Positive plate and battery cell

Abstract

The invention provides a positive plate and a battery cell, relates to the technical field of batteries, and is used for solving the technical problem of breakage of a pole piece caused by embossing on the pole piece in the related art, the positive plate comprises a current collector, two surfaces of the current collector are respectively provided with a first active material layer and a second active material layer, a plurality of convex parts are arranged on the first active material layer, and a plurality of concave parts corresponding to the convex parts are arranged on the second active material layer; each of the first active material layer and the second active material layer comprises a plurality of active material particles. By limiting the particle size distribution of the active material particles in the active material layer, when the large and small particles in the active material layer are mixed and the convex part and the concave part are processed on the positive plate, the small particles are stressed to slide towards two sides and are filled among the large particles, so that the current collector is prevented from being torn while the particles are prevented from being broken; and meanwhile, the height of the lug boss is ensured to meet a preset requirement.

Description

[0001] This application is a divisional application. The original application has the application number 202411894731.5 and the original application date is December 20, 2024. The entire contents of the original application are incorporated herein by reference. Technical Field

[0002] This application relates to the field of lithium-ion battery technology, and in particular to a positive electrode and a battery cell. Background Technology

[0003] With the rapid development of lithium-ion battery technology, people have higher requirements for the energy density, cycle life, and safety performance of lithium-ion batteries. During the charging and discharging process, the negative electrode of a lithium-ion battery expands, and the interlayer of the electrode is squeezed. This interlayer squeezing leads to insufficient electrolyte and poor wetting, causing rapid capacity decay and hindering lithium-ion transport in electrolyte-deficient areas, which can easily lead to lithium plating and affect the safety of the cell. Summary of the Invention

[0004] In view of the above problems, this application provides a positive electrode sheet and a battery cell to solve the technical problem in the above-mentioned related technologies that insufficient electrolyte between layers and poor wetting will cause rapid capacity decay of the battery.

[0005] To achieve the above objectives, the embodiments of this application provide the following technical solutions:

[0006] This application provides a positive electrode sheet, comprising: a current collector, a first active material layer, and a second active material layer; the current collector has a first surface and a second surface opposite to each other along the thickness direction of the electrode sheet, the first active material layer is disposed on the first surface, and the second active material layer is disposed on the second surface; the first active material layer has a plurality of protrusions, and the second active material layer has a plurality of recesses corresponding to the protrusions; both the first active material layer and the second active material layer include a plurality of active material particles, the active material particles including lithium iron phosphate, lithium manganese iron phosphate, lithium manganese phosphate, and Li. a1 Co x1 M1 k1 O 2、 Li a2 Ni x2 Co y2 D z2 M2 k2At least one of O2, wherein 0.85≤a1≤1.1, 0.85≤a2≤1.1, 0.85≤x1≤1.05, 0.3≤x2≤0.98, 0≤y2≤0.5, 0≤z2≤0.5, 0≤k1≤0.15, 0≤k2≤0.15; D includes at least one of Mn and Al, M1 includes at least one of Al, Mg, Ti, Zr, Y, La, W, B, Nb and Mn, M2 includes at least one of Mg, Ti, Zr, Y, La, W, B, Nb, and the particle size distribution of the active material layer particles satisfies: Dv10:Dv50:Dv90=1:(2~8):(3~16).

[0007] In one embodiment of this application, Dv10 is 2μm~8μm; and / or Dv50 is 11μm~19μm; and / or Dv90 is 22μm~32μm.

[0008] In one embodiment of this application, the protrusion has a first intersection point, which intersects with the plane containing the surface of the first active material layer; in the electrode thickness direction, the first intersection point and the highest protrusion point of the protrusion have a first vertical distance H1, H1=3-40μm; the thickness of the current collector is a first thickness H2, H2=6-20μm; in the electrode thickness direction, both the first active material layer and the second active material layer have a second thickness H3, H3=30-150μm; the first vertical distance H1, the first thickness H2, the second thickness H3 and the second particle size D2 have the following relationship: (H1+Dv50) / (H2+2H3)=0.1~0.8.

[0009] In one embodiment of this application, the tensile strength M of the current collector is ≥50MPa along both the width and length directions of the electrode; and / or, the first vertical distance H1 has the following relationship with the tensile strength M: 0.05≤H1 / M≤0.4.

[0010] In one embodiment of this application, the current collector has a fracture elongation N1, the fracture elongation N1 ≥ 2%; and / or the first vertical distance H1 has the following relationship with the fracture elongation N1: 10 ≤ H1 / N1 ≤ 60.

[0011] In one embodiment of this application, the current collector includes an aluminum foil having an elongation N2 of 0.5% to 2%.

[0012] In one embodiment of this application, the protrusion has an arc-shaped outer surface located in the first active material layer, and the projection of the arc-shaped outer surface in the electrode thickness direction has a first width R1; the recess has an arc-shaped inner surface located in the second active material layer, and the projection of the arc-shaped inner surface in the electrode thickness direction has a second width R2; the first width R1 and the second width R2 have the following relationship: R1 / R2 = 1.01~1.3; and / or the first width R1 and the first vertical distance H1 have the following relationship: R1 / H1 = 50~800.

[0013] In one embodiment of this application, the arc-shaped outer surface has a first area S1, and the projection of the arc-shaped outer surface in the electrode thickness direction has a second area S2; the arc-shaped inner surface has a third area S3, and the projection of the arc-shaped inner surface in the electrode thickness direction has a fourth area S4; the first area S1, the second area S2, the third area S3 and the fourth area S4 have the following relationship: S1 / S2 = 1.05~1.8; and / or S3 / S4 = 1.1~1.8.

[0014] In one embodiment of this application, the center interval between the projections of two adjacent protrusions in the electrode thickness direction is a first distance L1; there is a straight section between two adjacent protrusions, and the straight section has a second distance L2 in the electrode length direction or the electrode width direction; the first distance L1 and the second distance L2 have the following relationship: L1 / L2=1.05~3.

[0015] In one embodiment of this application, a first tangent is tangent to the first intersection point, and the angle between the first tangent and the plane containing the surface of the first active material layer is a first included angle a1; the recessed portion has a second intersection point, and the second intersection point intersects the plane containing the surface of the second active material layer; a second tangent is tangent to the second intersection point, and the angle between the second tangent and the horizontal plane containing the surface of the second active material layer is a second included angle a2; the first included angle a1 and the second included angle a2 have the following relationship: a1-a2=0°~40°; and / or the first included angle a1 is 0°~90°; and / or the second included angle a2 is 0°~90°.

[0016] In one embodiment of this application, the sum of the projected areas of the plurality of protrusions in the thickness direction of the electrode sheet is a fifth area S11, and the projected area of ​​the electrode sheet in the thickness direction is a sixth area S; the fifth area S11 and the sixth area S have the following relationship: S11 / S = 0.1~0.95.

[0017] In one embodiment of this application, the head of the electrode includes a first clearance area, which has a third width M1 along the length of the electrode; the head of the electrode includes an initial bending segment, and the third width M1 is equal to the width of the initial bending segment ± 10 mm along the length of the electrode; or the head of the electrode includes an initial bending segment and a second bending segment, and the third width M1 is equal to the width of the initial bending segment + the width of the second bending segment ± 10 mm along the length of the electrode; and / or the tail of the electrode includes adjacent double-sided coating area and single-sided coating area, both surfaces of the double-sided coating area are provided with an active material layer, one surface of the single-sided coating area is provided with an active material layer, and the double-sided coating area and the single-sided coating area have a junction point; along the length of the electrode, a second clearance area is provided between the junction point and the protrusion, and the second clearance area has a fourth width M2, which is 2 mm to 30 mm.

[0018] In one embodiment of this application, the shape of the projection of the protrusion in the electrode thickness direction includes a circle, a semicircle, an ellipse, a plum blossom shape, or a polygon, etc.

[0019] This application embodiment also provides a battery cell, which includes the positive electrode sheet described above, and further includes a separator and a negative electrode sheet; the separator includes a substrate and a ceramic layer located on one side of the substrate and an adhesive layer located on the other side of the substrate, the ceramic layer being disposed opposite to the protrusion of the positive electrode sheet.

[0020] In one embodiment of this application, the ceramic layer is an inorganic ceramic particle coating, an inorganic ceramic particle + polyvinylidene fluoride coating, or an inorganic ceramic particle + polymethyl methacrylate + polyvinylidene fluoride coating; the content of inorganic ceramic particles in the ceramic layer is ≥50%; the inorganic ceramic particles include one or more of α-Al2O3, γ-Al2O3, Al2O3, SiO2, CeO2, MgAl2O4, ZrO, and TiO2.

[0021] The positive electrode sheet provided in this application embodiment has the following technical effects:

[0022] The embodiments of this application form multiple protrusions and corresponding recesses on the positive electrode sheet. The protrusions are formed by a portion of the positive electrode sheet protruding from one side surface to the other. First, the protrusions can effectively support the separator, ensuring sufficient separator space between the layers of the positive and negative electrode sheets and between the layers of the positive electrode sheet and the separator. This improves the distribution of electrolyte, increases the electrolyte storage capacity between layers, ensures good wetting effect, and avoids insufficient electrolyte wetting in the later stages of cycling. This eliminates the risk of insufficient electrolyte and insufficient wetting caused by repeated expansion and contraction of the negative electrode sheet during charging and discharging, which leads to repeated compression between the positive and negative electrode sheets inside the cell. It also improves the problems of interface deterioration between electrodes, poor negative electrode cycle stability, and reduced battery capacity retention, reduces the rate of battery capacity decay, and improves the cycle life of the cell.

[0023] Furthermore, forming multiple protrusions on the positive electrode sheet can improve its deformation capacity. When the positive electrode sheet comes into contact with the expanded negative electrode sheet, the protrusions on the positive electrode sheet can effectively absorb the expansion stress of the negative electrode sheet, buffering the expansion of the negative electrode sheet during battery cycling and preventing excessive expansion stress that could lead to cracks. Moreover, the protrusions on the positive electrode sheet can absorb some of the expansion stress of the negative electrode sheet, so that the negative electrode sheet does not rely entirely on its own material resistance during expansion, delaying fatigue of the negative electrode material and thus improving its service life.

[0024] Furthermore, limiting the particle size distribution of active material particles in the active material layer is primarily due to the fact that if most of the active material particles in the active material layer are too large, they will be difficult to move during the formation of protrusions, making it difficult to meet the required height of the protrusions. To achieve the required height, the stamping pressure would need to be increased, which would cause the large-diameter active material particles to break, reducing the energy output of the positive electrode. Moreover, increasing the stamping pressure could also cause the active material layer particles to crush the current collector of the positive electrode. Therefore, by limiting the particle size distribution of active material particles in the active material layer, large and small particles are mixed, and small particles can fill the spaces between large particles. During the processing of protrusions and depressions on the electrode, small particles are squeezed and slide to both sides, filling the spaces between large particles. This avoids the breakage of active material particles, protects the current collector from being torn, and ensures that the height of the protrusions meets the predetermined requirements. Attached Figure Description

[0025] 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.

[0026] Figure 1 A schematic diagram of the structure of the positive electrode provided in the embodiments of this application. Figure 1 ;

[0027] Figure 2 A schematic diagram of the structure of the positive electrode provided in the embodiments of this application. Figure 2 ;

[0028] Figure 3 A schematic diagram of the structure of the positive electrode provided in the embodiments of this application. Figure 3 ;

[0029] Figure 4 A schematic diagram of the structure of the positive electrode provided in the embodiments of this application. Figure 4 ;

[0030] Figure 5 A top view of the positive electrode sheet provided in an embodiment of this application;

[0031] Figure 6 A schematic diagram illustrating the double-sided coating and single-sided coating of the positive electrode sheet provided in the embodiments of this application;

[0032] Figure 7 A schematic diagram of the structure of the core provided in the embodiments of this application.

[0033] Figure label:

[0034] 100: current collector;

[0035] 110: Positive electrode plate; 120: Negative electrode plate; 130: Separator; 140: First center plane;

[0036] 200: First active substance layer;

[0037] 201: Protrusion;

[0038] 2011: Curved outer surface; 2012: Highest convex point; 2013: First intersection point;

[0039] 300: Second active substance layer;

[0040] 301: Depression;

[0041] 3011: Curved inner surface; 3012: Second intersection point;

[0042] 401: Tab; 402: Protective adhesive;

[0043] 501: First safe zone; 502: Second safe zone; 503: Third safe zone;

[0044] 600: Boundary point;

[0045] 601: First tangent; 602: Second tangent. Detailed Implementation

[0046] In a wound lithium-ion battery, the electrode components are stacked and wound to form a cell structure. The cross-section of the wound structure presents a flat elliptical structure with arc-shaped areas on both sides and a planar area in the middle. During the charging and discharging process, the positive and negative electrode plates of the lithium-ion battery will expand. The planar area can expand freely upward and downward, but the arc-shaped area is constrained in its outward expansion due to its structural characteristics and stress accumulation. This eventually leads to interlayer compression of the electrode plates, resulting in problems such as separator pore blockage, poor electrolyte wetting, and lithium plating.

[0047] At the same time, the compression of the arc area will also be transmitted to the flat area. Since the flat area has undergone the compression of the hot pressing process during production, the flat area will be compressed very tightly, which will lead to poor electrolyte wetting in the flat area.

[0048] The core provided in this application forms a positive electrode sheet after coating both sides of the current collector with active material layers. Then, a special roller is used to process protrusions and corresponding recesses on the positive electrode sheet. The combination of protrusions and recesses provides support for the contact between the separator and increases the micro-spacing between the positive electrode sheet 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 sheet. This avoids abnormal situations such as insufficient electrolyte, poor wetting, or even lithium plating on the negative electrode sheet caused by interlayer compression of the electrode sheet.

[0049] However, the process of machining protrusions and depressions on the positive electrode using special rollers can easily cause electrode breakage, which seriously affects production efficiency and process yield.

[0050] By limiting the particle size distribution of active material particles in the active material layer, the particles of different sizes are mixed in the active material layer, and small particles can fill the spaces between large particles. During the processing of protrusions and depressions on the positive electrode sheet, small particles are squeezed and slide to both sides, filling the spaces between large particles. This prevents the active material particles from breaking while protecting the current collector from being torn, and also ensures that the height of the protrusions meets the predetermined requirements.

[0051] 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.

[0052] In this embodiment of the application, the electrode thickness direction is the z-axis shown in the figure, the electrode length direction is the x-axis shown in the figure, and the electrode width direction is the y-axis shown in the figure.

[0053] refer to Figure 1 The positive electrode provided in this application embodiment includes: a current collector 100, a first active material layer 200, and a second active material layer 300.

[0054] The current collector 100 has a first surface and a second surface opposite each other along the electrode thickness direction (z-axis shown in the figure), a first active material layer 200 is disposed on the first surface, and a second active material layer 300 is disposed on the second surface.

[0055] The first active material layer 200 has a plurality of protrusions 201, and the second active material layer 300 has a plurality of recesses 301 corresponding to the protrusions 201.

[0056] The projection of the protrusion 201 onto the recess 301 means that the projection of the protrusion 201 along the electrode thickness direction (z-axis shown in the figure) covers the projection of the recess 301 along the electrode thickness direction.

[0057] The first active material layer 200 and the second active material layer 300 coated on the two surfaces of the current collector 100 are respectively provided with protrusions 201 and depressions 301, which can provide support for the membrane contact and increase the micro-spacing between the electrode and the membrane. These micro-spacings form a space that can accommodate the electrolyte, so that the electrolyte has sufficient wetting amount on the electrode and avoids abnormal situations such as insufficient electrolyte, poor wetting, or even lithium plating on the negative electrode caused by interlayer compression of the electrode.

[0058] Both the first active material layer 200 and the second active material layer 300 include multiple active material particles, including lithium iron phosphate, lithium manganese iron phosphate, lithium manganese phosphate, and Li. a1 Co x1 M1 k1 O 2、 Li a2 Ni x2 Co y2 D z2 M2 k2 At least one of O2.

[0059] Wherein, 0.85≤a1≤1.1, 0.85≤a2≤1.1, 0.85≤x1≤1.05, 0.3≤x2≤0.98, 0≤y2≤0.5, 0≤z2≤0.5, 0≤k1≤0.15, 0≤k2≤0.15.

[0060] D includes at least one of Mn and Al.

[0061] M1 includes at least one of Al, Mg, Ti, Zr, Y, La, W, B, Nb, and Mn.

[0062] M2 includes at least one of Mg, Ti, Zr, Y, La, W, B, and Nb.

[0063] The particle size distribution of the active material layer particles satisfies: Dv10:Dv50:Dv90=1:(2~8):(3~16).

[0064] Preferably, Dv10:Dv50:Dv90 = 1:(2~7):(5~13).

[0065] Wherein, Dv10 represents the particle size that accumulates to 10% of the volume in a volume-based particle size distribution; Dv50 represents the particle size that accumulates to 50% of the volume in a volume-based particle size distribution; and Dv90 represents the particle size that accumulates to 90% of the volume in a volume-based particle size distribution.

[0066] In other words, the first active material layer 200 and the second active material layer 300 contain a mixture of large and small particles, and the small particles can fill the spaces between the large particles. When the protrusions 201 and the depressions 301 are processed on the electrode, the small particles are squeezed and slide to both sides, filling the spaces between the large particles. This prevents the active material particles from breaking while protecting the current collector from being torn, and also ensures that the height of the protrusions 201 meets the predetermined requirements.

[0067] When Dv10 remains constant, the ratio of Dv50 to Dv10 is greater than 8, and the ratio of Dv90 to Dv10 is greater than 16. This indicates that the particle size accumulation is excessively large relative to the 10% volume accumulation, 50% volume accumulation, and 90% volume accumulation. This signifies that most active material particles in the active material layer are too large. During the processing of the protrusion 201 on the electrode, these large-diameter active material particles are difficult to move, resulting in insufficient height of the protrusion 201, insufficient depth of the recess 301, and unsatisfactory electrolyte wetting. Given the excessively large particle size of most active material particles, increasing the stamping pressure is necessary to achieve the required height of the protrusion 201. This would cause the large-diameter active material particles to break, reducing the energy utilization of the positive electrode. Furthermore, excessive stamping pressure could cause the active material layer particles to crush the current collector 100 of the positive electrode.

[0068] When Dv10 remains constant, the ratio of Dv50 to Dv10 is less than 2, and the ratio of Dv90 to Dv10 is less than 3, it indicates that the particle size differences reaching 10%, 50%, and 90% of the volume accumulation are small, making it impossible to achieve the effect of mixing large and small particles. The relatively smaller particles slide to both sides under the extrusion force, and the current collector of the positive electrode is directly subjected to pressure, which can easily lead to excessive pressure on the current collector 100 of the positive electrode and cause it to crack.

[0069] In the embodiments of this application, Dv10 is 2μm~8μm, indicating that among the multiple active material layer particles, the particle size that accumulates to 10% of the volume is between 2μm and 8μm; preferably, Dv10 is 2μm~7μm.

[0070] A Dv50 of 11 μm to 19 μm indicates that among the multiple active material layers, the particle size that accounts for 50% of the total volume is between 11 μm and 19 μm; preferably, Dv50 is between 12 μm and 16 μm.

[0071] A Dv90 of 22μm to 32μm indicates that 90% of the particles in the multiple active material layers have a particle size between 22μm and 32μm; preferably, Dv90 is 24μm to 32μm.

[0072] When Dv50 is between 11μm and 19μm, Dv90 is between 22μm and 32μm, but Dv10 is greater than 8μm, it indicates that the particle size of the small particles is too large. Most of the active material particles in the active material layer are too large. When processing the protrusion 201 on the electrode, the large-diameter active material particles are difficult to move, resulting in insufficient height of the protrusion 201 and insufficient depth of the recess 301, and unsatisfactory electrolyte wetting. In order to ensure the height of the protrusion 201, the continued stamping will also cause the large-diameter active material particles to break. The high stamping pressure will also cause the active material layer particles to crush the current collector 100 of the positive electrode.

[0073] When Dv50 is between 11μm and 19μm, Dv90 is between 22μm and 32μm, but Dv10 is less than 2μm, it indicates that the particle size of the small particles is too small, and the existence of small particles is meaningless. Most of the active material particles in the active material layer are large in diameter. Large-diameter active material particles are difficult to move, resulting in insufficient height of the protrusion 201 and insufficient depth of the depression 301, and unsatisfactory electrolyte wetting. In order to ensure the height of the protrusion 201, the large-diameter active material particles will be broken when the stamping continues. The high stamping pressure will also cause the active material layer particles to crush the current collector 100 of the positive electrode.

[0074] When Dv10 is between 2μm and 8μm, Dv90 is between 22μm and 32μm, but Dv50 is greater than 19μm, it indicates that the particle size of the large particles is too large. Most of the active material particles in the active material layer are too large. When processing the protrusion 201 on the electrode, the large-diameter active material particles are difficult to move, resulting in insufficient height of the protrusion 201 and insufficient depth of the recess 301, and unsatisfactory electrolyte wetting. In order to ensure the height of the protrusion 201, the continued stamping will also cause the large-diameter active material particles to break. The high stamping pressure will also cause the active material layer particles to crush the current collector 100 of the positive electrode.

[0075] When Dv10 is between 2μm and 8μm, Dv90 is between 22μm and 32μm, but Dv50 is less than 11μm, it indicates that the particle size of the large particles is too small. Most of the active material particles in the active material layer are small in size, resulting in a higher density of active material particles in the first active material layer 200 and the second active material layer 300, and fewer corresponding pores. When the relatively small particles slide to both sides under the extrusion pressure, they do not fill the space sufficiently, which will lead to the breakage of the active material particles and reduce the energy utilization of the positive electrode. At the same time, it will also cause the particles in the active material layer to crush the current collector 100 of the positive electrode.

[0076] When Dv10 is between 2μm and 8μm, Dv50 is between 11μm and 19μm, but Dv90 is greater than 32μm, it indicates that the particle size of the large particles is too large. Most of the active material particles in the active material layer are too large. When processing the protrusion 201 on the electrode, the large-diameter active material particles are difficult to move, resulting in insufficient height of the protrusion 201 and insufficient depth of the recess 301, and unsatisfactory electrolyte wetting. In order to ensure the height of the protrusion 201, the continued stamping will also cause the large-diameter active material particles to break. The high stamping pressure will also cause the active material layer particles to crush the current collector 100 of the positive electrode.

[0077] When Dv10 is between 2μm and 8μm, Dv50 is between 11μm and 19μm, but Dv90 is less than 22μm, it indicates that the particle size of the large particles is too small. Most of the active material particles in the active material layer are small in size, resulting in a higher density of active material particles in the first active material layer 200 and the second active material layer 300, and fewer corresponding pores. When the relatively small particles slide to both sides under the extrusion pressure, they do not fill the space sufficiently, which will lead to the breakage of the active material particles and reduce the energy utilization of the positive electrode. At the same time, it will also cause the particles in the active material layer to crush the current collector 100 of the positive electrode.

[0078] refer to Figure 2In this embodiment of the application, the protrusion 201 has a first intersection point 2013, which intersects with the plane containing the surface of the first active material layer 200; in the electrode thickness direction (z-axis shown in the figure), the first intersection point 2013 and the highest protrusion point 2012 of the protrusion 201 have a first vertical distance H1; the first vertical distance H1 = 3μm~40μm, preferably, the first vertical distance H1 = 3μm~30μm.

[0079] The first vertical distance H1 is the height of the protrusion 201. By limiting the height of the protrusion 201, a suitable gap can be made between the electrode and the diaphragm, which can provide support while avoiding excessive electrode thickness.

[0080] When the first vertical distance H1 is less than 3μm, it indicates that the protrusion 201 is too short and the support effect is not obvious. The protrusion 201 is an ineffective protrusion and cannot allow the electrolyte to wet sufficiently. When the first vertical distance H1 is greater than 40μm, it indicates that the protrusion 201 is too high, which will lead to severe delamination between the positive and negative electrodes and cause new interface problems.

[0081] The thickness of the current collector 100 is a first thickness H2, where the first thickness H2 = 6 μm to 20 μm; preferably, the first thickness H2 = 8 μm to 18 μm.

[0082] In the electrode thickness direction (z-axis shown in the figure), both the first active material layer 200 and the second active material layer 300 have a second thickness H3, H3 = 30-150 μm; the first vertical distance H1, the first thickness H2, the second thickness H3 and Dv50 have the following relationship: (H1 + Dv50) / (H2 + 2H3) = 0.1~0.8; preferably, (H1 + Dv50) / (H2 + 2H3) = 0.3~0.5.

[0083] The above relationship can better balance the height of the protrusion 201, avoiding damage to the current collector 100 and particle breakage. Here, H2+2H3 refers to the thickness of the entire electrode sheet, and H1+Dv50 represents the height of the protrusion's apex. When (H1+Dv50) / (H2+2H3) is greater than 0.5, the height of the protrusion 201's apex is too high, resulting in too many large particles. During electrode embossing, this can easily cause electrode breakage and particle breakage, and the excessively large particles at the protrusion's apex can also lead to powder shedding. When (H1+Dv50) / (H2+2H3) is less than 0.3, the height of the protrusion 201 is too small, failing to meet the wetting effect, or DV50 is too small, resulting in insufficient material compaction and making it difficult to guarantee the height of the protrusion 201.

[0084] In this embodiment, the tensile strength M of the current collector 100 is ≥50MPa along the width direction (y-axis shown in the figure) and the length direction (x-axis shown in the figure). The greater the height of the protrusion 201, the greater the compressive stress it causes to the current collector 100, and the greater the tensile strength M of the current collector 100 should be. A tensile strength M ≥50MPa of the current collector 100 can prevent the current collector 100 from breaking.

[0085] The first vertical distance H1 and the tensile strength M have the following relationship: 0.05≤H1 / M≤0.4; preferably, 0.1≤H1 / M≤0.2.

[0086] The first vertical distance H1 is the height of the protrusion 201. The higher the protrusion 201 is, the greater the compressive stress that the protrusion 201 causes to the current collector 100. Therefore, by limiting the relationship between the height of the protrusion 201 and the tensile strength of the current collector 100, the current collector 100 is prevented from breaking.

[0087] When H1 / M is greater than 0.4, it indicates that the protrusion 201 is too high and the tensile strength of the current collector 100 is insufficient. The greater the compressive stress caused by the protrusion 201 on the current collector 100, the more likely the current collector 100 will break. When H1 / M is less than 0.05, it indicates that the protrusion 201 is too low and the support effect is not obvious. The protrusion 201 is an ineffective protrusion and cannot allow the electrolyte to wet sufficiently.

[0088] In this embodiment, the current collector 100 has a breaking elongation N1, which is ≥2%. The larger the breaking elongation N1 of the current collector 100, the better the ductility of the current collector 100. A breaking elongation N1 ≥2% can prevent the current collector from breaking.

[0089] In this embodiment of the application, the first vertical distance H1 and the elongation at break N1 have the following relationship: 10≤H1 / N1≤60; preferably, 15≤H1 / N1≤50.

[0090] The greater the height of the protrusion 201, the greater the compressive stress it exerts on the current collector 100. Therefore, by limiting the relationship between the height of the protrusion 201 and the elongation at break N1 of the current collector 100, the current collector 100 is prevented from breaking.

[0091] When H1 / N1 is greater than 60, it indicates that the protrusion 201 is too high and the current collector 100 is not ductile enough. The greater the compressive stress caused by the protrusion 201 on the current collector 100, the more likely the current collector 100 will break. When H1 / N1 is less than 10, it indicates that the protrusion 201 is too low and the support effect is not obvious. The protrusion 201 is an ineffective protrusion and cannot allow the electrolyte to wet sufficiently.

[0092] In this embodiment, the current collector 100 includes an aluminum foil, on which a porous structure, an uneven structure, or a carbon material is disposed.

[0093] The perforated structure on the aluminum foil refers to punching holes in the aluminum foil to increase the coating amount of the active material layer; at the same time, it can improve the adhesion between the active material layer and the current collector 100, and prevent the current collector 100 from detaching from the active material layer when manufacturing the protrusion 201.

[0094] Setting a concave-convex structure on the aluminum foil refers to using a special roller to roll the current collector 100, forming multiple concave-convex structures on the current collector 100. The concave-convex structure increases the contact area between the active material layer and the current collector 100, thereby increasing the adhesion between the active material layer and the current collector 100, and preventing the current collector 100 from detaching from the active material layer when manufacturing the protrusion 201.

[0095] Carbon material is placed on aluminum foil to obtain carbon-containing aluminum foil. The carbon-containing aluminum foil can improve the adhesion between the active material layer and the current collector 100, and prevent the current collector 100 from detaching from the active material layer when manufacturing the protrusion 201.

[0096] The thickness of the aluminum foil is the same as the thickness of the current collector 100, and the first thickness H2 of the current collector 100 is 6-20 micrometers.

[0097] In this embodiment, the aluminum foil has an elongation N2 of 0.5% to 2%; preferably, the elongation N2 is 1% to 2%.

[0098] When manufacturing the protrusion 201, the aluminum foil will be squeezed. By limiting the elongation N2 of the aluminum foil, it is ensured that the aluminum foil is sufficient to support the elongation caused by processing the protrusion 201. When the active material particles squeeze the aluminum foil, the aluminum foil is prevented from breaking.

[0099] refer to Figure 3 In this embodiment of the application, the protrusion 201 has an arc-shaped outer surface 2011, which is located in the first active material layer 200. The projection of the arc-shaped outer surface 2011 on the electrode thickness direction (z-axis shown in the figure) has a first width R1. The recess 301 has an arc-shaped inner surface 3011, which is located in the second active material layer 300. The projection of the arc-shaped inner surface 3011 on the electrode thickness direction (z-axis shown in the figure) has a second width R2.

[0100] The first width R1 and the second width R2 have the following relationship: R1 / R2 = 1.01~1.3; preferably, R1 / R2 = 1.01~1.1.

[0101] By limiting the ratio of the first width R1 and the second width R2, the sharpness of the protrusion 201 can be limited, thus preventing the protrusion 201 from damaging the electrode.

[0102] The first width R1 can be 0.5 mm to 8 mm, preferably 1 mm to 4 mm.

[0103] When the first width R1 is less than 0.5mm, the width of the protrusion 201 is insufficient, the supporting effect is not obvious, and it cannot effectively improve the expansion of the negative electrode. When the first width R1 is greater than 8mm, the width of the protrusion 201 is too large. During the manufacturing process, the protrusion 201 is easily subjected to extrusion force, elongation force and cyclic expansion force, which causes the protrusion 201 to be over-deformed, causing the protrusion 201 to collapse and thus failing to effectively improve the expansion of the negative electrode.

[0104] The second width R2 can be 0.5 mm to 8 mm, preferably 0.8 mm to 4 mm.

[0105] When the second width R2 is less than 0.5mm, the width of the recess 301 is too small, resulting in insufficient electrolyte capacity and inability to effectively improve the electrolyte wetting effect. When the second width R2 is greater than 8mm, the width of the recess 301 is too large. During the manufacturing process, the recess 301 is easily subjected to extrusion force, elongation force and cyclic expansion force, which causes the recess 301 to undergo excessive deformation, causing the recess 301 to collapse and thus failing to effectively improve the electrolyte wetting effect.

[0106] In this embodiment of the application, the first width R1 and the first vertical distance H1 have the following relationship: R1 / H1=50~800; preferably, R1 / H1=100~300.

[0107] By limiting the projected width and height of the protrusion 201, a suitable gap can be made between the electrode and the diaphragm, that is, the protrusion 201 has a suitable deformation space and liquid storage space to provide sufficient support, thereby maximizing the benefit effect.

[0108] When the projected width of the protrusion 201 is small and the height of the protrusion 201 is high, the protrusion 201 is relatively sharp and can easily damage the electrode, affecting the safety performance of the battery.

[0109] When the projected width of the protrusion 201 is large and the height of the protrusion 201 is high, the protrusion 201 is relatively sharp and occupies too much space, exceeding the tensile strength of the electrode. This results in the tensile strength of the electrode being insufficient to support the deformation of the protrusion 201, which can easily cause the electrode to break.

[0110] When the projected width of the protrusion 201 is large and the height of the protrusion 201 is low, the support of the protrusion 201 is insufficient. During the manufacturing process, the protrusion 201 is easily subjected to extrusion and stretching forces, which can cause it to deform excessively and tend to flatten. This can lead to the collapse of the protrusion 201, which will not be able to improve the electrolyte wetting effect, increase the liquid storage capacity, or improve the negative electrode expansion.

[0111] When the projected width of the protrusion 201 is small and the height of the protrusion 201 is low, the protrusion 201 has insufficient support and occupies little space, which is not good for improving the electrolyte wetting effect, increasing the liquid storage capacity and negative electrode expansion.

[0112] Continue to refer to Figure 3 In this embodiment of the application, the arc-shaped outer surface 2011 has a first area S1, and the projection of the arc-shaped outer surface 2011 on the electrode thickness direction (z-axis shown in the figure) has a second area S2; the arc-shaped inner surface 3011 has a third area S3, and the projection of the arc-shaped inner surface 3011 on the electrode thickness direction has a fourth area S4.

[0113] The first area S1 and the second area S2 have the following relationship: S1:S2=1.05~1.8; preferably, S1:S2=1~1.4.

[0114] By limiting the above ratio, the volume of the protrusion 201 can be better controlled, so that the positive electrode has a suitable deformation space to improve the cycle performance of the battery, thereby achieving a better improvement effect.

[0115] When the first area S1 is large and the second area S2 is small, it indicates that the height of the protrusion 201 is relatively high, which can easily cause damage to the electrode and break the particles.

[0116] When the first area S1 is large and the second area S2 is large, it indicates that the height of the protrusion 201 is low and the support of the protrusion 201 is insufficient. During the manufacturing process, the protrusion 201 is easily subjected to excessive deformation due to extrusion and stretching forces, tending to flatten. This causes the protrusion 201 to collapse, which fails to improve the electrolyte wetting effect, increase the liquid storage capacity, and improve the negative electrode expansion.

[0117] When the first area S1 is small and the second area S2 is large, it indicates that the height of the protrusion 201 is low and the support of the protrusion 201 is insufficient. During the manufacturing process, the protrusion 201 is easily subjected to extrusion and stretching forces, which can cause it to deform excessively and tend to flatten. This can lead to the collapse of the protrusion 201, which will not be able to improve the electrolyte wetting effect, increase the liquid storage capacity, or improve the negative electrode expansion.

[0118] When the first area S1 is small and the second area S2 is small, it indicates that the height of the protrusion 201 is low and the space occupied by the protrusion 201 is small, which is not good for improving the electrolyte wetting effect, increasing the liquid storage capacity and the expansion of the negative electrode.

[0119] The third area S3 and the fourth area S4 have the following relationship: S3:S4 = 1.1~1.8; preferably, S3:S4 = 1.2~1.4.

[0120] By limiting the above ratio, the volume of the recess 301 can be better controlled, effectively improving the electrolyte wetting effect and increasing the electrolyte storage capacity.

[0121] When the third area S3 is large and the fourth area S4 is small, it indicates that the height of the recessed part 301 is relatively high, which can easily cause damage to the electrode and break the particles.

[0122] When the third area S3 is large and the fourth area S4 is large, it indicates that the height of the recessed part 301 is low. During the manufacturing process, the recessed part 301 is easily subjected to excessive deformation due to extrusion and stretching forces, tending to flatten out. This causes the protrusion 201 to collapse, thus failing to improve the electrolyte wetting effect and increase the electrolyte storage capacity.

[0123] When the third area S3 is small and the fourth area S4 is large, it indicates that the height of the recessed part 301 is low. During the manufacturing process, the recessed part 301 is easily subjected to excessive deformation due to extrusion and stretching forces, tending to flatten out. This causes the protrusion 201 to collapse, thus failing to improve the electrolyte wetting effect and increase the electrolyte storage capacity.

[0124] When the third area S3 is small and the fourth area S4 is small, it indicates that the height of the recessed part 301 is low and the space occupied by the recessed part 301 is small, which is not good for improving the electrolyte wetting effect, increasing the liquid storage capacity and the expansion of the negative electrode.

[0125] refer to Figure 1 In this embodiment of the application, the center interval of the projection of two adjacent protrusions 201 on the electrode thickness direction (z-axis shown in the figure) is a first distance L1; there is a straight section between two adjacent protrusions 201, and the straight section has a second distance L2 in the electrode length direction or in the electrode width direction.

[0126] The first distance L1 and the second distance L2 have the following relationship: L1 / L2 = 1.05~3; preferably, L1 / L2 = 1.1~2.

[0127] Limiting the ratio of the first distance L1 to the second distance L2 is equivalent to limiting the density of the protrusions 201, ensuring that there is a suitable spacing between the multiple protrusions 201, so that the protrusions 201 can be adjusted to a suitable volume, thereby providing sufficient support for the electrode and giving the electrode sufficient deformation space to alleviate expansion.

[0128] Wherein, the first distance L1 is 2mm~10mm; preferably, the first distance L1 is 3mm~8mm.

[0129] The second distance L2 is 0.5mm to 8mm; preferably, the second distance L2 is 1mm to 4m.

[0130] When the first distance L1 is less than 2mm, the protrusions 201 are too dense, and the electrode extension cannot meet the density of the protrusions 201. The protrusions 201 cannot be adjusted to a suitable volume, and the height of the protrusions 201 does not meet the requirements, resulting in less deformation space and the electrode being prone to breakage. When the first distance L1 is greater than 10mm, the protrusions 201 are too sparse, the protrusions 201 are too dispersed, and the supporting area of ​​the protrusions 201 is insufficient, thus failing to achieve the electrolyte wetting effect and improvement effect.

[0131] Similarly, when the second distance L2 is less than 0.5mm, the protrusions 201 are too dense, and the electrode extension cannot meet the density of the protrusions 201. The protrusions 201 cannot be adjusted to a suitable volume, and the height of the protrusions 201 does not meet the requirements, resulting in less deformation space and the electrode being prone to breakage. When the second distance L2 is greater than 8mm, the protrusions 201 are too sparse, the protrusions 201 are too dispersed, and the supporting area of ​​the protrusions 201 is insufficient, thus failing to achieve the electrolyte wetting effect and improvement effect.

[0132] refer to Figure 4 In this embodiment of the application, the first tangent 601 is tangent to the first intersection point 2013, and the angle between the first tangent 601 and the plane containing the surface of the first active material layer 200 is the first included angle a1; the recessed portion 301 has a second intersection point 3012, and the second intersection point 3012 intersects the plane containing the surface of the second active material layer 300; the second tangent 602 is tangent to the second intersection point 3012, and the angle between the second tangent 602 and the horizontal plane containing the surface of the second active material layer 300 is the second included angle a2.

[0133] The first included angle a1 and the second included angle a2 have the following relationship: a1-a2=0°~40°; preferably, a1-a2=5°~25°.

[0134] The first included angle a1 is 0°~90°; preferably, the first included angle a1 is 25°~80°.

[0135] The second included angle a2 is 0°~90°; preferably, the second included angle a2 is 5°~55°.

[0136] The first included angle a1 is equivalent to limiting the height and tilt angle of the protrusion 201. When the first included angle a1 is greater than 90°, the protrusion 201 is excessively bent, and the connection between the protrusion 201 and the straight section will break. When the first included angle a1 is less than 0°, the protrusion 201 tends to be straight, and the height of the protrusion 201 is insufficient, resulting in insufficient support of the protrusion 201, which is easily flattened during the process and cycle.

[0137] Limiting the second included angle a2 is equivalent to limiting the height and tilt angle of the recessed part 301. When the second included angle a2 is greater than 90°, the recessed part 301 is prone to breakage at the connection with the straight section. When the second included angle a2 is less than 0°, the recessed part 301 tends to be straight. The recessed part 301 occupies little space and cannot improve the electrolyte wetting effect or increase the liquid storage capacity.

[0138] In theory, when processing the protrusion 201, the second included angle a2 belongs to the pressure side, and the second included angle a2 is smaller than the first included angle a1, so as to avoid the breakage at the junction of the recessed part 301 and the straight section.

[0139] In this embodiment, the sum of the projected areas of the plurality of protrusions 201 in the electrode thickness direction (z-axis shown in the figure) is the fifth area S11, and the projected area of ​​the electrode in its thickness direction is the sixth area S.

[0140] The fifth area S11 and the sixth area S have the following relationship: S11 / S = 0.1~0.95; preferably, S11 / S = 0.3~0.8.

[0141] Each protrusion 201 can provide a support point, and multiple support points can disperse the expansion stress of the negative electrode to a certain extent; the limitation of the above ratio relationship can effectively ensure the contact area between the support point of the positive electrode and the negative electrode, so as to achieve the technical effect.

[0142] When the fifth area S11 is large, it indicates that the protrusion 201 accounts for a large proportion, and the electrode is easily damaged. When the fifth area S11 is small, it indicates that the protrusion 201 accounts for a small proportion, the supporting effect is not obvious, and the electrolyte cannot be sufficiently wetted.

[0143] refer to Figure 5 and Figure 6 In this embodiment of the application, the head of the electrode includes a first clearance area 501, and the first clearance area 501 has a third width M1 in the length direction of the electrode (x-axis shown in the figure); the head of the electrode includes an initial bending segment and a second bending segment, and in the length direction of the electrode, the third width M1 = the width of the initial bending segment ± 10 mm; or, the third width M1 = the width of the initial bending segment + the width of the second bending segment ± 10 mm.

[0144] The first clearance zone 501 can prevent the head of the electrode from folding during winding, thus solving the problem of unstable structure caused by the unstable head of the electrode during winding.

[0145] The tail of the electrode includes an adjacent double-sided coating area and a single-sided coating area. Both surfaces of the double-sided coating area are provided with an active material layer, and one surface of the single-sided coating area is provided with an active material layer. The double-sided coating area and the single-sided coating area have an intersection point 600. In the length direction of the electrode (x-axis shown in the figure), there is a second clearance area 502 between the intersection point 600 and the protrusion 201. The second clearance area 502 has a fourth width M2, which is 2mm to 30mm.

[0146] The tail of the electrode has an empty foil area, and the setting of the second empty foil area 502 can avoid the problem of foil damage in the empty foil area.

[0147] Continue to refer to Figure 5 In this embodiment of the application, in the electrode width direction (y-axis shown in the figure), the electrode includes a first edge and a second edge, and both the first edge and the second edge include a third clearance area 503 without a protrusion 201.

[0148] By creating a gap between the first and second edges, problems such as edge curling and poor interface uniformity caused by rolling stress can be prevented.

[0149] Continue to refer to Figure 5 In this embodiment of the application, the electrode sheet includes a fourth clearance area 504 without a protrusion 201. The fourth clearance area 504 is configured to have an electrode tab 401. The electrode tab 401 is disposed in the fourth clearance area 504 by an electrode tab protective adhesive 402. In the length direction of the electrode sheet (x-axis shown in the figure), there is a fifth width K between the edge of the electrode tab protective adhesive 402 and the protrusion 201. The fifth width K is 2mm to 30mm.

[0150] The fourth clearance zone 504 can prevent the electrode area where the tab 401 is located from being damaged by rolling stress, and ensure the welding stability and interface uniformity of the tab 401.

[0151] In this embodiment, the shape of the projection of the protrusion 201 on the electrode thickness direction (z-axis shown in the figure) includes a circle, a semi-circle, an ellipse, a plum blossom shape, or a polygon.

[0152] To avoid the protrusion 201 having sharp edges, prevent the edge of the protrusion 201 from piercing the diaphragm, causing a short circuit between the positive and negative electrodes and triggering a cell safety accident.

[0153] refer to Figure 7This application embodiment also provides a battery cell, which includes the positive electrode 110 described above; the battery cell also includes a negative electrode 120 and a separator 130 disposed between the positive electrode 110 and the negative electrode 120, the positive electrode 110, the negative electrode 120 and the separator 130 being wound around a first center surface 140.

[0154] The battery cell includes a flat region and arcuate regions located at opposite ends of the flat region. The surface of the first active material layer 200 is away from the first center surface 140, and the surface of the second active material layer 300 faces the first center surface 140.

[0155] The separator 130 includes a substrate, a ceramic layer on one side of the substrate, and an adhesive layer on the other side of the substrate. The ceramic layer is disposed opposite to the protrusion 201 of the positive electrode 110.

[0156] The substrate includes a multilayer microporous membrane composed of polyethylene, polypropylene, and polyethylene-polypropylene composite, and the ceramic layer located on one side of the substrate includes ceramic, polyvinylidene fluoride, or polymethyl methacrylate arranged in an array.

[0157] The ceramic layer opposite to the protrusion 201 includes an inorganic ceramic particle coating, an inorganic ceramic particle + polyvinylidene fluoride coating, or an inorganic ceramic particle + polymethyl methacrylate + polyvinylidene fluoride coating; the inorganic ceramic particle + polyvinylidene fluoride coating contains ≥50% inorganic ceramic particles; the inorganic ceramic particles include one or more of α-Al2O3, γ-Al2O3, Al2O3, SiO2, CeO2, MgAl2O4, ZrO, and TiO2.

[0158] The ceramic layer opposite to the protrusion 201 can improve the safety of the battery cell. During the manufacturing process of the protrusion 201, the protruding part of the active material layer may have sharp corners, and the ceramic layer can play a protective role to prevent the sharp corners from piercing the separator and causing short circuit problems.

[0159] Meanwhile, the adhesive layer on the other side of the substrate can ensure the adhesion of the interface and avoid lithium plating problems caused by poor interface adhesion.

[0160] The following detailed description of the above-mentioned core provided in this application is based on specific embodiments. The specific differences between the different embodiments are shown in Tables 1 and 2.

[0161] Example 1:

[0162] The battery fabrication in this embodiment includes the following steps:

[0163] 1. Preparation of positive electrode 110:

[0164] Lithium cobalt oxide, a conductive agent, and PVDF were mixed in a mass ratio of 97.6:1.4:1 and placed in NMP. The mixture was stirred until homogeneous to obtain a positive electrode slurry. The positive electrode slurry was then uniformly coated onto both the front and back surfaces of a current collector 100, forming a first active material layer 200 and a second active material layer 300 on the current collector 100. The current collector 100 had a thickness of 1.5 μm and a coating surface density of 0.01704 g / cm³. 2 After drying and rolling, positive electrode sheet 110 is obtained.

[0165] The particle size distribution of the active material layer particles in the first active material layer 200 and the second active material layer 300 includes: Dv10:Dv50:Dv90 = 1 / 4.5 / 9, Dv10 = 4.5μm, Dv50 = 14μm, Dv90 = 28μm.

[0166] The positive electrode 110 is rolled using an embossing roller to form multiple protrusions 201 on the first active material layer 200 and multiple recesses 301 opposite to the protrusions 201 on the second active material layer 300. The height of the protrusion 201 (first vertical distance H1), the thickness of the current collector 100 (first thickness H2), the thickness of the first active material layer 200 or the second active material layer 300 (second thickness H3), and the second particle size D2 have the following relationship: (H1 + Dv50) / (H2 + 2H3) = 0.4.

[0167] The ratio of the first vertical distance H1 to the tensile strength M of the current collector 100 is H1 / M = 0.15, the ratio of the first vertical distance H1 to the elongation at break N1 of the current collector 100 is H1 / N1 = 33, and the elongation of the aluminum foil is N2 = 1.5%.

[0168] The radius of the arc-shaped outer surface of the protrusion 201 is the first width R1, and the radius of the arc-shaped inner surface of the recess 301 is the second width R2; R1 / H1=200, R1 / R2=1.05.

[0169] The area of ​​the arc-shaped outer surface of the protrusion 201 is S1, and the area of ​​the arc-shaped outer surface projected in the electrode thickness direction is S2, S1 / S2=1.2; the area of ​​the arc-shaped inner surface of the recess 301 is S3, and the area of ​​the arc-shaped inner surface projected in the electrode thickness direction is S4, S3 / S4=1.3; the sum of the projected areas of the multiple protrusions 201 in the electrode thickness direction is S11, and the projected area of ​​the electrode in its thickness direction is S, S11 / S=0.6.

[0170] The center interval between the projections of two adjacent protrusions 201 in the electrode thickness direction is a first distance L1, and the straight section between two adjacent protrusions 201 has a second distance L2 in the electrode length direction or the electrode width direction, wherein L1 / L2=1.5.

[0171] The first included angle a1 of the protrusion 201 is 53°, the second included angle a2 of the recess 301 is 38°, and the relationship between the first included angle a1 and the second included angle a2 is a1-a2=15°.

[0172] 2. Preparation of negative electrode 120:

[0173] Silicon-containing artificial graphite, conductive carbon black, styrene-butadiene rubber, and sodium carboxymethyl cellulose were mixed in deionized water at a mass ratio of 97.2:0.5:1.3:1 and stirred evenly to obtain a negative electrode slurry; wherein, the silicon content in the silicon-containing artificial graphite was 10%.

[0174] The negative electrode slurry is uniformly coated on both the front and back surfaces of the negative electrode current collector. After baking and rolling, a negative electrode sheet 120 with a thickness of 220μm is obtained, and negative electrode tabs are welded on.

[0175] 3. Preparation of diaphragm 130:

[0176] A 9μm thick diaphragm 130 was prepared by using a substrate, ceramic, and adhesive coating.

[0177] 4. Electrolyte preparation:

[0178] The electrolyte includes lithium salt LiPF6 and solvents, the solvents being ethylene carbonate (EC), diethyl carbonate (DEC) and methyl ethyl carbonate (EMC), wherein the molar ratio of ethylene carbonate (EC), diethyl carbonate (DEC) and methyl ethyl carbonate (EMC) is DEC:EC:EMC=1:1:1.

[0179] 5. Assembly:

[0180] The positive electrode 110, separator 130 and negative electrode 120 are wound together to obtain the battery cell. The battery cell is then processed by packaging, baking, liquid injection, formation and secondary sealing to obtain the battery.

[0181] Example 2:

[0182] Example 2 is performed in accordance with Example 1, except that Dv10:Dv50:Dv90 = 1 / 5 / 9.5.

[0183] Example 3:

[0184] Example 3 is carried out with reference to Example 1, except that Dv10:Dv50:Dv90=1 / 10 / 20.

[0185] Example 4:

[0186] Example 4 is performed in accordance with Example 1, except that Dv10:Dv50:Dv90 = 1 / 1 / 2.

[0187] Example 5:

[0188] Example 5 was carried out in accordance with Example 1, except that Dv10 = 5μm.

[0189] Example 6:

[0190] Example 6 was carried out in accordance with Example 1, except that Dv10 = 9μm.

[0191] Example 7:

[0192] Example 7 was carried out in accordance with Example 1, except that Dv10 = 1 μm.

[0193] Example 8:

[0194] Example 8 was carried out in accordance with Example 1, except that Dv50 = 15 μm.

[0195] Example 9:

[0196] Example 9 was carried out in accordance with Example 1, except that Dv50 = 20 μm.

[0197] Example 10:

[0198] Example 10 was carried out in accordance with Example 1, except that Dv50 = 10 μm.

[0199] Example 11:

[0200] Example 11 was carried out in accordance with Example 1, except that Dv90 = 27 μm.

[0201] Example 12:

[0202] Example 12 was carried out in accordance with Example 1, except that Dv90 = 34 μm.

[0203] Example 13:

[0204] Example 13 was carried out in accordance with Example 1, except that Dv90 = 20 μm.

[0205] Example 14:

[0206] Example 14 was carried out in accordance with Example 1, except that (H1 + Dv50) / (H2 + 2H3) = 0.45.

[0207] Example 15:

[0208] Example 15 was carried out in accordance with Example 1, except that (H1 + Dv50) / (H2 + 2H3) = 0.9.

[0209] Example 16:

[0210] Example 16 is performed in accordance with Example 1, except that (H1 + Dv50) / (H2 + 2H3) = 0.05.

[0211] Example 17:

[0212] Example 17 was carried out in accordance with Example 1, except that H1 / M = 0.23.

[0213] Example 18:

[0214] Example 18 was carried out in accordance with Example 1, except that H1 / M=0.4.

[0215] Example 19:

[0216] Example 19 was carried out in accordance with Example 1, except that H1 / M = 0.02.

[0217] Example 20:

[0218] Example 20 is carried out with reference to Example 1, except that H1 / N1=35.

[0219] Example 21:

[0220] Example 21 is performed in accordance with Example 1, except that H1 / N1=79.

[0221] Example 22:

[0222] Example 22 is carried out in accordance with Example 1, except that H1 / N1=5.

[0223] Example 23:

[0224] Example 23 was carried out in accordance with Example 1, except that N2 = 1.30%.

[0225] Example 24:

[0226] Example 24 was carried out in accordance with Example 1, except that N2=3%.

[0227] Example 25:

[0228] Example 25 was carried out in accordance with Example 1, except that N2 = 0.20%.

[0229] Example 26:

[0230] Example 26 is performed in accordance with Example 1, except that R1 / H1=425.

[0231] Example 27:

[0232] Example 27 is performed in accordance with Example 1, except that R1 / H1=900.

[0233] Example 28:

[0234] Example 28 is performed in accordance with Example 1, except that R1 / H1=20.

[0235] Example 29:

[0236] Example 29 is performed in accordance with Example 1, except that R1 / R2 = 1.15.

[0237] Example 30:

[0238] Example 30 is carried out with reference to Example 1, except that R1 / R2=1.5.

[0239] Example 31:

[0240] Example 31 is carried out in accordance with Example 1, except that R1 / R2=1.

[0241] Example 32:

[0242] Example 32 is carried out with reference to Example 1, except that S1 / S2=1.4.

[0243] Example 33:

[0244] Example 33 is carried out with reference to Example 1, except that S1 / S2=2.

[0245] Example 34:

[0246] Example 34 is carried out with reference to Example 1, except that S1 / S2=1.

[0247] Example 35:

[0248] Example 35 is carried out with reference to Example 1, except that S3 / S4=1.4.

[0249] Example 36:

[0250] Example 36 is carried out with reference to Example 1, except that S3 / S4=2.

[0251] Example 37:

[0252] Example 37 is carried out with reference to Example 1, except that S3 / S4=1.

[0253] Example 38:

[0254] Example 38 is carried out with reference to Example 1, except that S11 / S=0.5.

[0255] Example 39:

[0256] Example 39 is carried out with reference to Example 1, except that S11 / S=1.

[0257] Example 40:

[0258] Example 40 is carried out with reference to Example 1, except that S11 / S=0.05.

[0259] Example 41:

[0260] Example 41 is performed in accordance with Example 1, except that L1 / L2=2.

[0261] Example 42:

[0262] Example 42 is performed in accordance with Example 1, except that L1 / L2=3.

[0263] Example 43:

[0264] Example 43 is carried out with reference to Example 1, except that L1 / L2=1.

[0265] Example 44:

[0266] Example 44 is carried out with reference to Example 1, except that a1 = 45 degrees and a1 - a2 = 7 degrees.

[0267] Example 45:

[0268] Example 45 is carried out in accordance with Example 1, except that a1 = 100 degrees and a1 - a2 = 62 degrees.

[0269] Example 46:

[0270] Example 46 is carried out with reference to Example 1, except that a1 = -10 degrees and a1 - a2 = -48 degrees.

[0271] Example 47:

[0272] Example 47 is carried out with reference to Example 1, except that a2 = 45 degrees and a1 - a2 = 8 degrees.

[0273] Example 48:

[0274] Example 48 is carried out in accordance with Example 1, except that a2 = 100 degrees and a1 - a2 = -47 degrees.

[0275] Example 49:

[0276] Example 49 is carried out with reference to Example 1, except that a2 = -10 degrees and a1 - a2 = 63 degrees.

[0277] Example 50:

[0278] Example 50 is carried out with reference to Example 1, except that a1 = 60 degrees, a2 = 30 degrees, and a1 - a2 = 30 degrees.

[0279] Example 51:

[0280] Example 51 is carried out in accordance with Example 1, except that a1 = 80 degrees, a2 = 30 degrees, and a1 - a2 = 50 degrees.

[0281] Example 52:

[0282] Example 52 is carried out with reference to Example 1, except that a1 = 40 degrees, a2 = 50 degrees, and a1 - a2 = -10 degrees.

[0283] Comparative Example 1:

[0284] Comparative Example 1 was carried out in accordance with Example 1, except that the lithium cobalt oxide particles in the first active material layer 200 and the second active material layer 300 in Comparative Example 1 had only one particle size, and both were large particles.

[0285] Comparative Example 2:

[0286] Comparative Example 2 was carried out in accordance with Example 1, except that the lithium cobalt oxide particles in the first active material layer 200 and the second active material layer 300 in Comparative Example 2 had only one particle size, and both were small particles.

[0287] Table 1:

[0288]

[0289]

[0290] Table 2:

[0291]

[0292]

[0293] The relevant performance of the batteries in the above embodiments and comparative examples was tested, and the test results are recorded in Table 3. The test methods are as follows:

[0294] 1. Liquid retention test

[0295] The electrolyte retention is the amount of electrolyte ultimately retained in the lithium-ion battery. To ensure that the electrolyte is consumed during the formation of the lithium-ion battery, a certain amount of electrolyte is usually injected in excess, and the excess electrolyte is then extracted after formation. The electrolyte retention is measured by weighing. The injected electrolyte volume is m1, the extracted electrolyte volume is m2, and the electrolyte retention is m1 - m2.

[0296] 2. Appearance of current collector 100 and positive electrode 110:

[0297] The shape of the protrusion 201 was observed using a 3D microscope, and the damage to the current collector 100 and the positive electrode 110 was also observed using a 3D microscope.

[0298] 3. Current collector tensile strength test

[0299] Using a vertical tensile testing machine, the current collectors obtained in the above embodiments and comparative examples are fixed on the clamps at both ends of the tensile testing machine, with the two ends of the clamps aligned. The tensile testing machine is started, and the machine moves at a speed of 10 mm / s until the current collector breaks. The tensile data is then read.

[0300] 4. Lithium plating on the negative electrode

[0301] After conducting cell expansion rate tests on the batteries obtained in the above embodiments and comparative examples, the batteries obtained in the above embodiments and comparative examples were fully charged and disassembled in a dry room environment. The presence and degree of lithium plating on the negative electrode were observed. The degree of lithium plating was divided into slight lithium plating and severe lithium plating. Slight lithium plating refers to the appearance of gray or grayish-black lithium plating at the interface. Severe lithium plating is characterized by a silvery-white appearance at the interface, indicating a larger amount of lithium plating.

[0302] 5. Infiltration Improvement Effect Test

[0303] After the battery is left to stand at room temperature (25℃) for 24 hours, it is disassembled and the wetting of the separator is observed. The size of the wetted area is estimated and compared, and divided into three levels: significant (wetting area of ​​60%~100%), moderate (wetting area of ​​30%~60%), and slight (wetting area of ​​0%~30%). The unwetting area is usually an irregular water ripple boundary, and the difference in area size can be directly observed by visual inspection.

[0304] Table 3:

[0305]

[0306]

[0307] As shown in Table 3, Comparative Example 1 exhibits low liquid retention and insignificant wetting effect; furthermore, the current collector and electrode are severely damaged. This is because large particles prevent the depth of the recessed portion 301 from being fully compressed, and the height of the protruding portion 201 is insufficient, resulting in unsatisfactory wetting. Furthermore, large particles are easily broken under pressure; if compressed too deeply, the particles will also crush the current collector 100. Comparative Example 2 also shows low liquid retention and insignificant wetting effect. This is because the small particles have low specific capacity and a smaller ultimate compaction, leading to insufficient height of the protruding portion 201.

[0308] The liquid retention capacity of Example 1 is higher than that of Comparative Examples 1 and 2, and there is no damage to the current collector and electrode in Example 1. This indicates that the mixture of large and small particles in the active material layer allows the small particles to fill the spaces between the large particles when they slide to both sides under force, thus preventing the particles from breaking and protecting the current collector from being torn.

[0309] As can be seen from Examples 2 to 4, when Dv50 and Dv90 are larger than Dv10, Dv50, and Dv90, the liquid retention is low and the wetting effect is not obvious; moreover, both the current collector and the electrode are severely damaged. This indicates that large particles prevent the depth of the recess 301 from being pressed down, and the height of the protrusion 201 is insufficient, resulting in unsatisfactory wetting; in addition, the particles are easily broken, and the particles may even crush the current collector 100. When Dv50 and Dv90 are smaller than Dv10, Dv50, and Dv90, there are more small particles, the specific capacity of the small particles is low, the ultimate compaction is small, and the height of the protrusion 201 is insufficient, resulting in low liquid retention and an insignificant wetting effect; at the same time, when the small particles slide to both sides under force, the filling space is insufficient, and the current collector 100 will be torn.

[0310] As can be seen from Examples 5 to 7, when Dv10 is greater than 8μm, the particle size of the small particles is too large. When the small particles slide to both sides under force, they cannot fill the gaps between the large particles, and the particles are easily broken. Moreover, the particles will also crush the current collector 100, causing serious damage to the current collector 100 and the electrode. When Dv10 is less than 2μm, the particle size of the small particles is too small, and the existence of the small particles is meaningless. The mixing effect of large and small particles cannot be achieved, and the current collector 100 will be torn, causing serious damage to the current collector 100.

[0311] As can be seen from Examples 8 to 13, when Dv50 is greater than 19 μm and Dv90 is greater than 32 μm, the particle size of the large particles is too large. The large particles cause the depth of the recess 301 to be insufficient, and the height of the protrusion 201 is insufficient, resulting in unsatisfactory wetting. Moreover, the particles are easily broken, and the particles will also crush the current collector 100, causing serious damage to the current collector 100. When Dv50 is less than 11 μm and Dv90 is less than 22 μm, the particle size of the small particles is too small, and the mixing effect of large and small particles cannot be achieved. The current collector 100 will be torn, causing serious damage to the current collector 100.

[0312] As can be seen from Examples 14 to 16, when (H1+Dv50) / (H2+2H3) is greater than 0.8, it indicates that the height of the protrusion 201 is too high, or the particle size is too large, which can easily cause electrode breakage and particle rupture; when (H1+Dv50) / (H2+2H3) is less than 0.1, it indicates that the height of the protrusion 201 is too small, or Dv50 is too small, the ultimate compaction of the material is too small, and it is not easy to ensure the height of the protrusion 201, resulting in poor wetting effect.

[0313] As can be seen from Examples 17 to 19, when H1 / M is greater than 0.4, it indicates that the height of the protrusion 201 is too high, causing excessive stretching of the foil and easily causing damage to the electrode buffer; when H1 / M is less than 0.05, it indicates that the height of the protrusion 201 is too small, resulting in poor wetting effect.

[0314] As can be seen from Examples 20 to 22, when H1 / N1 is greater than 60, it indicates that the height of the protrusion 201 is too high, causing excessive stretching of the foil and easily causing damage to the electrode buffer; when H1 / N1 is less than 10, it indicates that the height of the protrusion 201 is too small, resulting in poor wetting effect.

[0315] As can be seen from Examples 23 to 25, the particles will compress the aluminum foil during embossing, ensuring that the elongation rate N2 of the aluminum foil is 0.5% to 2% to avoid aluminum foil breakage; when the elongation rate N2 is less than 0.5%, the current collector 100 will be torn, causing serious damage to the current collector 100.

[0316] As can be seen from Examples 26 to 28, a wide range of R1 / H1 can provide a suitable gap between the electrode and the separator, that is, the protrusion 201 has suitable deformation space and liquid storage space to provide sufficient support, thereby maximizing the benefit effect. When R1 / H1 is greater than 800, the projected diameter of the protrusion 201 is small, the height of the protrusion 201 is high, and the protrusion 201 is too sharp, which can easily damage the electrode. When R1 / H1 is less than 50, the projected diameter of the protrusion 201 is large, the height of the protrusion 201 is low, the support of the protrusion 201 is insufficient, and the protrusion 201 is easily subjected to excessive deformation due to extrusion and stretching forces during the manufacturing process, tending to flatten, thereby causing the protrusion 201 to collapse and resulting in poor effect on electrolyte wetting, increasing liquid storage capacity, and improving negative electrode expansion.

[0317] As can be seen from Examples 29 to 31, when the ratio of the first radius R1 to the second radius R2 is greater than 1.3, the electrode is easily damaged, slight lithium plating will occur on the negative electrode, and the liquid retention is low, resulting in poor wetting effect. This is because the volume of the protrusion 201 is too large, and there is a crack at the highest point of the protrusion 201; while the volume of the recess 301 is too small, and the structure composed of the protrusion 201 and the recess 301 is prone to collapse, resulting in a small deformation space for the structure composed of the protrusion 201 and the recess 301, and insufficient electrolyte capacity. Conversely, when the ratio of the first radius R1 to the second radius R2 is less than 1.01, it indicates that the volume of the protrusion 201 is too small, while the volume of the recess 301 is too large, and the structure composed of the protrusion 201 and the recess 301 is prone to collapse, resulting in a small deformation space for the structure composed of the protrusion 201 and the recess 301, and insufficient electrolyte capacity.

[0318] As can be seen from Examples 32 to 37, when S1 / S2 is greater than 1.8, the outer surface area of ​​the protrusion 201 is large, while the projected area is small, indicating that the protrusion 201 is tall and easily damages the electrode and causes particle breakage. When S1 / S2 is less than 1.05, the outer surface area of ​​the protrusion 201 is small, while the projected area is large, indicating that the protrusion 201 is short, the support effect is not obvious, and the electrolyte cannot be sufficiently wetted. When S3 / S4 is greater than 1.8, the outer surface area of ​​the recess 301 is large, while the projected area is small, indicating that the recess 301 is tall and easily damages the electrode and causes particle breakage. When S3 / S4 is less than 1.1, the outer surface area of ​​the recess 301 is small, while the projected area is large, indicating that the recess 301 is short, the electrolyte wetting space is small, and the electrolyte cannot be sufficiently wetted.

[0319] As can be seen from Examples 38 to 40, when S11 / S is greater than 0.95, it indicates that the protrusion 201 accounts for a large proportion, and the electrode is easily damaged; when S11 / S is less than 0.1, it indicates that the protrusion 201 accounts for a small proportion, the support effect is not obvious, and the electrolyte cannot be sufficiently wetted.

[0320] As can be seen from Examples 41 to 43, when L1 / L2 is greater than 3, the spacing of the protrusions 201 is too small, and the electrode is easily damaged; when L1 / L2 is less than 1.05, the spacing of the protrusions 201 is too large, the protrusions 201 are too sparse, the support is insufficient, and the electrolyte cannot be sufficiently wetted.

[0321] As can be seen from Examples 44 to 46, when the first included angle a1 is greater than 90 degrees and the relationship between the first included angle a1 and the second included angle a2 (a1 - a2) is greater than 40 degrees, the electrode is damaged, the electrolyte retention is low, and the wetting effect is poor. This is because the tilt angle at the connection between the protrusion 201 and the straight section is too large, causing excessive bending and resulting in electrode damage. Simultaneously, the tilt angle between the protrusion 201 and the recess 301 is too large, making the structure formed by the protrusion 201 and the recess 301 unstable and prone to collapse under compressive stress, thus failing to allow sufficient electrolyte wetting. When the first included angle a1 is less than 0 degrees and the relationship between the first included angle a1 and the second included angle a2 (a1 - a2) is less than 0 degrees, it indicates that the protrusion 201 is too short, is an ineffective protrusion, has poor support, and fails to allow sufficient electrolyte wetting.

[0322] As can be seen from Examples 47 to 49, when the second included angle a2 is greater than 90 degrees and the relationship between the first included angle a1 and the second included angle a2 (a1 - a2) is less than 0 degrees, the electrode is damaged. This is because the tilt angle at the connection between the recessed portion 301 and the straight section is too large, causing excessive bending and resulting in electrode damage. Simultaneously, the tilt angle of the recessed portion 301 relative to the protrusion 201 is too large, making the structure formed by the protrusion 201 and the recessed portion 301 unstable and prone to collapse under compressive stress. When the second included angle a2 is less than 0 degrees and the relationship between the first included angle a1 and the second included angle a2 (a1 - a2) is greater than 40 degrees, the tilt angle of the recessed portion 301 relative to the protrusion 201 is too small, and the depth of the recessed portion 301 is shallow, failing to allow sufficient wetting of the electrolyte.

[0323] As can be seen from Examples 50 to 52, when the first included angle a1 and the second included angle a2 are both within the range of 0 degrees to 90 degrees, but a1 - a2 is greater than 40 degrees, it indicates that the tilt angle at the connection between the protrusion 201 and the straight section is too large, and the highest protrusion point of the protrusion 201 is prone to breakage, causing damage to the electrode sheet; when the first included angle a1 and the second included angle a2 are both within the range of 0 degrees to 90 degrees, but a1 - a2 is less than 0 degrees, it indicates that the tilt angle at the connection between the recessed part 301 and the straight section is too large, causing excessive bending and resulting in damage to the electrode sheet.

[0324] The various embodiments or embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the various embodiments can be referred to each other.

[0325] It should be noted that the terms "one embodiment," "embodiment," "exemplary embodiment," "some embodiments," etc., mentioned in the specification indicate that the described embodiment may include a specific feature, structure, or characteristic, 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.

[0326] 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 "a" or "the" can also be understood to convey either singular or plural usage.

[0327] 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).

[0328] 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.

[0329] 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: Current collector, first active material layer, and second active material layer; The current collector has a first surface and a second surface opposite to each other along the thickness direction of the electrode sheet, the first active material layer is disposed on the first surface, and the second active material layer is disposed on the second surface; The first active material layer has a plurality of protrusions, and the second active material layer has a plurality of recesses corresponding to the protrusions; Both the first and second active material layers include multiple active material particles, which include lithium iron phosphate, lithium manganese iron phosphate, lithium manganese phosphate, and Li. a1 Co x1 M1 k1 O 2、 Li a2 Ni x2 Co y2 D z2 M2 k2 At least one of O2, Wherein, 0.85≤a1≤1.1, 0.85≤a2≤1.1, 0.85≤x1≤1.05, 0.3≤x2≤0.98, 0≤y2≤0.5, 0≤z2≤0.5, 0≤k1≤0.15, 0≤k2≤0.15; D includes at least one of Mn and Al. M1 includes at least one of Al, Mg, Ti, Zr, Y, La, W, B, Nb, and Mn. M2 includes at least one of Mg, Ti, Zr, Y, La, W, B, and Nb. The particle size distribution of the active material particles satisfies: Dv10:Dv50:Dv90=1:(2~8):(3~16); The Dv10 is 2μm~8μm; and / or The Dv50 is 11μm~19μm; and / or The Dv90 is 22μm~32μm; The protrusion has a first intersection point, which intersects with the plane containing the surface of the first active material layer; In the electrode thickness direction, the first intersection point and the highest protrusion point of the protrusion have a first vertical distance H1, where H1 = 3-40 μm; The thickness of the current collector is a first thickness H2, where H2 = 6-20 μm; In the electrode thickness direction, both the first active material layer and the second active material layer have a second thickness H3, where H3 = 30-150 μm; The first vertical distance H1, the first thickness H2, the second thickness H3, and the Dv50 have the following relationship: (H1 + Dv50) / (H2 + 2H3) = 0.1~0.8; Along both the width and length directions of the electrode, the tensile strength M of the current collector is ≥ 50 MPa; and / or, The first vertical distance H1 and the tensile strength M have the following relationship: 0.05 ≤ H1 / M ≤ 0.4; The current collector has a breaking elongation N1, wherein the breaking elongation N1 ≥ 2%; and / or The first vertical distance H1 and the fracture elongation N1 have the following relationship: 10≤H1 / N1≤60; The current collector includes an aluminum foil, the aluminum foil having an elongation N2 of 0.5% to 2%; The protrusion has an arc-shaped outer surface, which is located in the first active material layer. The projection of the arc-shaped outer surface in the thickness direction of the electrode sheet has a first width R1. The recessed portion has an arc-shaped inner surface, which is located in the second active material layer. The projection of the arc-shaped inner surface in the electrode thickness direction has a second width R2. The first width R1 and the second width R2 have the following relationship: R1 / R2 = 1.01~1.3; and / or The first width R1 and the first vertical distance H1 have the following relationship: R1 / H1 = 50~800; The arc-shaped outer surface has a first area S1, and the projection of the arc-shaped outer surface in the electrode thickness direction has a second area S2; the arc-shaped inner surface has a third area S3, and the projection of the arc-shaped inner surface in the electrode thickness direction has a fourth area S4. The first area S1, the second area S2, the third area S3, and the fourth area S4 have the following relationship: S1 / S2 = 1.05~1.8; and / or S3 / S4 = 1.1~1.8; The center-to-center distance between the projections of two adjacent protrusions in the electrode thickness direction is a first distance L1; there is a straight section between two adjacent protrusions, and the straight section has a second distance L2 in the electrode length direction or in the electrode width direction. The first distance L1 and the second distance L2 have the following relationship: L1 / L2 = 1.05~3; The first tangent line is tangent to the first intersection point, and the angle between the first tangent line and the plane containing the surface of the first active material layer is the first included angle α1; The recessed portion has a second intersection point, which intersects with the plane containing the surface of the second active material layer; The second tangent is tangent to the second intersection point, and the angle between the second tangent and the horizontal plane containing the surface of the second active material layer is the second included angle a2; The first included angle a1 and the second included angle a2 have the following relationship: a1-a2=0°~40°; and / or The first included angle a1 is 0°~90°; and / or The second included angle a2 is 0°~90°; The sum of the projected areas of the plurality of protrusions in the thickness direction of the electrode sheet is the fifth area S11, and the projected area of ​​the electrode sheet in the thickness direction is the sixth area S. The fifth area S11 and the sixth area S have the following relationship: S11 / S = 0.1~0.

95.

2. The positive electrode sheet according to claim 1, characterized in that, The head of the electrode includes a first clearance area, which has a third width M1 along the length of the electrode. The head of the electrode includes an initial bending section, and along the length of the electrode, the third width M1 = the width of the initial bending section ± 10 mm; or The head of the electrode includes an initial bending section and a second bending section. In the length direction of the electrode, the third width M1 = the width of the initial bending section + the width of the second bending section ± 10 mm. and / or The tail of the electrode includes an adjacent double-sided coating area and a single-sided coating area. Both surfaces of the double-sided coating area are provided with an active material layer, and one surface of the single-sided coating area is provided with an active material layer. The double-sided coating area and the single-sided coating area have a junction point. Along the length of the electrode sheet, there is a second clearance area between the junction point and the protrusion, and the second clearance area has a fourth width M2, which is 2 mm to 30 mm.

3. The positive electrode sheet according to claim 1, characterized in that, The shape of the projection of the protrusion in the electrode thickness direction includes a circle, a semicircle, an ellipse, a plum blossom shape, or a polygon.

4. A battery cell, characterized in that, The positive electrode sheet includes any one of claims 1-3, and further includes a separator and a negative electrode sheet; The separator includes a substrate, a ceramic layer on one side of the substrate, and an adhesive layer on the other side of the substrate, wherein the ceramic layer is disposed opposite to the protrusion of the positive electrode.

5. The battery cell according to claim 4, characterized in that, The ceramic layer is an inorganic ceramic particle coating, an inorganic ceramic particle + polyvinylidene fluoride coating, or an inorganic ceramic particle + polymethyl methacrylate + polyvinylidene fluoride coating. The content of inorganic ceramic particles in the ceramic layer is ≥50%; The inorganic ceramic particles include one or more of α-Al2O3, γ-Al2O3, Al2O3, SiO2, CeO2, MgAl2O4, ZrO, and TiO2.

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