Negative electrode sheet, method for manufacturing the same, and solid-state battery

Abstract

The embodiment of the application discloses a negative plate and a preparation method thereof and a solid-state battery, and belongs to the technical field of solid-state batteries. The negative plate comprises a negative current collector and a negative active layer. The negative active layer is arranged on at least one side of the negative current collector in a first direction, and the negative active layer comprises a silicon-based negative material. A plurality of hole structures opening in the first direction are arranged on the negative active layer, and the bottom of the hole structure abuts against the negative current collector. The aperture of the hole structure is D, the center distance between adjacent hole structures is L, and the following conditions are met: 10 mu m <= D <= 100 mu m, and 2 <= L / D <= 100. The negative plate provided by the application can improve the electrolyte penetration effect, reduce the interface impedance, relieve the interface peeling, and at the same time, the high energy density is considered, and the comprehensive electrochemical performance of the silicon-based solid-state battery under low pressure is improved.

Description

Technical Field

[0001] This application relates to the field of solid-state battery technology, specifically to a negative electrode sheet and its preparation method, and a solid-state battery. Background Technology

[0002] All-solid-state batteries theoretically possess the advantage of high energy density. To ensure this high energy density, anode materials with high specific capacity are required. Silicon-based anode materials (including pure silicon, silicon-carbon, and silicon-oxygen materials) have broad application prospects in all-solid-state batteries due to their high theoretical capacity, low lithium intercalation potential, abundant reserves on Earth, and environmental friendliness. They are a key focus and hot topic in all-solid-state battery anode material research. Currently, silicon-based anode and all-solid-state battery technologies face several bottlenecks, mainly in insufficient control of material expansion and poor interface stability.

[0003] In related technologies, the expansion problem is mainly alleviated by means of material nano-sizing, carbon coating or composite structure, and the focus is mainly on the optimization of material composition. However, silicon-based anode sheets still have problems such as lack of expansion space and single ion transport path, which affect the electrochemical performance and cycle performance of all-solid-state batteries. Summary of the Invention

[0004] This application provides a negative electrode sheet and its preparation method, as well as a solid-state battery, which can improve the electrolyte permeation effect, reduce the interfacial impedance, and alleviate interfacial stripping while maintaining high energy density and improving the overall electrochemical performance of silicon-based all-solid-state batteries under low pressure.

[0005] According to a first aspect of this application, a negative electrode is provided, the negative electrode comprising: Negative electrode current collector; A negative electrode active layer is disposed on at least one side of the negative electrode current collector in a first direction, and the negative electrode active layer includes a silicon-based negative electrode material. The negative electrode active layer is provided with multiple pore structures that open along the first direction, and the bottom of the pore structure abuts against the negative electrode current collector; the pore diameter of the pore structure is D, and the center-to-center distance between adjacent pore structures is L, satisfying: 10μm≤D≤100μm, 2≤L / D≤100.

[0006] By creating a porous structure in the negative electrode active layer, a directional expansion release region can be constructed within the active layer, transforming the disordered expansion of the silicon-based negative electrode material into ordered deformation. The porous structure absorbs the volume changes of the silicon-based negative electrode material and provides stress buffer space, improving the cycle stability of the silicon-based negative electrode material. When the negative electrode is used in a solid electrolyte, the porous structure in the active layer can also accommodate the solid electrolyte, forming continuous ion transport channels. This allows the solid electrolyte to fill the interior of the negative electrode, reducing the interfacial impedance between the negative electrode and the solid electrolyte layer, and increasing the lateral shear force between them, thus reducing the risk of interfacial delamination. By ensuring that the pore size and center-to-center spacing between adjacent pores meet the above conditions, sufficient expansion buffer space can be provided, increasing the interfacial bonding effect between the negative electrode and the solid electrolyte while maintaining good capacity performance. In other words, the negative electrode provided in this application can improve electrolyte permeation, reduce interfacial impedance, alleviate interfacial delamination, and simultaneously achieve high energy density, improving the overall electrochemical performance of silicon-based all-solid-state batteries under low pressure.

[0007] In some embodiments, 20μm≤D≤50μm; And / or, 5≤L / D≤50.

[0008] By setting the pore size D of the porous structure between 20 μm and 50 μm, sufficient buffer space can be provided for the silicon-based anode material, ensuring buffering performance and improving the cycle stability of the silicon-based anode material. It also reduces the space occupied in the anode active layer, ensuring the loading of active material in the active layer and maintaining energy density. Furthermore, the pore size within this range helps the solid electrolyte fill the voids, forming continuous and stable ion transport channels and reducing interfacial impedance.

[0009] By satisfying 5≤L / D≤50, the pore size and center-to-center spacing of the pore structure can be balanced, ensuring the structural strength of the negative electrode active layer and enabling the pore structure on the negative electrode active layer to form a good synergistic effect, thus balancing the capacity utilization and interface performance of the negative electrode sheet.

[0010] In some embodiments, the thickness of the negative electrode active layer in the first direction is H, satisfying: 0.5≤D / H≤1.5.

[0011] By satisfying the ratio 0.5 ≤ D / H ≤ 1.5, the pore size of the porous structure and the thickness of the negative electrode active layer can work synergistically. This ensures that the buffer space provided by the porous structure can absorb the volume changes of the silicon-based negative electrode material in the negative electrode active layer during charge and discharge, and prevents the reduction in the active material loading in the negative electrode active layer due to excessively large pore size, thus balancing cycle performance and energy density. Simultaneously, satisfying 0.5 ≤ D / H ≤ 1.5 also helps improve the filling effect of the electrolyte slurry on the porous structure, which is beneficial for forming a good ion transport network and reducing interfacial impedance. Furthermore, the synergistic effect between the pore size of the porous structure and the thickness of the negative electrode active layer also contributes to improving the structural stability of the negative electrode active layer.

[0012] In some embodiments, the silicon-based anode material includes at least one of nano-silicon materials, micro-silicon materials, silicon-oxygen materials, and silicon-carbon materials.

[0013] The aforementioned silicon-based materials have a high theoretical specific capacity, which helps to improve the energy density of solid-state batteries, and are also low in cost.

[0014] In some embodiments, the negative electrode active layer includes a first sub-active layer and a second sub-active layer, the first sub-active layer and the second sub-active layer being located on opposite sides of the negative electrode current collector in a first direction; The pore structures in the first sub-active layer are arranged opposite to the pore structures in the second sub-active layer, or the pore structures in the first sub-active layer are arranged alternately with the pore structures in the second sub-active layer.

[0015] When the pore structures in the first and second sub-active layers are arranged opposite each other, lithium ions can be directly transported through the negative electrode and fluid at the oppositely arranged pore structures during charging and discharging, which can shorten the transport path of lithium ions in the negative electrode active layer and improve ion transport efficiency. When the pore structures in the first and second sub-active layers are arranged alternately, lithium ions can still be transported through a shorter path, and the overall mechanical properties of the negative electrode sheet can be improved.

[0016] According to a second aspect of this application, a method for preparing a negative electrode sheet is also provided, comprising: We provide negative electrode current collectors and negative electrode slurries; The negative electrode slurry is coated on at least one side of the negative electrode current collector in the first direction to form a negative electrode active layer; A porous structure is formed in the negative electrode active layer to obtain a negative electrode sheet; The bottom of the pore structure is in contact with the negative electrode current collector; the pore diameter of the pore structure is D, and the center-to-center distance between adjacent pore structures is L, satisfying: 10μm≤D≤100μm, 2≤L / D≤100.

[0017] The method for preparing the negative electrode provided in this application has all the beneficial effects of the negative electrode as described above, and will not be repeated here.

[0018] In some embodiments, a porous structure is formed in the negative electrode active layer, including: A mask template is set on the side of the negative electrode active layer away from the negative electrode current collector, and a hole structure is formed on the negative electrode active layer by a laser array.

[0019] By using the positioning function of the photomask and the precise control of the laser array, it is possible to form a pore structure of specific size, shape and distribution in the negative electrode active layer, thereby improving the accuracy of pore structure forming.

[0020] According to a third aspect of this application, a solid-state battery is also provided, comprising a negative electrode sheet as described above, and / or a negative electrode sheet prepared by the method described above.

[0021] The solid-state battery provided in this application has all the beneficial effects of the negative electrode sheet as described above, which will not be repeated here.

[0022] In some embodiments, a solid-state battery further includes a solid electrolyte layer and a positive electrode. A solid electrolyte layer is disposed between the negative electrode and the positive electrode, and the solid electrolyte layer is embedded in at least part of the porous structure of the negative electrode.

[0023] By placing a solid electrolyte layer between the negative and positive electrodes, the two electrodes can be isolated, preventing short circuits. Embedding the solid electrolyte layer into at least part of the porous structure of the negative electrode shortens the lithium-ion transport path between them, improves interfacial contact performance, reduces impedance, and enables mechanical bonding, reducing the risk of interface delamination and enhancing the structural stability of the solid-state battery.

[0024] In some embodiments, the solid electrolyte layer includes a solid electrolyte with a particle size D90 of W, where 2 ≤ D / W ≤ 500.

[0025] By satisfying 2≤D / W≤500, the solid electrolyte in the solid electrolyte layer can fill the porous structure without causing blockage, while ensuring good interfacial contact between the solid electrolytes and improving ionic conductivity. The combination of the porous structure and the solid electrolyte increases the contact area and mechanical interlocking between the negative electrode active layer and the solid electrolyte through the embedded structure, improving the bonding strength between them and reducing the risk of interfacial delamination.

[0026] In some embodiments, 5 ≤ D / W ≤ 100; And / or, 0.5μm≤W≤15μm; And / or, the solid electrolyte includes at least one of lithium phosphorus sulfide, lithium phosphorus sulfide chloride, and lithium germanium phosphorus sulfide.

[0027] By satisfying 5 ≤ D / W ≤ 100, the compatibility between the solid electrolyte and the porous structure can be improved, ensuring filling effect, forming a good ion transport network, and guaranteeing the mechanical interlocking between the solid electrolyte layer and the negative electrode active layer. By satisfying 0.5 μm ≤ W ≤ 15 μm, good contact can be formed between the solid electrolytes in the solid electrolyte layer, constructing an excellent ion transport network, and allowing the solid electrolytes in the porous structure to form good stacking, providing buffer space for the expansion of silicon-based negative electrode materials. The solid electrolyte includes at least one of the sulfide solid electrolytes such as lithium phosphorus-sulfur, lithium phosphorus-sulfur-chloride, and lithium germanium phosphorus-sulfur, which have excellent ionic conductivity and chemical stability, ensuring the electrochemical performance and cycle stability of solid-state batteries. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the cross-sectional structure of the negative electrode sheet provided in the embodiments of this application. Figure 1 ; Figure 2 This is a schematic diagram of the cross-sectional structure of the negative electrode sheet provided in the embodiments of this application. Figure 2 ; Figure 3 This is a top view of the negative electrode sheet provided in the embodiments of this application; Figure 4 This is a cross-sectional schematic diagram of the composite structure of the negative electrode sheet and the solid electrolyte layer provided in the embodiments of this application.

[0030] Explanation of reference numerals in the attached figures: 10. Negative electrode sheet; 11. Negative electrode current collector; 12. Negative electrode active layer; 121. First sub-active layer; 122. Second sub-active layer; 123. Pore structure; 20. Solid electrolyte layer. Detailed Implementation

[0031] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0032] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". The terms first, second, third, etc., are used merely as illustrative and do not impose numerical requirements or establish an order. Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the present invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single digits within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0033] Firstly, such as Figures 1-3 As shown, this application embodiment provides a negative electrode sheet 10, which includes a negative electrode current collector 11 and a negative electrode active layer 12. The negative electrode active layer 12 is disposed on at least one side of the negative electrode current collector 11 in a first direction, and the negative electrode active layer 12 includes a silicon-based negative electrode material. The negative electrode active layer 12 has a plurality of pore structures 123 opening along the first direction, and the bottom of the pore structures 123 abuts against the negative electrode current collector 11. The pore diameter of the pore structure 123 is D, and the center-to-center distance between adjacent pore structures 123 is L, satisfying: 10μm≤D≤100μm, 2≤L / D≤100.

[0034] By creating a porous structure 123 on the negative electrode active layer 12, a directional expansion release region can be constructed within the negative electrode active layer 12, transforming the disordered expansion of the silicon-based negative electrode material into ordered deformation. The porous structure 123 absorbs the volume change of the silicon-based negative electrode material and provides stress buffer space, thereby improving the cycle stability of the silicon-based negative electrode material. When the negative electrode sheet 10 is applied to a solid electrolyte, the porous structure 123 on the negative electrode active layer 12 can also accommodate the solid electrolyte, forming continuous ion transport channels. This allows the solid electrolyte to fill the interior of the negative electrode sheet 10, reducing the interfacial impedance between the negative electrode sheet 10 and the solid electrolyte layer 20, and increasing the lateral shear force between the negative electrode sheet 10 and the solid electrolyte layer 20, thus reducing the risk of interfacial delamination. By ensuring that the pore size of the porous structure 123 and the center-to-center distance between adjacent porous structures 123 meet the above conditions, sufficient expansion buffer space can be provided, increasing the interfacial bonding effect between the negative electrode sheet 10 and the solid electrolyte, while maintaining good capacity performance of the negative electrode sheet 10. That is, the negative electrode 10 provided in this application can improve the electrolyte permeation effect, reduce the interfacial impedance, and alleviate interfacial stripping while maintaining high energy density and improving the overall electrochemical performance of solid-state batteries.

[0035] For example, the pore size D of the hole structure 123 can be 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm or 100μm. L / D can be 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or 100.

[0036] For example, the outline shape of the hole structure 123 can be circular, square, hexagonal, etc. When the outline of the hole structure 123 is circular, the aperture refers to the diameter of the outline of the hole structure 123. When the hole structure 123 is other shapes, the aperture refers to the diameter of the circumcircle of the outline of the hole structure 123.

[0037] It should be noted that the center-to-center distance L between adjacent hole structures 123 refers to the distance from the center point of one hole structure 123 to the center point of another adjacent hole structure 123. The first direction is... Figures 1-2 The direction indicated by the X-axis.

[0038] In some embodiments, 20μm≤D≤50μm.

[0039] By setting the pore size D of the pore structure 123 between 20 μm and 50 μm, sufficient buffer space can be provided for the silicon-based anode material, ensuring buffering performance and improving the cycle stability of the silicon-based anode material. It also reduces the space occupied in the anode active layer 12, ensuring the loading of the active material in the anode active layer 12 and maintaining energy density. Simultaneously, the pore size within this range also helps to fill the voids with solid electrolyte, forming continuous and stable ion transport channels and reducing interfacial impedance.

[0040] In some embodiments, 5 ≤ L / D ≤ ​​50.

[0041] By satisfying 5≤L / D≤50, the pore size and center-to-center spacing of the pore structure 123 can be balanced, ensuring the structural strength of the negative electrode active layer 12, and enabling the pore structure 123 on the negative electrode active layer 12 to form a good synergistic effect, balancing the capacity utilization and interface performance of the negative electrode sheet 10.

[0042] In some embodiments, the thickness of the negative electrode active layer 12 in the first direction is H, satisfying: 0.5≤D / H≤1.5.

[0043] By satisfying 0.5 ≤ D / H ≤ 1.5, the pore size of the porous structure 123 and the thickness of the negative electrode active layer 12 can synergistically work together. This ensures that the buffer space provided by the porous structure 123 can absorb the volume changes of the silicon-based negative electrode material in the negative electrode active layer 12 during charging and discharging, and prevents the reduction of the active material loading in the negative electrode active layer 12 due to excessively large pore size, thus balancing cycle performance and energy density. Simultaneously, satisfying 0.5 ≤ D / H ≤ 1.5 also helps improve the electrolyte's filling effect on the porous structure 123, which is beneficial for forming a good ion transport network and reducing interfacial impedance. Furthermore, by ensuring the synergistic effect between the pore size of the porous structure 123 and the thickness of the negative electrode active layer 12, the structural stability of the negative electrode active layer 12 is also improved.

[0044] For example, D / H can be 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4 or 1.5.

[0045] In some embodiments, the pore density on the negative electrode active layer 12 is 0.08‰-196.25‰.

[0046] Pore ​​density refers to the ratio of the total area of ​​the pore structures 123 in the negative electrode active layer 12 to the total area of ​​the negative electrode active layer 12. With a pore density of 0.08‰-196.25‰ on the negative electrode active layer 12, a reasonable buffer space can be formed on the negative electrode active layer 12, effectively absorbing the volume expansion of the silicon-based negative electrode material during charging and discharging, and ensuring the loading of active material in the negative electrode active layer 12, thus ensuring the capacity of the negative electrode sheet 10. Furthermore, within the above-mentioned pore density range, the solid electrolyte filled in the negative electrode active layer 12 can also form a good ion transport network, ensuring the rate performance and power density of the solid-state battery.

[0047] For example, it can be 0.08‰, 1‰, 10‰, 50‰, 100‰, 150‰, 190‰ or 196.25‰.

[0048] Taking a square negative electrode and a circular perforated structure as an example, the electrode area S = a × b, and the pore density = [(a / L) × (b / L) × π × (D / 2)]. 2 ] / (a×b)=(πD 2 ) / (4L 2 (). Where a and b represent the length and width of the negative electrode, respectively.

[0049] In some embodiments, the pore density on the negative electrode active layer 12 is 0.314‰-31.4‰.

[0050] With a pore density of 0.314‰-31.4‰ on the negative electrode active layer 12, a good ion transport network can be formed while taking into account both the expansion effect of the buffer silicon-based negative electrode material and high energy density, and the structural strength of the negative electrode active layer 12 can be guaranteed.

[0051] In some embodiments, the silicon-based anode material includes at least one of nano-silicon materials, micro-silicon materials, silicon-oxygen materials, and silicon-carbon materials.

[0052] The aforementioned silicon-based materials have a high theoretical specific capacity, which helps to improve the energy density of solid-state batteries, and are also low in cost.

[0053] It should be noted that, in addition to silicon-based anode materials, the negative electrode active layer 12 may also include other anode active materials, such as graphite.

[0054] In some embodiments, such as Figure 1 As shown, the negative electrode active layer 12 includes a first sub-active layer 121 and a second sub-active layer 122, which are located on opposite sides of the negative electrode current collector 11 in a first direction. The pore structure 123 in the first sub-active layer 121 is disposed opposite to the pore structure 123 in the second sub-active layer 122.

[0055] When the pore structures 123 in the first sub-active layer 121 and the second sub-active layer 122 are arranged opposite to each other, lithium ions can be directly transported through the negative electrode and fluid at the oppositely arranged pore structures 123 during charging and discharging, which can shorten the transport path of lithium ions in the negative electrode active layer 12 and improve the ion transport efficiency.

[0056] In some embodiments, such as Figure 2 As shown, the pore structures 123 in the first sub-active layer 121 and the pore structures 123 in the second sub-active layer 122 are arranged alternately.

[0057] When the pore structures 123 in the first sub-active layer 121 and the second sub-active layer 122 are arranged alternately, lithium ions can still be transported through a shorter path, and the overall mechanical properties of the negative electrode 10 can be improved.

[0058] In some embodiments, the plurality of pore structures 123 in the negative electrode active layer 12 are arranged in parallel to each other, or the plurality of pore structures 123 in the negative electrode active layer 12 are arranged in an alternating manner.

[0059] The porous structures 123 in the negative electrode active layer 12 can be arrayed in different forms. Parallel porous structures 123 can form regular ion transport channels, optimize ion transport paths, and ensure uniform stress distribution in the negative electrode active layer 12, thereby enhancing structural stability. Staggered porous structures 123 can form a three-dimensional interconnected ion transport network, reducing polarization caused by excessive local concentration gradients and helping to improve crack propagation resistance.

[0060] Secondly, embodiments of this application also provide a method for preparing a negative electrode 10, comprising: Provides negative electrode current collector 11 and negative electrode slurry; The negative electrode slurry is coated on at least one side of the negative electrode current collector 11 in the first direction to form a negative electrode active layer 12; A hole structure 123 is formed on the negative electrode active layer 12 to obtain the negative electrode sheet 10; The bottom of the perforated structure 123 is in contact with the negative electrode current collector 11; the diameter of the perforated structure 123 is D, and the center-to-center distance between adjacent perforated structures 123 is L, satisfying: 10μm≤D≤100μm, 2≤L / D≤100.

[0061] The method for preparing the negative electrode 10 provided in this application has all the beneficial effects of the negative electrode 10 as described above, and will not be repeated here.

[0062] In some embodiments, a porous structure 123 is formed in the negative electrode active layer 12, including: A mask template is set on the side of the negative electrode active layer 12 away from the negative electrode current collector 11, and a hole structure 123 is formed on the negative electrode active layer 12 by a laser array.

[0063] By using the positioning function of the photomask and the precise control of the laser array, a hole structure 123 of specific size, shape and distribution can be formed in the negative electrode active layer 12, thereby improving the accuracy of the hole structure 123 forming.

[0064] In addition to the above methods, the shape and arrangement of the pore structure 123 on the negative electrode active layer 12 can also be controlled by the geometric distribution of the laser point source and by controlling parameters such as the laser irradiation frequency and irradiation duration.

[0065] According to a third aspect of this application, a solid-state battery is also provided, comprising the negative electrode 10 as described above, and / or comprising the negative electrode 10 prepared by the method described above.

[0066] The solid-state battery provided in this application has all the beneficial effects of the negative electrode 10 as described above, which will not be repeated here.

[0067] In some embodiments, such as Figure 4 As shown, the solid-state battery also includes a solid electrolyte layer 20 and a positive electrode. The solid electrolyte layer 20 is disposed between the negative electrode 10 and the positive electrode, and the solid electrolyte layer 20 is embedded in at least a portion of the pore structure 123 of the negative electrode 10.

[0068] By disposing the solid electrolyte layer 20 between the negative electrode 10 and the positive electrode, the two electrodes can be isolated, preventing short circuits. By embedding the solid electrolyte layer 20 into at least a portion of the porous structure 123 of the negative electrode 10, the transport path of lithium ions between the negative electrode 10 and the solid electrolyte layer 20 can be shortened, improving the interfacial contact performance between them, reducing impedance, and enabling them to form a mechanical bond, reducing the risk of interface delamination and improving the structural stability of the solid-state battery.

[0069] In some embodiments, the solid electrolyte layer 20 includes a solid electrolyte with a particle size D90 of W, where 2 ≤ D / W ≤ 500.

[0070] By satisfying 2≤D / W≤500, the solid electrolyte in the solid electrolyte layer 20 can be fully filled into the porous structure 123 without causing the porous structure 123 to be blocked. This also ensures good interfacial contact between the solid electrolytes and improves ionic conductivity. Through the cooperation between the porous structure 123 and the solid electrolyte, the embedded structure increases the contact area and mechanical interlocking between the negative electrode active layer 12 and the solid electrolyte, improving the bonding strength between the negative electrode active layer 12 and the solid electrolyte layer 20 and reducing the risk of interfacial delamination between them.

[0071] For example, D / W can be 2, 5, 10, 20, 50, 100, 150, 200, 250, 300, 350, 400, 450 or 500.

[0072] It is understandable that the particle size D90 of solid electrolytes refers to the particle size of 90% of solid electrolyte particles being smaller than this value. The particle size D90 of solid electrolytes is obtained by testing with a laser particle size analyzer.

[0073] In some embodiments, 5 ≤ D / W ≤ 100.

[0074] By satisfying 5≤D / W≤100, the cooperation effect between the solid electrolyte and the porous structure 123 can be improved, the filling effect can be guaranteed, a good ion transport network can be formed, and the mechanical interlocking effect between the solid electrolyte layer 20 and the negative electrode active layer 12 can be guaranteed.

[0075] In some embodiments, 0.5 μm ≤ W ≤ 15 μm.

[0076] By satisfying 0.5μm≤W≤15μm, the solid electrolyte in the solid electrolyte layer 20 can form good contact, construct an excellent ion transport network, and the solid electrolyte in the porous structure 123 can form good stacking, providing a buffer space for the expansion of the silicon-based anode material.

[0077] For example, the size can be 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm or 15μm.

[0078] In some embodiments, the solid electrolyte includes at least one of lithium phosphorus sulfide, lithium phosphorus sulfide chloride, and lithium germanium phosphorus sulfide.

[0079] Solid electrolytes include at least one of sulfide solid electrolytes such as lithium phosphorus-sulfur, lithium phosphorus-sulfur-chloride, and lithium germanium-phosphorus-sulfur. They have excellent ionic conductivity and chemical stability, which can ensure the electrochemical performance and cycle stability of solid-state batteries.

[0080] For example, the negative electrode 10 includes a silicon-based negative electrode material, a solid electrolyte, a conductive agent, and a binder. The silicon-based negative electrode material, solid electrolyte, conductive agent, and binder are mixed and homogenized to obtain a negative electrode slurry. This slurry is then coated onto the negative electrode current collector 11, the solvent is dried, and the mixture is rolled to obtain the negative electrode 10. The conductive agent in the negative electrode 10 can be at least one of conductive carbon black, conductive graphite, carbon fiber, carbon nanotubes, and vapor-deposited carbon fiber. The binder can be one or more of the following materials: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyamide (PA), polyimide (PI), polyvinylpyrrolidone (PVP), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyamide-imide (PAI), polyethylene oxide (PEO), polystyrene (PS), polystyrene-acrylonitrile-butadiene rubber (PS-NBR), styrene-butadiene rubber (SBR), and hydrogenated nitrile-butadiene rubber (HNBR). The solvent can be a non-polar solvent such as p-xylene or butyl butyrate.

[0081] For example, the preparation method of the positive electrode sheet can be as follows: mixing and grinding the positive electrode active material, solid electrolyte, conductive agent and binder, and then mixing with a solvent to obtain a positive electrode slurry; coating the positive electrode slurry onto the surface of the positive electrode current collector; and obtaining the positive electrode sheet by drying and rolling. The positive electrode active material can be at least one of ternary materials, lithium iron phosphate materials, and lithium cobalt oxide materials. The conductive agent can be at least one of conductive carbon black, conductive graphite, carbon fiber, carbon nanotubes, and vapor-deposited carbon fiber. The binder can be one or more of the following materials: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyamide (PA), polyimide (PI), polyvinylpyrrolidone (PVP), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyamide-imide (PAI), polyethylene oxide (PEO), polystyrene (PS), polystyrene-acrylonitrile-butadiene rubber (PS-NBR), styrene-butadiene rubber (SBR), and hydrogenated nitrile-butadiene rubber (HNBR). The solvent can be a non-polar solvent such as p-xylene or butyl butyrate.

[0082] For example, the assembly method of solid-state battery can be as follows: a layer of solid electrolyte slurry is coated on the surface of negative electrode 10, and after drying to remove the solvent, a composite structure is obtained. After stacking positive electrode and composite structure, a core is obtained. Then, after shaping, spot welding, casing, encapsulation, isostatic pressing and other processes, a solid-state battery is obtained.

[0083] The embodiments of this application are further illustrated below with reference to specific examples. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of this application. Experimental methods in the following embodiments that do not specify specific conditions are generally performed according to the conditions recommended by the manufacturer.

[0084] Example 1 A negative electrode current collector 11 and a negative electrode slurry are provided; wherein, the negative electrode current collector 11 is a copper foil, and the mass ratio of silicon carbide material, lithium phosphorus sulfur chlorine, vapor-deposited carbon fiber (VGCF) and polyvinylidene fluoride (PVDF) in the negative electrode slurry is 70:28:1:1. The negative electrode slurry is coated on both sides of the negative electrode current collector 11 in the first direction to form the negative electrode active layer 12; A mask is set on the surface of the negative electrode active layer 12, and the negative electrode active layer 12 is photo-etched by a laser array to form a circular hole structure 123 on the negative electrode active layer 12, thereby obtaining the negative electrode sheet 10. The pore structure 123 has an opening along a first direction, and its bottom abuts against the negative electrode current collector 11. The pore diameter of the pore structure 123 is 50 μm, the center-to-center distance between adjacent pore structures 123 is 1000 μm, the single-sided thickness of the negative electrode active layer 12 is 50 μm (H=50 μm), and the pore density is 1.96‰.

[0085] Example 2 The difference between this embodiment and Embodiment 1 is that the aperture of the hole structure 123 is 20μm, and the center-to-center distance between adjacent hole structures 123 is 160μm. All other conditions are the same as in Embodiment 1.

[0086] Example 3 The difference between this embodiment and Embodiment 1 is that the aperture of the hole structure 123 is 10 μm, and the center-to-center distance between adjacent hole structures 123 is 20 μm. All other conditions are the same as in Embodiment 1.

[0087] Example 4 The difference between this embodiment and Embodiment 1 is that the aperture of the hole structure 123 is 100μm, and the center-to-center distance between adjacent hole structures 123 is 10000μm. All other conditions are the same as in Embodiment 1.

[0088] Example 5 The difference between this embodiment and Embodiment 1 is that the thickness of the negative electrode active layer 12 on one side is 25 μm, while all other conditions are the same as in Embodiment 1.

[0089] Example 6 The difference between this embodiment and Embodiment 1 is that the thickness of the negative electrode active layer 12 on one side is 150 μm, while all other conditions are the same as in Embodiment 1.

[0090] Comparative Example 1 The difference between this comparative example and Example 1 is that no pore structure 123 is formed on the negative electrode active layer 12, while the other conditions are the same as in Example 1.

[0091] Comparative Example 2 The difference between this comparative example and Example 1 is that the center-to-center distance between adjacent hole structures 123 is 50 μm, while all other conditions remain the same as in Example 1.

[0092] Comparative Example 3 The difference between this comparative example and Example 1 is that the center-to-center distance between adjacent hole structures 123 is 5500 μm, while all other conditions remain the same as in Example 1.

[0093] Comparative Example 4 The difference between this comparative example and Example 1 is that the aperture of the hole structure 123 is 1010 μm, and the center-to-center distance between adjacent hole structures 123 is 4040 μm. All other conditions are the same as in Example 1.

[0094] Comparative Example 5 The difference between this comparative example and Example 1 is that the aperture of the hole structure 123 is 1010 μm, and the center-to-center distance between adjacent hole structures 123 is 51510 μm. All other conditions are the same as in Example 1.

[0095] The negative electrode 10 from Examples 1-6 and Comparative Examples 1-5 were stacked with the positive electrode 20 solid electrolyte layer to form an all-solid-state pouch battery. The solid electrolyte layer 20 was obtained by coating the surface of the negative electrode 10 with a solid electrolyte slurry and then drying it. The solid electrolyte in the slurry was lithium phosphorus sulfur chloride, with a particle size D90 of 10 μm (W=10 μm). The positive electrode included a positive current collector and a positive active layer coated on opposite sides of the current collector. The current collector was aluminum foil. The mass ratio of the positive active material (NCM811), solid electrolyte (lithium phosphorus sulfur chloride), conductive agent (vapor-grown carbon fiber VGCF), and vinylidene fluoride (PVDF) in the positive active layer was 70:28:1:1. The assembly method of the all-solid-state soft-pack battery is as follows: the positive electrode sheet, negative electrode sheet 10 and solid electrolyte layer 20 are stacked in a stacking machine to obtain a stacked core, and then the core is obtained by hot pressing, spot welding, casing, encapsulation and isostatic pressing.

[0096] The relevant parameters of the negative electrode in Examples 1-6 and Comparative Examples 1-5 are shown in Table 1: Table 1

[0097] Under a test pressure of 10 MPa, the first-cycle discharge capacity and the discharge capacity retention rate after 100 cycles of the all-solid-state pouch cells prepared by the negative electrode sheet 10 in Examples 1-6 and Comparative Examples 1-5 were tested respectively. The method for testing the first-cycle coulombic efficiency is as follows: Using an electrochemical test cabinet, the battery is charged at a constant current rate of 0.1C to 4.2V, and then charged at a constant voltage rate until the current is less than 0.02C to obtain the first-cycle charging capacity. After the battery is allowed to rest for 30 minutes, it is discharged at a constant current rate of 0.1C to 2.5V to obtain the first-cycle discharging capacity. The first-cycle coulombic efficiency = first-cycle discharging capacity / first-cycle charging capacity × 100%. The method for testing the cycle capacity retention rate is as follows: Using an electrochemical test cabinet, the battery is charged at a constant current rate of 1C to 4.2V, and then charged at a constant voltage rate until the current is less than 0.05C. After the battery is allowed to rest for 30 minutes, it is discharged at a constant current rate of 1C to 2.5V. After resting for 30 minutes, the above charge and discharge method is repeated. The 100-cycle capacity retention rate = 100th-cycle discharging capacity / 1st-cycle discharging capacity × 100%. The test results are shown in Table 2. Table 2

[0098] As shown in Table 2, compared with Comparative Example 1 (without holes), the all-solid-state batteries prepared with negative electrode sheets in Examples 1-6 of this application have higher 0.1C first-cycle discharge specific capacity and 1C 100-cycle discharge capacity retention rate. That is, the all-solid-state batteries prepared with negative electrode sheets in Examples 1-6 of this application can effectively improve the discharge performance and cycle performance under low pressure compared with the all-solid-state batteries prepared with negative electrode sheets in Comparative Example 1.

[0099] As can be seen from the comparison of Example 1, Comparative Example 1 and Comparative Example 2, the center-to-center spacing between adjacent hole structures 123 in Comparative Example 2 is small, and the hole structures 123 are too dense. Although they have a good effect on improving cycle performance, they have a significant impact on the energy density of the all-solid-state battery.

[0100] As can be seen from the comparison of Example 1, Comparative Example 1 and Comparative Example 3, due to the large center-to-center spacing between adjacent hole structures 123 in Comparative Example 3, the hole structures 123 are too sparse, and the energy density and cycle performance of the all-solid-state battery are not significantly improved compared to Comparative Example 1. Example 1 has a significant advantage over Comparative Example 3.

[0101] As can be seen from the comparison of Example 1, Comparative Example 1 and Comparative Example 4, the pore size of the negative electrode structure 123 in Comparative Example 4 is relatively large and dense, which will affect the processing performance during electrolyte membrane coating, and thus easily lead to electrolyte slurry leakage, affecting the capacity of the all-solid-state battery, but improving the cycle performance.

[0102] As can be seen from the comparison of Example 1, Comparative Example 1 and Comparative Example 5, the pore size of the hole structure 123 in Comparative Example 5 is relatively large but relatively sparse, which affects the processing performance, and therefore there is no significant improvement effect compared to Comparative Example 1.

[0103] A comparison of Examples 1-6 shows that in Example 1, the pore size and distribution of the negative electrode pore structure 123 are reasonable, significantly improving the discharge and cycle performance of the silicon-carbon based all-solid-state battery under low voltage. In Example 2, the pore size is smaller and the density of the pore structure 123 is higher than in Example 1, resulting in a significant improvement in cycle performance, but a slight decrease in discharge performance compared to Example 1. In Example 3, the pore size of the negative electrode pore structure 123 is smaller and more dense, increasing the effect of electrolyte slurry filling into the pore structure 123 during electrolyte membrane coating, but the improvement in capacity utilization and cycle performance is relatively moderate. In Example 4, the pore size of the negative electrode pore structure 123 is moderate but relatively sparse, resulting in a significant improvement in the capacity utilization of the all-solid-state battery, but a moderate improvement in cycle performance alone. In Example 5, the high D / H ratio of the negative electrode has a certain impact on processing performance, and the improvement in capacity utilization and cycle performance of the all-solid-state battery is lower compared to Example 1. In Example 6, the negative electrode has a low D / H ratio, which makes it easy for the electrolyte slurry to leak into the interior of the negative electrode, affecting the lithium-ion transport effect. Compared with Example 1, the effect on capacity utilization and cycle performance improvement of the all-solid-state battery is generally limited.

[0104] In summary, the negative electrode sheet provided in this application, by creating a porous structure on the negative electrode active layer, can construct a directional expansion release region within the negative electrode active layer. This transforms the disordered expansion of the silicon-based negative electrode material into ordered deformation. The porous structure absorbs the volume changes of the silicon-based negative electrode material and provides stress buffer space, thereby improving the cycle stability of the silicon-based negative electrode material. When the negative electrode sheet is applied to a solid electrolyte, the porous structure on the negative electrode active layer can also accommodate the solid electrolyte, forming continuous ion transport channels. This allows the solid electrolyte to fill the interior of the negative electrode sheet, reducing the interfacial impedance between the negative electrode sheet and the solid electrolyte layer, and increasing the lateral shear force between the negative electrode sheet and the solid electrolyte layer, thus reducing the risk of interfacial delamination. By ensuring that the pore size of the porous structure and the center-to-center distance between adjacent porous structures meet the above conditions, sufficient expansion buffer space can be provided, increasing the interfacial bonding effect between the negative electrode sheet and the solid electrolyte while maintaining good capacity performance of the negative electrode sheet. The embodiments of this application, through the pore size of the pore structure and the center-to-center spacing between adjacent pore structures, can improve the electrolyte permeation effect, reduce the interface impedance, alleviate interface peeling, and at the same time maintain high energy density, thereby improving the overall electrochemical performance of silicon-based all-solid-state batteries under low pressure.

[0105] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A negative electrode sheet, characterized in that, The negative electrode includes: Negative electrode current collector; A negative electrode active layer is disposed on at least one side of the negative electrode current collector in a first direction, and the negative electrode active layer comprises a silicon-based negative electrode material; The negative electrode active layer is provided with a plurality of pore structures opening along a first direction, and the bottom of the pore structure abuts against the negative electrode current collector; the pore diameter of the pore structure is D, and the center distance between adjacent pore structures is L, satisfying: 10μm≤D≤100μm, 2≤L / D≤100.

2. The negative electrode sheet according to claim 1, characterized in that, 20μm≤D≤50μm; And / or, 5≤L / D≤50.

3. The negative electrode sheet according to claim 1, characterized in that, The thickness of the negative electrode active layer in the first direction is H, which satisfies: 0.5≤D / H≤1.

5.

4. The negative electrode sheet according to claim 1, characterized in that, The silicon-based anode material includes at least one of nano-silicon materials, micro-silicon materials, silicon-oxygen materials, and silicon-carbon materials.

5. The negative electrode sheet according to any one of claims 1-4, characterized in that, The negative electrode active layer includes a first sub-active layer and a second sub-active layer, the first sub-active layer and the second sub-active layer being located on opposite sides of the negative electrode current collector in the first direction; The pore structures in the first sub-active layer are arranged opposite to the pore structures in the second sub-active layer, or the pore structures in the first sub-active layer are arranged alternately with the pore structures in the second sub-active layer.

6. A method for preparing a negative electrode sheet, characterized in that, include: We provide negative electrode current collectors and negative electrode slurries; The negative electrode slurry is coated onto at least one side of the negative electrode current collector in a first direction to form a negative electrode active layer; A porous structure is formed in the negative electrode active layer to obtain the negative electrode sheet; The bottom of the perforated structure abuts against the negative electrode current collector; The aperture of the hole structure is D, and the center-to-center distance between adjacent hole structures is L, satisfying: 10μm≤D≤100μm, 2≤L / D≤100.

7. The method for preparing the negative electrode sheet according to claim 6, characterized in that, The method of creating a porous structure on the negative electrode active layer includes: A mask template is provided on the side of the negative electrode active layer away from the negative electrode current collector, and the hole structure is formed on the negative electrode active layer by a laser array.

8. A solid-state battery, characterized in that, Includes the negative electrode sheet as described in any one of claims 1-5, and / or includes the negative electrode sheet prepared by the method described in any one of claims 6-7.

9. The solid-state battery according to claim 8, characterized in that, The solid-state battery also includes a solid electrolyte layer and a positive electrode sheet; The solid electrolyte layer is disposed between the negative electrode and the positive electrode, and the solid electrolyte layer is embedded in at least a portion of the pore structure of the negative electrode.

10. The solid-state battery according to claim 9, characterized in that, The solid electrolyte layer includes a solid electrolyte with a particle size D90 of W, where 2 ≤ D / W ≤ 500.

11. The solid-state battery according to claim 10, characterized in that, 5≤D / W≤100; And / or, 0.5μm≤W≤15μm; And / or, the solid electrolyte includes at least one of lithium phosphorus sulfide, lithium phosphorus sulfide chloride, and lithium germanium phosphorus sulfide.

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