting, and OCV.

[0113] The electrolyte is a commercially available conventional electrolyte, and the lithium salt in it is LiFP6.

[0114] Comparative Example 1 differs from Example 1 in that it does not have a safety coating;

[0115] Example 2 differs from Example 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 1 μm.

[0116] Example 3 differs from Example 1 in that the safety coating has a particle size of 20 nm and does not have a textured structure; it is designated as Comparative Example 2. That is, Example 3 can also be an embodiment of this application where the current collector does not have a textured structure.

[0117] Example 4 differs 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 5 μm.

[0118] Example 5 differs 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.

[0119] Example 6 differs from Example 1 in that the height of the second protrusion in the textured region is 6 μm and the thickness of the positive current collector is 6 μm.

[0120] Example 7 differs from Example 1 in that the height of the second protrusion in the textured area is 5 μm, the thickness of the flat part is 2 μm, and the thickness of the protrusion is 0.75 μm.

[0121] Example 8 differs from Example 1 in that the height of the second protrusion in the textured area is 1 μm and the thickness of the flat portion is 7 μm.

[0122] Example 9 differs from Example 1 in that the distribution density of the second protrusion is 50.

[0123] Example 10 differs from Example 1 in that the distribution density of the second protrusion is 200, while the distribution density of the first protrusion is 20.

[0124] Example 11 differs from Example 1 in that it does not have the first depression and the first protrusion, serving as Comparative Example 3.

[0125] The testing methods for each parameter include:

[0126] Distribution density of the first protrusion: After discharging the fresh battery to 0% SOC, the positive electrode sheet was disassembled and removed. A portion of the positive electrode sheet 100 was cut off, and the part with the coating 120 on both sides of the positive electrode sheet 100 was cut off. The cutting length was 50cm and the cutting width was 40cm. The number of the first protrusions was recorded under a 3D contour microscope, and the distribution density y of the first protrusion was calculated. Then, this part of the positive electrode sheet 100 was soaked in NMP solvent for 12h and the surface positive electrode coating 120 was gently wiped off with a non-woven cloth. The number of texture structures was recorded under a 3D contour microscope, and the distribution density x of the second protrusion was calculated.

[0127] The height of the second protrusion of the texture structure: The height of the second protrusion of the texture structure is detected using CP, section or droplet molding.

[0128] 5C rate discharge retention rate: Keep the battery in a constant temperature room or incubator at 25℃ for 2 hours, use 0.2C constant current and constant voltage to the upper limit voltage, cut off current 0.02C, let stand for 5 minutes, then discharge at 0.2C to 3.0V, cycle 3T, and take the maximum capacity of the 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 stand for 5 minutes, then discharge at 5C constant current to 3.0V, and record the discharge capacity C1. C1 / C0 is the battery 5C rate discharge retention rate.

[0129] Needle penetration pass rate: Before needle penetration, perform 5 cycles at room temperature (charge to the upper limit voltage at 0.5C, cut off at 0.02C, and discharge to 3.0V at 0.5C). The needle penetration test should be completed within 2 days after the cycle. The cell should be fully charged at 0.5C, CV 0.02C, and tested 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 penetrate the cell at three positions: left, center, and right (printed side down, pitted side up). The needle penetration positions on the left and right sides should be 7.5mm ± 2.5mm from the edge. The needle speed should be 30mm / s. The needle should remain inside the battery. The test should be stopped when the temperature drops to 20% of the peak temperature. 5 cells should be tested at each position. A cell that does not catch fire or explode is considered to have passed.

[0130] Table 1. Positive electrode parameters for each embodiment and comparative example.

[0131]

[0132] Table 2. Battery performance test results for each embodiment and comparative example.

[0133]

[0134] As can be seen from Examples 1, 2, 3, and 4 and Comparative Example 1, the safety coating can increase the battery's needle penetration pass rate and improve battery safety. The height of the second protrusion in the textured 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 and the height of the second protrusion being too large or too small, which could cause the safety coating particles to fall off or the safety coating to crack, resulting in a decrease in battery safety performance.

[0135] In conjunction with Examples 1, 2, and 3, if the height of the second protrusion of the textured structure is small, it will result in a small surface roughness of the current collector, which may easily cause the adhesion between the safety coating and the active material layer to fall off.

[0136] In conjunction with Examples 1, 4, and 5, if the height of the second protrusion of the textured structure is too large, the surface roughness of the safety coating will be too large. When combined with safety coating particles with larger particle sizes, the safety coating is prone to cracking, resulting in the current collector being exposed.

[0137] In conjunction with Examples 1 and 6, if the height of the second protrusion of the textured structure is too large and the thickness of the positive current collector is small, it will lead to uneven stress on the current collector, and the current collector may break.

[0138] Combining Examples 1 and 7, if the thickness of the safety coating is insufficient, the positive electrode impedance can be reduced to a certain extent, thereby improving the battery rate performance, but the battery safety will be reduced.

[0139] In conjunction with Examples 1 and 8, if the height of the second protrusion of the textured structure is too low, it may also lead to a decrease in the surface roughness of the safety coating, which may cause the adhesion between the safety coating and the active material layer to fall off, thereby reducing the safety of the battery.

[0140] In conjunction with Examples 1, 2, 9, 10, and 11, the presence or absence of a textured structure is an important indicator of battery safety, but the correlation between textured structure and battery rate performance is relatively weak. The distribution density of the first protrusion and the first depression has little impact on the battery rate performance; however, the presence or absence of the first protrusion and the first depression has a significant impact on the battery rate performance.

[0141] It should be noted that the embodiments referred to in the specification, such as "one embodiment," "embodiment," "exemplary embodiment," and "some embodiments," may include specific features, structures, or characteristics, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Moreover, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments, whether explicitly described or not, is within the knowledge scope of those skilled in the art.

[0142] Generally speaking, terms should be understood at least in part by their use in context. For example, at least in part by context, the term "one or more" as used in the text can be used to describe any feature, structure, or characteristic of the singular meaning, or a combination of features, structures, or characteristics of the plural meaning. Similarly, at least in part by context, terms such as "one" or "" can also be understood to convey either singular or plural usage.

[0143] It should be readily understood that the terms “on,” “above,” and “on top of” in this disclosure should be interpreted in the broadest possible sense, such that “on” means not only “directly on something” but also “on something” with an intermediate feature or layer therebetween, and that “above” or “on top of” means not only “on top of something” but also “on top of something” without an intermediate feature or layer therebetween (i.e., directly on something).

[0144] Furthermore, for ease of explanation, spatially relative terms such as "below," "below," "under," "above," and "above" may be used 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 other than those shown in the figures. The device may have other orientations (rotated 90 degrees or in other orientations), and the spatially relative descriptive terms used herein may be interpreted accordingly.

[0145] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A positive electrode plate, characterized in that, include: A current collector, the current collector comprising a first surface and a second surface opposite each other along the thickness direction; The coating includes 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 opposite to 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. The first region is provided with a plurality of first protrusions and a first recess corresponding to the first protrusions. The first protrusions are formed by the safety coating and active material layer on the first surface protruding toward the second surface. The safety coating forms protrusions and recesses that match the first protrusion and the first recess; The active material layer includes active material particles, and at least a portion of the active material particles located on the protrusions of the active material layer are embedded in the safety coating.

2. The positive electrode sheet according to claim 1, characterized in that, The current collector, the safety coating, and the active material layer all form protrusions and recesses that are adapted to the first protrusion and the first recess.

3. The positive electrode sheet according to claim 1, characterized in that, The shape of the projection of the first protrusion onto the reference plane can be any one of the following: circular, elliptical, linear, wavy, polygonal, or capsule-shaped. The reference plane 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 of the positive electrode sheet, the length of the first coating layer is greater than the length of the second coating layer, and the region of the first coating layer extending beyond the second coating layer on the positive electrode sheet constitutes a single-sided coating area, with a gap between the first region and the single-sided coating area; and / or, The positive electrode includes a tab connection region that exposes the current collector. The positive electrode also has a tab connected to the current collector in the tab connection region. There is a gap between the first region and the tab connection region, and / or... The positive electrode includes a first edge and a second edge located on both sides of the first region along the width direction of the positive electrode, and a third edge located on one side of the first region along the length direction of the positive electrode. A spacing distance is provided between the first region and the first edge and / or the second edge; and / or, A gap is provided between the first region 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 ≤ 10 mm; 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 of the positive electrode sheet, the distance between the first region and the third edge is: 0 < A ≤ 20 mm.

6. The positive electrode sheet according to any one of claims 1-5, characterized in that, The current collector is provided with multiple textured structures, including a second protrusion on the first surface of the current collector and a second groove on the second surface of the current collector.

7. The positive electrode sheet according to claim 6, characterized in that, The distribution density x of the second protrusion and the distribution density y of the first protrusion satisfy: 1.2≤x / y≤10.

8. The positive electrode sheet according to claim 6, characterized in that, The height h1 of the second protrusion and the thickness h2 of the current collector satisfy the following condition: 0.08 ≤ h1 / h2 ≤ 0.

8.

9. The positive electrode sheet according to claim 6, characterized in that, The safety coating also includes a flat portion located outside the protrusion, wherein the depth h5 of the second groove and the thickness h3 of the flat portion satisfy: 0.45≤h3 / h5≤6.

10. The positive electrode sheet according to claim 6, characterized in that, The ratio of the depth h5 of the second groove to the particle size of the safety coating ranges from 20 to 5000.

11. The positive electrode sheet according to any one of claims 1-5, characterized in that, The safety coating includes at least one of lithium iron phosphate, alumina, boehmite, lithium vanadium phosphate, magnesium oxide, silicon oxide, and calcium oxide.

12. A battery cell, characterized in that, include: Negative electrode plate; Diaphragm; The positive electrode sheet according to any one of claims 1-11, wherein the positive electrode sheet, the separator and the negative electrode sheet are stacked and then wound to form a wound battery cell.

13. A battery, characterized in that, Includes the battery cell as described in claim 12.

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