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, and the particle size distribution of the active material particles meets the formula: Dv10: Dv50: Dv90 = 1: (2-8): (3-16). 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

Technical Field

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

[0002] With the rapid development of lithium-ion battery technology, people have higher requirements for the energy density, cycle life and safety performance of lithium-ion batteries. During the charging and discharging process of lithium-ion batteries, the negative electrode sheet will expand, and the interlayer of the electrode sheet will be squeezed. The interlayer squeezing will lead to insufficient interlayer electrolyte and poor infiltration, which will not only cause the battery capacity to decay rapidly, but also hinder the transmission of lithium ions in the electrolyte-deficient area, which is easy to cause lithium precipitation, affecting the safety of the battery cell. Summary of the invention

[0003] In view of the above problems, the embodiments of the present application provide a positive electrode sheet and a battery cell to solve the technical problems in the above-mentioned related technologies, such as insufficient electrolyte between layers and poor wetting, which may cause rapid attenuation of battery capacity.

[0004] In order to achieve the above objectives, the embodiments of the present application provide the following technical solutions:

[0005] The present 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 arranged on the first surface, and the second active material layer is arranged on the second surface; the first active material layer is provided with a plurality of protrusions, and the second active material layer is provided with a plurality of recessed portions corresponding to the protrusions; the first active material layer and the second active material layer each include a plurality of active material particles, and the active material particles include lithium iron phosphate, lithium manganese iron phosphate, lithium manganese phosphate, Li a1 Co x1 M1 k1 O 2、 Li a2 Ni x2 Co y2 D z2 M2 k2O2, 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, and M2 includes at least one of Mg, Ti, Zr, Y, La, W, B, Nb. The particle size distribution of the active material layer particles satisfies: Dv10:Dv50:Dv90=1:(2~8):(3~16).

[0006] In one embodiment of the present application, the Dv10 is 2 μm to 8 μm; and / or the Dv50 is 11 μm to 19 μm; and / or the Dv90 is 22 μm to 32 μm.

[0007] In one embodiment of the present application, the raised portion has a first intersection, which intersects with the plane where the surface of the first active material layer is located; in the thickness direction of the pole piece, the first intersection and the highest raised point of the raised portion 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 thickness direction of the pole piece, the first active material layer and the second active material layer both 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.

[0008] In one embodiment of the present application, along the width direction and length direction of the pole piece, 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.

[0009] In one embodiment of the present application, the current collector has a fracture elongation N1, and the fracture elongation N1 ≥ 2%; and / or the first vertical distance H1 and the fracture elongation N1 have the following relationship: 10≤H1 / N1≤60.

[0010] In one embodiment of the present application, the current collector includes aluminum foil, and the aluminum foil has an elongation N2, and the elongation N2 is 0.5% to 2%.

[0011] In one embodiment of the present application, the raised portion has an arcuate outer surface, the arcuate outer surface is located in the first active material layer, and the projection of the arcuate outer surface in the thickness direction of the pole piece has a first width R1; the recessed portion has an arcuate inner surface, the arcuate inner surface is located in the second active material layer, and the projection of the arcuate inner surface in the thickness direction of the pole piece 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.

[0012] In one embodiment of the present application, the curved outer surface has a first area S1, and the projection of the curved outer surface in the direction of the thickness of the pole piece has a second area S2; the curved inner surface has a third area S3, and the projection of the curved inner surface in the direction of the thickness of the pole piece 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.

[0013] In one embodiment of the present application, the center interval between the projections of two adjacent protrusions in the thickness direction of the pole piece is a first distance L1; there is a straight section between the two adjacent protrusions, and the straight section has a second distance L2 in the length direction of the pole piece or in the width direction of the pole piece; the first distance L1 and the second distance L2 have the following relationship: L1 / L2=1.05~3.

[0014] In one embodiment of the present application, a first tangent line is tangent to the first intersection point, and an angle between the first tangent line and the plane where the surface of the first active material layer is located is a first angle a1; the recessed portion has a second intersection point, and the second intersection point intersects with the plane where the surface of the second active material layer is located; a second tangent line is tangent to the second intersection point, and an angle between the second tangent line and the horizontal plane where the surface of the second active material layer is located is a second angle a2; the first angle a1 and the second angle a2 have the following relationship: a1-a2=0°~40°; and / or the first angle a1 is 0°~90°; and / or the second angle a2 is 0°~90°.

[0015] In one embodiment of the present application, the sum of the projection areas of the plurality of protrusions in the thickness direction of the pole piece is a fifth area S11, and the projection area of ​​the pole piece in its 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.

[0016] In one embodiment of the present application, the head of the pole piece includes a first avoidance zone, and in the length direction of the pole piece, the first avoidance zone has a third width M1; the head of the pole piece includes an initial bending section, and in the length direction of the pole piece, the third width M1=the width of the initial bending section±10mm; or the head of the pole piece includes an initial bending section and a second bending section, and in the length direction of the pole piece, the third width M1=the width of the initial bending section+the width of the second bending section±10mm; and / or the tail of the pole piece includes adjacent double-sided coating areas and single-sided coating areas, both surfaces of the double-sided coating areas are provided with active material layers, one of the surfaces of the single-sided coating areas is provided with an active material layer, and the double-sided coating area and the single-sided coating area have an intersection point; in the length direction of the pole piece, there is a second avoidance zone between the intersection point and the raised portion, and the second avoidance zone has a fourth width M2, and the fourth width M2 is 2mm~30mm.

[0017] In one embodiment of the present application, the projection of the protrusion in the thickness direction of the pole piece has a shape including a circle, a semicircle, an ellipse, a plum blossom or a polygon.

[0018] An embodiment of the present application also provides a battery cell, which includes the positive electrode sheet described above, and also includes a diaphragm and a negative electrode sheet; the diaphragm includes a substrate and a ceramic layer located on one side of the substrate and a glue layer located on the other side of the substrate, and the ceramic layer is arranged opposite to the raised portion of the positive electrode sheet.

[0019] In one embodiment of the present 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.

[0020] The positive electrode sheet provided in the embodiment of the present application has the following technical effects:

[0021] The embodiments of the present application form a plurality of raised portions and a plurality of corresponding recessed portions on the positive electrode sheet, wherein the raised portions are formed by part of the positive electrode sheet protruding from one surface to the other surface; firstly, the raised portions can effectively support the diaphragm, ensure that there is sufficient diaphragm space between the layers of the positive electrode sheet and the negative electrode sheet and between the layers of the positive electrode sheet and the diaphragm, improve the distribution of the electrolyte, increase the liquid storage capacity between the layers, ensure a good wetting effect, and avoid insufficient electrolyte infiltration in the late stage of the cycle, thereby eliminating the risk of insufficient electrolyte and insufficient infiltration caused by multiple squeezing between the positive and negative electrode sheets inside the battery cell due to repeated expansion and contraction of the negative electrode sheet during the charge and discharge process, improve the problems of interface deterioration between the electrode sheets, poor cycle stability of the negative electrode, and reduced battery capacity retention rate, reduce the decay rate of the battery capacity, and improve the cycle life of the battery cell.

[0022] In addition, forming multiple protrusions on the positive electrode sheet can improve the deformation capacity of the positive electrode sheet. When the positive electrode sheet contacts the expanded negative electrode sheet, the protrusions on the positive electrode sheet can effectively absorb the expansion stress of the negative electrode sheet, which can buffer the expansion of the negative electrode sheet during the battery cycle and avoid excessive expansion stress of the negative electrode sheet and cracks. Moreover, the protrusions set on the positive electrode sheet can absorb part of the expansion stress of the negative electrode sheet, so that the negative electrode sheet does not completely rely on the resistance of its own material when expanding, delaying the fatigue of the negative electrode material, thereby increasing the service life of the negative electrode sheet.

[0023] In addition, the particle size distribution of the active material particles in the active material layer is limited mainly because if the particle size of most of the active material particles in the active material layer is too large, when forming the protrusion, the large-sized active material particles are difficult to move, resulting in the height of the protrusion being difficult to meet the requirements. If the height of the protrusion is to meet the requirements, the stamping pressure needs to be increased, which will cause the large-sized active material particles to break and reduce the energy output of the positive electrode sheet. In addition, increasing the stamping pressure will also cause the active material layer particles to squeeze and crack the current collector of the positive electrode sheet. Therefore, by limiting the particle size distribution of the active material particles in the active material layer, large and small particles are mixed in the active material layer, and small particles can be filled between large particles. In the process of machining the protrusions and recessed portions on the electrode sheet, the small particles slide to both sides due to the extrusion force and are filled between the large particles. While avoiding the breakage of the active material particles, the current collector is protected from being torn, and the height of the protrusion can be guaranteed to meet the predetermined requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 Schematic diagram of the structure of the positive electrode sheet provided in the embodiment of the present application Figure 1 ;

[0026] Figure 2 Schematic diagram of the structure of the positive electrode sheet provided in the embodiment of the present application Figure 2 ;

[0027] Figure 3 Schematic diagram of the structure of the positive electrode sheet provided in the embodiment of the present application Figure 3 ;

[0028] Figure 4 Schematic diagram of the structure of the positive electrode sheet provided in the embodiment of the present application Figure 4 ;

[0029] Figure 5 A schematic diagram of the top view of the positive electrode sheet provided in an embodiment of the present application;

[0030] Figure 6 Schematic diagram of double-sided coating and single-sided coating of the positive electrode sheet provided in the embodiment of the present application;

[0031] Figure 7 A schematic diagram of the structure of the winding core provided in an embodiment of the present application.

[0032] Reference numerals:

[0033] 100: current collector;

[0034] 110: positive electrode sheet; 120: negative electrode sheet; 130: separator; 140: first center plane;

[0035] 200: first active material layer;

[0036] 201: raised portion;

[0037] 2011: arc-shaped outer surface; 2012: highest convex point; 2013: first intersection point;

[0038] 300: second active material layer;

[0039] 301: recessed portion;

[0040] 3011: arc inner surface; 3012: second intersection point;

[0041] 401: Tab; 402: Protective glue;

[0042] 501: first air avoidance zone; 502: second air avoidance zone; 503: third air avoidance zone;

[0043] 600: Junction point;

[0044] 601: first tangent line; 602: second tangent line. DETAILED DESCRIPTION

[0045] In a wound lithium-ion battery, the electrode assembly is stacked and wound to form a wound structure of the battery cell. The cross-section of the wound structure presents a flat elliptical structure, with arc areas on both sides of the elliptical structure and a flat area in the middle of the elliptical structure. During the charge and discharge process of the lithium-ion battery, the positive and negative electrodes of the battery will expand. The flat area can expand freely upward and downward, but the arc area is constrained from expanding outward due to its structural characteristics and stress accumulation, and eventually the electrode layers are squeezed, resulting in problems such as diaphragm blockage, poor electrolyte infiltration, and lithium precipitation.

[0046] At the same time, the extrusion of the arc area will also be transmitted to the flat area. Since the flat area has undergone extrusion in the hot pressing process during the production process, the flat area will be squeezed very tightly, which will lead to poor electrolyte infiltration in the flat area.

[0047] The winding core provided in the embodiment of the present application forms a positive electrode sheet after coating the active material layer on both sides of the current collector, and then a special roller is used to process a protrusion and a recessed portion corresponding to the protrusion on the positive electrode sheet. The combination of the protrusion and the recessed portion provides support for the contact of the diaphragm, increases the micro-spacing between the positive electrode sheet and the diaphragm, and these micro-spacings form a space that can accommodate the electrolyte, so that the electrolyte has sufficient infiltration amount to the electrode sheet, avoiding the abnormal situation of insufficient electrolyte between the electrode sheet and the diaphragm, poor infiltration, and even lithium deposition on the negative electrode sheet due to interlayer extrusion of the electrode sheet.

[0048] However, in the process of machining the raised and recessed parts on the positive electrode sheet using special rollers, the electrode sheet may easily break, seriously affecting production efficiency and process yield.

[0049] By limiting the particle size distribution of the active material particles in the active material layer, large and small particles are mixed in the active material layer, and small particles can be filled between large particles; in the process of processing the protrusions and recesses on the positive electrode sheet, the small particles slide to both sides due to the extrusion force and are filled between the large particles; while avoiding the breakage of the active material particles, the current collector is protected from being torn, and at the same time, the height of the protrusion can be guaranteed to meet the predetermined requirements.

[0050] In order to make the above-mentioned purposes, features and advantages of the embodiments of the present application more obvious and understandable, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of this application.

[0051] In the embodiment of the present application, the thickness direction of the pole piece is the z-axis shown in the figure, the length direction of the pole piece is the x-axis shown in the figure; the width direction of the pole piece is the y-axis shown in the figure.

[0052] refer to Figure 1 The positive electrode sheet provided in the embodiment of the present application includes: a current collector 100 , a first active material layer 200 and a second active material layer 300 .

[0053] The current collector 100 has a first surface and a second surface opposite to each other along the thickness direction of the electrode sheet (z axis shown in the figure), the first active material layer 200 is arranged on the first surface, and the second active material layer 300 is arranged on the second surface.

[0054] The first active material layer 200 is provided with a plurality of protrusions 201 , and the second active material layer 300 is provided with a plurality of depressions 301 corresponding to the protrusions 201 .

[0055] The protrusion 201 corresponds to the recess 301 in that the projection of the protrusion 201 along the thickness direction of the pole piece (z axis shown in the figure) covers the projection of the recess 301 along the thickness direction of the pole piece.

[0056] The protrusions 201 and the depressions 301 are respectively arranged on the first active material layer 200 and the second active material layer 300 coated on the two surfaces of the current collector 100, which can provide support for the contact of the diaphragm and increase the micro-spacing between the electrode sheet and the diaphragm. These micro-spacings form a space for accommodating the electrolyte, so that the electrolyte has sufficient infiltration amount to the electrode sheet, avoiding the abnormal situation of insufficient electrolyte between the electrode sheet and the diaphragm, poor infiltration and even lithium deposition on the negative electrode sheet due to interlayer extrusion of the electrode sheet.

[0057] The first active material layer 200 and the second active material layer 300 each include a plurality of active material particles, the active material particles including lithium iron phosphate, lithium manganese iron phosphate, lithium manganese phosphate, Li a1 Co x1 M1 k1 O 2、 Li a2 Ni x2 Co y2 D z2 M2 k2 At least one of O2.

[0058] Among them, 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.

[0059] D includes at least one of Mn and Al.

[0060] M1 includes at least one of Al, Mg, Ti, Zr, Y, La, W, B, Nb and Mn.

[0061] M2 includes at least one of Mg, Ti, Zr, Y, La, W, B, and Nb.

[0062] The particle size distribution of the active material layer particles satisfies: Dv10:Dv50:Dv90=1:(2-8):(3-16).

[0063] Preferably, Dv10:Dv50:Dv90=1:(2-7):(5-13).

[0064] Among them, Dv10 represents the particle size at which the volume accumulation reaches 10% in the volume-based particle size distribution; Dv50 represents the particle size at which the volume accumulation reaches 50% in the volume-based particle size distribution; Dv90 represents the particle size at which the volume accumulation reaches 90% in the volume-based particle size distribution.

[0065] That is to say, 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 be filled between the large particles. When the protrusions 201 and the depressions 301 are processed on the electrode sheet, the small particles slide to both sides due to the extrusion force and are filled between the large particles. This prevents the active material particles from breaking while protecting the current collector from being torn, and at the same time ensures that the height of the protrusion 201 meets the predetermined requirements.

[0066] When Dv10 is unchanged, the ratio of Dv50 to Dv10 is greater than 8, and the ratio of Dv90 to Dv10 is greater than 16, the particle size at which the volume accumulation reaches 10% is too large, and the particle size at which the volume accumulation reaches 90% is too large; this indicates that the particle size of most active material particles in the active material layer is too large, and when processing the protrusion 201 on the electrode sheet, the active material particles with large particle size are difficult to move, resulting in insufficient height of the protrusion 201, insufficient depth of the recess 301, and unsatisfactory electrolyte infiltration. Under the premise that the particle size of most active material particles is too large, in order to make the height of the protrusion 201 meet the requirements, the stamping pressure needs to be increased, which will cause the active material particles with large particle size to break and reduce the energy output of the positive electrode sheet; at the same time, the high stamping pressure will also cause the active material layer particles to squeeze the collector 100 of the positive electrode sheet.

[0067] When Dv10 remains unchanged, the ratio of Dv50 and Dv10 is less than 2, and the ratio of Dv90 and Dv10 is less than 3, it means that the particle size at which the volume accumulation reaches 10%, the particle size at which the volume accumulation reaches 50%, and the particle size at which the volume accumulation reaches 90% are slightly different, and the effect of mixing large and small particles cannot be achieved; the relatively small particles slide to both sides due to the extrusion pressure, and the current collector of the positive electrode sheet is directly affected by the pressure, which can easily cause the current collector 100 of the positive electrode sheet to be subjected to excessive pressure and fracture.

[0068] In the embodiment of the present application, Dv10 is 2 μm to 8 μm, which means that among the particles of the multiple active material layers, the particle size of which the cumulative volume reaches 10% is between 2 μm and 8 μm; preferably, Dv10 is 2 μm to 7 μm.

[0069] Dv50 is 11 μm to 19 μm, which means that among the particles of the multiple active material layers, the particle size of which the cumulative volume reaches 50% is between 11 μm and 19 μm; preferably, Dv50 is 12 μm to 16 μm.

[0070] Dv90 is 22 μm to 32 μm, which means that among the particles of the multiple active material layers, the particle size of which the cumulative volume reaches 90% is between 22 μm and 32 μm; preferably, Dv90 is 24 μm to 32 μm.

[0071] When Dv50 is between 11μm and 19μm, Dv90 is between 22μm and 32μm, but Dv10 is greater than 8μm; it means that the particle size of the small particles is too large, and the particle size of most active material particles in the active material layer is too large. When processing the protrusion 201 on the electrode sheet, the large-sized active material particles are difficult to move, resulting in insufficient height of the protrusion 201, insufficient depth of the recessed portion 301, and unsatisfactory electrolyte infiltration; in order to ensure the height of the protrusion 201, continued stamping will also cause the large-sized active material particles to break, and the high stamping pressure will also cause the active material layer particles to squeeze the collector 100 of the positive electrode sheet.

[0072] When Dv50 is between 11μm and 19μm, Dv90 is between 22μm and 32μm, but Dv10 is less than 2μm; it means that the particle size of the small particles is too small, the existence of the small particles is meaningless, most of the active material particles in the active material layer are large in size, and the large-size active material particles are difficult to move, resulting in insufficient height of the protrusion 201, insufficient depth of the recessed portion 301, and unsatisfactory electrolyte infiltration; in order to ensure the height of the protrusion 201, continued stamping will also cause the large-size active material particles to break, and the high stamping pressure will also cause the active material layer particles to squeeze the collector 100 of the positive electrode sheet.

[0073] When Dv10 is between 2μm and 8μm, Dv90 is between 22μm and 32μm, but Dv50 is greater than 19μm; it means that the particle size of the large particles is too large, and the particle size of most active material particles in the active material layer is too large. When processing the protrusion 201 on the electrode sheet, the large-sized active material particles are difficult to move, resulting in insufficient height of the protrusion 201, insufficient depth of the recessed portion 301, and unsatisfactory electrolyte infiltration; in order to ensure the height of the protrusion 201, continued stamping will also cause the large-sized active material particles to break, and the high stamping pressure will also cause the active material layer particles to squeeze the collector 100 of the positive electrode sheet.

[0074] When Dv10 is between 2μm and 8μm, Dv90 is between 22μm and 32μm, but Dv50 is less than 11μm; it means that the particle size of the large particles is too small, and most of the active material particles in the active material layer are small in size, resulting in the active material particles being stacked in the first active material layer 200 and the second active material layer 300. The greater the density, the fewer the corresponding pores; the small particles with relatively small particle sizes are insufficient to fill the space when they slide to both sides under the extrusion force, which will cause the active material particles to break and reduce the energy output of the positive electrode; at the same time, the active material layer particles will also cause the positive electrode current collector 100 to be squeezed and cracked.

[0075] When Dv10 is between 2μm and 8μm, Dv50 is between 11μm and 19μm, but Dv90 is greater than 32μm; it means that the particle size of the large particles is too large, and the particle size of most active material particles in the active material layer is too large. When processing the protrusion 201 on the electrode sheet, the large-sized active material particles are difficult to move, resulting in insufficient height of the protrusion 201, insufficient depth of the recessed portion 301, and unsatisfactory electrolyte infiltration; in order to ensure the height of the protrusion 201, continued stamping will also cause the large-sized active material particles to break, and the high stamping pressure will also cause the active material layer particles to squeeze the collector 100 of the positive electrode sheet.

[0076] When Dv10 is between 2μm and 8μm, Dv50 is between 11μm and 19μm, but Dv90 is less than 22μm; it means that the particle size of the large particles is too small, and most of the active material particles in the active material layer are small in size, resulting in the active material particles being stacked in the first active material layer 200 and the second active material layer 300. The greater the density, the fewer the corresponding pores; the small particles with relatively small particle sizes are squeezed to both sides and slide due to the insufficient filling space, which will cause the active material particles to break and reduce the energy output of the positive electrode; at the same time, the active material layer particles will also cause the positive electrode current collector 100 to be squeezed and cracked.

[0077] refer to Figure 2In the embodiment of the present application, the raised portion 201 has a first intersection 2013, and the first intersection 2013 intersects with the plane where the surface of the first active material layer 200 is located; in the thickness direction of the electrode sheet (the z-axis shown in the figure), the first intersection 2013 and the highest raised point 2012 of the raised portion 201 have a first vertical distance H1; the first vertical distance H1=3μm~40μm, preferably, the first vertical distance H1=3μm~30μm.

[0078] 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 provided between the pole piece and the diaphragm, thereby providing support and preventing the pole piece from being too thick.

[0079] When the first vertical distance H1 is less than 3 μm, it means that the protrusion 201 is too short and the supporting effect is not obvious. The protrusion 201 is an invalid protrusion and cannot allow sufficient infiltration of the electrolyte. When the first vertical distance H1 is greater than 40 μm, it means that the protrusion 201 is too high, which will lead to serious stratification between the positive and negative electrode sheets and cause new interface problems.

[0080] The thickness of the current collector 100 is a first thickness H2, and the first thickness H2=6 μm to 20 μm; preferably, the first thickness H2=8 μm to 18 μm.

[0081] In the thickness direction of the electrode (z-axis shown in the figure), the first active material layer 200 and the second active material layer 300 both 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.

[0082] The above relationship can better balance the height of the protrusion 201, avoiding damage to the current collector 100 and particle rupture, wherein H2+2H3 refers to the thickness of the entire pole piece, and H1+Dv50 represents the height of the apex of the protrusion. When (H1+Dv50) / (H2+2H3) is greater than 0.5, the height of the apex of the protrusion 201 is too high, and the particle size of the large particles is too large and too many, which can easily cause the pole piece to be damaged and the particles to be ruptured when the pole piece is embossed, and the particles at the apex of the protrusion are too large and can easily cause powder loss; when (H1+Dv50) / (H2+2H3) is less than 0.3, the height of the protrusion 201 is too small, and the wetting effect is not satisfied, or DV50 is too small, and the ultimate compaction of the material is too small, and it is difficult to ensure the height of the protrusion 201.

[0083] In the embodiment of the present application, along the width direction of the pole piece (the y-axis shown in the figure) and the length direction of the pole piece (the x-axis shown in the figure), the tensile strength M of the current collector 100 is ≥50MPa; 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. The tensile strength M of the current collector 100 ≥50MPa can prevent the current collector 100 from breaking.

[0084] 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.

[0085] The first vertical distance H1 is the height of the protrusion 201 . The higher the protrusion 201 is, the greater the compressive stress caused by the protrusion 201 on the current collector 100 is. 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.

[0086] When H1 / M is greater than 0.4, it means that the protrusion 201 is too high and the tensile strength of the current collector 100 is insufficient. The greater the extrusion stress caused by the protrusion 201 on the current collector 100, the more likely it is that the current collector 100 will break. When H1 / M is less than 0.05, it means that the protrusion 201 is too short and the supporting effect is not obvious. The protrusion 201 is an invalid protrusion and cannot allow sufficient infiltration of the electrolyte.

[0087] In the embodiment of the present application, the current collector 100 has a fracture elongation N1, and the fracture elongation N1 is ≥ 2%. The larger the fracture elongation N1 of the current collector 100 is, the better the ductility of the current collector 100 is. The fracture elongation N1 ≥ 2% can prevent the current collector from breaking.

[0088] In the embodiment of the present 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.

[0089] The greater the height of the protrusion 201 is, the greater the compressive stress it causes to the current collector 100 is. Therefore, by limiting the relationship between the height of the protrusion 201 and the fracture elongation N1 of the current collector 100 , the current collector 100 is prevented from being broken.

[0090] When H1 / N1 is greater than 60, it means that the protrusion 201 is too high and the ductility of the current collector 100 is insufficient. The greater the extrusion stress caused by the protrusion 201 on the current collector 100, the more likely it is that the current collector 100 will break. When H1 / N1 is less than 10, it means that the protrusion 201 is too short and the supporting effect is not obvious. The protrusion 201 is an invalid protrusion and cannot allow sufficient infiltration of the electrolyte.

[0091] In the embodiment of the present application, the current collector 100 includes an aluminum foil, and a hole structure, a concave-convex structure or a carbon material is provided on the aluminum foil.

[0092] The hole structure provided 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 to prevent the current collector 100 from being separated from the active material layer when the protrusion 201 is manufactured.

[0093] Providing a concave-convex structure on the aluminum foil means using a special roller to roll the current collector 100 to form 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 separating from the active material layer when the protrusion 201 is manufactured.

[0094] A carbon material is disposed on the aluminum foil to obtain a carbon-containing aluminum foil, which can improve the adhesion between the active material layer and the current collector 100 and prevent the current collector 100 from being separated from the active material layer when the protrusion 201 is manufactured.

[0095] The thickness of the aluminum foil is also the thickness of the current collector 100 , and the first thickness H2 of the current collector 100 is 6-20 μm.

[0096] In the embodiment of the present application, the aluminum foil has an elongation N2, and the elongation N2 is 0.5% to 2%; preferably, the elongation N2 is 1% to 2%.

[0097] When manufacturing the protrusion 201, the aluminum foil will be squeezed. By limiting the elongation rate N2 of the aluminum foil, it is ensured that the aluminum foil can sufficiently support the elongation caused by processing the protrusion 201, and when the active material particles squeeze the aluminum foil, the aluminum foil is prevented from breaking.

[0098] refer to Figure 3 In the embodiment of the present application, the raised portion 201 has a curved outer surface 2011, the curved outer surface 2011 is located in the first active material layer 200, and the projection of the curved outer surface 2011 in the thickness direction of the pole piece (the z-axis shown in the figure) has a first width R1; the recessed portion 301 has a curved inner surface 3011, the curved inner surface 3011 is located in the second active material layer 300, and the projection of the curved inner surface 3011 in the thickness direction of the pole piece (the z-axis shown in the figure) has a second width R2.

[0099] 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.

[0100] By limiting the ratio of the first width R1 to the second width R2 , the sharpness of the protrusion 201 can be limited, thereby preventing the protrusion 201 from causing damage to the pole piece.

[0101] The first width R1 may be 0.5 mm to 8 mm. Preferably, the first width R1 may be 1 mm to 4 mm.

[0102] When the first width R1 is less than 0.5 mm, the width of the protrusion 201 is insufficient, the supporting effect is not obvious, and the negative electrode expansion cannot be effectively improved; when the first width R1 is greater than 8 mm, the width of the protrusion 201 is too large, and the protrusion 201 is easily affected by the extrusion force, the stretching force and the cyclic expansion force during the manufacturing process, thereby causing the protrusion 201 to be excessively deformed, causing the protrusion 201 to collapse and unable to effectively improve the negative electrode expansion.

[0103] The second width R2 may be 0.5 mm to 8 mm. Preferably, the second width R2 may be 0.8 mm to 4 mm.

[0104] When the second width R2 is less than 0.5 mm, the width of the recessed portion 301 is too small, resulting in insufficient electrolyte accommodation space and unable to effectively improve the electrolyte infiltration effect; when the second width R2 is greater than 8 mm, the width of the recessed portion 301 is too large, and the recessed portion 301 is easily affected by extrusion force, stretching force and cyclic expansion force during the manufacturing process, thereby causing the recessed portion 301 to deform excessively, causing the recessed portion 301 to collapse and unable to effectively improve the electrolyte infiltration effect.

[0105] In the embodiment of the present application, the first width R1 and the first vertical distance H1 have the following relationship: R1 / H1=50-800; preferably, R1 / H1=100-300.

[0106] By limiting the projection width and height of the protrusion 201 , a suitable gap can be provided between the pole piece 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.

[0107] When the projection width of the protrusion 201 is small and the height of the protrusion 201 is high, the protrusion 201 is relatively sharp and easily causes damage to the electrode sheet, thus affecting the safety performance of the battery.

[0108] When the projection width of the protrusion 201 is large and the height of the protrusion 201 is high, the protrusion 201 is relatively sharp and the protrusion 201 occupies too much space, exceeding the ductility of the pole piece, resulting in the ductility of the pole piece being insufficient to support the deformation of the protrusion 201, which can easily cause the pole piece to break.

[0109] When the projection width of the protrusion 201 is large and the height of the protrusion 201 is low, the support of the protrusion 201 is insufficient, and the protrusion 201 is easily subjected to extrusion force and stretching force during the manufacturing process, resulting in excessive deformation and tending to be flattened, causing the protrusion 201 to collapse and fail to improve the electrolyte infiltration effect, increase the liquid storage capacity, and improve the negative electrode expansion.

[0110] When the projection width of the protrusion 201 is small and the height of the protrusion 201 is low, the support of the protrusion 201 is insufficient and the protrusion 201 occupies a small space, which has poor effects on improving the electrolyte infiltration effect, increasing the liquid storage capacity and improving the negative electrode expansion.

[0111] Continue to refer Figure 3 In the embodiment of the present application, the arcuate outer surface 2011 has a first area S1, and the projection of the arcuate outer surface 2011 in the direction of the thickness of the pole piece (the z-axis shown in the figure) has a second area S2; the arcuate inner surface 3011 has a third area S3, and the projection of the arcuate inner surface 3011 in the direction of the thickness of the pole piece has a fourth area S4.

[0112] 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.

[0113] By limiting the above ratio, the volume of the protrusion 201 can be better regulated, so that the positive electrode has a suitable deformation space, which can improve the cycle performance of the battery, thereby achieving a better improvement effect.

[0114] When the first area S1 is large and the second area S2 is small, it means that the height of the protrusion 201 is relatively high, which may easily cause damage to the pole piece and particle breakage.

[0115] When the first area S1 is large and the second area S2 is large, it means that the height of the protrusion 201 is low and the support of the protrusion 201 is insufficient. The protrusion 201 is easily deformed by excessive extrusion force and stretching force during the manufacturing process and tends to be flattened, resulting in the collapse of the protrusion 201 and the inability to improve the electrolyte infiltration effect, increase the liquid storage capacity, and improve the negative electrode expansion.

[0116] When the first area S1 is small and the second area S2 is large, it means that the height of the protrusion 201 is relatively low and the support of the protrusion 201 is insufficient. The protrusion 201 is easily subjected to extrusion force and stretching force during the manufacturing process and is excessively deformed and tends to be flattened, resulting in the collapse of the protrusion 201 and being unable to improve the electrolyte infiltration 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 small, it means that the height of the protrusion 201 is low and the protrusion 201 occupies a small space, which has poor improvement on the electrolyte infiltration effect, the increase of the liquid storage amount and the negative electrode expansion.

[0118] 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.

[0119] By limiting the above ratio, the volume of the recessed portion 301 can be better regulated, thereby effectively improving the electrolyte infiltration effect and increasing the electrolyte storage capacity.

[0120] When the third area S3 is large and the fourth area S4 is small, it means that the height of the recessed portion 301 is relatively high, which may easily cause damage to the electrode and particle breakage.

[0121] When the third area S3 is large and the fourth area S4 is large, it means that the height of the recessed portion 301 is low, and the recessed portion 301 is easily deformed by excessive extrusion force and stretching force during the manufacturing process and tends to be flattened, resulting in the collapse of the raised portion 201 and the inability to improve the electrolyte infiltration effect and increase the liquid storage capacity.

[0122] When the third area S3 is small and the fourth area S4 is large, it means that the height of the recessed portion 301 is relatively low. The recessed portion 301 is easily deformed by excessive extrusion force and stretching force during the manufacturing process and tends to be flattened, resulting in the collapse of the raised portion 201 and the inability to improve the electrolyte infiltration effect and increase the liquid storage capacity.

[0123] When the third area S3 is small and the fourth area S4 is small, it means that the height of the recessed portion 301 is relatively low and the recessed portion 301 occupies a small space, which does not improve the electrolyte infiltration effect, increase the liquid storage capacity and the negative electrode expansion well.

[0124] refer to Figure 1 In the embodiment of the present application, the center interval of the projections of two adjacent protrusions 201 in the thickness direction of the pole piece (z axis shown in the figure) is a first distance L1; there is a straight section between the two adjacent protrusions 201, and the straight section has a second distance L2 in the length direction of the pole piece or in the width direction of the pole piece.

[0125] The first distance L1 and the second distance L2 have the following relationship: L1 / L2=1.05-3; preferably, L1 / L2=1.1-2.

[0126] The limitation on 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 supporting force for the pole piece, so that the pole piece has sufficient deformation space to alleviate expansion.

[0127] The first distance L1 is 2 mm to 10 mm; preferably, the first distance L1 is 3 mm to 8 mm.

[0128] The second distance L2 is 0.5 mm to 8 mm; preferably, the second distance L2 is 1 mm to 4 mm.

[0129] When the first distance L1 is less than 2 mm, the protrusions 201 are too dense, the extension of the pole piece 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 pole piece is easy to break. When the first distance L1 is greater than 10 mm, the protrusions 201 are too sparse, the protrusions 201 are too dispersed, and the support area of ​​the protrusions 201 is insufficient, so that the electrolyte infiltration effect and improvement effect cannot be achieved.

[0130] Similarly, when the second distance L2 is less than 0.5 mm, the protrusions 201 are too dense, the extension of the pole piece 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 pole piece is easy to break. When the second distance L2 is greater than 8 mm, the protrusions 201 are too sparse, the protrusions 201 are too dispersed, and the support area of ​​the protrusions 201 is insufficient, so that the electrolyte infiltration effect and improvement effect cannot be achieved.

[0131] refer to Figure 4 In the embodiment of the present application, the first tangent line 601 is tangent to the first intersection point 2013, and the angle between the first tangent line 601 and the plane where the surface of the first active material layer 200 is located is a first angle a1; the recessed portion 301 has a second intersection point 3012, and the second intersection point 3012 intersects with the plane where the surface of the second active material layer 300 is located; the second tangent line 602 is tangent to the second intersection point 3012, and the angle between the second tangent line 602 and the horizontal plane where the surface of the second active material layer 300 is located is a second angle a2.

[0132] The first angle a1 and the second angle a2 have the following relationship: a1-a2=0°~40°; preferably, a1-a2=5°~25°.

[0133] The first angle a1 is 0° to 90°; preferably, the first angle a1 is 25° to 80°.

[0134] The second angle a2 is 0° to 90°; preferably, the second angle a2 is 5° to 55°.

[0135] Limiting the first angle a1 is equivalent to limiting the height and inclination angle of the protrusion 201. When the first 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 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 supporting force of the protrusion 201, which is easily flattened during the process and cycle.

[0136] Limiting the second angle a2 is equivalent to limiting the height and inclination angle of the recessed portion 301. When the second angle a2 is greater than 90°, the recessed portion 301 is prone to breakage at the connection with the straight section; when the second angle a2 is less than 0°, the recessed portion 301 tends to be straight, and the recessed portion 301 occupies a small space, which cannot improve the electrolyte infiltration effect and increase the liquid storage capacity.

[0137] Theoretically, when processing the raised portion 201 , the second angle a2 belongs to the pressure-bearing side, and the second angle a2 is smaller than the first angle a1 to avoid fracture at the junction of the recessed portion 301 and the straight section.

[0138] In the embodiment of the present application, the sum of the projection areas of the plurality of protrusions 201 in the thickness direction of the pole piece (z axis shown in the figure) is a fifth area S11, and the projection area of ​​the pole piece in its thickness direction is a sixth area S.

[0139] 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.

[0140] Each protrusion 201 can provide a supporting point, and multiple supporting points can disperse the expansion stress of the negative electrode sheet to a certain extent; the limitation of the above ratio relationship can effectively ensure the contact area between the supporting point of the positive electrode sheet and the negative electrode sheet, and the technical effect has been achieved.

[0141] When the fifth area S11 is large, it means that the protrusion 201 accounts for a large proportion, and the electrode is easily damaged. When the fifth area S11 is small, it means that the protrusion 201 accounts for a small proportion, the supporting effect is not obvious, and the electrolyte cannot be sufficiently infiltrated.

[0142] refer to Figure 5 and Figure 6 In the embodiment of the present application, the head of the pole piece includes a first avoidance zone 501, and in the length direction of the pole piece (the x-axis shown in the figure), the first avoidance zone 501 has a third width M1; the head of the pole piece includes an initial bending section and a second bending section, and in the length direction of the pole piece, the third width M1=the width of the initial bending section±10mm; or, the third width M1=the width of the initial bending section+the width of the second bending section±10mm.

[0143] The first avoidance area 501 can prevent the head of the pole piece from being folded when entering the pole piece, thereby solving the problem of unstable structure caused by the head of the pole piece entering the pole piece unsteadily during winding.

[0144] The tail of the pole piece includes an adjacent double-sided coating area and a single-sided coating area, both surfaces of the double-sided coating area are provided with active material layers, one of the surfaces 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 600; in the length direction of the pole piece (the x-axis shown in the figure), there is a second avoidance area 502 between the junction point 600 and the raised portion 201, and the second avoidance area 502 has a fourth width M2, and the fourth width M2 is 2mm~30mm.

[0145] The tail of the pole piece has an empty foil area, and the provision of the second air-avoiding area 502 can avoid the problem of foil damage in the empty foil area.

[0146] Continue to refer Figure 5 In the embodiment of the present application, in the width direction of the pole piece (the y-axis shown in the figure), the pole piece includes a first edge and a second edge opposite to each other, and both the first edge and the second edge include a third avoidance area 503 where no protrusion 201 is provided.

[0147] By providing clearance for the first edge and the second edge, it is possible to prevent edge curling and poor interface uniformity of the first edge and the second edge caused by rolling stress.

[0148] Continue to refer Figure 5 In the embodiment of the present application, the pole piece includes a fourth air avoidance area 504 where no protrusion 201 is provided, and the fourth air avoidance area 504 is constructed to provide a pole ear 401, and the pole ear 401 is provided in the fourth air avoidance area 504 through a pole ear protection glue 402; in the length direction of the pole piece (the x-axis shown in the figure), there is a fifth width K between the edge of the pole ear protection glue 402 and the protrusion 201, and the fifth width K is 2mm to 30mm.

[0149] The fourth avoidance area 504 can prevent the pole piece region where the pole tab 401 is provided from being damaged due to rolling stress, thereby ensuring the welding stability and interface uniformity of the pole tab 401 .

[0150] In the embodiment of the present application, the shape of the projection of the protrusion 201 in the thickness direction of the pole piece (z axis shown in the figure) includes a circle, a semicircle, an ellipse, a plum blossom or a polygon.

[0151] Avoid sharp edges on the protrusion 201 to prevent the edge of the protrusion 201 from piercing the diaphragm, causing a short circuit between the positive and negative electrodes and causing a safety accident of the battery cell.

[0152] refer to Figure 7The embodiment of the present application also provides a battery cell, which includes the positive electrode sheet 110 described above; the battery cell also includes a negative electrode sheet 120, and a separator 130 arranged between the positive electrode sheet 110 and the negative electrode sheet 120, and the positive electrode sheet 110, the negative electrode sheet 120 and the separator 130 are wound around the first center plane 140.

[0153] The battery cell includes a straight region and arc regions at opposite ends of the straight region. The surface of the first active material layer 200 is away from the first central plane 140 , and the surface of the second active material layer 300 faces the first central plane 140 .

[0154] The diaphragm 130 includes a substrate, a ceramic layer located on one side of the substrate, and a glue layer located on the other side of the substrate. The ceramic layer is disposed opposite to the protrusion 201 of the positive electrode sheet 110 .

[0155] The substrate includes polyethylene, polypropylene and a multi-layer microporous membrane of polyethylene and polypropylene composite, and the ceramic layer located on one side of the substrate includes ceramic, polyvinylidene fluoride or array-arranged polymethyl methacrylate.

[0156] 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 content of inorganic ceramic particles in the inorganic ceramic particle + polyvinylidene fluoride coating is ≥50%; the inorganic ceramic particles include one or more of α-Al2O3, γ-Al2O3, Al2O3, SiO2, CeO2, MgAl2O4, ZrO and TiO2.

[0157] 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 portion 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 diaphragm and causing a short circuit.

[0158] At the same time, 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.

[0159] The above-mentioned winding core provided in the present application is described in detail below through specific embodiments, and the specific differences between different embodiments are shown in Table 1 and Table 2.

[0160] Embodiment 1:

[0161] The battery preparation of this embodiment includes the following steps:

[0162] 1. Preparation of positive electrode sheet 110:

[0163] Lithium cobalt oxide, conductive agent and PVDF were mixed in a mass ratio of 97.6:1.4:1 and placed in NMP, stirred evenly to prepare a positive electrode slurry; the positive electrode slurry was evenly coated on the front and back surfaces of the current collector 100 to form a first active material layer 200 and a second active material layer 300 on the current collector 100; the thickness of the current collector 100 was 1.5 μm, and the coating surface density was 0.01704 g / cm 2 After drying and rolling, the positive electrode sheet 110 is obtained.

[0164] 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 = 4.5 μm, Dv50 = 14 μm, Dv90 = 28 μm.

[0165] The positive electrode sheet 110 is rolled using an embossing roller to form a plurality of protrusions 201 on the first active material layer 200, and a plurality of depressions 301 arranged opposite to the protrusions 201 are formed on the second active material layer 300. The height first vertical distance H1 of the protrusion 201, the thickness first thickness H2 of the current collector 100, the thickness second thickness H3 of the first active material layer 200 or the second active material layer 300, and the second particle size D2 have the following relationship: (H1+Dv50) / (H2+2H3)=0.4.

[0166] 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 N2 of the aluminum foil is 1.5%.

[0167] 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.

[0168] The area of ​​the arcuate outer surface of the raised portion 201 is S1, and the area of ​​the projection of the arcuate outer surface in the thickness direction of the pole piece is S2, S1 / S2=1.2; the area of ​​the arcuate inner surface of the recessed portion 301 is S3, and the area of ​​the projection of the arcuate inner surface in the thickness direction of the pole piece is S4, S3 / S4=1.3; the sum of the projection areas of multiple raised portions 201 in the thickness direction of the pole piece is S11, and the projection area of ​​the pole piece in its thickness direction is S, S11 / S=0.6.

[0169] The center interval of the projections of two adjacent protrusions 201 in the thickness direction of the pole piece is a first distance L1, and the straight section between the two adjacent protrusions 201 has a second distance L2 in the length direction of the pole piece or in the width direction of the pole piece, wherein L1 / L2=1.5.

[0170] The first angle a1 of the protruding portion 201 is 53°, the second angle a2 of the recessed portion 301 is 38°, and the relationship between the first angle a1 and the second angle a2 is a1-a2=15°.

[0171] 2. Preparation of negative electrode sheet 120:

[0172] Silicon-containing artificial graphite, conductive carbon black, styrene-butadiene rubber and sodium carboxymethyl cellulose are mixed in deionized water according to a mass ratio of 97.2:0.5:1.3:1, and stirred evenly to obtain a negative electrode slurry; wherein the silicon content in the silicon-containing artificial graphite is 10%.

[0173] The negative electrode slurry is evenly coated on the front and back surfaces of the negative electrode current collector, and after baking and rolling, a negative electrode sheet 120 with a thickness of 220 μm is obtained, and the negative electrode ear is welded.

[0174] 3. Preparation of diaphragm 130:

[0175] The 9 μm thick diaphragm 130 is manufactured by using a substrate, ceramics, and glue coating.

[0176] 4. Preparation of electrolyte:

[0177] The electrolyte includes lithium salt LiPF6 and a solvent, and the solvent includes ethylene carbonate (EC), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC), wherein the molar ratio of ethylene carbonate (EC), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC) is DEC:EC:EMC=1:1:1.

[0178] 5. Assembly:

[0179] The positive electrode sheet 110, the separator 130 and the negative electrode sheet 120 are wound to obtain a cell, and the cell is then packaged, baked, injected, formed, and sealed to obtain a battery.

[0180] Embodiment 2:

[0181] Example 2 is carried out with reference to Example 1, except that Dv10:Dv50:Dv90=1 / 5 / 9.5.

[0182] Embodiment 3:

[0183] Example 3 is carried out with reference to Example 1, except that Dv10:Dv50:Dv90=1 / 10 / 20.

[0184] Embodiment 4:

[0185] Example 4 is carried out with reference to Example 1, except that Dv10:Dv50:Dv90=1 / 1 / 2.

[0186] Embodiment 5:

[0187] Example 5 is carried out with reference to Example 1, except that Dv10=5 μm.

[0188] Embodiment 6:

[0189] Example 6 is carried out with reference to Example 1, except that Dv10=9 μm.

[0190] Embodiment 7:

[0191] Example 7 is carried out with reference to Example 1, except that Dv10=1 μm.

[0192] Embodiment 8:

[0193] Example 8 is carried out with reference to Example 1, except that Dv50=15 μm.

[0194] Embodiment 9:

[0195] Example 9 is carried out with reference to Example 1, except that Dv50=20 μm.

[0196] Embodiment 10:

[0197] Example 10 is carried out with reference to Example 1, except that Dv50=10 μm.

[0198] Embodiment 11:

[0199] Example 11 is carried out with reference to Example 1, except that Dv90=27 μm.

[0200] Embodiment 12:

[0201] Example 12 is carried out with reference to Example 1, except that Dv90=34μm.

[0202] Embodiment 13:

[0203] Example 13 is carried out with reference to Example 1, except that Dv90=20μm.

[0204] Embodiment 14:

[0205] Example 14 is carried out with reference to Example 1, except that (H1+Dv50) / (H2+2H3)=0.45.

[0206] Embodiment 15:

[0207] Example 15 is carried out with reference to Example 1, except that (H1+Dv50) / (H2+2H3)=0.9.

[0208] Embodiment 16:

[0209] Example 16 is carried out with reference to Example 1, except that (H1+Dv50) / (H2+2H3)=0.05.

[0210] Embodiment 17:

[0211] Example 17 is carried out with reference to Example 1, except that H1 / M=0.23.

[0212] Embodiment 18:

[0213] Example 18 is carried out with reference to Example 1, except that H1 / M=0.4.

[0214] Embodiment 19:

[0215] Example 19 was carried out with reference to Example 1, except that H1 / M=0.02.

[0216] Embodiment 20:

[0217] Example 20 is carried out with reference to Example 1, except that H1 / N1=35.

[0218] Embodiment 21:

[0219] Example 21 is carried out with reference to Example 1, except that H1 / N1=79.

[0220] Embodiment 22:

[0221] Example 22 is carried out with reference to Example 1, except that H1 / N1=5.

[0222] Embodiment 23:

[0223] Example 23 is carried out with reference to Example 1, except that N2=1.30%.

[0224] Embodiment 24:

[0225] Example 24 is carried out with reference to Example 1, except that N2=3%.

[0226] Embodiment 25:

[0227] Example 25 is carried out with reference to Example 1, except that N2=0.20%.

[0228] Embodiment 26:

[0229] Example 26 is carried out with reference to Example 1, except that R1 / H1=425.

[0230] Embodiment 27:

[0231] Example 27 is carried out with reference to Example 1, except that R1 / H1=900.

[0232] Embodiment 28:

[0233] Example 28 is carried out with reference to Example 1, except that R1 / H1=20.

[0234] Embodiment 29:

[0235] Example 29 is carried out with reference to Example 1, except that R1 / R2=1.15.

[0236] Embodiment 30:

[0237] Example 30 is carried out with reference to Example 1, except that R1 / R2=1.5.

[0238] Embodiment 31:

[0239] Example 31 is carried out with reference to Example 1, except that R1 / R2=1.

[0240] Embodiment 32:

[0241] Example 32 is carried out with reference to Example 1, except that S1 / S2=1.4.

[0242] Embodiment 33:

[0243] Example 33 is carried out with reference to Example 1, except that S1 / S2=2.

[0244] Embodiment 34:

[0245] Example 34 is carried out with reference to Example 1, except that S1 / S2=1.

[0246] Embodiment 35:

[0247] Example 35 is carried out with reference to Example 1, except that S3 / S4=1.4.

[0248] Embodiment 36:

[0249] Example 36 is carried out with reference to Example 1, except that S3 / S4=2.

[0250] Embodiment 37:

[0251] Example 37 is carried out with reference to Example 1, except that S3 / S4=1.

[0252] Embodiment 38:

[0253] Example 38 is carried out with reference to Example 1, except that S11 / S=0.5.

[0254] Embodiment 39:

[0255] Example 39 is carried out with reference to Example 1, except that S11 / S=1.

[0256] Embodiment 40:

[0257] Example 40 is carried out with reference to Example 1, except that S11 / S=0.05.

[0258] Embodiment 41:

[0259] Example 41 is carried out with reference to Example 1, except that L1 / L2=2.

[0260] Embodiment 42:

[0261] Example 42 is carried out with reference to Example 1, except that L1 / L2=3.

[0262] Embodiment 43:

[0263] Example 43 is carried out with reference to Example 1, except that L1 / L2=1.

[0264] Embodiment 44:

[0265] Example 44 is carried out with reference to Example 1, except that a1=45 degrees, a1-a2=7 degrees.

[0266] Embodiment 45:

[0267] Example 45 is carried out with reference to Example 1, except that a1=100 degrees and a1-a2=62 degrees.

[0268] Embodiment 46:

[0269] Example 46 is carried out with reference to Example 1, except that a1 = -10 degrees, a1-a2 = -48 degrees.

[0270] Embodiment 47:

[0271] Example 47 is carried out with reference to Example 1, except that a2=45 degrees and a1-a2=8 degrees.

[0272] Embodiment 48:

[0273] Example 48 is carried out with reference to Example 1, except that a2 = 100 degrees and a1-a2 = -47 degrees.

[0274] Embodiment 49:

[0275] Example 49 is carried out with reference to Example 1, except that a2 = -10 degrees, a1-a2 = 63 degrees.

[0276] Embodiment 50:

[0277] Example 50 is carried out with reference to Example 1, except that a1=60 degrees, a2=30 degrees, and a1-a2=30 degrees.

[0278] Embodiment 51:

[0279] Example 51 is carried out with reference to Example 1, except that a1=80 degrees, a2=30 degrees, and a1-a2=50 degrees.

[0280] Embodiment 52:

[0281] Example 52 is carried out with reference to Example 1, except that a1=40 degrees, a2=50 degrees, and a1-a2=-10 degrees.

[0282] Comparative Example 1:

[0283] Comparative Example 1 is carried out with reference to Example 1, except that in Comparative Example 1, the particle size of the lithium cobalt oxide particles in the first active material layer 200 and the second active material layer 300 is only one type, and both are large particles.

[0284] Comparative Example 2:

[0285] Comparative Example 2 is carried out with reference to Example 1, except that in Comparative Example 2, the particle size of the lithium cobalt oxide particles in the first active material layer 200 and the second active material layer 300 is only one type, and both are small particles.

[0286] Table 1:

[0287]

[0288]

[0289] Table 2:

[0290]

[0291]

[0292] The relevant performances of the batteries in the above embodiments and comparative examples were tested, and the test results are recorded in Table 3. The test method is as follows:

[0293] 1. Liquid retention test

[0294] The liquid retention volume is the amount of electrolyte that is ultimately retained in the lithium-ion battery. In order to ensure the consumption of electrolyte during the formation of the lithium-ion battery, a certain amount of electrolyte is usually injected, and then the excess electrolyte is extracted after formation; it is measured by weighing, the injection volume m1, the electrolyte extraction volume m2, and the liquid retention volume = m1-m2.

[0295] 2. Appearance of the current collector 100 and the positive electrode sheet 110:

[0296] The shape of the protrusion 201 was observed using a 3D microscope, and the damage of the current collector 100 and the positive electrode sheet 110 was observed using a 3D microscope.

[0297] 3. Current collector tensile strength test

[0298] A vertical tensile testing machine was used for testing. The current collectors obtained in the above embodiments and comparative examples were fixed on the clamps at both ends of the tensile testing machine. The two ends of the clamps were aligned. The tensile equipment button was started. The equipment moved at a speed of 10 mm / s until the current collector broke, and the tensile data was read out.

[0299] 4. Lithium deposition on negative electrode

[0300] After the battery obtained in the above embodiment and the comparative example was subjected to the cell expansion rate test, the battery obtained in the above embodiment and the comparative example was fully charged, and the battery was disassembled in a dry room environment to observe whether lithium deposition occurred on the negative electrode sheet and the degree of lithium deposition. The degree of lithium deposition is divided into slight lithium deposition and severe lithium deposition. Slight lithium deposition refers to the occurrence of lithium deposition at the interface when the color of the lithium deposition is gray or gray-black. In severe lithium deposition, the interface appears silvery white, and the amount of lithium deposition is relatively large.

[0301] 5. Wetting improvement effect test

[0302] The battery was left at room temperature (25°C) for 24 hours, and the wetting of the diaphragm was observed after disassembly. The area of ​​the wetted part was estimated and compared, and divided into three levels: significant (wetting area of ​​60% to 100%), moderate (wetting area of ​​30% to 60%), and slight (wetting area of ​​0% to 30%). The non-wetted area is usually an irregular water pattern boundary, and the difference in area size can be directly observed visually.

[0303] Table 3:

[0304]

[0305]

[0306] As shown in Table 3, the liquid retention of Comparative Example 1 is low, and the wetting effect is not obvious; and the current collector and the electrode are seriously damaged. The reason is that the large particles make the depth of the concave part 301 unable to be pressed down, the height of the protrusion 201 is not enough, and the wetting is not ideal; and the large particles are easily broken by squeezing; if the pressure is too deep, the particles will also squeeze the current collector 100. The liquid retention of Comparative Example 2 is low, and the wetting effect is not obvious; the reason is that the small particles have low specific capacity and the ultimate compaction is small, resulting in insufficient height of the protrusion 201.

[0307] The liquid retention amount of Example 1 is higher than that of Comparative Examples 1 and 2, and the current collector and the electrode are not damaged in Example 1; this indicates that large and small particles are mixed in the active material layer, so that when the small particles slide to both sides under force, they can be filled between the large particles, thereby avoiding particle rupture and protecting the current collector from being torn.

[0308] From Example 2 to Example 4, it can be seen that when Dv10, Dv50, and Dv90, Dv50 and Dv90 are larger, the liquid retention is low and the wetting effect is not obvious; and the current collector and the electrode are both seriously damaged; it means that the large particles cause the depth of the recessed portion 301 to be unable to be pressed down, the height of the raised portion 201 is insufficient, and the wetting is not ideal; and the particles are easy to break, and the particles will also squeeze the current collector 100. When Dv10, Dv50, and Dv90, Dv50 and Dv90 are smaller, there are more small particles, the small particles have low gram capacity, the ultimate compaction is small, and the height of the raised portion 201 is insufficient, resulting in low liquid retention and insignificant wetting effect; at the same time, when the small particles are forced to slide to both sides, the filling space is insufficient, and the current collector 100 will be torn apart.

[0309] It can be seen from Examples 5 to 7 that when Dv10 is greater than 8 μm, the particle size of the small particles is too large, and the small particles cannot be filled between the large particles when they slide to both sides under force, and the particles are easily broken; and the particles will also squeeze the current collector 100, causing serious damage to the current collector 100 and the electrode; when Dv10 is less than 2 μm, the particle size of the small particles is too small, and the existence of the small particles is meaningless, and the effect of mixing large and small particles cannot be achieved, and the current collector 100 will be torn apart, causing serious damage to the current collector 100.

[0310] It can be seen from Examples 8 to 13 that 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 recessed portion 301 to be unable to be pressed down, the height of the raised portion 201 to be insufficient, and the wetting is not ideal; the particles are easily broken, and the particles will also squeeze 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 effect of mixing large and small particles cannot be achieved, the current collector 100 will be torn, causing serious damage to the current collector 100.

[0311] It can be seen from Examples 14 to 16 that when (H1+Dv50) / (H2+2H3) is greater than 0.8, it means that the height of the protrusion 201 is too high, or the particle size of the large particles is too large, which can easily cause damage to the pole piece and particle rupture; when (H1+Dv50) / (H2+2H3) is less than 0.1, it means 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 difficult to ensure the height of the protrusion 201, resulting in poor wetting effect.

[0312] It can be seen from Examples 17 to 19 that 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 cathode ray tube; 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.

[0313] It can be seen from Examples 20 to 22 that when H1 / N1 is greater than 60, it means that the height of the protrusion 201 is too high, causing excessive stretching of the foil and easily causing damage to the cathode ray tube; when H1 / N1 is less than 10, it means that the height of the protrusion 201 is too small, resulting in poor wetting effect.

[0314] It can be seen from Examples 23 to 25 that the particles will squeeze the aluminum foil during embossing, ensuring that the elongation N2 of the aluminum foil is 0.5% to 2% to avoid aluminum foil breakage; when the elongation N2 is less than 0.5%, the current collector 100 will be torn, causing serious damage to the current collector 100.

[0315] From Example 26 to Example 28, it can be seen that R1 / H1 can make the gap between the pole piece and the diaphragm suitable within a wide range, that is, the protrusion 201 has a suitable deformation space and liquid storage space to provide sufficient support, thereby maximizing the benefit effect. When R1 / H1 is greater than 800, the projection diameter of the protrusion 201 is small, the height of the protrusion 201 is high, and the protrusion 201 is too sharp, which is easy to cause damage to the pole piece; when R1 / H1 is less than 50, the projection diameter of the protrusion 201 is large, the height of the protrusion 201 is low, and the support of the protrusion 201 is insufficient. The protrusion 201 is easily deformed by excessive extrusion force and extension force during the manufacturing process and tends to be flattened, so that the protrusion 201 collapses and has poor effects on electrolyte infiltration, increasing the storage capacity, and improving the negative electrode expansion.

[0316] From Example 29 to Example 31, it can be seen that when the ratio of the first radius R1 to the second radius R2 is greater than 1.3, the pole piece is easily damaged, slight lithium deposition will occur at the negative electrode, and the liquid retention is low, and the wetting effect is poor; the reason is that 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 recessed portion 301 is too small, the structure composed of the protrusion 201 and the recessed portion 301 is easy to collapse, resulting in a small deformation space for the structure composed of the protrusion 201 and the recessed portion 301, and insufficient electrolyte accommodation space. On the contrary, when the ratio of the first radius R1 to the second radius R2 is less than 1.01, it means that the volume of the protrusion 201 is too small, and the volume of the recessed portion 301 is too large, the structure composed of the protrusion 201 and the recessed portion 301 is easy to collapse, the deformation space of the structure composed of the protrusion 201 and the recessed portion 301 is small, and the electrolyte accommodation space is insufficient.

[0317] It can be seen from Examples 32 to 37 that when S1 / S2 is greater than 1.8, the outer surface area of ​​the raised portion 201 is large, while the projected area is small, indicating that the raised portion 201 is high, which is easy to cause damage to the pole piece and particle crushing; when S1 / S2 is less than 1.05, the outer surface area of ​​the raised portion 201 is small, while the projected area is large, indicating that the raised portion 201 is low, the supporting effect is not obvious, and the electrolyte cannot be sufficiently infiltrated. When S3 / S4 is greater than 1.8, the outer surface area of ​​the recessed portion 301 is large, while the projected area is small, indicating that the recessed portion 301 is high, which is easy to cause damage to the pole piece and particle crushing; when S3 / S4 is less than 1.1, the outer surface area of ​​the recessed portion 301 is small, while the projected area is large, indicating that the recessed portion 301 is low, the electrolyte infiltration space is small, and the electrolyte cannot be sufficiently infiltrated.

[0318] It can be seen from Examples 38 to 40 that when S11 / S is greater than 0.95, it means that the protrusion 201 accounts for a large proportion and the electrode is easily damaged; when S11 / S is less than 0.1, it means that the protrusion 201 accounts for a small proportion, the supporting effect is not obvious, and the electrolyte cannot be sufficiently infiltrated.

[0319] It can be seen from Examples 41 to 43 that when L1 / L2 is greater than 3, the spacing between the protrusions 201 is too small and the electrode is easily damaged; when L1 / L2 is less than 1.05, the spacing between the protrusions 201 is too large, the protrusions 201 are too sparse, and the supporting force is insufficient, making it impossible for the electrolyte to be adequately infiltrated.

[0320] From Example 44 to Example 46, it can be seen that when the first angle a1 is greater than 90 degrees, and the relationship a1-a2 between the first angle a1 and the second angle a2 is greater than 40 degrees, the electrode is damaged, the liquid retention is low, and the infiltration effect is poor; the reason is that the inclination angle at the connection between the protrusion 201 and the straight section is too large, causing excessive bending, resulting in damage to the electrode; at the same time, the inclination angle of the protrusion 201 relative to the recessed portion 301 is too large, and the structure composed of the protrusion 201 and the recessed portion 301 is unstable, and it is easy to collapse when subjected to extrusion stress, and the electrolyte cannot be sufficiently infiltrated. When the first angle a1 is less than 0 degrees, and the relationship a1-a2 between the first angle a1 and the second angle a2 is less than 0 degrees, it means that the protrusion 201 is short, the protrusion 201 is an invalid protrusion, the support effect is poor, and the electrolyte cannot be sufficiently infiltrated.

[0321] It can be seen from Examples 47 to 49 that when the second angle a2 is greater than 90 degrees, and the relationship a1-a2 between the first angle a1 and the second angle a2 is less than 0 degrees, the pole piece is damaged; the reason is that the inclination angle at the connection between the recessed portion 301 and the straight section is too large, causing excessive bending, resulting in damage to the pole piece; at the same time, the inclination angle of the recessed portion 301 relative to the protruding portion 201 is too large, and the structure composed of the protruding portion 201 and the recessed portion 301 is unstable and easily collapses when subjected to extrusion stress. When the second angle a2 is less than 0 degrees, and the relationship a1-a2 between the first angle a1 and the second angle a2 is greater than 40 degrees, the inclination angle of the recessed portion 301 relative to the protruding portion 201 is too small, and the depth of the recessed portion 301 is shallow, which cannot allow sufficient infiltration of the electrolyte.

[0322] It can be seen from Example 50 to Example 52 that the first angle a1 and the second angle a2 are both within the range of 0 degrees to 90 degrees, but when a1-a2 is greater than 40 degrees, it means that the inclination angle of the connection between the raised portion 201 and the straight section is too large, and the highest raised point of the raised portion 201 is easily broken, causing damage to the pole piece; the first angle a1 and the second angle a2 are both within the range of 0 degrees to 90 degrees, but when a1-a2 is less than 0 degrees, it means that the inclination angle of the connection between the recessed portion 301 and the straight section is too large, causing excessive bending, resulting in damage to the pole piece.

[0323] In this specification, each embodiment or example is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referenced to each other.

[0324] It should be noted that the phrases "one embodiment", "an embodiment", "an exemplary embodiment", "some embodiments", etc. mentioned in the specification indicate that the described embodiments may include certain features, structures or characteristics, but not every embodiment may include the certain features, structures or characteristics. In addition, such phrases do not necessarily refer to the same embodiment. In addition, when describing certain features, structures or characteristics in conjunction with an embodiment, it is within the knowledge of those skilled in the art to implement such features, structures or characteristics in conjunction with other embodiments, whether explicitly or not explicitly described.

[0325] In general, terms should be understood, at least in part, by the context in which they are used. For example, the term "one or more" as used herein may be used to describe any feature, structure, or characteristic in a singular sense, or may be used to describe a combination of features, structures, or characteristics in a plural sense, depending, at least in part, on the context. Similarly, terms such as "a," "an," or "the" may also be understood to convey singular usage or to convey plural usage, depending, at least in part, on the context.

[0326] It should be easily understood that “on,” “above,” and “over” in the present disclosure should be interpreted in the broadest manner, so that “on” not only means “directly on something,” but also includes the meaning of “on something” with intervening features or layers therebetween, and “above” or “over” not only includes the meaning of “above” or “over,” but also may include the meaning of “above” or “over something” with no intervening features or layers therebetween (i.e., directly on something).

[0327] In addition, spatially relative terms, such as "below," "below," "beneath," "above," "above," etc., may be used herein for ease of description to describe the relationship of one element or feature relative to other elements or features as shown in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation shown in the figures. The device may have other orientations (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein may likewise be interpreted accordingly.

[0328] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A positive electrode sheet, characterized in that: include: a current collector, 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 arranged on the first surface, and the second active material layer is arranged on the second surface; The first active material layer is provided with a plurality of protrusions, and the second active material layer is provided with a plurality of depressions corresponding to the protrusions; The first active material layer and the second active material layer each include a plurality of active material particles, the active material particles including lithium iron phosphate, lithium manganese iron phosphate, lithium manganese phosphate, Li a1 Co x1 M1 k1 O 2、 Li a2 Ni x2 Co y2 D z2 M2 k2 At least one of O2, Among them, 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 layer particles satisfies: Dv10:Dv50:Dv90=1:(2-8):(3-16).

2. The positive electrode sheet according to claim 1, characterized in that: The Dv10 is 2 μm to 8 μm; and / or The Dv50 is 11 μm to 19 μm; and / or The Dv90 is 22 μm to 32 μm.

3. The positive electrode sheet according to claim 1, characterized in that: The protrusion has a first intersection, and the first intersection intersects with a plane where the surface of the first active material layer is located; In the thickness direction of the pole piece, the first intersection point and the highest protrusion point of the protrusion portion have a first vertical distance H1, H1 = 3-40 μm; The thickness of the current collector is a first thickness H2, where H2=6-20 μm; In the thickness direction of the electrode sheet, the first active material layer and the second active material layer both have a second thickness H3, 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.

4. The positive electrode sheet according to claim 3, characterized in that: The tensile strength M of the current collector along the width direction and the length direction of the pole piece is ≥50MPa; and / or, The first vertical distance H1 and the tensile strength M have the following relationship: 0.05≤H1 / M≤0.

4.

5. The positive electrode sheet according to claim 3, characterized in that: The current collector has a fracture elongation N1, and the fracture elongation N1 is ≥ 2%; and / or The first vertical distance H1 and the elongation at break N1 have the following relationship: 10≤H1 / N1≤60.

6. The positive electrode sheet according to claim 1, characterized in that: The current collector comprises aluminum foil, The aluminum foil has an elongation N2, and the elongation N2 is 0.5% to 2%.

7. The positive electrode sheet according to claim 3, characterized in that: The protrusion has an arc-shaped outer surface, the arc-shaped outer surface is located in the first active material layer, and 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, the arc-shaped inner surface is located in the second active material layer, and the projection of the arc-shaped inner surface in the thickness direction of the electrode sheet 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.

8. The positive electrode sheet according to claim 7, characterized in that: The arc-shaped outer surface has a first area S1, and the projection of the arc-shaped outer surface in the thickness direction of the pole piece 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 thickness direction of the pole piece 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.

9. The positive electrode sheet according to claim 1, characterized in that: The center interval of the projections of two adjacent protrusions in the thickness direction of the pole piece 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 length direction of the pole piece or in the width direction of the pole piece; The first distance L1 and the second distance L2 have the following relationship: L1 / L2=1.05-3.

10. The positive electrode sheet according to claim 3, characterized in that: The first tangent line is tangent to the first intersection point, and the angle between the first tangent line and the plane where the surface of the first active material layer is located is a first angle a1; The recessed portion has a second intersection point, and the second intersection point intersects with the plane where the surface of the second active material layer is located; The second tangent line is tangent to the second intersection point, and the angle between the second tangent line and the horizontal plane where the surface of the second active material layer is located is a second angle a2; The first angle a1 and the second angle a2 have the following relationship: a1-a2=0°-40°; and / or The first angle a1 is 0° to 90°; and / or The second angle a2 is between 0° and 90°.

11. The positive electrode sheet according to claim 1, characterized in that: The sum of the projection areas of the plurality of protrusions in the thickness direction of the pole piece is a fifth area S11, and the projection area of ​​the pole piece in the thickness direction thereof is a sixth area S; The fifth area S11 and the sixth area S have the following relationship: S11 / S=0.1-0.

95.

12. The positive electrode sheet according to claim 1, characterized in that: The head of the pole piece includes a first air-avoiding area, and in the length direction of the pole piece, the first air-avoiding area has a third width M1; The head of the pole piece includes an initial bending section, and in the length direction of the pole piece, the third width M1=the width of the initial bending section±10mm; or The head of the pole piece includes an initial bending section and a second bending section. In the length direction of the pole piece, the third width M1=the width of the initial bending section+the width of the second bending section±10mm; and / or The tail of the pole piece 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, 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; In the length direction of the pole piece, a second clearance area is provided between the intersection point and the protruding portion, the second clearance area has a fourth width M2, and the fourth width M2 is 2 mm to 30 mm.

13. The positive electrode sheet according to claim 1, characterized in that: The projection of the protrusion in the thickness direction of the pole piece may have a shape including a circle, a semicircle, an ellipse, a plum blossom or a polygon.

14. A battery cell, characterized in that: A positive electrode sheet according to any one of claims 1 to 13, further comprising a separator and a negative electrode sheet; The diaphragm includes a substrate, a ceramic layer located on one side of the substrate, and a glue layer located on the other side of the substrate, and the ceramic layer is arranged opposite to the protruding portion of the positive electrode sheet.

15. The battery cell according to claim 14, 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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