Positive pole piece and battery

Abstract

The invention provides a positive pole piece and a battery. The positive pole piece comprises a current collector and a functional layer, the current collector is provided with N first concave structures, the opening ends of the first concave structures are located on the functional surface of the current collector, and N is greater than or equal to 1; the functional layer comprises a planar functional layer and a concave functional layer, the planar functional layer is arranged on the plane where the functional surface is located, and the concave functional layer is at least partially embedded into the first concave structure; the concave functional layer sequentially comprises a first safe priming coat and a second active layer in the direction far away from the current collector; and the planar functional layer sequentially comprises a second safe priming coat and a second active layer along the direction far away from the current collector. According to the positive pole piece provided by the invention, the energy density, the cycle performance and the weight impact test passing rate of the battery can be improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of secondary batteries, and particularly relates to a positive pole piece and a battery. BACKGROUND

[0002] Lithium ion batteries are widely used in many fields such as electronic products, electric vehicles and energy storage, which greatly improves people's social life and production. At the same time, lithium ion batteries also have great safety risks, especially when subjected to mechanical abuse (such as needle puncture), the short circuit contact between the current collector and the active material layer is the most likely factor to cause fire and explosion. In order to improve the safety performance of lithium ion batteries, a safety coating is usually set between the current collector and the active layer to prevent the direct contact between the current collector and the active material layer. However, the poor contact between the safety coating and the functional surface of the current collector will cause problems such as cycle deterioration, and in addition, the poor contact between the safety coating and the functional surface of the current collector, especially when the battery is impacted by a heavy object, is still prone to fire and explosion.

[0003] Therefore, how to balance the improvement of the energy density, cycle performance and heavy object impact test pass rate of the battery is a technical problem to be solved in the field. SUMMARY

[0004] The application provides a positive pole piece to solve the problem of poor contact between the bottom coating and the functional surface of the current collector in the prior art, thereby balancing the improvement of the energy density, cycle performance and heavy object impact test pass rate of the battery.

[0005] The application also provides a battery, which can balance the improvement of the energy density and safety performance of the battery due to the inclusion of the above-mentioned positive pole piece.

[0006] In one aspect, the application provides a positive pole piece, comprising a current collector and a functional layer;

[0007] The current collector is provided with N first recess structures, and the opening end of the first recess structure is located on the functional surface of the current collector, N>1;

[0008] The functional layer comprises a planar functional layer and a recess functional layer, wherein the orthographic projection of the planar functional layer overlaps the functional surface, and the orthographic projection of the recess functional layer overlaps the first recess structure;

[0009] The recess functional layer comprises a first safety bottom coating and a first active layer in sequence in the direction away from the current collector;

[0010] The planar functional layer comprises a second safety bottom coating and a second active layer in sequence in the direction away from the current collector;

[0011] The thickness of the first safety bottom coating is H1, and the thickness of the first active layer is H2;

[0012] the second safety undercoat layer has a thickness of H3, and the second active layer has a thickness of H4;

[0013] the recess functional layer is embedded in the first recess structure part, the second safety undercoat layer has a thickness of h1, and the current collector has a thickness of H;

[0014] 0.3 μm < H1-H3≤H, 0.3 μm < H2-H4≤H, and 0.3 μm < h1≤H.

[0015] The positive electrode tab as described above, the compaction density of the recess functional layer is D1, the compaction density of the planar functional layer is D2, and 0 < D2-D1≤2.5 g / cm3.

[0016] The positive electrode tab as described above, the porosity of the functional layer is 8%-40%; preferably 10-30%;

[0017] And / or, the porosity of the recess functional layer is ε1, the porosity of the planar functional layer is ε2, and 5% < ε1-ε2≤32%.

[0018] The positive electrode tab as described above, the first safety undercoat layer includes N second recess structures near the surface of the first active layer, the opening end of the second recess structure faces the first active layer; and the depth of the second recess structure is 0.3 μm < h2 < H.

[0019] The positive electrode tab as described above, the included angle between the side wall of the first recess structure and the first plane is α1, the included angle between the side wall of the second recess structure and the first plane is β1, and α1>β1, 10° < α1≤90°.

[0020] The first plane is parallel to the functional surface of the current collector.

[0021] The positive electrode tab as described above is prepared by including the following steps:

[0022] A safety undercoat layer slurry is arranged on the first functional surface of the current collector, a recess structure forming treatment is performed on the second functional surface of the current collector, and then a safety undercoat layer slurry and an active layer slurry are sequentially coated on the second functional surface and the recess structure to obtain the tab.

[0023] Preferably, the recess structure forming treatment is a laser treatment.

[0024] The first functional surface and the second functional surface are distributed on opposite sides in the thickness direction of the current collector.

[0025] The positive electrode tab as described above, the first active layer and the second active layer comprise active materials, a-Dv10 of the active materials satisfies: a-Dv10≤0.2d1 with the opening end aperture d1 of the second recessed structure;

[0026] And / or, the first safety primer and the second safety primer comprise functional materials, b-Dv50 of the functional materials satisfies: b-Dv50≤0.2d2 with the opening end aperture d2 of the first recessed structure;

[0027] Preferably, a-Dv10 is 1-10 μm, b-Dv50 is 0.2-2 μm, d1 is 10-150 μm, and d2 is 10-150 μm.

[0028] The positive electrode tab as described above, the first recessed structure opening end has a protrusion, the height of the protrusion is d, the thickness of the second safety primer is H3, and d:H3=1:(1-15) is satisfied.

[0029] Preferably, d is 0.1-3 μm, and H3 is 1-10 μm.

[0030] The positive electrode tab as described above, the first active layer and / or the second active layer comprises at least one of lithium cobaltate, lithium manganate, lithium nickel cobalt manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium-rich manganese-based material, lithium nickel cobalt aluminum, lithium titanate, lithium nickel manganate, lithium nickel cobalt manganese aluminum.

[0031] The functional material of the first safety primer and / or the second primer comprises at least one of aluminum oxide, bormite, titanium dioxide, titanium oxide, zirconium oxide, silicon dioxide, lithium iron phosphate, lithium manganese iron phosphate, magnesium oxide, zinc oxide, quartz stone.

[0032] Still another aspect of the present application provides a battery comprising the positive electrode tab as described above, the opening direction of the first recessed structure of the positive electrode tab is towards the side away from the center of the battery cell where the positive electrode tab is located.

[0033] The battery as described above further comprises a negative electrode tab, the negative electrode tab comprises a silicon-based material; the silicon-based material comprises at least one of silicon-carbon, silicon-oxygen, silicon element, and silicon alloy.

[0034] The implementation of the present application has at least the following beneficial effects:

[0035] The positive electrode tab provided by the application can guarantee the load capacity of the coating in the case that the coating in different areas of the tab has a thickness difference, help ensure the mass energy density of the battery without excessively damaging the current collector, and the first recessed structure can increase the contact area between the safety base coating and the current collector, and the first safety base coating and the second safety base coating have better bonding effect with the current collector by the cohesion between the base coating components inside and outside the first recessed structure, which increases the peeling difficulty of the base coating and improves the cycle deterioration problem caused by the poor contact between the base coating and the functional surface of the current collector. In addition, when the battery is deformed or broken inwardly due to the impact of a heavy object, the first safety base coating filled into the first recessed structure can slide and spread inwardly along the destruction direction, effectively protecting the fracture surface of the current collector from being exposed, avoiding the short circuit problem caused by the exposure of the fracture surface of the current collector, so as to improve the energy density, cycle performance and heavy object impact performance of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is a schematic diagram of the partial structure of the cross section of the positive electrode tab in an embodiment of the application;

[0037] Figure 2 is a schematic diagram of the partial structure of the cross section of the positive electrode tab in another embodiment of the application;

[0038] Figure 3 is a schematic diagram of the top view structure of the current collector in the positive electrode tab in another embodiment of the application;

[0039] Figure 4 is a SEM diagram of the partial positive electrode tab in embodiment 1 of the application;

[0040] Figure 5 is a schematic diagram of the partial structure of the current collector in the positive electrode tab in another embodiment of the application;

[0041] Figure 6 is a schematic diagram of the partial structure of the cross section of the positive electrode tab in another embodiment of the application.

[0042] Explanation of reference signs:

[0043] 1-current collector; 101-first safety base coating; 102-second safety base coating; 103-first active layer; 104-second active layer; A-plane functional area, B-recess functional area; 2-first recessed structure; 3-second recessed structure; 4-protrusion. DETAILED DESCRIPTION

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0045] Figures 1 to 3 In the diagram, the X direction is the length direction of current collector 1, the Y direction is the width direction of current collector 1, and the Z direction is the thickness direction of current collector 1.

[0046] This invention provides a positive electrode sheet, such as... Figure 1 As shown, it includes a current collector 1 and a functional layer; the current collector 1 is provided with N first recessed structures 2, and the opening end of the first recessed structure 2 is located on the functional surface of the current collector 1, N≥1; the functional layer includes a planar functional layer A and a recessed functional layer B, wherein the orthographic projection of the planar functional layer A overlaps with the functional surface, and the orthographic projection of the recessed functional layer B overlaps with the first recessed structure 2; the recessed functional layer B includes a first safety base layer 101 and a first active layer 103 in sequence along the direction away from the current collector 1; the planar functional layer A includes a first safety base layer 101 and a first active layer 103 in sequence along the direction away from the current collector 1; the planar functional layer A includes a first safety base layer 101 and a first active layer 103 in sequence along the direction away from the current collector 1. The first direction includes a second safety base layer 102 and a second active layer 104 in sequence; the thickness of the first safety base layer 101 is H1, and the thickness of the first active layer 103 is H2; the thickness of the second safety base layer 102 is H3, and the thickness of the second active layer 104 is H4; the thickness of the second safety base layer 102 embedded in the recessed functional layer B of the first recessed structure 2 is h1, and the thickness of the current collector 1 is H; satisfying: 0.3μm

[0047] The functional surfaces of a current collector refer to the outermost surfaces along its length and width directions, i.e., the two largest and opposite surfaces among the six surfaces of the current collector, for example... Figure 1 and Figure 2 The first functional surface 11 and the second functional surface 12 in the middle.

[0048] The first recessed structure 2 of the present invention is a cavity structure formed by the recess of the first functional surface 11 into the second functional surface 12. Specifically, conventional methods in the art can be used to provide the first recessed structure 2 with a cavity in the current collector 1. For example, mechanical drilling, laser drilling, electro- or thermal laser melting, radiation melting, chemical etching, friction drilling, and other processing methods can be used.

[0049] The depth of the first recessed structure 2 in the thickness direction of the current collector 1 can be selected according to the actual situation. When the depth of the first recessed structure 2 in the thickness direction of the current collector 1 is consistent with the thickness of the current collector 1, such as...​Figure 1 , Figure 2 , Figure 6 As shown, the first recessed structure 2 has two oppositely arranged ends, which intersect with the first functional surface 11 and the second functional surface 12 respectively. At this time, the gap formed on the first functional surface 11 and the second functional surface 12 is the opening of the first recessed structure 2. When the first recessed structure 2 does not penetrate the current collector 1 in the thickness direction of the current collector 1, the opening of the first recessed structure 2 is the gap on the first functional surface 11.

[0050] When the first recessed structure 2 is disposed on the first functional surface 11, the shape of the first recessed structure 2 can be observed to be circular (e.g., along the thickness direction of the current collector 1) on one side of the first functional surface 11. Figure 3 As shown), circles, rings (as shown) Figure 3 (As shown), triangles, squares, rhombuses, etc. This invention does not impose excessive limitations.

[0051] The number of first recessed structures 2 can be one or more. When there are multiple first recessed structures 2, the multiple first recessed structures 2 are distributed in the extension direction of the current collector 1, and any two recessed structures are independent of each other and have no overlapping or covering relationship.

[0052] It should be noted that the present invention does not impose any special limitation on the three-dimensional shape of the first recessed structure 2. When there are multiple first recessed structures 2, each of the multiple first recessed structures 2 is set independently, and their cross-sectional shapes in the planes containing the thickness and width are independent. For example, some of the first recessed structures 2 have a triangular cross-sectional shape, and some of the first recessed structures 2 have a trapezoidal cross-sectional shape; some of the first recessed structures 2 have a depth consistent with the thickness of the current collector 1 (in this case, the first recessed structure 2 can be understood as a through hole), and some of the first recessed structures 2 have a depth inconsistent with the thickness of the current collector 1 (in this case, the first recessed structure 2 can be understood as a blind hole).

[0053] In one specific embodiment, the first recessed structure 2 is a conical hole. The diameter d1 of the opening end of the conical hole and the centerline distance L between adjacent conical holes satisfy the following relationship: 1 ≤ d1 / L ≤ 10. Here, the diameter of the opening end of the conical hole refers to the diameter of the conical hole facing the current collector functional surface; the centerline distance L between adjacent conical holes can be understood as the sum of the distance between two adjacent conical holes and the radius of their opening ends. By limiting the relationship between d1 and L, the pore density can be kept within the above range, thereby balancing the improvement of the mechanical strength of the current collector 1 and the safety performance of the battery.

[0054] The taper of the conical hole is 1:(0.05~10), where the taper of the conical hole refers to the ratio of the diameter of the opening end of the conical hole to its depth. In some embodiments, d1 is 5~100μm, for example, the range of 5μm, 10μm, 15μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm or any two of these; L is 10~1000μm, for example, the range of 10μm, 20μm, 30μm, 50μm, 100μm, 200μm, 300μm, 500μm, 1000μm or any two of these.

[0055] like Figure 1 , Figure 2 As shown, the functional layer includes a planar functional layer A and a recessed functional layer B, wherein the orthographic projection of the planar functional layer A overlaps with the functional surface, and the orthographic projection of the recessed functional layer B overlaps with the first recessed structure 2.

[0056] In detail, planar functional layer A refers to the coating on the functional surface of the current collector 1 without the first recessed structure 2, while recessed functional layer B refers to the coating that overlaps with the orthographic projection of the first recessed structure 2. In this invention, the composition of the first safety primer 101 and the second safety primer 102 can be the same or different. The composition of the first safety primer 101 and the second safety primer 102 includes functional materials, wherein the functional materials can be at least one of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxide phosphate, lithium-rich manganese-based materials, lithium nickel cobalt aluminum oxide, lithium titanate, alumina, boehmite, titanium dioxide, zirconium oxide, and silicon dioxide, or at least one of their modifications.

[0057] The composition of the first active layer 103 and the second active layer 104 may be the same or different. The first active layer 103 and the second active layer 104 include active materials, which include at least one of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxide phosphate, lithium-rich manganese-based materials, lithium nickel cobalt aluminum oxide, lithium titanate, alumina, boehmite, titanium dioxide, zirconium oxide, zinc oxide, silicon dioxide, silicon carbide, silicon nitride, conductive polymers and their modifiers.

[0058] Furthermore, the first active layer 103 and the second active layer 104 contain a conductive agent, wherein the conductive agent includes at least one selected from conductive carbon black, acetylene black, graphite, graphene, carbon nanotubes, carbon nanofibers, conductive polythiophene, conductive polypyrrole, and conductive polyaniline. This ensures a reduced possibility of short circuits while providing a good conductive network, guaranteeing smooth electron conduction between the active layer and the current collector 1, thereby enabling the battery to achieve excellent safety performance while also possessing good cycle performance.

[0059] Each of the first safety primer 101, the second safety primer 102, the first active layer 103, and the second active layer 104 independently contains an adhesive. The adhesive includes at least one of the following: polyvinylidene fluoride (PVDF), polyvinylidene chloride (PVDC), polytetrafluoroethylene (PTFE), polyhexafluoropropylene (PHEP), polyacrylic acid, polyacrylate, polyamide, polyacrylonitrile, sodium carboxymethyl cellulose, polyvinylpyrrolidone (PVP), polyvinyl ether, polymethyl methacrylate (PMMA), styrene-butadiene rubber (SBR), polyethylene oxide (PEB), styrene-butadiene emulsion, styrene-acrylic emulsion, ethyl polyacrylate, butyl polymethacrylate, ethylene-vinyl acetate copolymer, and polyvinyl acetate, or at least a modified form or copolymer thereof. For example, copolymers of PVDF include PVDF-trifluoroethylene, PVDF-tetrafluoroethylene, PVDF-hexafluoroethylene, and PVDF-hexafluoropropylene. This ensures excellent adhesion between the first safety primer 101, the second safety primer 102, the first active layer 103, and the second active layer 104, improving the cycle stability of the positive electrode.

[0060] In this invention, the thickness H1 of the first safety primer 101, the thickness H3 of the second safety primer 102, the thickness H2 of the first active layer 103, and the thickness H4 of the second active layer 104 refer to the average thickness.

[0061] Wherein, the thickness H1 of the first safety base coating 101 refers to the dimension of the first safety base coating corresponding to the first recessed structure 2 along the center line of the first recessed structure 2, which can also be understood as the vertical distance from the lowest point of the first safety base coating 101 corresponding to the first recessed structure 2 to the side of the first safety base coating 101 away from the current collector; similarly, the thickness H2 of the first active layer 103 corresponding to the first recessed structure 2 refers to the dimension of the first active layer 103 corresponding to the first recessed structure 2 along the center line of the first recessed structure 2; and the thicknesses H3 and H4 of the second safety base coating 102 and the second active layer 104 are the dimensions of the second safety base coating 102 and the second active layer 104 corresponding to the functional surface in the thickness direction of the current collector 1. Wherein, the center line of the first recessed structure 2 is parallel to the thickness direction of the positive electrode current collector 1. By controlling 0.3μm

[0062] ​Furthermore, in one specific embodiment of the present invention, the compaction density of the recessed functional layer A is D1, and the compaction density of the planar functional layer B is D2, where 0 < D2 - D1 ≤ 2.5 g / cm³. 3 .

[0063] In this invention, compaction density refers to average compaction density. The difference between the average compaction density D1 of the concave functional layer A and the average compaction density D2 of the planar functional layer B can be observed using scanning electron microscopy, determined by testing porosity with a true density meter, or determined by other commonly used testing methods in the field.

[0064] The positive electrode sheet provided by this invention not only has good energy density and cycle performance, but also a good pass rate in heavy object impact tests. The inventors believe that the reason may be that by setting different compaction densities in different areas, the wetting effect of the battery electrolyte is improved, providing stress release points for electrode expansion and deformation within a certain range, effectively improving the battery's safety performance, especially the battery safety under mechanical damage conditions.

[0065] Furthermore, in a specific embodiment of the present invention, the porosity of the functional layer is 8%-40%, preferably 10-30%; and / or, the porosity of the recessed functional layer is ε1, and the average porosity of the planar functional layer is ε2, satisfying: 5 < ε1 - ε2 ≤ 32%.

[0066] The porosity mentioned in this invention is the average porosity.

[0067] The average porosity of the functional layer refers to the average porosity of all coatings on the current collector 1, namely the average porosity of the first safety base coating 101, the second safety base coating 102, the first active layer 103, and the second active layer 104.

[0068] Specifically, the average porosity of the functional layer is 8-40%, for example, the average porosity of the functional layer includes, but is not limited to, a range of 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, or any two of these.

[0069] The average porosity of the concave functional layer is ε1, and the average porosity of the planar functional layer is ε2, with 5% < ε1 - ε2 ≤ 32%. For example, ε1 - ε2 includes, but is not limited to, a range of 5%, 10%, 15%, 20%, 25%, 30%, 32%, or any two of these.

[0070] When the average porosity of the functional layer and the average porosity of different regions satisfy the above relationship, the porosity difference at different positions after rolling provides stress release space for the positive electrode expansion deformation within a certain range of the battery, provides more storage space for the electrolyte, and can also improve the wetting effect of the battery electrolyte, alleviate the cell deformation caused by battery expansion, which is conducive to improving the transport of lithium ions in the positive electrode sheet while taking into account the cycle performance and energy density of the battery. At the same time, when the electrode sheet is damaged by external force, it will break at the concave structure, and the safety bottom coating will slide along the direction of force to the fracture surface to prevent short circuit caused by direct contact between the fracture surfaces.

[0071] Furthermore, in one specific embodiment of the present invention, such as Figure 1 , Figure 2 As shown, the surface of the first safety base layer 101 near the first active layer 103 includes N second recessed structures 3, the opening end of the second recessed structure 3 facing the first active layer 103; the depth of the second recessed structure 3 is h2, and 0.3μm < h2 < H.

[0072] The opening end of the second recessed structure 3 is located at the intersection of the first safety base coating 101 and the first active layer 103, and the first active layer 103 is embedded in the second recessed structure 3.

[0073] The second recessed structure 3 and the first recessed structure 2 coexist. When projected along the thickness direction of the current collector, the second recessed structure 3 and the first recessed structure 2 overlap.

[0074] The distance between the bottom surface of the first active layer 103, which is parallel to the functional surface, and the lowest point of the second recessed structure 3 is the depth h2 of the second recessed structure 3, as shown in the figure below. Figure 1 As shown.

[0075] In detail, h2 includes, but is not limited to, 1 micrometer, 4 micrometer, 10 micrometer, and 20 micrometer.

[0076] When h2 is within the above range, the compaction density of the positive active layer in the region corresponding to the second recessed structure 3 will be lower than the compaction density of the positive active layer with the second recessed structure 3 after rolling.

[0077] Furthermore, in one specific embodiment of the present invention, such as Figure 2 As shown, the angle between one side of the sidewall of the first recessed structure 2 and the first plane is α1, and the angle between the sidewall of the second recessed structure 3 and the first plane is β1, satisfying: α1>β1, 10<α1≤90°; wherein, the first plane is parallel to the functional surface of the current collector 1.

[0078] Specifically, the first recessed structure 2 is essentially a recess on the current collector 1 relative to the functional surface, and the sidewall of the recess has an angle with the first plane. The second recessed structure 3 is essentially a recess of the first safety primer layer relative to a plane that is parallel to the functional surface and overlaps with part of the upper end of the first safety primer layer, and the sidewall of the first plane of the recess also has a certain angle.

[0079] When the side of the first safety primer 101 that contacts the sidewall of the first recessed structure 2 is planar, the angle α1 between the side of the first safety primer 101 that is close to the sidewall of the first recessed structure 2 and the first plane refers to the angle between the plane of the first safety primer 101 that contacts the sidewall of the first recessed structure 2 and the first plane. Similarly, when the side of the first active layer 103 that contacts the second recessed structure 3 is planar, the angle β1 between the side of the first active layer 103 that is close to the sidewall of the second recessed structure 3 and the first plane refers to the angle between the plane of the first active layer 103 that contacts the second recessed structure 3 and the first plane.

[0080] When the side of the first safety primer 101 that contacts the sidewall of the first recessed structure 2 is arc-shaped, the angle α1 between the side of the first safety primer 101 near the sidewall of the first recessed structure 2 and the first plane refers to the angle between the plane formed by the line connecting the two ends of the arc surface of the first safety primer 101 that contacts the sidewall of the first recessed structure 2 and the first plane. Similarly, when the side of the first active layer 103 that contacts the second recessed structure 3 is arc-shaped, the angle β1 between the side of the first active layer 103 near the sidewall of the second recessed structure 3 and the first plane refers to the angle between the plane formed by the line connecting the two ends of the arc surface of the first active layer 103 that contacts the second recessed structure 3 and the first plane.

[0081] In one specific embodiment, laser drilling is used to create the recessed structure. As the laser energy melts the current collector, less and less current collector melts as the opening points to the other side, resulting in the sidewalls of the blind or through hole not being perpendicular. By controlling the angular relationship between the first recessed structure 2 and the second recessed structure 3 and the first plane, the actual depth and area of ​​a single first recessed structure 2 can be better controlled, thereby controlling the amount of material loaded in the first recessed structure 2 and further improving the mechanical properties of the positive electrode sheet while maintaining a certain thickness.

[0082] Furthermore, in a specific embodiment of the present invention, the positive electrode sheet is prepared by the following steps: a safety undercoating slurry is applied to a first functional surface of the current collector, a recessed structure is created on a second functional surface of the current collector, and then a safety undercoating slurry and an active layer slurry are sequentially applied to another functional surface and the recessed structure to obtain the electrode sheet; preferably, the recessed structure creation process is laser processing; the first functional surface and the second functional surface are distributed on opposite sides of the current collector in the thickness direction.

[0083] It is understandable that the above-mentioned process of creating a concave structure requires drilling based on the morphological characteristics of the first concave structure and parameters such as the distribution density and location of the first concave structure.

[0084] The process of creating a concave structure can be carried out by mechanical drilling, electric or thermal laser melting, radiation melting, chemical corrosion, friction drilling, etc. Preferably, the process of creating a concave structure is laser processing. Laser processing can not only achieve high-precision and high-efficiency processing, but also meet the complex structural and functional requirements of the current collector, and avoid additional problems caused by the process of creating a concave structure.

[0085] This invention avoids slurry leakage through the pores by first coating one functional surface, then drilling holes, and finally coating another functional surface. It also prevents wrinkling or breakage of the current collector. Furthermore, by coating one functional surface before drilling, the application of a safety undercoat to the other functional surface creates a difference in compaction density across different areas of the current collector during the rolling process. This difference in compaction density provides stress relief points for the positive electrode's expansion and deformation within a certain range, effectively improving battery safety. It also effectively controls the overall thickness and weight of the battery, ensuring that energy density is not reduced while significantly improving battery safety.

[0086] Furthermore, in a specific embodiment of the present invention, the first active layer 103 and the second active layer 104 include active materials, wherein the a-Dv10 of the active material and the pore diameter d1 at the opening end of the second recessed structure 3 satisfy: a-Dv10≤0.2d1; and / or, the first safety base coating 101 and the second safety base coating 102 include functional materials, wherein the b-Dv50 of the functional material and the pore diameter d2 at the opening end of the first recessed structure 2 satisfy: b-Dv50≤0.2d2; preferably, a-Dv10 is 1-10μm, b-Dv50 is 0.2-2μm, d1 is 10-150μm, and d2 is 10-150μm.

[0087] Where a-Dv10 represents the particle size corresponding to a cumulative volume distribution percentage of 10% for the active material, and b-Dv50 represents the particle size corresponding to a cumulative volume distribution percentage of 50% for the functional material, both in μm.

[0088] By defining the relationship between the aperture d1 of the first recessed structure 2 and the particle size distribution of the functional material, and the relationship between the aperture d2 of the second recessed structure 3 and the particle size of the active material, some functional material particles can be embedded in the first recessed structure 2, and some active material particles, or at least a portion of the active material particles, can be embedded in the second recessed structure 3 to increase the contact area. When this positive electrode is applied to a battery, and the opening of the first recessed structure 2 faces away from the center of the cell, if the battery is deformed or broken inwards due to external force, the first recessed structure 2 will make it easier for the fracture surface of the current collector 1 to occur at the first recessed structure 2. The functional material can slide and spread inwards in accordance with the direction of damage, effectively protecting the fracture surface of the current collector 1 from exposure, thereby avoiding short circuit problems caused by the exposure of the fracture surface of the current collector 1 and improving the safety performance of the battery.

[0089] Furthermore, in one specific embodiment of the present invention, such as Figure 5 As shown, the outer periphery of the opening end of the first recessed structure 2 has a protrusion 4, the height of the protrusion 4 is d, and the thickness of the second safety primer 102 is H3, satisfying: d:H3=1:(1-15); preferably, d is 0.1-3μm, and H3 is 1-10μm.

[0090] When the thickness of the protrusion and the second safety base coating satisfies the above relationship, the height of the safety base coating above the protrusion 4 is sufficient to ensure that the functional layer particles cover the protrusion, preventing the protrusion from being exposed and directly contacting the active material layer, thus reducing the risk of direct leakage of the current collector when the electrode breaks.

[0091] Furthermore, in a specific embodiment of the present invention, the first active layer and / or the second active layer includes at least one of lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxide phosphate, lithium-rich manganese-based materials, lithium nickel cobalt aluminum oxide, lithium titanate, lithium nickel manganese oxide, and lithium nickel cobalt manganese aluminum oxide; the functional material of the first safety base coating and / or the second base coating includes at least one of alumina, boehmite, titanium dioxide, zirconium oxide, silicon dioxide, lithium iron phosphate, lithium manganese iron phosphate, and quartz.

[0092] When the aforementioned materials are used for the safety coating, it not only provides good protection but also allows the active layer of the electrode to adhere more tightly to the surface of the safety coating, improving the cycle interface and extending battery life.

[0093] In one specific embodiment, the above-mentioned positive electrode sheet is used to make the battery cell. It should be noted that the battery cell provided by the present invention is preferably suitable for lithium-ion batteries; of course, it is also suitable for sodium-ion batteries and other battery cells, and no further limitations are made here.

[0094] When the aforementioned positive electrode is a positive electrode sheet, the battery cell of the present invention further includes a negative electrode sheet and a separator. The separator is used to separate the positive electrode sheet and the negative electrode sheet, preventing them from directly contacting each other. The battery cell can be a wound structure, a stacked structure, etc., and the present invention does not impose any limitations on it. Specifically, the battery cell can be a wound structure formed by stacking and winding positive electrode sheets, separators, and negative electrode sheets, or it can be a stacked structure formed by sequentially stacking multiple positive electrode sheets, separators, and negative electrode sheets.

[0095] Of course, if the above-mentioned positive electrode is a negative electrode, the battery cell of the present invention also includes a positive electrode and a separator.

[0096] Because the battery cell of the present invention includes the positive electrode plate as described above, the battery cell has excellent safety performance.

[0097] In another aspect, the present invention provides a battery, including a positive electrode as described above, wherein the opening direction of the first recessed structure of the positive electrode is directed toward the side away from the center of the cell where the positive electrode is located.

[0098] The battery of the present invention is preferably a lithium-ion battery, including but not limited to pouch batteries, square batteries, cylindrical batteries, etc.

[0099] The opening end of the first recessed structure 2 faces away from the center of the cell, that is, the opening end of the first recessed structure 2 faces the outside of the cell. In this way, when the cell is damaged by external force and deforms or breaks inward, the functional layer material covering the inner surface of the first recessed structure 2 can slide and spread inward in the direction of damage, effectively protecting the fracture surface of the current collector 1 from exposure, thereby avoiding short circuit problems caused by the exposure of the fracture surface of the current collector 1.

[0100] A battery for charging / discharging can be formed by mounting the battery cell and protection circuit together inside an aluminum-plastic film. The quality of the battery cell directly determines the quality of the battery. Due to the use of the aforementioned electrode plates, the battery of this invention exhibits excellent performance in terms of safety and other aspects.

[0101] The battery also includes an electrolyte. Specifically, the battery cell is packaged and then injected with an electrolyte. The battery is then produced through processes such as formation, capacity testing, and OCV.

[0102] Furthermore, in one specific embodiment of the present invention, the battery further includes a negative electrode sheet, which comprises a silicon-based material, including at least one of silicon-carbon, silicon-oxygen, elemental silicon, and silicon alloy.

[0103] When the negative electrode sheet includes silicon-based materials of the above type, the cycle expansion rate of the battery assembled from the silicon-based negative electrode is reduced while the active material of the negative electrode is limited to the above range, which helps to improve the energy density and dynamic performance of the battery.

[0104] The present invention will be further described below through specific embodiments and comparative examples. Unless otherwise specified, the reagents, materials and instruments used below are all conventional reagents, materials and instruments, all of which are commercially available, and the reagents and materials involved can also be synthesized by conventional synthetic methods.

[0105] Example 1

[0106] I. Preparation of the positive electrode sheet

[0107] (1) Preparation of the first safety primer and the second safety primer slurry: Metal oxide particles, carbon black and polyvinylidene fluoride (PVDF) in a mass ratio of 85:5:10 are mixed in N-methylpyrrolidone (NMP) and stirred evenly to obtain the first safety primer slurry and the second safety primer slurry.

[0108] Preparation of the first and second active layer slurries: Lithium cobalt oxide, carbon black, and polyvinylidene fluoride (PVDF) in a mass ratio of 96:1:3 are mixed in N-methylpyrrolidone (NMP) and stirred evenly to obtain the active layer slurry.

[0109] (2) The second safety base coating slurry from step (1) is applied to a preset position on the second functional surface 12 of the positive current collector (aluminum foil), and then dried to form the second functional surface 12.

[0110] (3) Drilling process: The first functional surface 11 of the positive electrode current collector is processed by drilling equipment to form a first recessed structure 2, so that the positive electrode current collector includes a first recessed structure 2 with a blind hole morphology and a first recessed structure 2 with a through hole morphology.

[0111] (4) The first safety primer coating slurry is coated on the first functional surface 11 of the current collector and dried to form the first functional surface 11. Then, the first active layer slurry and the second active layer slurry are coated on the surfaces of the first and second safety primer coatings and dried to form the first active layer and the second active layer, thus obtaining the initial positive electrode film.

[0112] After rolling and slitting the initial positive electrode film, a positive electrode sheet is obtained.

[0113] II. Preparation of the negative electrode sheet

[0114] Graphite, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC) in a mass ratio of 97:1.5:1.5 were mixed with deionized water and stirred evenly to obtain a negative electrode coating slurry.

[0115] The negative electrode coating slurry is coated onto the surface of the negative electrode current collector, and the negative electrode sheet is obtained after drying, rolling, and slitting.

[0116] III. Battery Preparation

[0117] The positive electrode, separator, and negative electrode are stacked and wound in sequence to obtain a core; wherein the opening ends of the blind holes and through holes face the side away from the center of the core;

[0118] Lithium-ion batteries are produced by processing battery cells through processes such as encapsulation, electrolyte injection, formation, capacity testing, and OCV.

[0119] Figure 4 This is a partial SEM image of the positive electrode sheet provided in this embodiment.

[0120] Example 2

[0121] The preparation process is basically the same as that in Example 1, except that in the preparation process of the positive electrode sheet, the power of the drilling machine is reduced so that the depth of the first recessed structure is smaller than that in Example 1, as shown in Tables 1 and 2. Other conditions remain unchanged, and the positive electrode sheet of this example is obtained.

[0122] In the battery manufacturing process, the positive electrode sheet of Example 1 is replaced with the positive electrode sheet of this example.

[0123] Example 3

[0124] The preparation process is basically the same as that in Example 1, except that: in the preparation process of the positive electrode sheet, the number of the first recessed structure is less than that in Example 1 by adjusting the drilling spacing of the drilling machine, as shown in Tables 1 and 2. Other conditions remain unchanged, and the positive electrode sheet of this example is obtained.

[0125] In the battery manufacturing process, the positive electrode sheet of Example 1 is replaced with the positive electrode sheet of this example.

[0126] Example 4

[0127] The preparation process is basically the same as that in Example 1, except that: in the preparation process of the positive electrode sheet, the parameters of the first safety base layer, the second safety base layer, the first active layer, and the second active layer are changed by increasing the coating thickness of the base layer, as shown in Tables 1 and 2. Other conditions remain unchanged, and the positive electrode sheet of this example is obtained.

[0128] In the battery manufacturing process, the positive electrode sheet of Example 1 is replaced with the positive electrode sheet of this example.

[0129] Example 5

[0130] The preparation process is basically the same as that in Example 1, except that: in the preparation process of the positive electrode sheet, by reducing the roller pressure and reducing the roller compaction, the average porosity of the functional layer and the active material layer is increased, and the parameter reaction between ε1, ε2, D1, and D2 is changed, as shown in Tables 1 and 2. Other conditions remain unchanged, and the positive electrode sheet of this example is obtained.

[0131] In the battery manufacturing process, the positive electrode sheet of Example 1 is replaced with the positive electrode sheet of this example.

[0132] Example 6

[0133] The preparation process is basically the same as that in Example 1, except that: in the preparation process of the positive electrode sheet, the drilling parameters of mechanical drilling are adjusted so that the aperture of the opening end of the first recessed structure is larger than that in Example 1, as shown in Tables 1 and 2. Other conditions remain unchanged, and the positive electrode sheet of this example is obtained.

[0134] In the battery manufacturing process, the positive electrode sheet of Example 1 is replaced with the positive electrode sheet of this example.

[0135] Example 7

[0136] The positive electrode sheet provided in this embodiment is prepared in the same way as in Example 1, except that:

[0137] Step 3) In the battery preparation process, the positive electrode, separator and negative electrode are stacked in sequence to obtain the battery cell; however, the opening ends of the blind holes and through holes are oriented in the opposite direction to those in Example 1, and are on both sides close to the center of the stack.

[0138] Example 8

[0139] The preparation process is basically the same as that in Example 1, except that: in the preparation process of the positive electrode, by adjusting the types of active materials and functional materials, a-Dv10 is greater than 0.2d1 and b-Dv50 is greater than 0.2d2, as shown in Tables 1 and 2. Other conditions remain unchanged, and the positive electrode of this example is obtained.

[0140] In the battery manufacturing process, the positive electrode sheet of Example 1 is replaced with the positive electrode sheet of this example.

[0141] Example 9

[0142] The preparation process is basically the same as that in Example 1, except that: in the preparation process of the positive electrode sheet, by reducing the thickness of the bottom coating, the height d of the protrusion is controlled to be higher than H3, and d:H3 does not satisfy d:H3=1:(1-15), as shown in Table 1 and Table 2. Other conditions remain unchanged, and the positive electrode sheet of this example is obtained.

[0143] In the battery manufacturing process, the positive electrode sheet of Example 1 is replaced with the positive electrode sheet of this example.

[0144] Example 10

[0145] The preparation process is basically the same as that in Example 1, except that: in the preparation process of the positive electrode sheet, the positive electrode sheet of this example is obtained by adjusting the type of active material and functional material, as well as the drilling parameters and rolling process, as shown in Tables 1 and 2, while keeping other conditions unchanged.

[0146] In the battery manufacturing process, the positive electrode sheet of Example 1 is replaced with the positive electrode sheet of this example.

[0147] Example 11

[0148] The preparation process is basically the same as that in Example 1, except that: in the preparation process of the positive electrode sheet, the positive electrode sheet of this example is obtained by adjusting the type of active material and functional material, as well as the drilling parameters and rolling process, as shown in Tables 1 and 2, while keeping other conditions unchanged.

[0149] In the preparation of the negative electrode, graphite is replaced with silicon-carbon material.

[0150] In the battery manufacturing process, the positive electrode sheet of Example 1 is replaced with the positive electrode sheet of this example.

[0151] Comparative Example 1

[0152] The preparation process is basically the same as that in Example 1, except that step (3) is omitted, that is, no drilling is performed, and other conditions remain unchanged to obtain the positive electrode sheet of this example.

[0153] Comparative Example 2

[0154] I. Preparation of the positive electrode sheet

[0155] (1) Drilling process: The first functional surface 11 of the positive current collector is processed by the high power of the drilling equipment to form a recessed structure, so that the positive current collector includes a recessed structure whose morphology is entirely through holes.

[0156] (2) Preparation of the base coating slurry: Metal oxide particles, carbon black and polyvinylidene fluoride (PVDF) in a mass ratio of 85:5:10 are mixed in N-methylpyrrolidone (NMP) and stirred evenly to obtain the base coating slurry;

[0157] Preparation of active layer slurry: Lithium cobalt oxide, carbon black and polyvinylidene fluoride (PVDF) in a mass ratio of 96:1:3 are mixed in N-methylpyrrolidone (NMP) and stirred evenly to obtain active layer slurry;

[0158] (3) The bottom coating slurry in step (2) is applied to a preset position of the second functional surface 12 of the positive current collector (aluminum foil), and then dried to form the second functional surface 12.

[0159] (4) The base coating slurry is coated on the first functional surface 11 of the current collector, and after drying, the base coating of the first functional surface 11 is formed. Then, the active layer slurry is coated on the surface of the base coating, and after drying, the active layer is formed to obtain the initial positive electrode film.

[0160] By controlling the parameters of the roller pressing and compaction, the initial positive electrode film is rolled and then slit to obtain the positive electrode sheet.

[0161] II. Preparation of the negative electrode sheet

[0162] Graphite, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC) in a mass ratio of 97:1.5:1.5 were mixed with deionized water and stirred evenly to obtain a negative electrode coating slurry.

[0163] The negative electrode coating slurry is coated onto the surface of the negative electrode current collector, and the negative electrode sheet is obtained after drying, rolling, and slitting.

[0164] III. Battery Preparation

[0165] The positive electrode, separator, and negative electrode are stacked and wound in sequence to obtain a core; wherein the opening ends of the blind holes and through holes face the side away from the center of the core;

[0166] Lithium-ion batteries are produced by processing battery cells through processes such as encapsulation, electrolyte injection, formation, capacity testing, and OCV.

[0167] Comparative Example 3

[0168] The preparation process is basically the same as that in Example 1, except that: the first safety base coating and the second safety base coating are not set, that is, the surface of the current collector and the interior of the first recessed structure are filled and coated with the first active layer and the second active layer, wherein the composition of the first active layer and the second active layer is the same, and other conditions remain unchanged, thus obtaining the positive electrode sheet of this embodiment.

[0169] Comparative Example 4

[0170] The preparation process is basically the same as that in Example 1, except that the coating thickness and rolling process are adjusted to control H1-H3 to be less than 0.2 μm and H2-H4 to be less than 0.2 μm, while other conditions remain unchanged, to obtain the positive electrode sheet of this example.

[0171] Test case

[0172] 1. Impact test

[0173] The battery was placed at room temperature and charged at a constant current of 1C to a voltage of 4.5V. Then it was charged at a constant voltage until the current dropped to 0.05C. Charging was stopped, and then it was discharged at a constant current of 1C to 3.0V. This cycle was repeated for 5T. After the battery was fully charged for the last time, a heavy object impact test was conducted within 24 hours: The battery cell was placed on a flat surface, and a steel column with a diameter of 15.8±0.2mm was placed in the center of the battery cell with the longitudinal axis of the steel column parallel to the plane. A weight of 9.1±0.1kg was dropped freely from a height of 610±25mm onto the steel column above the center of the battery. After the test, the battery was observed for 6 hours. If the battery did not catch fire or explode, the test was considered passed. The number of passes / the number of tests was the pass rate of the heavy object impact test. The number of tests was 20.

[0174] 2. Needle prick pass rate test

[0175] Fully charge the battery and maintain the test environment temperature at 25±2℃. Use a 4mm steel needle to pierce the center of the battery perpendicularly to the battery plane at a speed of 0.1mm / s. Hold for 5 minutes. If the battery does not catch fire or explode, the test is considered passed. The number of passes divided by the number of tests is the needle penetration test pass rate. The number of tests is 15.

[0176] 3. Energy density test

[0177] Using a battery charge / discharge tester, the battery was charged at 25°C with a constant current of 0.5C to 4.25V, then charged with a constant voltage until the current dropped to 0.02C. After resting for 5 minutes, the battery was discharged at a constant current of 0.5C to 3V, and the initial discharge capacity Q of the battery was recorded. 放 and the first discharge energy E 放 Weigh the battery and record the mass as W. Calculate the mass energy density ED = E. 放 / W.

[0178] 4. Cyclic performance test

[0179] Test method: At 25℃, the lithium-ion battery is charged and discharged at a rate of 0.7C charging / 0.5C discharging. The discharge capacity Q2 of the 500th charge and discharge cycle and the discharge capacity Q1 of the 1st charge and discharge cycle are recorded. Capacity retention rate = Q2 / Q1×100%.

[0180] The test results are shown in Table 3.

[0181] Table 1

[0182]

[0183] Table 2

[0184]

[0185]

[0186] Table 3

[0187]

[0188] As shown in Table 3, the battery in the current collector embodiment has a high pass rate in mechanical abuse safety tests (especially heavy object impact test and nail penetration test), does not catch fire or explode, and has a higher capacity retention rate than the control group in long cycle test at 1.5C rate, indicating a higher battery mass energy density.

[0189] The preferred embodiments and experimental verifications of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the protection scope of the present invention.

Claims

1. A positive electrode sheet, characterized by, The collector and the functional layer are included; The collector is provided with N first recess structures, and the opening end of the first recess structure is located on the functional surface of the collector, N≥1; The functional layer includes a planar functional layer and a recess functional layer, wherein the orthographic projection of the planar functional layer overlaps the functional surface, and the orthographic projection of the recess functional layer overlaps the first recess structure; The recess functional layer includes a first security primer layer and a first active layer in sequence in the direction away from the collector; The planar functional layer includes a second security primer layer and a second active layer in sequence in the direction away from the collector; The thickness of the first security primer layer is H1, and the thickness of the first active layer is H2; The thickness of the second security primer layer is H3, and the thickness of the second active layer is H4; The second security primer layer thickness of the recess functional layer embedded in the first recess structure part is h1, and the thickness of the collector is H; Satisfies: 0.3 μm < H1-H3 ≤ H, 0.3 μm < H2-H4 ≤ H; 0.3 μm < h1 ≤ H.

2. The cathode electrode of claim 1, wherein The compaction density of the recess functional layer is D1, the compaction density of the planar functional layer is D2, 0 < D2-D1≤2.5 g / cm 3 .

3. The cathode electrode of claim 1, wherein The porosity of the functional layer is 8%-40%; preferably 10-30%; And / or, the porosity of the recess functional layer is ε1, and the porosity of the planar functional layer is ε2, which satisfies: 5% < ε1-ε2 ≤ 32%.

4. The cathode electrode of claim 1, wherein The surface of the first security primer layer close to the first active layer includes N second recess structures, and the opening end of the second recess structure faces the first active layer; the depth of the second recess structure is 0.3 μm < h2 < H.

5. The cathode electrode of claim 4, wherein, The angle between one side of the side wall of the first recess structure and the first plane is α1, and the angle between the side wall of the second recess structure and the first plane is β1, which satisfies: α1> β1, 10° < α1 ≤ 90°; Wherein, the first plane is parallel to the functional surface of the collector.

6. The cathode sheet of claim 1, wherein, The positive electrode sheet is prepared by including the following steps: A security primer layer slurry is arranged on the first functional surface of the collector, and a recess structure processing is performed on the second functional surface of the collector, and then a security primer layer slurry and an active layer slurry are coated in sequence on the second functional surface and the recess structure to obtain an electrode sheet; Preferably, the recess structure processing is laser processing; The first functional surface and the second functional surface are distributed on the opposite sides of the thickness direction of the collector.

7. The cathode electrode of claim 4, wherein, The first active layer and the second active layer include an active material, and the a-Dv10 of the active material satisfies: a-Dv10 ≤ 0.2d1, wherein d1 is the opening end aperture of the second recess structure; And / or, the first security primer layer and the second security primer layer include a functional material, and the b-Dv50 of the functional material satisfies: b-Dv50 ≤ 0.2d2, wherein d2 is the opening end aperture of the first recess structure; Preferably, a-Dv10 is 1-10 μm, b-Dv50 is 0.2-2 μm, d1 is 10-150 μm, and d2 is 10-150 μm.

8. The cathode sheet of claim 1, wherein, The opening end of the first recess structure has a protrusion, the height of the protrusion is d, and the thickness of the second security primer layer is H3, which satisfies: d:H3 = 1:(1-15); Preferably, d is 0.1-3 μm, and H3 is 1-10 μm.

9. The cathode electrode of claim 1, wherein, The first active layer and / or the second active layer comprises at least one of lithium cobaltate, lithium manganate, lithium nickel cobalt manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium-rich manganese-based material, lithium nickel cobalt aluminum, lithium titanate, lithium nickel manganate, lithium nickel cobalt manganese aluminum. The functional material of the first safety primer layer and / or the second primer layer comprises at least one of aluminum oxide, bormite, titanium dioxide, titanium oxide, zirconium oxide, silicon dioxide, lithium iron phosphate, lithium manganese iron phosphate, magnesium oxide, zinc oxide, quartz stone.

10. A battery, characterized by The positive electrode tab comprises the first recess structure opening direction of the positive electrode tab facing away from the center of the battery cell.

11. The battery of claim 10, wherein, The negative electrode tab comprises a silicon-based material; the silicon-based material comprises at least one of silicon-carbon, silicon-oxygen, silicon element, silicon alloy.

Images