Battery

Abstract

The invention provides a battery. The battery comprises a positive plate, a diaphragm and a negative plate which are laminated, the positive plate comprises a positive current collector and a positive functional layer, the positive current collector is provided with N sunken structures, the opening ends of the sunken structures are located on the functional surface of the positive current collector, the positive functional layer covers at least part of the surface of at least one functional surface of the positive current collector and is embedded into part of the sunken structures, and N is greater than or equal to 1; the size of the opening end of the sunken structure is d, and the positive electrode functional layer comprises a safety priming coat and a positive electrode active layer which are stacked in the direction gradually away from the functional surface of the positive electrode current collector; the negative plate comprises a negative active layer containing a silicon-based material, and Dv50 and d of the silicon-based material meet the condition that d is greater than or equal to Dv50 and less than or equal to 10 * Dv50. According to the battery, the problem that the cyclic expansion rate of a battery assembled by a silicon-based negative electrode in the prior art is relatively high can be solved, and the cyclic expansion rate of the battery is remarkably reduced.

Description

Technical Field

[0001] This invention belongs to the field of secondary battery technology, and specifically relates to a battery. Background Technology

[0002] With the booming development of the new energy industry, lithium-ion batteries are gradually moving towards higher energy density and longer cycle life. Silicon-based materials, due to their high theoretical specific capacity and high lithium intercalation potential, are gradually becoming alternatives to graphite as lithium battery anode materials. However, unlike graphite's intercalation and lithium insertion, silicon-based materials undergo significant volume expansion and contraction during charging and discharging. This leads to excessive expansion, causing battery deformation or damage, thus affecting the battery's safety, cycle performance, and lifespan. Therefore, reducing the cycle expansion rate of batteries assembled with silicon-based anodes is a pressing technical problem that needs to be solved in this field. Summary of the Invention

[0003] This invention provides a battery that solves the problem of high cycle expansion rate in batteries assembled with silicon-based negative electrodes in the prior art, and can significantly reduce the cycle expansion rate of the battery.

[0004] In one aspect, the present invention provides a battery comprising a positive electrode, a separator, and a negative electrode stacked together;

[0005] The positive electrode sheet includes a positive current collector and a positive electrode functional layer. The positive current collector has N recessed structures, the opening ends of which are located on the functional surface of the positive current collector. The positive electrode functional layer covers at least a portion of at least one functional surface of the positive current collector and is embedded in a portion of the recessed structures, where N ≥ 1. The size of the opening end of each recessed structure is d.

[0006] The positive electrode functional layer includes a safety base layer and a positive electrode active layer stacked together, arranged in a direction that gradually moves away from the positive electrode current collector functional surface;

[0007] The negative electrode includes a negative electrode active layer containing silicon-based material, wherein the Dv50 and d of the silicon-based material satisfy Dv50≤d≤10×Dv50.

[0008] As described above, the Dv50 of the battery is 5-15μm.

[0009] As described above, in the battery, the ratio of the total area of ​​the opening end of the recessed structure to the total area of ​​the positive electrode current collector is X, and the mass percentage of silicon-based material in the negative electrode active layer is Y, satisfying: 1 / 4Y≤X≤4Y;

[0010] Preferably, Y ≤ X.

[0011] In the battery described above, Y is 1-30 wt.%.

[0012] The silicon-based material includes at least one of silicon-carbon, silicon-oxygen, silicon alloy, and elemental silicon.

[0013] Preferably, the silicon-based material comprises silicon-carbon, wherein the silicon-carbon comprises silicon dispersed in a porous carbon framework.

[0014] As described above, the edge of the opening of the recessed structure contains a protruding structure, the width of the protruding structure is w, the height is h1, and the size of the opening end of the recessed structure is d.

[0015] Where 1μm≤w≤d×2, 0.1μm≤h1≤d×2.

[0016] As described above, in the battery, the opening size of the recessed structure is d, and the distance between the opening centers of adjacent recessed structures is L, where 1≤L / d≤10;

[0017] And / or, the thickness of the positive current collector is H, and the depth of the recessed structure is h2, satisfying: 1≤H / h2≤5.

[0018] In the battery described above, d is 5–100 μm, L is 10–1000 μm, h2 is 1–20 μm, and H is 5–20 μm.

[0019] As described above, along the length direction of the battery, the positive electrode current collector includes a first region and a second region. The first region has M1 recessed structures, and the second region has M2 recessed structures, where M1≥1 and M2≥1.

[0020] The positive electrode functional layer covers the surface of the first region;

[0021] The second region is provided with a safety primer and a protective layer stacked in the direction away from the current collector, or the second region is provided with a protective layer.

[0022] As described above, the safety undercoat of the battery comprises inorganic particles, which include at least one of aluminum oxide, boehmite, titanium dioxide, silicon dioxide, zinc oxide, zirconium oxide, magnesium oxide, silicon carbide, silicon nitride, lithium iron phosphate, and lithium manganese iron phosphate.

[0023] The active material of the active layer includes at least one of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium-rich manganese-based materials, lithium nickel oxide, and lithium nickel manganese oxide.

[0024] The protective layer comprises inorganic particles, which include at least one of alumina, boehmite, titanium dioxide, silicon dioxide, zinc oxide, zirconium oxide, magnesium oxide, silicon carbide, and silicon nitride.

[0025] Preferably, the inorganic particles have a Dv10 of 0.05–0.5 μm and a Dv50 of 0.1–2 μm; the active material has a Dv10 of 1–15 μm and a Dv50 of 2–30 μm.

[0026] The positive electrode of the battery described above is prepared by a method comprising the following steps:

[0027] A slurry with a positive electrode functional layer is formed on the first functional surface of the positive electrode current collector. After drying, a recessed structure is formed on the second functional surface of the positive electrode current collector. Then, a slurry with a positive electrode functional layer is formed on the second functional surface and the recessed structure. After drying and rolling, the positive electrode sheet is obtained.

[0028] The first functional surface and the second functional surface are located on opposite sides in the thickness direction of the current collector;

[0029] Preferably, the process of creating the recessed structure is laser processing.

[0030] As described above, the opening end of the recessed structure faces away from the center of the battery.

[0031] The implementation of this invention has at least the following beneficial effects:

[0032] The battery provided by this invention utilizes a positive electrode current collector with a recessed structure and defines the relationship between the particle size distribution of silicon-based material in the negative electrode active layer and the size of the opening end of the recessed structure. This reduces the compaction density of the positive electrode active material layer when the areal density of the positive electrode active material layer corresponding to the recessed structure remains constant. On the one hand, this provides expansion space and thickness release space for the expansion of the corresponding silicon-based negative electrode, reduces the compressive force on the negative electrode current collector, and reduces the deformation and expansion of the battery during cycle charging and discharging, thereby reducing the cycle expansion rate of the battery. On the other hand, by setting the recessed structure and the safety undercoating layer, when the battery is damaged by external force, the positive electrode sheet is more likely to break at the recessed structure. At this time, the safety undercoating layer slides along the direction of force to the fracture surface, which not only prevents short circuits caused by contact between the fracture surfaces, but also prevents short circuits caused by direct contact between the positive electrode current collector and the negative electrode sheet, thus improving the safety of the battery. Attached Figure Description

[0033] Figure 1 This is a partial structural schematic diagram of the battery cross-section in one embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of the cross-sectional structure of the positive electrode plate in a battery according to one embodiment of the present invention;

[0035] Figure 3 This is a schematic diagram of the cross-sectional structure of the positive electrode plate in a battery according to another embodiment of the present invention;

[0036] Figure 4 This is a schematic diagram of the cross-sectional structure of the positive current collector in the positive electrode sheet according to one embodiment of the present invention;

[0037] Figure 5 This is a schematic diagram of the cross-sectional structure of the positive current collector in the positive electrode sheet according to another embodiment of the present invention;

[0038] Figure 6 This is a top view schematic diagram of the positive current collector in a positive electrode sheet according to one embodiment of the present invention;

[0039] Figure 7 This is a partial cross-sectional structural diagram of the positive current collector in a positive electrode sheet according to an embodiment of the present invention;

[0040] Figure 8 This is a top-view photograph of the positive current collector in a positive electrode sheet according to one embodiment of the present invention;

[0041] Figure 9 This is a partial SEM image of the cross-section of the positive electrode at the first magnification in one embodiment of the present invention;

[0042] Figure 10 This is a partial SEM image of the cross-section of the positive electrode at the second magnification in one embodiment of the present invention;

[0043] Figure 11 This is a schematic diagram of the cross-sectional structure of the positive current collector in the positive electrode sheet according to one embodiment of the present invention.

[0044] Explanation of reference numerals in the attached figures:

[0045] 1-Positive current collector; 11-First functional surface; 12-Second functional surface; 101-Positive functional layer; 102-Safety primer layer; 103-Positive active layer; 104-Protective layer;

[0046] 2- Negative electrode current collector; 201- Negative electrode active layer;

[0047] 3-Concave structure; 301-Protruding structure;

[0048] 4-Septum. Detailed Implementation

[0049] 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.

[0050] Figures 1 to 7In the diagram, the X direction is the length direction of the positive electrode current collector 1, the Y direction is the width direction of the positive electrode current collector 1, and the Z direction is the thickness direction of the positive electrode current collector 1.

[0051] The present invention provides a battery comprising a positive electrode, a separator 4, and a negative electrode stacked together. The positive electrode includes a positive current collector 1 and a positive functional layer 101. The positive current collector 1 is provided with N recessed structures 3, the opening ends of the recessed structures 3 being located on the functional surface of the positive current collector 1. The positive functional layer 101 covers at least a portion of the surface of at least one functional surface of the positive current collector 1 and is embedded in a portion of the recessed structures 3, where N≥1. The size of the opening end of the recessed structure 3 is d. The positive functional layer 101 includes a safety undercoat 102 and a positive active layer 103 stacked together in a direction gradually moving away from the functional surface of the positive current collector 1. The negative electrode includes a negative active layer 201 containing silicon-based material, wherein the Dv50 of the silicon-based material and d satisfy Dv50≤d≤10×Dv50.

[0052] The battery of the present invention includes a positive electrode, a separator 4, and a negative electrode stacked sequentially. The separator 4 is located between the positive and negative electrode, serving to isolate the positive and negative electrode and prevent electrons from freely passing through, while allowing lithium ions in the electrolyte to freely pass between the positive and negative electrode.

[0053] The positive current collector 1 and the negative current collector 2 each have two maximum and opposite functional surfaces. For example, the positive current collector 1 includes a first functional surface 11 and a second functional surface 12 that are arranged opposite to each other. The recessed structure 3 is disposed on the first functional surface 11 or the second functional surface 12, and correspondingly, the opening end of the recessed structure 3 is connected to the first functional surface 11 or the second functional surface 12.

[0054] The recessed structure 3 can be a through hole or a blind hole, meaning that the recessed structure 3 may or may not penetrate the positive current collector 1 in the thickness direction. When the recessed structure 3 is a blind hole, its end is connected only to the first functional surface 11 or the second functional surface 12; when the recessed structure 3 is a through hole, its two ends are connected to the first functional surface 11 and the second functional surface 12, respectively. Specifically, as shown... Figure 4 , Figure 9 , Figure 10 As shown, the recessed structure 3 is a blind hole, and the end of the recessed structure 3 is only connected to the first functional surface 11, as shown. Figure 1 , Figure 2 , Figure 3 , Figure 5 , Figure 7 As shown, the recessed structure 3 is a through hole, and the two ends of the recessed structure 3 are connected to the first functional surface 11 and the second functional surface 12, respectively.

[0055] like Figures 1 to 8As shown, the number of recessed structures 3 on the positive electrode current collector 1 can be one or more. When there are multiple recessed structures 3, they are spaced apart along the extension direction of the positive electrode current collector 1. It can also be understood that under incident light parallel to the thickness direction of the positive electrode current collector 1, the projections of any two recessed structures 3 onto a common plane are independent of each other, without any overlap or covering relationship. Here, the common plane refers to a plane parallel to the functional surface of the positive electrode current collector 1. For example... Figure 6 As shown, multiple recessed structures 3 are uniformly distributed in a linear array along the length or width of the positive electrode current collector 1.

[0056] It should be noted that when there are multiple recessed structures 3, each of the multiple recessed structures 3 is an independent through hole or blind hole.

[0057] The positive electrode functional layer 101 covers at least a portion of the surface of at least one functional surface of the positive electrode current collector 1 and fills the partially recessed structure 3. In detail, the positive electrode functional layer 101 covers part or all of the surface of one or two functional surfaces of the positive electrode current collector 1, while the positive electrode functional layer 101 fills the partially recessed structure 3.

[0058] like Figure 11 As shown, in a direction that gradually moves away from the functional surface of the positive current collector 1, the positive electrode functional layer 101 includes a safety base layer 102 and a positive electrode active layer 103 stacked sequentially, wherein the safety base layer 102 fills the recessed structure 3 and covers part of the functional surface, and the positive electrode active layer 103 covers the safety base layer 102.

[0059] The safety primer 102 includes inorganic particles, specifically, the inorganic particles may include at least one of alumina, boehmite, titanium dioxide, silicon dioxide, zinc oxide, zirconium oxide, magnesium oxide, silicon carbide, and silicon nitride.

[0060] The positive electrode active layer 103 includes a positive electrode active material. Specifically, the positive electrode active material may include lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium manganese iron phosphate, ternary system (lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide) or any other lithium transition metal oxide.

[0061] Both the safety primer layer 102 and the positive electrode active layer 103 independently include an adhesive. The adhesive may include at least one of the following: polyethylene oxide, styrene-butadiene rubber, polyvinylidene fluoride, polyvinylidene fluoride-trifluoroethylene, polyvinylidene fluoride-tetrafluoroethylene, polyvinylidene fluoride-hexafluoroethylene, polyvinylidene fluoride-hexafluoropropylene, styrene-butadiene emulsion, styrene-acrylic emulsion, ethyl polyacrylate, polymethyl methacrylate, polyacrylonitrile, polybutyl methacrylate, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate, and polyurethane. This ensures that the positive electrode active layer 103 and the safety primer layer 102 are firmly bonded to the positive electrode current collector 1.

[0062] Both the safety undercoat 102 and the positive electrode active layer independently include a conductive agent, which may include at least one of conductive carbon black, acetylene black, graphite, graphene, carbon nanotubes, carbon nanofibers, conductive polythiophene, conductive polypyrrole, and conductive polyaniline. This ensures that while reducing the possibility of short circuits, it also provides the positive electrode active layer 103 and the safety undercoat 102 with a good conductive network, guaranteeing smooth electron conduction between the positive electrode active layer 103, the safety undercoat 102, and the positive electrode current collector 1. This results in the battery achieving both excellent safety performance and good cycle performance.

[0063] The negative electrode includes a negative electrode active layer 201 containing silicon-based material, which includes at least one of elemental silicon, silicon alloy, silicon oxide, and silicon carbon.

[0064] In one specific embodiment, the silicon-based material is a silicon-carbon material, in which silicon particles are distributed within a porous carbon framework. That is, the silicon-carbon comprises porous carbon and silicon particles embedded within the porous carbon framework. Thus, the porous carbon possesses certain mechanical strength and conductivity, which can improve the compressive strength and conductivity of the negative electrode. By embedding silicon particles, the energy density of the battery can be increased, and the breakage of silicon particles during the volume expansion and contraction of the silicon-based material can be prevented, thus avoiding problems such as poor electrical contact and improving the battery's cycle performance.

[0065] It is understood that in the negative electrode sheet of the present invention, the negative electrode current collector 2 can be copper foil, but is not limited thereto. The material of the negative electrode active material layer 201 may contain at least one of other negative electrode active materials such as graphite, hard carbon, and lithium titanate, in addition to silicon-based materials. In some embodiments, the negative electrode sheet comprises the following components by mass content: 85-99% negative electrode active material, 0.1-5% conductive agent, and 0.1-10% binder, wherein the negative electrode active material includes silicon-based materials and graphite; the silicon-based material includes at least one of elemental silicon, silicon alloy, silicon oxide, and silicon carbon. Thus, while reducing the cycle expansion rate of the battery assembled with a silicon-based negative electrode, limiting the negative electrode active material to the above-mentioned range helps to balance improving the energy density and kinetic performance of the battery.

[0066] The size d of the opening end of the recessed structure 3 and the Dv50 of the silicon-based material satisfy Dv50 ≤ d ≤ 10 × Dv50. Here, the size d of the opening end of the recessed structure 3 refers to the distance between the two points furthest apart at the edge of the opening. For example, when the opening is circular, the size d of the opening of the recessed structure 3 is the diameter of the circle; when the opening is rectangular, the size d of the opening of the recessed structure is the length of the diagonal of the rectangle. The particle size Dv50 of the silicon-based material represents the particle size corresponding to a cumulative volume distribution percentage of 50% for the silicon-based material. The units of d and Dv50 are μm.

[0067] The recessed structure 3 in the positive electrode current collector 1 can reduce the cycle expansion rate of the battery. By limiting the relationship between the particle size Dv50 of the silicon-based material and the pore size d at the opening end of the recessed structure 3, the thickness increases when the areal density of the positive electrode active material layer corresponding to the recessed structure remains unchanged, thereby reducing the compaction density of the positive electrode active material layer. On the one hand, this provides expansion space and thickness release space for the expansion of the corresponding silicon-based negative electrode; on the other hand, it reduces the extrusion pressure on the negative electrode current collector, reduces the deformation and expansion of the battery during cycle charging and discharging, thereby reducing the cycle expansion rate of the battery.

[0068] Furthermore, in one specific embodiment of the present invention, Dv50 is 5-15 μm.

[0069] In detail, Dv50 includes, but is not limited to, a range of 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, or any combination thereof.

[0070] When the silicon-based material Dv50 in the negative electrode active layer 201 meets the above range, it can not only provide more space for the expansion of the negative electrode active layer 201 and reduce the cycle expansion rate of the battery, but also when the battery is damaged by external force, the positive electrode sheet will break at the recessed structure, causing the safety bottom coating to slide along the direction of force to the fracture surface, preventing the fracture surfaces from contacting each other and causing a short circuit, thus further ensuring the safety performance of the battery.

[0071] Furthermore, in a specific embodiment of the present invention, the ratio of the total area of ​​the opening end of the recessed structure 3 to the total area of ​​the positive electrode current collector 1 is X, and the mass percentage of silicon-based material in the negative electrode active layer is Y, satisfying: 1 / 4Y≤X≤4Y; preferably, Y≤X.

[0072] In detail, the total area of ​​the open end of the recessed structure 3 refers to the sum of the areas of the open ends of all the recessed structures 3 in the positive electrode current collector 1, while the area of ​​the original functional surface of the current collector refers to the area of ​​the single-sided functional surface that has not been treated and does not contain the recessed structure 3, such as the area of ​​the first functional surface or the area of ​​the second functional surface that has not been perforated.

[0073] By defining the above relationship, it is possible to ensure that the recessed structure 3 provides space for the expansion of the negative electrode active layer 201, thereby reducing the extrusion pressure on the negative electrode current collector, reducing the deformation and expansion of the battery during cycling, reducing the extrusion pressure on the negative electrode current collector, further reducing the cycle expansion rate, and also taking into account energy density and improving lithium plating.

[0074] Furthermore, in a specific embodiment of the present invention, Y is 1-30 wt.%; the silicon-based material includes at least one of silicon-carbon, silicon-oxygen, silicon alloy, and elemental silicon; preferably, the silicon-based material is silicon-carbon, which includes silicon dispersed in a porous carbon framework.

[0075] Specifically, Y includes, but is not limited to, a range of 1 wt.%, 5 wt.%, 10 wt.%, 20 wt.%, 25 wt.%, 30 wt.%, or any combination thereof. When Y falls within the above range, it enables the negative electrode to form an effective conductive network, ensuring good electronic conductivity of the electrode, improving charge and discharge efficiency, and mitigating the volume expansion effect of silicon. This enhances battery performance while maintaining high cycle stability and structural stability.

[0076] Among them, silicon-carbon materials can combine the advantages of silicon and carbon to overcome the shortcomings of single materials. On the one hand, they can form a good conductive network and improve the charging and discharging efficiency of the battery. On the other hand, silicon-carbon materials can effectively alleviate the volume change of silicon during charging and discharging, reduce mechanical stress, and improve the structural stability and cycle life of the negative electrode.

[0077] Furthermore, in one specific embodiment of the present invention, such as Figure 4 , Figure 5 As shown, the edge of the opening of the recessed structure 3 is surrounded by a protruding structure 301. The width of the protruding structure 301 is w, the height is h1, and the maximum size of the opening end of the recessed structure 3 is d; where 1μm≤w≤d×2, 0.1μm≤h1≤d×2.

[0078] The outer periphery of the opening end of the recessed structure 3 can also be understood as the area around the surface where the opening end is located. The protruding structure 301 refers to an outer circular structure formed along the radial direction of the inner circle of the positive electrode current collector 1, with the opening end of the recessed structure 3 as the inner circle, extending away from the opening end of the recessed structure 3. The inner and outer circles form a ring structure. Simultaneously, in the thickness direction of the positive electrode current collector 1, the protruding structure 301 protrudes away from the functional surface of the positive electrode current collector 1, with the surface where the opening end of the recessed structure 3 is located as the reference. The inner and outer circles in the ring structure are connected by the protruding structure. The width w of the protruding structure 301 is the distance extended away from the opening end of the recessed structure 3, with the inner circle as the reference. The height h1 of the protruding structure 301 refers to the height of the protrusion in the thickness direction of the positive electrode current collector 1, with the surface where the opening end of the recessed structure 3 is located as the reference, extending away from the positive electrode current collector 1.

[0079] Wherein, the maximum size d of the opening end of the recessed structure 3 refers to the diameter of the large opening end of the recessed structure 3. By limiting w, h1 and d to satisfy the above relationship, the size of the protruding structure 301 is avoided from being too wide or too thick, which would affect the material loading and adhesion of the safety base coating. This ensures that the coating area of ​​the safety base coating is within a reasonable range, thereby guaranteeing the stability of the positive electrode and the energy density of the battery.

[0080] Furthermore, in a specific embodiment of the present invention, the opening end size of the recessed structure 3 is d, the distance between the opening centers of the recessed structure is L, wherein 1≤L / d≤10; and / or, the thickness of the current collector is H, and the depth of the recessed structure is h2, satisfying: 1≤H / h2≤5.

[0081] Specifically, the opening end dimension d of the recessed structure 3 and the centerline distance L between adjacent recessed structures 3 satisfy the following relationship: 1 ≤ L / d ≤ 10. Here, the opening end dimension d of the recessed structure 3 refers to the diameter of the larger opening end of the recessed structure 3; the centerline distance L between adjacent recessed structures 3 can be understood as the sum of the distance between two adjacent recessed structures 3 and the radius of their opening ends. By limiting the relationship between L and d, the pore density can be kept within the above range. This not only avoids the situation where the electrode mechanical strength is too low and easily broken due to excessively dense recessed structures, but also prevents the situation where the protection effect is too poor due to insufficient recessed structures. Furthermore, when the parameters of the recessed structure meet the above range, the current collector can break along the recessed structure when it fails, allowing the safety undercoating to provide protection.

[0082] The depth h2 of the recessed structure 3 and the thickness H of the positive electrode current collector 1 satisfy the following relationship: 1≤H / h2≤5, where the depth of the recessed structure 3 is the dimension of the recessed structure 3 in the thickness direction of the positive electrode current collector 1. When H / h2=1, the depth of the recessed structure 3 is consistent with the thickness of the positive electrode current collector 1, that is, the recessed structure 3 is a through hole; when 1<H / h2≤5, the recessed structure 3 is a blind hole, that is, it does not penetrate the positive electrode current collector 1 in the thickness direction.

[0083] In one specific embodiment, the cross-section of the recessed structure 3 is an isosceles triangle or an isosceles trapezoid, that is, the recessed structure 3 is a tapered hole, and the taper of the recessed structure 3 is 1:(0.05~10); wherein, the taper of the recessed structure 3 refers to the ratio of the diameter d of the opening end of the recessed structure 3 to the depth h2. By limiting the taper of the recessed structure 3, recessed structures 3 of different sizes can be set.

[0084] Furthermore, in a specific embodiment of the present invention, d is 5-100 μm, L is 10-1000 μm, h2 is 1-20 m, and H is 5-20 μm.

[0085] Specifically, d is 5–100 μm, for example, 5 μm, 10 μm, 15 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm or any combination thereof; L is 10–1000 μm, for example, 10 μm, 20 μm, 30 μm, 50 μm, 100 μm, 200 μm, 300 μm, 500 μm, 1000 μm or any combination thereof. m is a range consisting of any two of them; h2 is 1 to 20 μm, for example, 1 μm, 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm or any two of them; H is 5 to 20 μm, for example, 5 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm or any two of them.

[0086] When the above range is met, the distribution and morphology of the depression structure on the current collector can be guaranteed to be within a suitable range. If it is not within the above range, there will be insufficient protection of the fracture surface when the current collector breaks, poor safety improvement effect, or the current collector strength will decrease significantly and the band will break, and the impedance will increase significantly.

[0087] Furthermore, in a specific embodiment of the present invention, along the length direction, the positive electrode current collector includes a first region and a second region. The first region has M1 recessed structures, and the second region has M2 recessed structures, where M1≥1 and M2≥1. The positive electrode functional layer covers the surface of the first region. The second region is provided with a safety base layer and a protective layer stacked in a direction away from the current collector, or the second region is provided with a protective layer.

[0088] like Figure 2 As shown, the positive electrode current collector includes a first region covered with a positive electrode functional layer, and a second region adjacent to the first region along the length direction is covered with a protective layer.

[0089] For example Figure 3 As shown, the positive current collector includes a first region covered with a positive functional layer, and a safety base layer and a protective layer are stacked in a direction away from the current collector along the length direction of the first region.

[0090] The protective layer may not contain conductive materials, while the safety primer layer may contain conductive materials.

[0091] By providing a protective layer 104 on a section of the positive electrode current collector 1 along its length and a protective structure 3 along its functional surface, the problem of burrs on the positive electrode current collector 1 piercing the separator 4 and causing battery failure can be avoided.

[0092] In this invention, when the protective layer 104 is located at one end of the current collector 1 near the length direction, the battery including the electrode is a wound battery, and the protective layer 104 is located at the tail of the wound battery.

[0093] Further, in a specific embodiment of the present invention, the safety base coating comprises inorganic particles, wherein the inorganic particles include at least one of alumina, boehmite, titanium dioxide, silicon dioxide, zinc oxide, zirconium oxide, magnesium oxide, silicon carbide, silicon nitride, lithium iron phosphate, and lithium manganese iron phosphate; the active material of the active layer comprises at least one of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium-rich manganese-based materials, lithium nickel oxide, and lithium nickel manganese oxide; the protective layer comprises inorganic particles, wherein the inorganic particles include at least one of alumina, boehmite, titanium dioxide, silicon dioxide, zinc oxide, zirconium oxide, magnesium oxide, silicon carbide, and silicon nitride; preferably, the Dv10 of the inorganic particles is 0.05-0.5 μm, and the Dv50 is 0.1-2 μm; the Dv10 of the active material is 1-15 μm, and the Dv50 is 2-30 μm.

[0094] When material types within the above particle size range are selected, not only can they provide protection, but they can also maintain the electrochemical performance of the battery.

[0095] Furthermore, in a specific embodiment of the present invention, the positive electrode sheet is prepared by the following steps: a slurry with a positive electrode functional layer is formed on a first functional surface of the positive electrode current collector, and after drying, a recessed structure is formed on a second functional surface of the positive electrode current collector. Subsequently, the slurry with the positive electrode functional layer is processed on the second functional surface and the recessed structure, and after drying and rolling, a positive electrode sheet is obtained; the first functional surface and the second functional surface are located on opposite sides of the current collector thickness direction; preferably, the recessed structure formation process is laser processing.

[0096] It is understandable that a recessed structure 3 can be set on another functional surface of the positive electrode current collector 1 by drilling. During the drilling process, the drilling process needs to be carried out according to the morphological characteristics of the recessed structure 3 and parameters such as the distribution density and position distribution of the recessed structure.

[0097] The drilling process can be performed using conventional methods in the art, as long as it can form a recessed structure 3. For example, the drilling process can be performed using laser processing, mechanical drilling, electric or thermal laser melting, radiation melting, chemical etching, friction drilling, etc., with laser processing being the preferred choice.

[0098] The present invention avoids the problem of slurry leakage from the holes by first coating one functional surface, then setting the recessed structure 3 on another functional surface, and finally coating another functional surface. It also avoids the problem of wrinkling or breaking of the positive current collector 1.

[0099] Furthermore, in one specific embodiment of the present invention, the opening end of the recessed structure faces the side away from the center of the battery.

[0100] The opening end of the recessed structure 3 faces away from the center of the battery, that is, the opening end of the recessed structure 3 faces the outside of the battery. In this way, when the battery is damaged by external force and deforms or breaks inward, the functional layer material covering the inner surface of the recessed structure 3 can slide and spread inward in the direction of damage, effectively protecting the fracture surface of the positive current collector 1 from exposure, thereby avoiding short circuit problems caused by the exposure of the fracture surface of the positive current collector 1.

[0101] The battery of the present invention is preferably a lithium-ion battery, including but not limited to pouch batteries, square batteries, cylindrical batteries, etc.

[0102] A battery for charging / discharging is formed by mounting the battery and protection circuit together inside an aluminum-plastic film. The quality of the battery directly determines its overall quality; due to the use of the aforementioned electrode plates, the battery of this invention exhibits excellent performance in terms of safety and other aspects.

[0103] The battery also includes an electrolyte. Specifically, the battery is produced by injecting an electrolyte after it is encapsulated, and then undergoing processes such as formation, capacity testing, and OCV.

[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 safety primer slurry: Silica, conductive carbon black (SP), polyvinylidene fluoride (PVDF) and N-methylpyrrolidone (NMP) are mixed and stirred evenly to obtain safety primer slurry; wherein, the mass ratio of LFP:SP:PVDF is 90:5:5; the Dv10 of silica is 0.1μm and the Dv50 is 1μm;

[0108] Preparation of positive electrode active layer slurry: Lithium cobalt oxide (LCO), conductive carbon black (SP), polyvinylidene fluoride (PVDF) and N-methylpyrrolidone (NMP) are mixed and stirred evenly to obtain positive electrode active material layer slurry; wherein, the mass ratio of LCO, SP and PVDF is 97:1:2; the Dv10 of lithium cobalt oxide is 10μm and the Dv50 is 15μm;

[0109] Preparation of protective layer slurry: Alumina (Al2O3), polyvinylidene fluoride (PVDF) and N-methylpyrrolidone (NMP) are mixed and stirred evenly to obtain ceramic layer slurry; wherein, the mass ratio of Al2O3 to PVDF is 90:10;

[0110] (2) Apply the safety undercoating slurry from step (1) to a portion of the second functional surface 12 of the positive current collector 1 (aluminum foil), and after drying, form a safety undercoating 102 on the second functional surface 12. Then, apply the positive active layer slurry from step (1) to the surface of the safety undercoating 102, and after drying, form a positive active layer 103 on the second functional surface 12. Apply the safety undercoating slurry to the surface of the safety undercoating 102 at the tail of the positive current collector 1, and after drying, form a safety undercoating 4 on the second functional surface 12.

[0111] (3) A hole is formed at a preset position on the first functional surface 11 of the positive current collector 1 using a drilling device to form a recessed structure 3. The recessed structure is a hole structure with d = 50 μm, X = 20%, W = 10 μm, h1 = 1 μm, L = 100 μm, h2 = 8 μm, and H = 8 μm.

[0112] (4) The safety primer slurry from step (1) is applied to a portion of the first functional surface 11 of the positive electrode current collector 1 (aluminum foil). After drying, a safety primer 102 is formed on the first functional surface 11. Then, the positive electrode active layer slurry from step (1) is applied to the surface of the portion of the safety primer 102. After drying, a positive electrode active layer 103 is formed. A protective layer slurry is applied to the surface of the portion of the safety primer 102 of the positive electrode current collector 1. After drying, rolling, and slitting, the following is obtained: Figure 1 The positive electrode.

[0113] II. Preparation of the negative electrode sheet

[0114] Silicon carbon, graphite, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC) and deionized water are mixed and stirred evenly to obtain a negative electrode slurry. The negative electrode slurry is coated on the functional surface of the negative electrode current collector 2 to form a negative electrode active material layer 201. After drying, rolling and slitting, a negative electrode sheet is obtained. The mass ratio of silicon carbon, graphite, styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) is 5:90:3:2, and the silicon carbon particle size is 5μm.

[0115] III. Battery Preparation

[0116] The positive electrode, separator 4, and negative electrode are stacked and wound in sequence to obtain a core; wherein the second functional surface 12 faces the side away from the center of the core, so that the opening end of the recessed structure 3 is away from the winding center.

[0117] Example 2

[0118] The preparation process of this embodiment is basically the same as that of Example 1, except that: in the preparation of the negative electrode, the mass ratio of silicon carbon material, graphite, styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) is 10:85:3:2, and other conditions remain unchanged, thus obtaining the negative electrode of this embodiment;

[0119] In the battery manufacturing process, the negative electrode sheet of Example 1 is replaced with the negative electrode sheet of this example.

[0120] Example 3

[0121] The preparation process of this embodiment is basically the same as that of Example 1, except that in the preparation of the negative electrode, the mass ratio of silicon carbon material, graphite, styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) is 20:75:3:2, and other conditions remain unchanged, thus obtaining the negative electrode of this embodiment;

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

[0123] Example 4

[0124] The preparation process of this embodiment is basically the same as that of Example 1, except that in the preparation of the negative electrode, the mass ratio of silicon carbon material, graphite, styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) is 25:70:3:2, and other conditions remain unchanged, thus obtaining the negative electrode of this embodiment;

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

[0126] Example 5

[0127] The preparation process of this embodiment is basically the same as that of Example 1, except that: in the preparation of the negative electrode, the mass ratio of silicon carbon material, graphite, styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) is 30:65:3:2, and other conditions remain unchanged, thus obtaining the negative electrode of this embodiment;

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

[0129] Example 6

[0130] The preparation process of this embodiment is basically the same as that of Example 1, except that in the preparation of the positive electrode, d is 30 μm and Y is 7% in step (3), and other conditions remain unchanged, thus obtaining the positive electrode of this embodiment;

[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 7

[0133] The preparation process of this embodiment is basically the same as that of Example 1, except that: in the preparation of the positive electrode, Y is 9% and L is 150μm in step (3), and other conditions remain unchanged, so as to obtain the positive electrode of this embodiment;

[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 8

[0136] The preparation process of this embodiment is basically the same as that of Example 1, except that: in the preparation of the positive electrode, Y is 5% and L is 200μm in step (3), and other conditions remain unchanged, so as to obtain the positive electrode of this embodiment;

[0137] In the battery manufacturing process, the positive electrode sheet of Example 1 is replaced with the positive electrode sheet of this example.

[0138] Example 9

[0139] The preparation process of this embodiment is basically the same as that of Example 1, except that: in the preparation of the positive electrode, step (3) h2 is 4μm, and other conditions remain unchanged, thus obtaining the positive electrode of this embodiment;

[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 10

[0142] The preparation process of this embodiment is basically the same as that of Example 1, except that: in the preparation of the positive electrode, step (3) h2 is 2μm, and other conditions remain unchanged, thus obtaining the positive electrode of this embodiment;

[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 11

[0145] The preparation process of this embodiment is basically the same as that of Example 1, except that: in the preparation of the positive electrode, in step (3) h2 is 12μm, H is 12μm, and other conditions remain unchanged, thus obtaining the positive electrode of this embodiment;

[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 12

[0148] The preparation process of this embodiment is basically the same as that of Example 1, except that: in the preparation of the positive electrode, in step (3) h2 is 20μm, H is 20μm, and other conditions remain unchanged, thus obtaining the positive electrode of this embodiment;

[0149] In the battery manufacturing process, the positive electrode sheet of Example 1 is replaced with the positive electrode sheet of this example.

[0150] Example 13

[0151] The preparation process of this embodiment is basically the same as that of Example 1, except that: in the preparation of the positive electrode, in step (3) h2 is 2μm, H is 20μm, and other conditions remain unchanged, thus obtaining the positive electrode of this embodiment;

[0152] In the battery manufacturing process, the positive electrode sheet of Example 1 is replaced with the positive electrode sheet of this example.

[0153] Example 14

[0154] The preparation process of this embodiment is basically the same as that of Example 1, except that in the preparation of the positive electrode, step (3) d is 250 μm, L is 500 μm, and other conditions remain unchanged, thus obtaining the positive electrode of this embodiment;

[0155] In the battery manufacturing process, the positive electrode sheet of Example 1 is replaced with the positive electrode sheet of this example.

[0156] Example 15

[0157] The preparation process of this embodiment is basically the same as that of Example 1, except that in the preparation of the positive electrode, step (3) d is 150 μm, L is 500 μm, Y is 7%, and other conditions remain unchanged to obtain the positive electrode of this embodiment;

[0158] In the battery manufacturing process, the positive electrode sheet of Example 1 is replaced with the positive electrode sheet of this example.

[0159] Example 16

[0160] The preparation process of this embodiment is basically the same as that of Example 1, except that in the preparation of the positive electrode, step (3) d is 100 μm, L is 500 μm, Y is 3%, and other conditions remain unchanged to obtain the positive electrode of this embodiment;

[0161] In the battery manufacturing process, the positive electrode sheet of Example 1 is replaced with the positive electrode sheet of this example.

[0162] Example 17

[0163] The preparation process in this embodiment is basically the same as in Example 1, except that silica is replaced with magnesium oxide in the safety primer slurry. Figure 2 The structure shown is used to coat the current collector to obtain the positive electrode sheet of this embodiment;

[0164] In the battery manufacturing process, the positive electrode sheet of Example 1 is replaced with the positive electrode sheet of this example.

[0165] Example 18

[0166] The preparation process of this embodiment is basically the same as that of Example 1, except that: in the preparation of the negative electrode, the silicon-carbon material is replaced with silicon-oxygen material to obtain the negative electrode of this embodiment;

[0167] During the preparation of the positive electrode sheet, the drilling parameters were adjusted as shown in Table 1; silicon dioxide was replaced with titanium dioxide, with a Dv10 of 0.05 μm and a Dv50 of 0.1 μm; lithium cobalt oxide was replaced with lithium manganese oxide, with a Dv10 of 1 μm and a Dv50 of 2 μm.

[0168] In the battery manufacturing process, the negative electrode sheet of Example 1 is replaced with the negative electrode sheet of this example; the positive electrode sheet of Example 1 is replaced with the positive electrode sheet of this example.

[0169] Example 19

[0170] The preparation process of this embodiment is basically the same as that of Example 1, except that: in the preparation of the negative electrode, silicon-carbon material is replaced with silicon-oxygen material to obtain the negative electrode of this embodiment; in the preparation of the positive electrode, the drilling parameters are adjusted, as shown in Table 1; silicon dioxide is replaced with magnesium oxide, with a Dv10 of 0.5 μm and a Dv50 of 2 μm; lithium cobalt oxide is replaced with lithium manganese iron phosphate, with a Dv10 of 15 μm and a Dv50 of 30 μm.

[0171] In the battery manufacturing process, the negative electrode sheet of Example 1 is replaced with the negative electrode sheet of this example; the positive electrode sheet of Example 1 is replaced with the positive electrode sheet of this example.

[0172] Comparative Example 1

[0173] The preparation process of this comparative example is basically the same as that of Example 1, except that: in the preparation of the positive electrode sheet, step (3) is omitted, that is, no drilling is performed, and other conditions remain unchanged, so as to obtain the positive electrode sheet of this comparative example.

[0174] In the battery manufacturing process, the positive electrode sheet of Example 1 was replaced with the positive electrode sheet of this comparative example.

[0175] Comparative Example 2

[0176] The preparation process of this comparative example is basically the same as that of Example 2, except that in the preparation of the negative electrode sheet, graphite, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), and deionized water are mixed and stirred evenly to obtain a negative electrode slurry; wherein the mass ratio of graphite, styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) is 95:3:2. In the battery preparation process, the negative electrode sheet of Example 1 is replaced with the negative electrode sheet of this comparative example.

[0177] Comparative Example 3

[0178] The preparation process of this comparative example is basically the same as that of Example 1, except that step (2) is omitted in the preparation of the positive electrode, that is, there is no safety undercoat, and other conditions remain unchanged, so as to obtain the positive electrode of this example.

[0179] In the battery manufacturing process, the positive electrode sheet of Example 1 was replaced with the positive electrode sheet of this comparative example.

[0180] Comparative Example 4

[0181] The preparation process of this comparative example is basically the same as that of Example 1, except that the Dv50 of silicon-carbon is 20μm, and other conditions remain unchanged, thus obtaining the negative electrode sheet of this example.

[0182] In the battery manufacturing process, the negative electrode sheet of Example 1 was replaced with the negative electrode sheet of this comparative example.

[0183] The specific parameters of the positive electrode in the examples and comparative examples are shown in Table 1.

[0184] Test case

[0185] 1. Piercing test

[0186] Fully charge the battery, place the fully charged battery on the nail penetration test equipment, start the equipment, and drive the nail (3mm in diameter) perpendicularly into the center of the battery at a speed of 200mm / s. After holding for 10 minutes, remove the nail. If the battery does not catch fire or explode, the test is considered passed. The number of passes / the number of tests is the screw test pass rate. The number of tests is 10.

[0187] 2. Impact test

[0188] Place the battery at room temperature and charge the lithium-ion battery at a constant current of 1C until the voltage reaches 4.5V. Then charge it at a constant voltage until the current drops to 0.05C, and stop charging. Next, discharge it at a constant current of 1C until it reaches 3.0V. Repeat this cycle for 5T. After the battery is fully charged for the last time, conduct a heavy object impact test within 24 hours: Place the battery on a flat surface and place a steel column with a diameter of 15.8±0.2mm in the center of the battery. The longitudinal axis of the steel column is parallel to the plane. Let a weight of 9.1±0.1kg fall freely from a height of 610±25mm onto the steel column above the center of the battery. After the test, observe for 6 hours. If the battery does not catch fire or explode, the test is considered passed. The number of passes / the number of tests is the screw test pass rate. The number of tests is 10.

[0189] 3. Room temperature cyclic expansion rate

[0190] The thickness of the battery was measured using a PPG thickness gauge at 25°C. Then, the lithium-ion battery was charged to 4.5V at 3C at 25°C, switched to constant voltage charging to a charging current of 0.05C, and discharged to 3V at 1.5C. This charge-discharge cycle was repeated 800 times. The thickness of the lithium-ion battery was measured and recorded every 100T cycles. The room temperature cycle expansion rate was calculated as (thickness after the 800th cycle - battery thickness before the cycle) / battery thickness before the cycle.

[0191] Table 1

[0192]

[0193]

[0194] Table 2

[0195]

[0196]

[0197] Comparative examples and comparative examples show that, compared to conventional batteries, lithium-ion batteries made using the batteries of this invention effectively reduce the room temperature cycling expansion rate. Simultaneously, they effectively improve the pass rate of puncture and heavy object impact tests, significantly enhancing safety. In contrast, the battery provided in Comparative Example 2 contains graphite material in its negative electrode but does not contain silicon-based (silicon-carbon) material. Compared to silicon-based materials, graphite negative electrodes exhibit lower high-temperature cycling expansion rates, higher puncture pass rates, and higher heavy object impact pass rates.

[0198] 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 battery, characterized by, The positive electrode sheet, the separator, and the negative electrode sheet are stacked; The positive electrode sheet comprises a positive electrode current collector and a positive electrode functional layer, the positive electrode current collector is provided with N recess structures, the opening end of the recess structure is located on the functional surface of the positive electrode current collector, the positive electrode functional layer covers at least part of the surface of at least one functional surface of the positive electrode current collector and is embedded in part of the recess structure, N≥1; the size of the opening end of the recess structure is d, The positive electrode functional layer comprises a safety primer layer and a positive electrode active layer which are stacked in the direction gradually away from the functional surface of the positive electrode current collector; The negative electrode sheet comprises a negative electrode active layer containing a silicon-based material, the Dv50 of the silicon-based material and d satisfy Dv50≤d≤10×Dv50.

2. The battery of claim 1, wherein, Dv50 is 5-15 μm.

3. The battery of claim 1, wherein, The total area ratio of the opening end of the recess structure to the total area of the positive electrode current collector is X, the mass percentage of the silicon-based material in the negative electrode active layer is Y, and 1 / 4Y≤X≤4Y is satisfied; Preferably, Y≤X.

4. The battery of claim 3, wherein, The Y is 1-30 wt.%; The silicon-based material comprises at least one of silicon carbon, silicon oxygen, silicon alloy, and silicon element; Preferably, the silicon-based material comprises silicon carbon, and the silicon carbon comprises silicon dispersed in a porous carbon skeleton.

5. The battery of claim 1, wherein, The edge of the opening of the recess structure surrounds a protruding structure, the width of the protruding structure is w, the height is h1, and the size of the opening end of the recess structure is d; Wherein, 1 μm≤w≤d×2, 0.1 μm≤h1≤d×2.

6. The battery of claim 1, wherein, The size of the opening end of the recess structure is d, and the distance between the centers of adjacent recess structures is L, wherein 1≤L / d≤10; And / or, the thickness of the positive electrode current collector is H, and the depth of the recess structure is h2, and 1≤H / h2≤5 is satisfied.

7. The battery of claim 6, wherein, d is 5-100 μm, L is 10-1000 μm, h2 is 1-20 μm, and H is 5-20 μm.

8. The battery of claim 1, wherein, In the length direction, the positive electrode current collector comprises a first region and a second region, the first region has M1 recess structures, and the second region has M2 recess structures, M1≥1, and M2≥1; The positive electrode functional layer covers the surface of the first region; The second region is stacked with a safety primer layer and a protective layer in the direction away from the current collector, or the second region is provided with a protective layer.

9. The battery of claim 8, wherein, The safety primer layer comprises inorganic particles, and the inorganic particles comprise at least one of alumina, boehmite, titanium dioxide, silicon dioxide, zinc oxide, zirconium oxide, magnesium oxide, silicon carbide, silicon nitride, lithium iron phosphate, and lithium manganese iron phosphate; The active material of the active layer comprises at least one of lithium iron phosphate, lithium cobaltate, lithium manganate, lithium manganese iron phosphate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium-rich manganese-based material, lithium nickelate, and lithium nickel manganate; The protective layer comprises inorganic particles, and the inorganic particles comprise at least one of alumina, boehmite, titanium dioxide, silicon dioxide, zinc oxide, zirconium oxide, magnesium oxide, silicon carbide, and silicon nitride. Preferably, the inorganic particles have a Dv10 of 0.05-0.5 μm and a Dv50 of 0.1-2 μm; the active material has a Dv10 of 1-15 μm and a Dv50 of 2-30 μm.

10. The battery of any one of claims 1-9, wherein, The positive electrode sheet is prepared by a method comprising the following steps: A slurry of a positive electrode functional layer is arranged on a first functional surface of a positive electrode current collector, dried, and then a concave structure is formed on a second functional surface of the positive electrode current collector, after which a slurry of a positive electrode functional layer is arranged on the second functional surface and at the concave structure, and after drying and rolling, the positive electrode sheet is obtained; The first functional surface and the second functional surface are located on opposite sides in the thickness direction of the current collector; Preferably, the concave structure is formed by laser processing.

11. The battery of any one of claims 1-10, wherein, The opening end of the concave structure faces away from the center of the battery.

Images