Positive plate, battery cell and lithium ion secondary battery

Abstract

The utility model relates to the field of batteries, and discloses a positive plate, a battery cell and a lithium ion secondary battery, the positive plate comprises a current collector and a positive active material layer located on a first surface and / or a second surface of the current collector, and the first surface and the second surface are two opposite surfaces in a first direction; at least one positive active material layer comprises a pore region and a splicing region, and the pore region comprises a concave part; the splicing areas are located between every two adjacent pore areas. The concave part is arranged on the positive active material layer, so that the contact area between the electrolyte and the positive plate is increased, and the infiltration effect of the positive plate can be improved; and no positive active material layer is arranged at the concave part, so that the weight of the positive plate can be reduced. The splicing area not only can reduce the reduction of the positive active material layer and enhance the structural stability of the positive material, but also can be used as a stress buffer area in the winding process of the positive plate to prevent the positive plate from being broken.

Description

Technical Field

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

[0002] Lithium-ion batteries mainly rely on the back-and-forth insertion and deintercalation of lithium ions between the positive and negative electrodes to work, and have the advantages of long cycle life and high energy density.

[0003] To achieve higher energy density in lithium-ion batteries, the electrodes are gradually being developed in the direction of high compaction and thicker electrodes. This has led to the problem of electrolyte wetting in the electrodes. The wettability of the positive electrode has a significant impact on the capacity, cycle life, and charging speed of lithium-ion batteries. Currently, the electrolyte infiltrates through the micropores of the positive electrode, but the surface of the positive electrode is relatively dense after compaction, resulting in poor wetting and the problem of lithium deposition. In addition, the positive electrode is prone to breakage when subjected to tensile stress during the winding process.

[0004] Therefore, how to solve the above technical problems should be the focus of those skilled in the art. Utility Model Content

[0005] The purpose of the present application is to provide a positive electrode sheet, a battery cell and a lithium-ion secondary battery to enhance the wetting effect of the positive electrode sheet, improve lithium deposition, and avoid the breakage of the positive electrode sheet.

[0006] To solve the above technical problems, the present application provides a positive electrode sheet, comprising: a current collector, and a positive electrode active material layer located on a first surface and / or a second surface of the current collector, wherein the first surface and the second surface are two surfaces opposite to each other in a first direction;

[0007] At least one layer of the positive electrode active material layer includes a pore area and a splicing area, and the pore area includes a concave portion;

[0008] The splicing area is located between two adjacent pore areas.

[0009] In one embodiment, the pore region includes a first pore partition and / or a second pore partition, wherein the first pore partition is distributed along the second direction and located at an edge portion of the positive electrode active material layer, and the second pore partition is distributed along the third direction and located at a middle portion of the positive electrode active material layer;

[0010] The splicing area includes a first splicing partition and / or a second splicing partition, the first splicing partition is located between adjacent first pore partitions, and the second splicing partition is located between adjacent second pore partitions;

[0011] The second direction is perpendicular to the third direction, and the second direction and the third direction are respectively perpendicular to the first direction.

[0012] In one embodiment, the length of the first splicing partition in the second direction ranges from 0.1 mm to 5 mm;

[0013] And / or, the width of the second splicing partition in the third direction ranges from 0.1 mm to 5 mm;

[0014] and / or, the ratio of the area of the first splicing partition to the area of the first pore partition is in a range of 0.001 to 0.01;

[0015] And / or, the ratio of the area of the second splicing partition to the area of the second pore partition is in the range of 0.005 to 0.2.

[0016] In one embodiment, the concave portion includes concave holes, and the density of the concave holes in the first pore partition ranges from 0.5 to 10 per mm. 2 ;

[0017] And / or, the concave portion includes concave holes, and the density of the concave holes in the second pore partition ranges from 0.5 to 10 per mm 2 ;

[0018] and / or a ratio of an area occupied by the concave portion in the first pore partition to a total area of the positive electrode active material layer is in a range of 0.0006 to 0.35;

[0019] And / or, the ratio of the area occupied by the concave portion in the second pore partition to the total area of the positive electrode active material layer is in a range of 0.0001 to 0.35.

[0020] And / or, in the third direction, the distance between the first pore partition and the edge of the positive electrode active material layer is in a range of 0.2 mm to 5 mm.

[0021] In one embodiment, the present invention further comprises: a third splicing partition;

[0022] The third splicing partition is located between the first pore partition and the second pore partition.

[0023] In one embodiment, the aperture area includes a first region and a second region, the first region is close to the splicing area, and a first distance between the recesses in the first region is smaller than a second distance between the recesses in the second region.

[0024] In one embodiment, the ratio of the first distance to the second distance ranges from 0.5 to 0.999.

[0025] In one embodiment, the depth of the concave portion ranges from 5 μm to 30 μm, and / or the spacing between the concave portions ranges from 100 μm to 300 μm, and / or the width of the concave portion ranges from 50 μm to 200 μm.

[0026] In one embodiment, the projection of the concave portion on the positive electrode active material layer on the first surface of the current collector on the current collector and the projection of the concave portion on the positive electrode active material layer on the second surface of the current collector on the current collector are staggered; or,

[0027] A projection of the concave portion on the positive electrode active material layer on the first surface of the current collector on the current collector overlaps with a projection of the concave portion on the positive electrode active material layer on the second surface of the current collector on the current collector.

[0028] In one embodiment, it further includes:

[0029] A protective layer is located between the positive electrode active material layer and the current collector.

[0030] In one embodiment, the ratio of the thickness of the protection layer to the depth of the recess is in a range of 0.06-4.

[0031] The present application also provides a battery cell, comprising a winding core, wherein the winding core comprises a stacked and wound positive electrode sheet, a separator, and a negative electrode sheet, and the positive electrode sheet is any one of the positive electrode sheets described above.

[0032] In one embodiment, the positive electrode sheet includes a bent area and a straight area, and the bent area includes a concave portion;

[0033] And / or, in one embodiment, a portion of the straight area connected to the bending area contains a concave portion.

[0034] In one embodiment, in the positive electrode sheet located in the innermost layer of the battery cell, a ratio of an area of the pore region corresponding to the bending region to an area of the pore region is in a range of 0.12 to 0.4;

[0035] And / or, in the positive electrode sheet located at the outermost layer of the battery cell, the ratio of the area of the pore region corresponding to the bending region to the area of the pore region is in a range of 0.4 to 1;

[0036] The innermost positive electrode sheet refers to the positive electrode sheet closest to the center of the winding core, and the outermost positive electrode sheet refers to the positive electrode sheet farthest from the center of the winding core.

[0037] In one embodiment, along the winding direction of the core, the area of the pore region in the positive electrode sheet corresponding to the flat region gradually decreases.

[0038] In one embodiment, the ratio of the area of the flat region with the recessed portions to the area of the pore region of the innermost positive electrode sheet is in a range of 0.5 to 0.9999.

[0039] And / or, for the positive electrode sheet located in the outermost layer, the ratio of the area of the flat area with the recessed portions to the area of the pore area is in the range of 0.001 to 0.3; wherein, the positive electrode sheet in the innermost layer refers to the positive electrode sheet closest to the center of the winding core, and the positive electrode sheet in the outermost layer refers to the positive electrode sheet farthest from the center of the winding core.

[0040] In one embodiment, in the third direction, the distance between the edge of the positive electrode sheet and the edge of the negative electrode sheet ranges from 0.1 mm to 5 mm; and / or,

[0041] In the third direction, the distance between the concave portion closest to the edge of the positive electrode sheet and the edge of the negative electrode sheet is in the range of 0.3 mm to 5 mm; and / or,

[0042] In the third direction, the distance between the concave portion closest to the edge of the positive electrode sheet and the excess area of the negative electrode sheet is in the range of 0.1 mm to 1.5 mm; the excess area of the negative electrode sheet is the area where the negative electrode sheet exceeds the positive electrode sheet in the third direction.

[0043] In one embodiment, along the winding direction of the core, the positive electrode sheet includes an insulating layer, the insulating layer covering the current collector and the positive electrode active material layer, and the length of the insulating layer located on the positive electrode active material layer ranges from 0.1 mm to 10 mm; and / or,

[0044] Along the winding direction of the winding core, the distance between the concave portion closest to the edge of the positive electrode sheet and the edge of the positive electrode sheet ranges from 0.1 mm to 10 mm.

[0045] In one embodiment, along the winding direction of the core, the insulating layer covers the current collector and the positive active material layer, and there is a gap between the recessed portion closest to the edge of the positive electrode sheet and the insulating layer; or, the recessed portion closest to the edge of the positive electrode sheet is at least partially located within the coverage area of the insulating layer.

[0046] In one embodiment, the negative electrode sheet is provided with linear grooves extending along the width direction of the negative electrode sheet, and the projection of the linear grooves on the positive electrode sheet overlaps with the recessed portion on the positive electrode sheet.

[0047] In one embodiment, the depth of the wire groove is in the range of 5 μm to 30 μm, and / or the width of the wire groove is in the range of 50 μm to 500 μm, and / or the spacing of the wire groove is in the range of 0.1 mm to 5 mm.

[0048] The present application also provides a lithium-ion secondary battery, which includes any of the above-mentioned battery cells.

[0049] A positive electrode sheet provided in the present application includes: a current collector, a positive electrode active material layer located on the first surface and / or second surface of the current collector, wherein the first surface and the second surface are two surfaces opposite to each other in a first direction; at least one layer of the positive electrode active material layer includes a pore area and a splicing area, the pore area includes a recess; and the splicing area is located between two adjacent pore areas.

[0050] In the positive electrode sheet of the present application, a pore area and a splicing area are provided on the positive electrode active material layer. A recess is provided in the pore area, and the contact area between the electrolyte and the positive electrode sheet is increased, and the electrolyte can enter the recess. The electrolyte can not only infiltrate the positive electrode sheet from the surface of the active material layer, but also infiltrate the active material layer through the recess, thereby improving the infiltration effect of the positive electrode sheet. Furthermore, the improved infiltration effect can also accelerate the deintercalation and intercalation of lithium ions and improve the lithium precipitation phenomenon of the battery; there is no positive electrode active material layer in the recess, which can also reduce the weight of the positive electrode sheet. In addition, a splicing area is also provided between the pore areas. The splicing area can not only reduce the reduction of the positive electrode active material layer and enhance the structural stability of the positive electrode material, but also serve as a stress buffer when the positive electrode sheet is subjected to tensile stress during the winding process, thereby preventing the positive electrode sheet from breaking.

[0051] In addition, the present application also provides a battery cell and a lithium-ion secondary battery having the above-mentioned positive electrode sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the embodiments of the present application or the technical solutions of the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0053] Figure 1 A schematic cross-sectional view of a positive electrode sheet provided in an embodiment of the present application Figure 1 ;

[0054] Figure 2 A partial top view of a positive electrode provided in an embodiment of the present application Figure 1 ;

[0055] Figure 3 A top view of a positive electrode provided in an embodiment of the present application Figure 1 ;

[0056] Figure 4 A partial top view of a positive electrode provided in an embodiment of the present application Figure 2;

[0057] Figure 5 A top view of a positive electrode provided in an embodiment of the present application Figure 2 ;

[0058] Figure 6 A partial top view of a positive electrode provided in an embodiment of the present application Figure 3 ;

[0059] Figure 7 A top view of a positive electrode provided in an embodiment of the present application Figure 3 ;

[0060] Figure 8 A partial top view of a positive electrode provided in an embodiment of the present application Figure 4 ;

[0061] Figure 9 A schematic diagram of a recess provided in an embodiment of the present application;

[0062] Figure 10 Schematic diagram of the projection of a concave portion on the current collector provided in an embodiment of the present application Figure 1 ;

[0063] Figure 11 Schematic diagram of the projection of a concave portion on the current collector provided in an embodiment of the present application Figure 2 ;

[0064] Figure 12 A schematic cross-sectional view of a positive electrode sheet provided in an embodiment of the present application Figure 2 ;

[0065] Figure 13 A schematic cross-sectional view of a battery cell provided in an embodiment of the present application;

[0066] Figure 14 A schematic diagram of the distribution of positive and negative electrodes in a battery cell provided in an embodiment of the present application;

[0067] Figures 15 to 17 Schematic diagram of the ends of different positive electrode sheets provided in the embodiments of the present application;

[0068] Figure 18 A top view of a negative electrode sheet in a battery cell provided in an embodiment of the present application;

[0069] Figure 19 A schematic diagram of a winding core provided in an embodiment of the present application;

[0070] In the figure, 100, positive electrode sheet, 200, negative electrode sheet, 300, insulating layer, 400, separator, 1, current collector, 2, positive electrode active material layer, 3, recess, 4, protective layer, 5, wire groove, 21, pore area, 22, splicing area, 211, first pore partition, 212, second pore partition, 221, first splicing partition, 222, second splicing partition, 223, third splicing partition, 224, first area, 225, second area, 31, recess projection. DETAILED DESCRIPTION

[0071] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific embodiments. Obviously, the embodiments described are only a 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 those skilled in the art without making any creative efforts are within the scope of protection of the present application.

[0072] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0073] As mentioned in the background technology section, the positive electrode sheet is compacted at high pressure (compaction density is 4.2g / cm 3 When the electrolyte is above 0.5, the effect of infiltration of the electrolyte through the micropores of the positive electrode sheet is relatively poor.

[0074] In view of this, the present application provides a positive electrode sheet 100, please refer to Figures 1 to 2 ,include:

[0075] A current collector 1, a positive electrode active material layer 2 located on a first surface and / or a second surface of the current collector 1, wherein the first surface and the second surface are two surfaces opposite to each other in a first direction Z;

[0076] At least one positive electrode active material layer 2 includes a pore area 21 and a splicing area 22, and the pore area 21 includes a concave portion 3;

[0077] The splicing area 22 is located between two adjacent pore areas 21 .

[0078] The recessed portion 3 is formed by the surface of the positive electrode active material layer 2 being recessed along the first direction Z and / or the direction opposite to the first direction Z.

[0079] The current collector 1 may be aluminum foil, and the material of the positive electrode active material layer 2 may be lithium cobaltate, lithium manganate, lithium nickelate, lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese iron phosphate, etc., which are not limited in this embodiment.

[0080] When the positive electrode sheet 100 is made into a battery cell, a positive electrode active material layer 2 is provided on the side of the positive electrode sheet 100 corresponding to the negative electrode sheet. That is, when the positive electrode sheet 100 is located in the innermost layer or outermost layer of the battery cell, the positive electrode active material layer 2 is provided on the first surface or the second surface of the current collector 1; when the positive electrode sheet 100 is located in the middle position, the positive electrode active material layer 2 is provided on both the first surface and the second surface of the current collector 1.

[0081] The first direction Z is also the direction of the thickness of the positive electrode sheet 100 .

[0082] For example, when the positive electrode sheet 100 is placed horizontally, the first direction Z points upward, and the recess 3 on the positive electrode active material layer 2 located on the upper surface of the current collector 1 is recessed from the surface of the positive electrode active material layer 2 along a direction opposite to the first direction Z, and the recess 3 on the positive electrode active material layer 2 located on the lower surface of the current collector 1 is recessed from the surface of the positive electrode active material layer 2 along the first direction Z.

[0083] The recesses 3 of the pore area 21 can be arranged in a matrix, and the specific number is not limited in this embodiment. The distance between the recesses 3 can be equal. The distance between the recesses 3 is the distance between the centers of two adjacent recesses 3.

[0084] The concave portion 3 may be a concave hole and / or a groove, which is not limited in this embodiment and can be set at will.

[0085] The splicing area 22 has no recess 3 and is located between two adjacent pore areas 21 and connected to the two adjacent pore areas 21. The splicing area 22 can serve as a stress buffer for the positive electrode sheet 100 to reduce the risk of the positive electrode sheet 100 breaking.

[0086] In the positive electrode sheet 100 of this embodiment, a pore area 21 and a splicing area 22 are provided on the positive electrode active material layer 2. A recess 3 is provided in the pore area 21. The contact area between the electrolyte and the positive electrode sheet 100 is increased, and the electrolyte can enter the recess 3. The electrolyte can not only infiltrate the positive electrode sheet 100 from the surface of the active material layer, but also infiltrate the active material layer through the recess 3, thereby improving the infiltration effect of the positive electrode sheet 100. Furthermore, the improved infiltration effect can also accelerate the deintercalation and intercalation of lithium ions and improve the lithium precipitation phenomenon of the battery. There is no positive electrode active material layer 2 in the recess 3, which can also reduce the weight of the positive electrode sheet 100. In addition, a splicing area 22 is provided between the pore areas 21. The splicing area 22 can not only reduce the reduction of the positive electrode active material layer 2 and enhance the structural stability of the positive electrode material, but also serve as a stress buffer when the positive electrode sheet 100 is subjected to tensile stress during the winding process, thereby preventing the positive electrode sheet 100 from breaking.

[0087] Please refer to Figures 3 and 4On the basis of the above embodiment, in one embodiment of the present application, the pore region includes a first pore partition 221 , and the first pore partition 221 is distributed along the second direction Y and is located at the edge of the positive electrode active material layer 2 ;

[0088] The splicing area includes a first splicing partition 221 , and the first splicing partition 221 is located between adjacent first pore partitions 221 ; the second direction Y is perpendicular to the first direction Z.

[0089] The second direction Y is also the direction along which the length of the positive electrode sheet 100 lies.

[0090] As an implementation method, the concave portions 3 in each row of two adjacent first pore partitions 211 can be aligned, such as Figure 3 shown.

[0091] As another possible implementation method, the concave portions 3 in each row of two adjacent first pore partitions 211 are not aligned, but staggered by a certain distance, such as Figure 4 shown.

[0092] In the third direction X, in two corresponding rows of recesses 3, the offset distance A between the centers of the recesses 3 may range from 0 to 0.6 mm. For example, the offset distance A may be 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, etc.

[0093] In this embodiment, the pore area is only located at the edge area of the positive electrode sheet 100, and the splicing area is also located at the edge area. The splicing area can serve as a stress buffer zone at the edge to reduce stress during battery manufacturing.

[0094] In one embodiment of the present application, the length L1 of the first splicing partition 221 in the second direction Y may be in the range of 0.1 mm to 5 mm.

[0095] Exemplarily, the length L1 of the first splicing partition 221 in the second direction Y can be 0.1 mm, 0.6 mm, 1 mm, 1.5 mm, 3 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, etc.

[0096] Please refer to Figures 5 and 6 Based on the above embodiment, in one embodiment of the present application, the pore region includes a second pore partition 212, and the second pore partition 212 is distributed along the third direction and is located in the middle part of the positive electrode active material layer;

[0097] The splicing area includes a second splicing partition, and the second splicing partition 222 is located between adjacent second pore partitions 212; the third direction X is perpendicular to the first direction Z, and the second direction Y and the third direction X are perpendicular to the first direction Z respectively.

[0098] The third direction X is also the direction of the width of the positive electrode sheet 100

[0099] As an implementation method, the recesses 3 in each row of two adjacent second pore partitions 212 can be aligned, such as Figure 5 shown.

[0100] As another possible implementation method, the recesses 3 in each row of two adjacent second pore partitions 212 are not aligned, but staggered by a certain distance, such as Figure 6 shown.

[0101] In the second direction Y, the distance B between the centers of the recesses 3 in two corresponding rows of recesses 3 may be 0-0.6 mm. For example, the distance B may be 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, etc.

[0102] In one embodiment of the present application, a width W1 of the second splicing partition 222 in the third direction X may be in a range of 0.1 mm to 5 mm.

[0103] Illustratively, the width W1 of the second splicing partition 222 may be 0.1 mm, 0.6 mm, 1 mm, 1.5 mm, 3 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, etc.

[0104] In this embodiment, the second pore partition 212 extends only along the third direction X of the positive electrode sheet 100. When the positive electrode sheet 100 is wound, the second splicing partition 222 can improve stress release after winding and avoid sheet breakage during the winding process.

[0105] Please refer to Figure 7 Based on the above embodiment, in one embodiment of the present application, the pore area 21 includes a first pore partition 211 and a second pore partition 212, the first pore partition 211 is distributed along the second direction Y, and the second pore partition 212 is distributed along the third direction X;

[0106] The splicing area 22 includes a first splicing partition 221 and a second splicing partition 222 . The first splicing partition 221 is located between adjacent first pore partitions 211 , and the second splicing partition 222 is located between adjacent second pore partitions 212 .

[0107] The second direction Y is perpendicular to the third direction X, and the second direction Y and the third direction X are perpendicular to the first direction Z respectively.

[0108] In this embodiment, the first pore partition 211 is located at the edge region of the positive electrode sheet 100 , and the second pore partition 212 is located at a portion of the region between the edge regions of the positive electrode sheet 100 .

[0109] The length L1 of the first splicing partition 221 may range from 0.1 mm to 5 mm. For example, the length L1 of the first splicing partition 221 in the second direction Y may be 0.1 mm, 0.6 mm, 1 mm, 1.5 mm, 3 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, etc.

[0110] The second splicing partition 222 is located between adjacent second pore partitions 212 .

[0111] In one embodiment of the present application, a width W1 of the second splicing partition 222 in the third direction X may be in a range of 0.1 mm to 5 mm.

[0112] Exemplarily, the width W1 of the second splicing partition 222 can be 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 1 mm, 1.5 mm, 3 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, etc.

[0113] The first splicing partition 221 can serve as a stress buffer at the edge, and the second splicing partition 222 can serve together with the first splicing partition 221 as a stress buffer during the electrode production process.

[0114] In one embodiment of the present application, the spacing D between the recesses 3 in the first pore partition 211 and the second pore partition 212 can be 100 μm to 300 μm. For example, the spacing D between the recesses 3 can be 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, etc. The spacing between the recesses 3 is the distance between the centers of two adjacent recesses 3.

[0115] The spacing between the recesses 3 in the first pore partition 211 and the second pore partition 212 can be equal, and the spacing between the recesses 3 is highly consistent, ensuring that the electrolyte infiltration speed of each part of the positive electrode sheet 100 is consistent and the migration speed of lithium ions is consistent.

[0116] In one embodiment of the present application, a pore region may be provided in the middle portion of the positive electrode active material layer, and no splicing region may be provided.

[0117] On the basis of any of the above embodiments, in one embodiment of the present application, the recess 3 includes concave holes, and the density of the concave holes in the first pore partition 211 can be in the range of 0.5 to 10 per mm. 2 and / or, the concave portion 3 includes concave holes, and the density of the concave holes in the second pore partition 212 can be in the range of 0.5 to 10 per mm 2 , in order to improve the wetting effect and dynamic performance of the positive electrode.

[0118] For example, the density of the concave holes in the first pore partition 211 can be 0.5, 1, 2, 5, 7, 9, 10, etc.; the density of the concave holes in the second pore partition 212 can be 0.5, 1, 2, 5, 7, 9, 10, etc.

[0119] The density of the concave portions 3 in the first pore partition 211 refers to the number of concave portions 3 per unit area in the first pore partition 211 ; the density of the concave portions 3 in the second pore partition 212 refers to the number of concave portions 3 per unit area in the second pore partition 212 .

[0120] On the basis of any of the above embodiments, in one embodiment of the present application, the ratio of the area occupied by the recessed portion 3 in the first pore partition 211 to the total area of the positive electrode active material layer 2 is in a range of 0.0006 to 0.35.

[0121] The area occupied by the recesses 3 in the first pore partition 211 is the sum of the areas of all the recesses 3 in the first pore partition 211 .

[0122] Illustratively, the ratio of the area occupied by the concave portion 3 in the first pore partition 211 to the total area of the positive electrode active material layer 2 can be 0.0006, 0.001, 0.005, 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, etc.

[0123] The ratio of the area occupied by the recesses 3 in the first pore partition 211 to the total area of the positive electrode active material layer 2 can be adjusted by adjusting the number and size of the recesses 3 .

[0124] The recess 3 in the first pore partition 211 can increase the local electrolyte infiltration speed, accelerate the embedding and de-embedding of lithium ions, and solve the lithium deposition phenomenon in the edge area.

[0125] Table 1 shows the relationship between the ratio R1 of the area occupied by the concave portion 3 in the first pore partition 211 to the total area of the positive electrode active material layer 2 and the electrolyte infiltration time T1.

[0126] Table 1 shows that when the ratio R1 of the area occupied by the recessed portion 3 in the first pore partition 211 to the total area of the positive electrode active material layer 2 is between 0.0006 and 0.35, the wetting time T1 changes, and the wetting time T1 decreases as the ratio R1 increases. When the ratio R1 of the area occupied by the recessed portion 3 in the first pore partition 211 to the total area of the positive electrode active material layer 2 is outside the range of 0.0006-0.35, that is, when the ratio R1 is 0.0001, 0.00005, 0.4, 0.5, and 0.6, the wetting time does not change, indicating that the ratio R1 of the area occupied by the recessed portion 3 in the first pore partition 211 to the total area of the positive electrode active material layer 2 has no effect on the wetting time T1.

[0127] Table 1

[0128] Ratio R1 Infiltration time T1 0.00005 140s 0.0001 140s 0.0006 140s 0.001 138s 0.005 136s 0.01 132s 0.05 131s 0.1 128s 0.15 125s 0.2 124s 0.35 121s 0.4 121s 0.5 121s 0.6 121s

[0129] Based on any of the above embodiments, in one embodiment of the present application, the ratio of the area occupied by the recessed portion 3 in the second pore partition 212 to the total area of the positive electrode active material layer 2 is in a range of 0.0001 to 0.35.

[0130] The area occupied by the recesses 3 in the second pore partition 212 is the sum of the areas of all the recesses 3 in the second pore partition 212 .

[0131] Illustratively, the ratio of the area occupied by the concave portion 3 in the second pore partition 212 to the total area of the positive electrode active material layer 2 can be 0.0001, 0.001, 0.005, 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, etc.

[0132] The ratio of the area occupied by the middle recesses 3 in the second pore partition 212 to the total area of the positive electrode active material layer 2 can be adjusted by adjusting the number and size of the recesses 3 .

[0133] The concave portion 3 of the second pore partition 212 can increase the local electrolyte infiltration speed, accelerate the embedding and de-embedding of lithium ions, and at the same time solve the lithium deposition phenomenon at the bend of the positive electrode sheet 100 after winding.

[0134] Table 2 shows the relationship between the ratio R2 of the area occupied by the recessed portion 3 in the second pore partition 212 to the total area of the positive electrode active material layer 2 and the electrolyte infiltration time T2.

[0135] Table 2 shows that when the ratio R2 of the area occupied by the concave portion 3 in the second pore partition 212 to the total area of the positive electrode active material layer 2 is in the range of 0.0001 to 0.35, the wetting time T1 changes, and the wetting time T2 decreases as the ratio R2 increases. When the ratio R2 of the area occupied by the concave portion 3 in the second pore partition 212 to the total area of the positive electrode active material layer 2 is outside the range of 0.0001 to 0.35, that is, when it is 0.00005, 0.4, 0.5, and 0.6, the wetting time does not change, indicating that the ratio R2 of the area occupied by the concave portion 3 in the second pore partition 212 to the total area of the positive electrode active material layer 2 has no effect on the wetting time T2.

[0136] Table 2

[0137] Ratio R2 Infiltration time T2 0.00005 138s 0.0001 138s 0.0006 138s 0.001 136s 0.005 134s 0.01 133s 0.05 131s 0.1 127s 0.15 126s 0.2 125s 0.35 124s 0.4 124s 0.5 124s 0.6 124s

[0138] like Figure 7 As shown, based on any of the above embodiments, in one embodiment of the present application, in the third direction X, the distance C between the first pore partition 211 and the edge of the positive electrode active material layer 2 can range from 0.2 mm to 1.5 mm.

[0139] For example, the distance C between the first pore partition 211 and the edge of the positive electrode active material layer 2 may be 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, 1 mm, 1.3 mm, 1.5 mm, etc.

[0140] After the edge of the positive electrode sheet 100 is cut, the bonding force of the edge positive electrode active material layer 2 is poor. A certain distance is left between the first pore partition 211 and the edge of the positive electrode active material layer 2 to prevent powder from falling off when the laser acts on the edge of the positive electrode sheet 100 during the production of the recess 3.

[0141] like Figure 7 As shown, based on any of the above embodiments, in one embodiment of the present application, the positive electrode sheet 100 may further include: a third splicing partition 223 , and the third splicing partition 223 is located between the first pore partition 211 and the second pore partition 212 .

[0142] When the positive electrode sheet 100 is wound, the third splicing partition 223 can improve stress release after winding, avoid sheet breakage during the winding process, and improve the electrochemical performance of the battery.

[0143] The width W2 of the third splicing partition 223 in the third direction X may range from 0.1 mm to 0.6 mm. For example, the width W2 of the third splicing partition 223 may be 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, etc.

[0144] In one embodiment of the present application, the ratio of the area of the first splicing partition 221 to the area of the first pore partition 211 may be in the range of 0.001 to 0.01.

[0145] For example, the ratio of the area of the first splicing partition 221 to the area of the first pore partition 211 may be 0.001, 0.005, 0.01, etc.

[0146] The dynamic performance of the first splicing partition 221 is weaker than that of the first pore partition 211. The area of the first splicing partition 221 is set smaller, much smaller than the area of the first pore partition 211, so as to minimize the negative impact of the weak dynamic performance brought by the first splicing partition 221.

[0147] In one embodiment of the present application, the ratio of the area of the second splicing partition 222 to the area of the second pore partition 212 may be in the range of 0.005 to 0.2.

[0148] For example, the ratio of the area of the second stitching partition 222 to the area of the second pore partition 212 may be 0.005, 0.01, 0.05, 0.1, 0.15, 0.2, or the like.

[0149] The dynamic performance of the second splicing partition 222 is weaker than that of the second pore partition 212. The area of the second splicing partition 222 is set smaller, much smaller than the area of the second pore partition 212, so as to minimize the negative impact of the weak dynamic performance brought by the second splicing partition 222.

[0150] Please refer to Figure 8 Based on any of the above embodiments, in one embodiment of the present application, the pore area 21 includes a first area 213 and a second area 214, the first area 213 is close to the splicing area 22, and the first distance d1 between the recesses in the first area 213 is smaller than the second distance d2 between the recesses in the second area 214.

[0151] The pore area 21 in this embodiment may be a first pore partition distributed along the second direction Y, and / or a second pore partition distributed along the third direction X. The length of the first region 224 in the first pore partition in the second direction Y may range from 0.2 mm to 3 mm, for example, 0.2 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, etc.; the width of the first region 224 in the second pore partition in the third direction X may range from 0.2 mm to 3 mm, for example, 0.2 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, etc.

[0152] Since there is no recess 3 in the splicing area 22, the dynamic performance is weak. By setting recesses 3 with smaller spacing in the area near the splicing area 22 in the pore area, the poor dynamics at the splicing area 22 and the pore area 21 can be compensated.

[0153] As an implementation method, the ratio of the first distance d1 to the second distance d2 is in a range of 0.5 to 0.999, so as to compensate for the effect of poor dynamics at the splicing point to the greatest extent possible.

[0154] For example, the ratio between the first distance d1 and the second distance d2 may be 0.5, 0.6, 0.7, 0.8, 0.9, 0.999, etc.

[0155] Please refer to Figure 9 On the basis of any of the above embodiments, in one embodiment of the present application, the depth h of the recess 3 ranges from 5 μm to 30 μm, and / or the spacing D between the recesses 3 ranges from 100 μm to 300 μm, and / or the width a of the recess 3 ranges from 50 μm to 200 μm, so as to increase the contact area between the positive electrode sheet 100 and the electrolyte, increase the liquid retention capacity of the battery, and improve the battery performance.

[0156] For example, the width of the recess 3 may be 50 μm, 80 μm, 100 μm, 120 μm, 150 μm, 200 μm, etc.

[0157] When the concave portion 3 is a concave hole, the width of the concave portion 3 is the hole diameter; when the concave portion 3 is a groove, the width of the concave portion 3 is the groove diameter.

[0158] For example, the depth h of the concave portion 3 in the pore area 21 may be 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, etc.

[0159] For example, the distance D between the concave portions 3 in the pore area 21 may be 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, etc.

[0160] The relationship between the depth h of the recess 3 and the liquid holding capacity of the battery is shown in Table 3.

[0161] Table 3 shows that the battery's liquid retention capacity changes when the depth h of the recess 3 ranges from 5 μm to 30 μm. As the depth h of the recess 3 increases, the battery's liquid retention capacity gradually increases. When the depth h of the recess 3 is less than 5 μm, there is no effect on the battery's liquid retention capacity.

[0162] Table 3

[0163] Depth of concave portion h / μm Battery liquid capacity / g 1 8.32 3 8.32 5 8.32 10 8.35 15 8.38 20 8.40 25 8.42 30 8.43

[0164] The relationship between the distance D between the recesses 3 and the liquid holding capacity of the battery is shown in Table 4.

[0165] Table 4 shows that the spacing D between the recesses 3 ranges from 100 μm to 300 μm. As the spacing D between the recesses 3 decreases, the battery's liquid retention gradually increases. When the spacing D between the recesses 3 is less than 100 μm and greater than 300 μm, it has no effect on the battery's liquid retention.

[0166] Table 4

[0167] Distance between recesses D / μm Battery liquid capacity / g 50 8.40 70 8.40 100 8.40 150 8.38 200 8.36 250 8.34 300 8.30 350 8.30 400 8.30

[0168] Please refer to Figures 10 and 11 On the basis of any of the above embodiments, in one embodiment of the present application, the projection of the recess 3 on the positive electrode active material layer 2 located on the first surface of the current collector 1 on the current collector 1 and the projection of the recess 3 on the positive electrode active material layer 2 located on the second surface of the current collector 1 on the current collector 1 are staggered with each other; or, the projection of the recess 3 on the positive electrode active material layer 2 located on the first surface of the current collector 1 on the current collector 1 and the projection of the recess 3 on the positive electrode active material layer 2 located on the second surface of the current collector 1 on the current collector 1 overlap.

[0169] Figure 10 and Figure 11The concave projection 31 indicated by the solid line and the concave projection 31 indicated by the dotted line respectively represent the projections of the concave portions 3 on the positive electrode active material layer 2 located on the first surface and the second surface of the current collector 1 on the current collector 1 .

[0170] In this embodiment, the positive electrode active material layer 2 is distributed on both the first and second surfaces of the current collector 1. The recesses 3 can be produced by laser drilling. Laser drilling of the positive electrode active material layer 2 may damage the current collector 1. Preferably, the recesses 3 on the positive electrode active material layer 2 on the first and second surfaces of the current collector 1 are staggered. This can reduce the effect of laser energy on the same location on the current collector 1, reduce the probability of damage to the current collector 1, and improve the yield of the current collector 1.

[0171] like Figure 12 As shown, based on any of the above embodiments, in one embodiment of the present application, the positive electrode sheet 100 may further include:

[0172] The protective layer 4 is located between the positive electrode active material layer 2 and the current collector 1 .

[0173] The material of the protective layer 4 is a conductive material, such as conductive ceramics, etc. The protective layer 4 can reduce the damage to the current collector 1 caused by the laser energy transmission during laser drilling, thereby reducing the probability of damage to the current collector 1.

[0174] As an implementation method, the ratio of the thickness t of the protective layer 4 to the depth h of the recess 3 is in the range of 0.06 to 4, so as to reduce the amount of material used in the protective layer 4 and reduce the production cost while achieving the protection effect on the current collector 1.

[0175] For example, the ratio of the thickness t of the protective layer 4 to the depth h of the recess 3 may be 0.06, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, etc.

[0176] For example, the depth h of the concave portion 3 on the positive electrode active material layer 2 may be in a range of 15 μm to 30 μm, and the thickness t of the protective layer 4 may be in a range of 2 μm to 50 μm.

[0177] For example, the depth h of the recess 3 may be 15 μm, 20 μm, 25 μm, 30 μm, etc. The thickness t of the protective layer 4 may be 2 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 40 μm, 50 μm, etc.

[0178] The present application also provides a battery cell, such as Figure 13 and Figure 19 As shown, it includes a winding core: the winding core includes a stacked and wound positive electrode sheet 100, a separator 400, and a negative electrode sheet 200, and the positive electrode sheet 100 is the positive electrode sheet 100 of any of the above embodiments.

[0179] The positive electrode sheets 100 and the negative electrode sheets 200 are alternately arranged, and the separator 400 is located between the positive electrode sheets 100 and the negative electrode sheets 200. The negative electrode sheets 200 and the separator 400 can be referred to in related art and will not be described in detail here.

[0180] In this embodiment, the battery cell is a wound battery cell, and a recess 3 is provided on the positive electrode sheet 100. The recess 3 is at least located in the bending area, which can improve the local wetting performance of the positive electrode sheet 100, accelerate the lithium ion insertion and extraction, and improve the local lithium deposition of the battery.

[0181] In one embodiment of the present application, the positive electrode sheet includes a bending region M and a straight region, and the bending region M includes a concave portion. As an implementation method, the pore region of the positive electrode sheet 100 may correspond only to the bending region.

[0182] As another possible implementation, the portion of the straight area N connected to the bending area M contains a concave portion, and the pore area of the positive electrode sheet 100 is correspondingly located in the bending area and the portion of the straight area N connected to the bending area.

[0183] The size of the flat area N having the concave portion 3 is not limited in this embodiment and depends on the circumstances.

[0184] The concave portions 3 are distributed on the bending area and the portion of the straight area connected to the bending area, which can enhance the lithium ion exchange in the inner bending area and the portion of the straight area connected to the bending area.

[0185] On the basis of the above embodiments, in one embodiment of the present application, in the positive electrode sheet 100 located in the innermost layer of the battery cell, the ratio of the area S2 in the pore area 21 corresponding to the bending area to the area S1 of the pore area 21 is in the range of 0.12~0.4, and / or, in the positive electrode sheet 100 located in the outermost layer of the battery cell, the ratio of the area S5 in the pore area 21 corresponding to the bending area to the area S4 of the pore area 21 is in the range of 0.4~1; wherein, the innermost positive electrode sheet refers to the positive electrode sheet closest to the center of the winding core, and the outermost positive electrode sheet refers to the positive electrode sheet farthest from the center of the winding core.

[0186] For example, the ratio of the area S2 of the pore region 21 corresponding to the bend region to the area S1 of the pore region 21 can be 0.12, 0.2, 0.3, 0.4, etc. The ratio of the area S5 of the pore region 21 corresponding to the bend region to the area S4 of the pore region 21 can be 0.4, 0.6, 0.8, 1, etc.

[0187] In the innermost positive electrode sheet 100 , the area S1 of the pore region 21 = the area S2 of the pore region 21 corresponding to the bending region + the area S3 of the pore region 21 corresponding to the straight region.

[0188] In the outermost positive electrode sheet 100 , the area S4 of the pore region 21 = the area S5 of the pore region 21 corresponding to the bending region + the area S6 of the pore region 21 corresponding to the straight region.

[0189] The pore region 21 is distributed in the bending region and part of the straight region. The area of the pore region 21 distributed on the bending region is much smaller than the area of the pore region 21. The bending region and the part of the straight region connected to the bending region are most likely to experience lithium deposition after long cycles. By providing a recess 3 on the bending region and the part of the straight region connected to the bending region, the lithium ion exchange in the internal bending region and the part of the straight region connected to the bending region can be enhanced, thereby reducing the probability of lithium deposition.

[0190] On the basis of any of the above embodiments, in one embodiment of the present application, along the winding direction of the core, the area of the pore region 21 in the positive electrode sheet 100 corresponding to the flat region gradually decreases.

[0191] That is, among the layers of positive electrode sheets 100 in the battery cell, the area of the pore area 21 on the innermost positive electrode sheet 100 corresponding to the flat area is the largest, and the area of the pore area 21 on the outermost positive electrode sheet 100 corresponding to the flat area is the smallest.

[0192] As an implementation method, for the positive electrode sheet 100 located in the innermost layer, the ratio of the area S3 of the flat area with the recess 3 to the area S1 of the pore area 21 is in the range of 0.5~0.9999; and / or, for the positive electrode sheet 100 located in the outermost layer, the ratio of the area S6 of the flat area with the recess 3 to the area S4 of the pore area 21 is in the range of 0.001~0.3; wherein, the innermost positive electrode sheet refers to the positive electrode sheet closest to the center of the winding core, and the outermost positive electrode sheet refers to the positive electrode sheet farthest from the center of the winding core.

[0193] For example, on the innermost positive electrode sheet 100 , the ratio of the area S3 of the flat region where the recesses 3 are distributed to the area S1 of the pore region 21 may be 0.5, 0.6, 0.7, 0.8, 0.9, 0.9999, etc.

[0194] For example, on the outermost positive electrode sheet 100 , the ratio of the area S6 of the flat region of the recess 3 to the area S4 of the pore region 21 may be 0.001, 0.005, 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, etc.

[0195] The positive electrode sheet 100 located in the innermost layer has poor dynamics. More recesses 3 in the pore area 21 distributed in the flat area can improve the local dynamic performance and reduce the risk of thermal analysis.

[0196] Please refer to Figure 14Based on any of the above embodiments, in one embodiment of the present application, in the third direction X, the distance G between the edge of the positive electrode sheet 100 and the edge of the negative electrode sheet 200 ranges from 0.1 mm to 5 mm.

[0197] For example, the distance G between the edge of the positive electrode sheet 100 and the edge of the negative electrode sheet 200 may be 0.1 mm, 0.5 mm, 0.7 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 5 mm, etc.

[0198] By leaving a certain distance between the edge of the positive electrode sheet 100 and the edge of the negative electrode sheet 200, lithium deposition caused by the positive electrode active material exceeding the negative electrode active material can be prevented.

[0199] Please refer to Figure 14 Based on any of the above embodiments, in one embodiment of the present application, in the third direction X, the distance E between the recess 3 closest to the edge of the positive electrode sheet 100 and the edge of the negative electrode sheet 200 ranges from 0.3 mm to 5 mm.

[0200] For example, the distance E between the recess 3 closest to the edge of the positive electrode sheet 100 and the edge of the negative electrode sheet 200 can be 0.3 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, etc.

[0201] The concave portion 3 at the edge of the positive electrode sheet 100 leaves a certain distance from the edge of the negative electrode sheet 200, which can prevent lithium deposition caused by the positive electrode active material exceeding the negative electrode active material. At the same time, the edge concave portion 3 is beneficial to the lithium ion exchange speed at the edge, avoiding local lithium deposition.

[0202] Please refer to Figure 14 Based on any of the above embodiments, in one embodiment of the present application, in the third direction X, the distance F between the recess 3 closest to the edge of the positive electrode sheet 100 and the excess area of the negative electrode sheet 200 ranges from 0.1 mm to 1.5 mm; the excess area of the negative electrode sheet is the area where the negative electrode sheet exceeds the positive electrode sheet in the third direction X.

[0203] For example, the distance F between the concave portion 3 closest to the edge of the positive electrode sheet 100 and the overhang area of the negative electrode sheet 200 may be 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, etc.

[0204] The distance F between the recess 3 closest to the edge of the positive electrode sheet 100 and the excess area of the negative electrode sheet 200 can be adjusted by adjusting the position of the recess 3 on the positive electrode sheet 100 and the length of the negative electrode sheet 200 .

[0205] The presence of the concave portion 3 closest to the edge of the positive electrode sheet 100 can enhance the insertion and extraction of lithium ions at the edge, thereby improving its initial discharge efficiency.

[0206] Table 5 shows the relationship between the distance F between the recess 3 closest to the edge of the positive electrode sheet 100 and the overhang region of the negative electrode sheet 200 and the initial discharge efficiency. As shown in Table 5, when the distance F between the recess 3 closest to the edge of the positive electrode sheet 100 and the overhang region of the negative electrode sheet 200 ranges from 0.1 mm to 1.5 mm, the initial discharge efficiency can be adjusted by adjusting the distance F between the recess 3 closest to the edge of the positive electrode sheet 100 and the overhang region of the negative electrode sheet 200. When the distance F between the recess 3 closest to the edge of the positive electrode sheet 100 and the overhang region of the negative electrode sheet 200 is less than 0.1 mm and greater than 1.5 mm, the initial discharge efficiency is not affected.

[0207] Table 5

[0208] Distance F / mm First discharge efficiency 0.01 95.8% 0.05 95.8% 0.1 95.8% 0.5 95.6% 1 95.4% 1.5 95.3% 2 95.3% 2.5 95.3%

[0209] Please refer to Figure 15 On the basis of any of the above embodiments, in one embodiment of the present application, along the winding direction of the core, the positive electrode sheet includes an insulating layer 300, and the insulating layer 300 covers the current collector 1 and the positive electrode active material layer 2, and the length L2 of the insulating layer 300 located on the positive electrode active material layer 2 ranges from 0.1 mm to 10 mm.

[0210] For example, the length L2 of the insulating layer 300 on the positive electrode active material layer 2 may be 0.1 mm, 1 mm, 3 mm, 5 mm, 7 mm, 10 mm, etc.

[0211] The insulating layer 300 may be located at the end of the wound positive electrode sheet 100. The insulating layer 300 covers the current collector 1 and the positive active material layer 2, increasing the adhesion area between the insulating layer 300 and the positive electrode sheet 100 and improving the bonding strength between the insulating layer 300 and the positive electrode sheet 100.

[0212] In one embodiment of the present application, along the winding direction of the core, a distance L3 between the recess 3 closest to the edge of the positive electrode sheet 100 and the edge of the positive electrode sheet 100 ranges from 0.1 mm to 10 mm.

[0213] For example, the distance L3 between the concave portion 3 closest to the edge of the positive electrode sheet 100 and the edge of the positive electrode sheet 100 may be 0.1 mm, 1 mm, 3 mm, 5 mm, 7 mm, 10 mm, etc.

[0214] The distance between the recess 3 closest to the edge of the positive electrode sheet 100 in the winding direction and the edge of the positive electrode sheet 100, that is, the distance between the recess 3 closest to the edge of the positive electrode sheet 100 in the second direction Y and the edge of the positive electrode sheet 100, leaving a certain distance can prevent powder from falling off the edge of the end.

[0215] Please refer to Figures 15 to 17 On the basis of any of the above embodiments, in one embodiment of the present application, at the end of the positive electrode sheet 100, the insulating layer 300 covers the current collector 1 and the positive electrode active material layer 2, and the recess 3 closest to the edge of the positive electrode sheet 100 is at least partially located in the coverage area of the insulating layer 300; or, there is a gap between the recess 3 closest to the edge of the positive electrode sheet 100 and the insulating layer 300, such as Figure 16 shown.

[0216] The present application does not limit the positional relationship between the recess 3 closest to the edge of the positive electrode sheet 100 and the coverage area of the insulating layer 300. For example, the recess 3 closest to the edge of the positive electrode sheet 100 can be just covered by the insulating layer 300, in which case the edge of the insulating layer 300 is flush with the side of the recess 3 away from the end of the positive electrode sheet in the second direction Y. Alternatively, the edge of the insulating layer 300 extends beyond the side of the recess 3 away from the end of the positive electrode sheet in the second direction Y, such as Figure 15 shown.

[0217] In one embodiment of the present application, the concave portion 3 closest to the edge of the positive electrode sheet 100 may also be in contact with the insulating layer 300, such as Figure 17 shown.

[0218] The insulating layer 300 can be located at the tail of the positive electrode sheet 100. The positional relationship between the insulating layer 300 and the concave portion 3 closest to the edge of the positive electrode sheet 100 is preferably Figure 15 or Figure 16 In the end area, except for the area covered by the end tape, there is a recess 3 as much as possible, which can improve the dynamic performance of the edge of the pole piece end.

[0219] Please refer to Figure 13 and Figure 18 The negative electrode sheet 200 is provided with line grooves 5 extending along the width direction of the negative electrode sheet. The projection of the line grooves 5 on the positive electrode sheet overlaps with the recessed portion 3 on the positive electrode sheet 100 .

[0220] As an implementable embodiment, the depth of the wire groove 5 ranges from 5 μm to 30 μm, and / or the width of the wire groove 5 ranges from 50 μm to 500 μm, and / or the spacing of the wire groove 5 ranges from 0.1 mm to 5 mm.

[0221] The recess 3 on the positive electrode sheet 100 and the wire groove 5 on the negative electrode sheet 200 can jointly improve the dynamic performance of the battery, increase the lithium ion exchange rate, and ultimately enhance the fast charging capability of the battery.

[0222] For example, the width of the wire groove 5 may be 50 μm, 80 μm, 100 μm, 150 μm, 200 μm, 300 μm, 400 μm, 500 μm, etc. The pitch of the wire groove 5 may be 0.1 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, etc.

[0223] The present application also provides a lithium-ion secondary battery, which includes the battery cell of any of the above embodiments.

[0224] The battery also includes a membrane shell, a positive electrode ear and a negative electrode ear. The battery cell is located in the membrane shell. The positive electrode ear is connected to the positive electrode sheet in the battery cell, and the negative electrode ear is connected to the negative electrode sheet in the battery cell. The positive electrode ear and the negative electrode ear are partially exposed outside the membrane shell.

[0225] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0226] The above is a detailed introduction to the positive electrode sheet, battery cell and lithium-ion secondary battery provided by the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the scheme and core ideas of the present application. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the present application.

Claims

1. A positive electrode sheet, characterized in that: include: a current collector, and a positive electrode active material layer located on a first surface and / or a second surface of the current collector, wherein the first surface and the second surface are two surfaces opposite to each other in a first direction; At least one layer of the positive electrode active material layer includes a pore area and a splicing area, and the pore area includes a concave portion; The splicing area is located between two adjacent pore areas.

2. The positive electrode sheet according to claim 1, wherein: The pore region includes a first pore partition and / or a second pore partition, wherein the first pore partition is distributed along the second direction and located at an edge portion of the positive electrode active material layer, and the second pore partition is distributed along the third direction and located at a middle portion of the positive electrode active material layer; The splicing area includes a first splicing partition and / or a second splicing partition, the first splicing partition is located between adjacent first pore partitions, and the second splicing partition is located between adjacent second pore partitions; The second direction is perpendicular to the third direction, and the second direction and the third direction are respectively perpendicular to the first direction.

3. The positive electrode sheet according to claim 2, wherein: The length of the first splicing partition in the second direction ranges from 0.1 mm to 5 mm; And / or, the width of the second splicing partition in the third direction ranges from 0.1 mm to 5 mm; and / or, the ratio of the area of the first splicing partition to the area of the first pore partition is in a range of 0.001 to 0.01; And / or, the ratio of the area of the second splicing partition to the area of the second pore partition is in the range of 0.005 to 0.

2.

4. The positive electrode sheet according to claim 2, wherein: The concave portion includes concave holes, and the density of the concave holes in the first pore partition ranges from 0.5 to 10 per mm. 2 ; And / or, the concave portion includes concave holes, and the density of the concave holes in the second pore partition ranges from 0.5 to 10 per mm 2 ; and / or a ratio of an area occupied by the concave portion in the first pore partition to a total area of the positive electrode active material layer is in a range of 0.0006 to 0.35; And / or, the ratio of the area occupied by the concave portion in the second pore partition to the total area of the positive electrode active material layer is in a range of 0.0001 to 0.35; And / or, in the third direction, the distance between the first pore partition and the edge of the positive electrode active material layer is in a range of 0.2 mm to 5 mm.

5. The positive electrode sheet according to claim 2, wherein: Also includes: The third splicing partition; The third splicing partition is located between the first pore partition and the second pore partition.

6. The positive electrode sheet according to claim 1, wherein: The aperture area includes a first region and a second region, the first region is close to the splicing area, and a first distance between the recesses in the first region is smaller than a second distance between the recesses in the second region.

7. The positive electrode sheet according to claim 6, wherein: The ratio of the first distance to the second distance ranges from 0.5 to 0.

999.

8. The positive electrode sheet according to claim 1, wherein: The depth of the concave portion is in the range of 5 μm to 30 μm, and / or the interval between the concave portions is in the range of 100 μm to 300 μm, and / or the width of the concave portion is in the range of 50 μm to 200 μm.

9. The positive electrode sheet according to claim 1, wherein: The projection of the concave portion on the positive electrode active material layer on the first surface of the current collector on the current collector and the projection of the concave portion on the positive electrode active material layer on the second surface of the current collector on the current collector are staggered; or, A projection of the concave portion on the positive electrode active material layer on the first surface of the current collector on the current collector overlaps with a projection of the concave portion on the positive electrode active material layer on the second surface of the current collector on the current collector.

10. The positive electrode sheet according to any one of claims 1 to 9, characterized in that: Also includes: A protective layer is located between the positive electrode active material layer and the current collector.

11. The positive electrode sheet according to claim 10, wherein: The ratio of the thickness of the protective layer to the depth of the recess is in the range of 0.06 to 4.

12. A battery cell, characterized in that: The invention comprises a winding core, wherein the winding core comprises a positive electrode sheet, a separator, and a negative electrode sheet that are stacked and wound together. The positive electrode sheet is the positive electrode sheet according to any one of claims 1 to 11.

13. The battery cell according to claim 12, wherein: The positive electrode sheet includes a bending area and a straight area, and the bending area contains a concave portion; And / or, the portion of the straight area connected to the bending area contains a concave portion.

14. The battery cell according to claim 13, wherein: In the positive electrode sheet located in the innermost layer of the battery cell, the ratio of the area of the pore region corresponding to the bending region to the area of the pore region is in a range of 0.12 to 0.4; And / or, in the positive electrode sheet located at the outermost layer of the battery cell, the ratio of the area of the pore region corresponding to the bending region to the area of the pore region is in a range of 0.4 to 1; and / or, along the winding direction of the core, the area of the pore region in the positive electrode sheet corresponding to the flat region gradually decreases; The innermost positive electrode sheet refers to the positive electrode sheet closest to the center of the winding core, and the outermost positive electrode sheet refers to the positive electrode sheet farthest from the center of the winding core.

15. The battery cell according to claim 14, wherein: For the innermost positive electrode sheet, the ratio of the area of the flat region with the recesses to the area of the pore region is in a range of 0.5 to 0.9999; And / or, for the positive electrode sheet located in the outermost layer, the ratio of the area of the flat area with the recessed portions to the area of the pore area is in the range of 0.001 to 0.3; wherein, the positive electrode sheet in the innermost layer refers to the positive electrode sheet closest to the center of the winding core, and the positive electrode sheet in the outermost layer refers to the positive electrode sheet farthest from the center of the winding core.

16. The battery cell according to claim 12, wherein: In the third direction, the distance between the edge of the positive electrode sheet and the edge of the negative electrode sheet ranges from 0.1 mm to 5 mm; and / or, In the third direction, the distance between the concave portion closest to the edge of the positive electrode sheet and the edge of the negative electrode sheet is in the range of 0.3 mm to 5 mm; and / or, In the third direction, the distance between the concave portion closest to the edge of the positive electrode sheet and the excess area of the negative electrode sheet is in the range of 0.1 mm to 1.5 mm; the excess area of the negative electrode sheet is the area where the negative electrode sheet exceeds the positive electrode sheet in the third direction.

17. The battery cell according to claim 12, wherein: Along the winding direction of the core, the positive electrode sheet includes an insulating layer, the insulating layer covers the current collector and the positive electrode active material layer, and the length of the insulating layer located on the positive electrode active material layer ranges from 0.1 mm to 10 mm; and / or, Along the winding direction of the winding core, the distance between the concave portion closest to the edge of the positive electrode sheet and the edge of the positive electrode sheet ranges from 0.1 mm to 10 mm.

18. The battery cell according to claim 17, wherein: Along the winding direction of the core, the insulating layer covers the current collector and the positive active material layer, and there is a gap between the recessed portion closest to the edge of the positive electrode sheet and the insulating layer; or, the recessed portion closest to the edge of the positive electrode sheet is at least partially located within the coverage area of the insulating layer.

19. The battery cell according to any one of claims 12 to 18, characterized in that: The negative electrode sheet is provided with line grooves extending along the width direction of the negative electrode sheet, and the projection of the line grooves on the positive electrode sheet overlaps with the recessed portion on the positive electrode sheet.

20. The battery cell according to claim 19, wherein: The depth of the wire groove is in the range of 5 μm to 30 μm, and / or the width of the wire groove is in the range of 50 μm to 500 μm, and / or the spacing of the wire groove is in the range of 0.1 mm to 5 mm.

21. A lithium ion secondary battery, characterized in that: The battery comprises the battery cell according to any one of claims 12 to 20.

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