Silicon negative electrode sheet and preparation method thereof, solid-state battery

Abstract

This invention provides a silicon anode sheet, its preparation method, and a solid-state battery. The silicon anode sheet of this invention comprises: a negative electrode current collector and a silicon anode slurry coated on the surface of the negative electrode current collector. The silicon anode slurry comprises a solid electrolyte, nano-silicon, mixed silicon carbon, a conductive agent, a binder, and a solvent. The mixed silicon carbon comprises a first silicon carbon and a second silicon carbon with different particle sizes. The particle size distribution D of the solid electrolyte is... 50 Particle size distribution D smaller than that of first silicon-carbon 50 And the particle size distribution D of the first silicon-carbon 50 Particle size distribution D smaller than that of second silicon-carbon 50 The silicon anode electrode provided by this invention, through the compounding of silicon-carbon particles of different sizes and solid electrolytes, provides more expansion space for nano-silicon, thereby effectively reducing the expansion rate of the silicon anode electrode.

Description

Technical Field

[0001] This application relates to the field of batteries, and in particular to a silicon anode sheet and its preparation method, and a solid-state battery. Background Art

[0002] Lithium-ion batteries are a crucial component of current clean energy and are widely used in various 3C products and electric vehicles. As the performance requirements for lithium-ion batteries increase, improving their energy density and addressing the safety issues of traditional liquid lithium-ion batteries, such as flammability and even explosion, have become urgent priorities. Consequently, research into developing all-solid-state lithium-ion batteries using solid electrolytes to replace liquid electrolytes has naturally become a global hot topic.

[0003] Currently, several types of anodes are commonly used in solid-state batteries. Anodes made from nano-silicon are widely used due to their high specific capacity. However, the volume expansion characteristics of nano-silicon cause the anode sheet to expand, leading to various drawbacks in the battery, such as the formation of numerous cracks inside the anode during cycling, preventing the battery from maintaining excellent cycle performance. Existing solutions often involve applying external force to the cell to counteract the expansion of the anode. However, this method requires high precision in external pressure control; unreasonable external pressure can lead to accelerated capacity decay and other problems, and presents significant operational challenges.

[0004] Therefore, for silicon anodes made from nano-silicon, there is an urgent need for a method that can effectively suppress the expansion of silicon anode sheets. Summary of the Invention

[0005] This application provides a silicon anode sheet and its preparation method, as well as a solid-state battery, to achieve the technical effect of reducing the expansion rate of the silicon anode sheet.

[0006] In a first aspect, the present invention provides a silicon negative electrode sheet, comprising: a negative electrode current collector and a silicon negative electrode slurry coated on the surface of the negative electrode current collector;

[0007] The silicon anode slurry includes a solid electrolyte, nano-silicon, mixed silicon carbon, conductive agent, binder, and solvent. The mixed silicon carbon includes first silicon carbon and second silicon carbon with different particle sizes.

[0008] Wherein, the particle size distribution D of the solid electrolyte 50 The particle size distribution D is smaller than that of the first silicon-carbon. 50 And the particle size distribution D of the first silicon-carbon 50 The particle size distribution D is smaller than that of the second silicon-carbon. 50 .

[0009] According to one embodiment of the present invention, the mass ratio of the mixed silicon-carbon to the nano-silicon is 80:20 to 97:3.

[0010] According to an embodiment of the present invention, the particle size distribution D of the first silicon carbide 50 = 3 to 6 μm; and / or, the particle size distribution D of the second silicon carbide 50 = 6 to 12 μm.

[0011] According to an embodiment of the present invention, the mass ratio of the first silicon carbide to the second silicon carbide in the mixed silicon carbide is 50:50 to 85:15.

[0012] According to an embodiment of the present invention, the first silicon carbide and / or the second silicon carbide is a carbon-silicon material with porous carbon as the skeleton.

[0013] According to an embodiment of the present invention, the mass ratio of the substance after mixing the mixed silicon carbide and the nano-silicon to the solid electrolyte is 60:40 to 90:10.

[0014] According to an embodiment of the present invention, the particle size distribution D of the solid electrolyte 50 = 0.3 to 1 μm.

[0015] According to an embodiment of the present invention, the solid electrolyte is a sulfide electrolyte.

[0016] According to an embodiment of the present invention, the sulfide electrolyte includes at least one of a binary Li2S-P2S5 system sulfide solid electrolyte, a thioargentite-type sulfide solid electrolyte, and a lithium phosphorus sulfur iodine-type sulfide solid electrolyte.

[0017] According to an embodiment of the present invention, the expressions of the binary Li2S-P2S5 system sulfide solid electrolyte and the thioargentite-type sulfide solid electrolyte are both xLi2S·(100 - x - z)A y S n ·zB;

[0018] where 0 < x < 100, y is 0, 1 or 2, n is 2y or 2y + 1, 0 ≤ z < 100 - x, A is B 3+ 、Si 4+ 、P 3+ 、P 5+ or Ge 4+ , B is LiCl, LiBr, LiI, Li3PO4, GeS2, P2O5, Li4SiO4 or P2S3;

[0019] and / or,

[0020] When the S-site doping element in the lithium phosphorus sulfur iodine-type sulfide solid electrolyte is a +5 valence element, the expression of the lithium phosphorus sulfur iodine-type sulfide solid electrolyte is ;

[0021] When the S-site dopant element is a +4 valence element, the expression for the lithium-phosphorus-sulfur-iodine type sulfide solid electrolyte is: ,

[0022] Where 0.01≤a≤2, 0.01≤b≤1, 0.01≤c≤1, A is the P-site dopant element, B is the S-site dopant element, and C is the I-site dopant element.

[0023] According to one embodiment of the present invention, the particle size distribution D of the nano-silicon is... 50 =20~200nm.

[0024] According to one embodiment of the present invention, the conductive agent is at least one of conductive carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, vapor-grown carbon fibers, graphene, and acetylene black.

[0025] And / or,

[0026] The adhesive is at least one of polytetrafluoroethylene, styrene-butadiene rubber, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, nitrile rubber, styrene-ethylene-butene-styrene copolymer, polyacrylic acid, and styrene-butadiene-styrene copolymer.

[0027] According to one embodiment of the present invention, the mass ratio of the solid electrolyte, the nano-silicon and the mixed silicon-carbon mixture to the conductive agent is 98.5:1.5 to 85:15.

[0028] According to one embodiment of the present invention, the binder accounts for 0.25% to 5% of the mass fraction of the silicon negative electrode sheet.

[0029] A second aspect of the present invention provides a method for preparing the above-mentioned silicon negative electrode sheet, comprising:

[0030] Mixed silicon-carbon and nano-silicon are combined in a mixer to obtain a silicon anode premix. The mixed silicon-carbon comprises a first silicon-carbon and a second silicon-carbon with different particle sizes. The particle size distribution D of the first silicon-carbon is... 50 The particle size distribution D is smaller than that of the second silicon-carbon. 50 ;

[0031] The silicon anode premix and solid electrolyte are ground in a high-energy mixer to obtain a silicon anode composite material. The particle size distribution D of the solid electrolyte is... 50 The particle size distribution D is smaller than that of the first silicon-carbon. 50 ;

[0032] The silicon anode composite material and the conductive agent are mixed in a mixer to obtain a silicon anode mixture.

[0033] The silicon anode mixture, binder, and solvent are homogenized using a homogenizing device to obtain a silicon anode slurry with a preset solid content.

[0034] The silicon anode slurry is coated onto the anode current collector to obtain the silicon anode sheet.

[0035] A third aspect of the present invention provides a solid-state battery, comprising: the silicon anode electrode as described in the first aspect.

[0036] A fourth aspect of the present invention provides an electrical device, comprising an electrical device body and the solid-state battery described in the third aspect.

[0037] The present invention has at least the following beneficial effects:

[0038] The silicon anode sheet provided by this invention uses a combination of silicon-carbon particles of different sizes and a solid electrolyte. Smaller particles fill the pores constructed by larger particles, thereby achieving the construction of multi-level pores and reducing the ineffective space between particles. This makes the spatial layout of particles in the silicon anode sheet more rational, thus providing more expansion space for nano-silicon and alleviating the expansion of the silicon anode sheet, achieving the technical effect of effectively reducing the expansion rate of the silicon anode sheet. Attached Figure Description

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0040] Figure 1 This is a schematic flowchart of the method for preparing the silicon negative electrode sheet provided in Embodiment 2 of the present invention. Detailed Implementation

[0041] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] Based on the above technical background, Embodiment 1 of the present invention provides a silicon negative electrode sheet, comprising: a negative electrode current collector and a silicon negative electrode slurry coated on the surface of the negative electrode current collector. The silicon negative electrode slurry comprises a solid electrolyte, nano-silicon, mixed silicon carbon, a conductive agent, a binder, and a solvent. The mixed silicon carbon comprises a first silicon carbon and a second silicon carbon with different particle sizes.

[0043] Among them, the particle size distribution D of the solid electrolyte 50 Particle size distribution D smaller than that of the first silicon-carbon 50 And the particle size distribution D of the first silicon-carbon 50 Particle size distribution D smaller than that of second silicon-carbon 50 .

[0044] According to the inventors' research, among commonly used silicon materials, the carbon structure in silicon-carbon can significantly suppress the volume expansion of silicon during cycling, exhibiting good cycling stability. However, the introduction of carbon into silicon-carbon reduces the nominal specific capacity of the silicon material. Nano-silicon, on the other hand, has a theoretical specific capacity of 4200 mAh / g, but it is prone to agglomeration and exhibits significant volume expansion, easily leading to numerous cracks within the electrode during cycling, thus failing to maintain excellent cycling performance. Therefore, this solution combines silicon-carbon and nano-silicon to achieve a balance between the high cycling stability of silicon-carbon and the high specific capacity of nano-silicon.

[0045] Based on this, and considering the impact of the expansion characteristics of nano-silicon, this invention is designed to combine silicon-carbon with different particle sizes and solid electrolytes, using smaller particles to fill the pores constructed by larger particles, thereby achieving the construction of multi-level pores, reducing the ineffective space between particles, and making the spatial layout of particles in the silicon anode sheet more rational. This provides more expansion space for nano-silicon, thereby alleviating the expansion of the silicon anode sheet and achieving the technical effect of effectively reducing the expansion rate of the silicon anode sheet.

[0046] Meanwhile, the filling of the pores created by the smaller particles with the larger particles results in a uniform distribution of particles of different sizes. This leads to a more uniform distribution of stress generated by the nano-silicon in the electrode, thus avoiding the formation of a large number of cracks in the electrode due to stress concentration.

[0047] Furthermore, according to the inventors' research, the rate performance of silicon anode sheets can be improved by combining silicon-carbon particles of different sizes with solid electrolytes. Specifically, in silicon-carbon of different sizes, the filling of pores created by larger particles with smaller particles can effectively shorten the electron transport distance and reduce the electron transport impedance, thereby improving rate performance. At the same time, the uniform distribution of solid electrolyte in the pores can form an efficient ion transport path, reducing the ion diffusion distance and further improving rate performance.

[0048] Therefore, based on the above description, the combination of silicon-carbon with different particle sizes and solid electrolyte can effectively improve the problem of silicon anode sheet expansion caused by the expansion characteristics of nano-silicon, and at the same time, it can also effectively improve the rate performance of silicon anode sheet.

[0049] In some embodiments, the mass ratio of mixed silicon-carbon to nano-silicon is 80:20 to 97:3.

[0050] It should be understood that, compared to nano-silicon, the structure of silicon-carbon itself determines that its expansion degree will be lower. Therefore, in this embodiment, the proportion of mixed silicon-carbon is higher than that of nano-silicon, which can avoid the problem of easy expansion caused by excessive nano-silicon in the silicon anode electrode.

[0051] Specifically, in the mixture of mixed silicon carbon and nano-silicon, the proportion of mixed silicon carbon is 80% to 97%. For example, the mass ratio of mixed silicon carbon to nano-silicon is 80:20, 82:18, 84:16, 86:14, 88:12, 90:10, 92:8, 94:6, 96:4, 97:3, etc., all within the range of 80:20 to 97:3. This invention does not limit the specific value of the mass ratio of mixed silicon carbon to nano-silicon.

[0052] In some embodiments, the particle size distribution D of the first silicon carbon 50 =3~6μm; and / or, the particle size distribution D of the second silicon-carbon 50 =6~12μm.

[0053] Specifically, in some cases, the particle size distribution D of the first silicon-carbon... 50 The particle size distribution D of the second silicon-carbon material can be any value between 3 and 6 μm. 50 Particle size distribution D larger than that of the first silicon-carbon 50 The value can be chosen freely; in some cases, the particle size distribution D of the second silicon-carbon... 50 The particle size distribution D of the first silicon-carbon material can be any value between 6 and 12 μm. 50 Particle size distribution D smaller than that of second silicon-carbon 50 The value can be chosen; in some cases, the particle size distribution D of the first silicon-carbon... 50 The particle size distribution D of the second silicon-carbon material can be any value between 3 and 6 μm. 50 It is 6~12μm.

[0054] For example, the particle size distribution D of the first silicon-carbon 50For example, the particle size distribution D of the second silicon-carbon material can be 3μm, 3.2μm, 3.4μm, 3.6μm, 3.8μm, 4μm, 4.2μm, 4.4μm, 4.6μm, 4.8μm, 5μm, 5.2μm, 5.4μm, 5.6μm, 5.8μm, or 6μm, or any two of the aforementioned values ​​can be selected to form a new range, and the values ​​taken within the new range; and / or, the particle size distribution D of the second silicon-carbon material. 50 For example, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 10.5μm, 11μm, 11.5μm, 12μm, or any two of the aforementioned values ​​can be selected to form a new range, and the values ​​taken within the new range.

[0055] In some embodiments, the mass ratio of the first silicon carbon to the second silicon carbon in the mixed silicon carbon is 50:50 to 85:15.

[0056] It should be understood that, considering the use of more small-diameter silicon-carbon particles (i.e., first silicon-carbon) and less large-diameter silicon-carbon particles (i.e., second silicon-carbon), the small-diameter silicon-carbon particles can fully fill the pores formed between the large-diameter silicon-carbon particles, which can further reduce the ineffective space between particles, making the spatial layout of particles in the silicon anode sheet more rational and providing more expansion space for nano-silicon. At the same time, since the specific surface area of ​​small-diameter silicon-carbon is larger, using more small-diameter silicon-carbon particles can further improve the rate performance of the silicon anode sheet.

[0057] For example, the mass ratio of the first silicon carbon to the second silicon carbon in the mixed silicon carbon is, for example, a value in the range of 50:50 to 85:15, such as 50:50, 55:45, 60:40, 65:35, 70:30, 75:25, 80:20, 85:15, etc. The present invention does not limit the specific value of the mass ratio of the first silicon carbon to the second silicon carbon in the mixed silicon carbon.

[0058] In some embodiments, the first silicon-carbon and / or the second silicon-carbon are silicon-carbon materials with a porous carbon framework.

[0059] It should be noted that the porous carbon-based silicon carbon material, with its three-dimensional network structure, can significantly suppress the volume expansion of silicon during cycling, preventing silicon particles from cracking and pulverizing due to expansion. Therefore, it has better cycling stability.

[0060] Optionally, the silicon carbide material with porous carbon as its framework can be prepared using a chemical vapor deposition (CVD) process.

[0061] In some embodiments, the mass ratio of the mixture of silicon-carbon and nano-silicon to the solid electrolyte is 60:40 to 90:10.

[0062] It should be understood that designing a smaller proportion of solid electrolyte compared to silicon material can reduce the proportion of inactive substances, thereby maintaining a high energy density in the silicon anode electrode.

[0063] For example, the mass ratio of the mixture of silicon carbon and nano-silicon to the solid electrolyte is, for example, 60:40, 65:35, 70:30, 75:25, 80:20, 85:15, 90:10, etc., which are values ​​in the range of 60:40 to 90:10. The present invention does not limit the specific value of the mass ratio of the mixture of silicon carbon and nano-silicon to the solid electrolyte.

[0064] In some embodiments, the particle size distribution D of the solid electrolyte is... 50 =0.3~1μm.

[0065] It should be understood that if the selected solid electrolyte has an excessively large particle size, new pores will form between the solid electrolyte particles, resulting in more unusable space. Therefore, by selecting a particle size distribution D... 50 Solid electrolytes in the range of 0.3~1μm can ensure that the solid electrolyte can be uniformly distributed in the pores of the mixed silicon and carbon. This ensures both a rational spatial layout to further reduce the expansion rate of the silicon anode sheet and the construction of an efficient ion transport path to further improve the rate performance of the silicon anode sheet.

[0066] Specifically, in practical applications, the particle size distribution D of the first silicon-carbon in the silicon anode slurry can be designed. 50 =3~6μm, particle size distribution of the second silicon-carbon D 50 =6~12μm, and the particle size distribution D of the solid electrolyte is... 50 =0.3~1μm.

[0067] For example, the particle size distribution D of a solid electrolyte 50 For example, the values ​​can be 0.3μm, 0.35μm, 0.4μm, 0.45μm, 0.5μm, 0.55μm, 0.6μm, 0.65μm, 0.7μm, 0.75μm, 0.8μm, 0.85μm, 0.9μm, 0.95μm, or 1μm, or any two of the aforementioned values ​​can be selected to form a new range, and the values ​​taken within the new range can be used.

[0068] In some embodiments, the solid electrolyte is a sulfide electrolyte.

[0069] Optionally, the sulfide electrolyte includes at least one of the following: binary Li2S-P2S5 system sulfide solid electrolyte, silver-germanium sulfide solid electrolyte, and lithium-phosphorus-sulfur-iodine (LPSI) type sulfide solid electrolyte.

[0070] It should be noted that, compared with other solid electrolytes such as oxide electrolytes, sulfide electrolytes have advantages such as high room-temperature ionic conductivity and low interfacial impedance with electrode materials, which helps to improve the rate performance of the silicon negative electrode sheet. Further, among sulfide electrolytes, the binary Li2S-P2S5 system sulfide solid electrolyte, the thiogermanate-type sulfide solid electrolyte, and the LPSI-type sulfide solid electrolyte have more stable performance and better effects when applied in the silicon negative electrode paste system of this solution.

[0071] In some embodiments, the expressions of both the binary Li2S-P2S5 system sulfide solid electrolyte and the thiogermanate-type sulfide solid electrolyte are xLi2S·(100-x-z)A y S n ·zB;

[0072] where 0 < x < 100, y is 0, 1 or 2, n is 2y or 2y + 1, 0 ≤ z < 100 - x, A is B 3+ 、Si 4+ 、P 3+ 、P 5+ or Ge 4+ ,B is LiCl, LiBr, LiI, Li3PO4, GeS2, P2O5, Li4SiO4 or P2S3;

[0073] In some embodiments, when the S-site doping element in the lithium phosphorus sulfur iodine type sulfide solid electrolyte is a +5 valence element, the expression of the lithium phosphorus sulfur iodine type sulfide solid electrolyte is ; when the S-site doping element is a +4 valence element, the expression of the LPSI-type sulfide solid electrolyte is ;

[0074] where 0.01 ≤ a ≤ 2, 0.01 ≤ b ≤ 1, 0.01 ≤ c ≤ 1, A is the P-site doping element, B is the S-site doping element, and C is the I-site doping element.

[0075] Optionally, the above S-site doping element includes O.

[0076] Optionally, the above I-site doping element includes Cl and / or Br.

[0077] In some embodiments, the particle size distribution D of the nanosilicon 50 = 20~200nm.

[0078] Exemplarily, the particle size distribution D of the nanosilicon 50For example, 20nm, 40nm, 60nm, 80nm, 100nm, 120nm, 140nm, 160nm, 180nm, 200nm, or any two of the aforementioned values ​​can be selected to form a new range, and the values ​​taken within the new range can be selected.

[0079] In some embodiments, the conductive agent is at least one of conductive carbon black, single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), vapor-grown carbon fiber (VGCF), graphene, and acetylene black.

[0080] It should be noted that by adding a conductive agent to the silicon anode slurry, the conductive agent forms an electronic conductivity "line," which can also ensure that the silicon anode sheet has good rate performance. Specifically, when the conductive agent is, for example, vapor-grown carbon fiber, the vapor-grown carbon fiber forms an electronic conductivity "long line," or when the conductive agent is, for example, carbon nanotubes, the carbon nanotubes form an electronic conductivity "short line." Since the lithiated nano-silicon will form a lithium-silicon alloy, and the lithium-silicon alloy has high electronic conductivity, the lithiated single-particle nano-silicon will act as an electronic conductivity "point." The continuous lithiated single-particle nano-silicon will form an electronic conductivity "surface." The three work together to form a three-dimensional conductive electron network of "points, lines, and surfaces," which is conducive to electron transport and can ensure that the silicon anode sheet has good rate performance.

[0081] Specifically, the conductive agent can be any one of the following substances: conductive carbon black, single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), vapor-grown carbon fibers (VGCFs), graphene, and acetylene black. It can also be a combination of any of the above substances, for example, it can be a combination of two, three, or more substances. In this respect, the embodiments of the present invention do not make specific limitations.

[0082] In some embodiments, the binder is at least one selected from polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), nitrile-butadiene rubber (NBR), styrene-ethylene-butylene-styrene copolymer (SEBS), polyacrylic acid (PAA), and styrene-butadiene-styrene copolymer (SBS).

[0083] Specifically, the binder can be any one of the following substances: polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), nitrile rubber (NBR), styrene-ethylene-butene-styrene copolymer (SEBS), polyacrylic acid (PAA), and styrene-butadiene-styrene copolymer (SBS). It can also be a combination of any number of the above substances, for example, it can be a combination of two, three, or more substances. In this embodiment of the invention, no specific limitation is made. Such a setting can effectively improve the versatility of the electrode sheet, so that the electrode sheet can meet various different application scenarios.

[0084] In some embodiments, the solvent comprises at least one of straight-chain alkanes, branched-chain alkanes, cycloalkanes, aromatic hydrocarbons, alkenes, cycloalkenes, and other weakly polar solvents.

[0085] Among them, the straight-chain alkane is at least one of n-hexane, n-pentane, isopentane, n-heptane, n-octane, isooctane, trichlorotrifluoroethane, dichloromethane, and trichloromethane; the branched-chain alkane is at least one of 2-methylpentane, 2,2-dimethylpentane, 3-methylpentane, 2,3-dimethylpentane, 2-methylhexane, 2,2-dimethylhexane, 3-methylhexane, 2,3-dimethylhexane, and 3-ethylhexane; the cycloalkanes are at least one of cyclohexane, cycloheptane, methylcyclohexane, tert-butylcyclohexane, and tetrahydrofuran; and the aromatic hydrocarbons are benzene, toluene, 1, At least one of 2-xylene, 1,3-xylene, 1,4-xylene, chlorobenzene, and o-dichlorobenzene; at least one of 1-hexene, 2-hexene, 1-heptene, 2-heptene, 1-octene, 2-octene, and vinyl dichloride; at least one of cyclopentene, cyclohexene, 1-methylcyclohexene, 4-methylcyclohexene, 1-ethylcyclohexene, and 1,4-dimethylcyclohexene; and at least one of other weakly polar solvents, including petroleum ether, trifluoroacetic acid, butyl chloride, trichloroethylene, carbon tetrachloride, propyl ether, diethyl ether, butyl acetate, and ethyl acetate.

[0086] Specifically, the binder can be any one of the above-mentioned straight-chain alkanes, branched-chain alkanes, cycloalkanes, aromatic hydrocarbons, alkenes, cycloalkenes and other weakly polar solvents, or it can be a combination of any number of the above-mentioned substances. For example, it can be a combination of two, three or more substances. In this respect, the embodiments of the present invention do not make specific limitations. Such a setting can effectively improve the versatility of the electrode sheet, so that the electrode sheet can meet various different application scenarios.

[0087] In some embodiments, the mass ratio of the solid electrolyte, nano-silicon, and mixed silicon-carbon mixture to the conductive agent is 98.5:1.5 to 85:15.

[0088] Specifically, in the mixture of solid electrolyte, nano-silicon, mixed silicon carbon, and conductive agent, the conductive agent accounts for 1.5% to 15%. For example, the mass ratio of the mixture of solid electrolyte, nano-silicon, and mixed silicon carbon to the conductive agent is, for example, 98.5:1.5, 98:2, 97:3, 96:4, 95:5, 94:6, 93:7, 92:8, 91:9, 90:10, 89:11, 88:12, 87:13, 86:14, 85:15, etc., within the range of 98.5:1.5 to 85:15. This invention does not limit the specific value of the mass ratio of the mixture of solid electrolyte, nano-silicon, and mixed silicon carbon to the conductive agent.

[0089] In some embodiments, the binder accounts for 0.25% to 5% of the mass fraction of the silicon anode sheet.

[0090] For example, the mass fraction of the binder in the silicon negative electrode sheet is, for example, 0.25%, 0.5%, 0.75%, 1%, 1.25%, 1.5%, 1.75%, 2%, 2.25%, 2.5%, 2.75%, 3%, 3.25%, 3.5%, 3.75%, 4%, 4.25%, 4.5%, 4.75%, 5%, or any two of the aforementioned values ​​can be selected to form a new range, and the values ​​taken within the new range can be used.

[0091] In this embodiment, by combining silicon-carbon with different particle sizes and solid electrolyte, smaller particles are used to fill the pores constructed by larger particles, thereby achieving the construction of multi-level pores. This reduces the ineffective space between particles, making the spatial layout of particles in the silicon anode sheet more rational, thus providing more expansion space for nano-silicon, thereby alleviating the expansion of the silicon anode sheet and achieving the technical effect of effectively reducing the expansion rate of the silicon anode sheet.

[0092] Embodiment 2 of the present invention provides a method for preparing the above-mentioned silicon negative electrode sheet. Figure 1 This is a schematic flowchart of the method for preparing the silicon negative electrode sheet provided in Embodiment 2 of the present invention, as shown below. Figure 1 As shown, the preparation method provided in this embodiment includes:

[0093] S101. Mix the mixed silicon carbon and nano silicon in a mixer to obtain silicon anode premix.

[0094] The mixed silicon-carbon comprises a first silicon-carbon and a second silicon-carbon with different particle sizes, wherein the particle size distribution D of the first silicon-carbon is... 50 Particle size distribution D smaller than that of second silicon-carbon 50 .

[0095] In this step, first silicon carbon and second silicon carbon with different particle sizes, as well as nano silicon, need to be weighed in proportion and then placed in a mixer for mixing to obtain silicon anode premix.

[0096] Optionally, the mass ratio of mixed silicon-carbon to nano-silicon is 80:20 to 97:3.

[0097] Optionally, the particle size distribution D of the first silicon-carbon 50 =3~6μm; and / or, the particle size distribution D of the second silicon-carbon 50 =6~12μm.

[0098] Optionally, the mass ratio of the first silicon carbon to the second silicon carbon in the mixed silicon carbon is 50:50 to 85:15.

[0099] Optionally, the first silicon-carbon and / or the second silicon-carbon are silicon-carbon materials with a porous carbon framework.

[0100] Optionally, the mixer may be a planetary ball mill, a high-speed mixer, or a pulverizer.

[0101] Optionally, the mixing time of the mixed silicon carbon and nano silicon in the mixer is 10~120 min.

[0102] S102. The silicon anode premix and solid electrolyte are ground in a high-energy mixer to obtain a silicon anode composite material.

[0103] Among them, the particle size distribution D of the solid electrolyte 50 Particle size distribution D smaller than that of the first silicon-carbon 50 .

[0104] In this step, the silicon anode premix and solid electrolyte need to be weighed in proportion and then placed in a high-energy mixer for grinding to obtain the silicon anode composite material.

[0105] Optionally, the mass ratio of the mixture of silicon carbon and nano-silicon (i.e., silicon anode premix) to the solid electrolyte is 60:40 to 90:10.

[0106] Optionally, the particle size distribution D of the solid electrolyte 50 =0.3~1μm.

[0107] Optionally, the solid electrolyte is a sulfide electrolyte. Specifically, the sulfide electrolyte may include at least one of the following: a binary Li2S-P2S5 system sulfide solid electrolyte, a sulfide-germanium ore type sulfide solid electrolyte, and an LPSI type sulfide solid electrolyte.

[0108] Optionally, the particle size distribution D of the nano-silicon 50 =20~200nm.

[0109] Optionally, the high-energy mixer can be a high-energy ball mill, a fusion coating machine, or a high-temperature coating machine.

[0110] Optionally, the silicon anode premix and solid electrolyte are ground in a high-energy mixer at a speed of 250~600 rpm for a mixing time of 10~120 min.

[0111] S103. The silicon anode composite material and the conductive agent are mixed in a mixer to obtain the silicon anode composite material.

[0112] In this step, the silicon anode composite material and the conductive agent need to be weighed according to the ratio and then placed in a mixer for mixing to obtain the silicon anode composite material.

[0113] Optionally, the conductive agent is at least one of conductive carbon black, single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), vapor-grown carbon fibers (VGCFs), graphene, and acetylene black.

[0114] Optionally, the mass ratio of the solid electrolyte, nano-silicon, and mixed silicon-carbon mixture (i.e., silicon anode composite) to the conductive agent is 98.5:1.5 to 85:15.

[0115] S104. The silicon anode mixture, binder and solvent are homogenized using a homogenizing device according to the preset solid content to obtain silicon anode slurry.

[0116] In this step, the silicon anode mixture, binder, and solvent are weighed according to the specified ratio, and then homogenized using a homogenizing device to obtain the silicon anode slurry according to the preset solid content.

[0117] The solid content refers to the percentage of the mass of solid components (usually silicon anode mix and binder) in the silicon anode slurry relative to the total mass of the silicon anode slurry.

[0118] Optionally, the preset solid content is 15% to 50%. For example, the solid content is 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%, or any two of the aforementioned values ​​can be selected to form a new range, and the values ​​taken within the new range can be selected.

[0119] Optionally, the binder is at least one of polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), nitrile rubber (NBR), styrene-ethylene-butene-styrene copolymer (SEBS), polyacrylic acid (PAA), and styrene-butadiene-styrene copolymer (SBS).

[0120] Optionally, the binder accounts for 0.25% to 5% of the mass fraction of the silicon anode sheet.

[0121] Optional homogenizing equipment includes planetary ball mills, homogenizing emulsifiers, defoamers, planetary homogenizers, magnetic stirrs, or high-speed dispersers.

[0122] Optionally, the time for homogenizing the silicon anode mixture, binder, and solvent using a homogenizing device is 30~360 minutes.

[0123] S105. Apply silicon anode paste to the anode current collector to obtain silicon anode sheet.

[0124] In this step, silicon anode paste needs to be coated onto the anode current collector, and after processing, silicon anode sheet is obtained.

[0125] Optionally, the silicon anode paste can be coated on one side of the anode current collector, or the silicon anode paste can be coated on both sides of the anode current collector.

[0126] Optionally, the silicon anode paste can be coated onto the anode current collector by gravure coating, dagger coating, metering rod coating, or groove coating.

[0127] Optionally, the negative electrode current collector can be carbon-coated copper foil, stainless steel foil, carbon-coated stainless steel foil, or carbon-coated composite copper foil.

[0128] In some embodiments, after the silicon anode slurry is coated onto the anode current collector, it is first placed in a forced-air drying oven for pre-drying, and then transferred to a vacuum drying oven for drying treatment to obtain a silicon anode sheet.

[0129] Optionally, the pre-drying temperature is 40~80℃ and the time is 30~720min.

[0130] Optionally, the drying process is carried out at a temperature of 90-150℃ for 2-12 hours.

[0131] The method for preparing the silicon anode sheet provided in this embodiment can be used for the silicon anode sheet in Embodiment 1 of the present invention, and the prepared silicon anode sheet has a low expansion rate.

[0132] Embodiment 3 of the present invention provides a solid-state battery, including the silicon anode sheet provided by the present invention.

[0133] In practical applications, solid-state batteries include a positive electrode, a solid electrolyte layer, and a silicon negative electrode provided by this invention. Specifically, the positive electrode includes a positive current collector and a positive active layer formed of a positive active material disposed on the surface of the current collector. The solid electrolyte can be a conventional solid electrolyte in the art, such as a sulfide electrolyte or an oxide electrolyte. This invention does not impose specific limitations on the selection and preparation of the positive electrode and solid electrolyte in solid-state batteries.

[0134] The solid-state battery provided by the present invention comprises a silicon anode sheet with low expansion rate and excellent rate performance, and the cycle stability and rate performance of the solid-state battery are also improved accordingly.

[0135] Embodiment 4 of the present invention provides an electrical device, including a main body of the electrical device and a solid-state battery provided by the present invention.

[0136] It should be noted that the present invention does not particularly limit the type of electrical device, which can be any electrical device including the battery, including but not limited to electric vehicles, mobile phones, portable devices, laptops, electric bicycles, electric toys, energy storage devices, etc.

[0137] The present invention will be further described below through specific embodiments.

[0138] Example 1

[0139] 1) Preparation of silicon negative electrode sheet:

[0140] S1. Weigh 40g of D 50 =4.5μm first silicon-carbon, 20g D 50 =8.2μm second silicon-carbon and 6.5g D 50 =100nm nano-silicon was mixed in a pulverizer for 1 minute to obtain silicon anode premix;

[0141] S2, Weigh 28.5g of D 50 =0.7μm Li7P2S8Br 0.5 I 0.5 The silicon anode premix was ground in a high-energy ball mill at 320 rpm for 20 min to obtain the silicon anode composite material.

[0142] S3. Weigh 0.5g of SWCNT, 2.5g of VGCF and silicon anode composite material and mix them in a planetary ball mill at 450rpm for 60min to obtain silicon anode mixture.

[0143] S4. Weigh 2g of SEBS as binder, use toluene as solvent to prepare the adhesive solution, mix it with the silicon anode mixture, and homogenize it in a planetary ball mill at 400rpm for 120min with a solid content of 40% to obtain a uniform silicon anode slurry.

[0144] S5. The slurry is applied to carbon-coated copper foil, pre-dried in a forced-air oven at 80°C for 60 minutes, and then transferred to a vacuum oven at 100°C for 8 hours to obtain a silicon negative electrode sheet.

[0145] 2) Preparation of the electrolyte layer:

[0146] Weigh Li according to the mass ratio 5.5 PS 4.5 Cl 1.5 And PTFE, and formed an electrolyte layer with a thickness of 80 μm, wherein Li 5.5 PS 4.5 Cl 1.5 The mass ratio is 99.5:0.5.

[0147] 3) Solid-state battery assembly:

[0148] The electrolyte layer is transferred onto a silicon anode electrode, a 50μm lithium-copper composite strip is used, and the electrode unit is die-cut to the designed size. It is then cold-pressed at 500MPa for 30s, stacked in the order of silicon anode electrode - electrolyte layer - lithium metal, and held at 2MPa for 30s to obtain a solid-state battery.

[0149] Example 2

[0150] 1) Preparation of silicon negative electrode sheet:

[0151] S1. Weigh 25g of D 50 =4.0μm first silicon-carbon, 25g D 50 =12.0μm second silicon-carbon and 6.1g D 50 =150nm nano-silicon was mixed in a pulverizer for 1 minute to obtain silicon anode premix;

[0152] S2, Weigh 37.4g of D 50 =0.5μm Li 5.8 PS 4.8 ClI 0.2 The silicon anode premix was ground in a high-energy ball mill at 400 rpm for 10 min to obtain the silicon anode composite material.

[0153] S3. Weigh 0.5g of SWCNT, 2.5g of VGCF, 1g of conductive carbon black and silicon anode composite material and mix them in a planetary ball mill at 400rpm for 40min to obtain silicon anode mixture.

[0154] S4. Weigh 2.5g of SBS as binder, use xylene and anisole (ratio 1:1) as solvents to prepare adhesive solution, mix with silicon anode mixture, and homogenize in a planetary ball mill at 420rpm for 100min with a solid content of 35% to obtain uniform silicon anode slurry.

[0155] S5. The slurry is applied to carbon-coated copper foil and pre-dried in a forced-air oven at 70°C for 40 minutes. Then, it is transferred to a vacuum oven and dried at 90°C for 6 hours to obtain a silicon negative electrode sheet.

[0156] 2) Preparation of electrolyte layer: Same as in Example 1.

[0157] 3) Solid-state battery assembly: Same as in Example 1.

[0158] Example 3

[0159] 1) Preparation of silicon negative electrode sheet:

[0160] S1. Weigh 35.5g of D 50 =6.3μm first silicon-carbon, 11.9g D 50 =7.5μm second silicon-carbon and 20g D 50 =150nm nano-silicon was mixed in a pulverizer for 1 minute to obtain silicon anode premix;

[0161] S2, Weigh 28.9g of D 50 Li = 0.8 μm 5.5 PS 4.5 Cl1.5 The silicon anode premix was ground in a high-energy ball mill at 320 rpm for 50 min to obtain the silicon anode composite material.

[0162] S3. Weigh 0.2g of SWCNT, 2g of VGCF and silicon anode composite material and mix them in a planetary ball mill at 400rpm for 40min to obtain silicon anode mixture.

[0163] S4. Weigh 0.75g of SEBS and 0.75g of SBS as binders, use xylene as a solvent to prepare the adhesive solution, mix it with the silicon anode mixture, and homogenize it in a planetary ball mill at 360rpm for 60min with a solid content of 45% to obtain a uniform silicon anode slurry.

[0164] S5. The slurry is applied to carbon-coated copper foil, pre-dried in a forced-air oven at 60°C for 60 minutes, and then transferred to a vacuum oven at 90°C for 16 hours to obtain a silicon negative electrode sheet.

[0165] 2) Preparation of electrolyte layer: Same as in Example 1.

[0166] 3) Solid-state battery assembly: Same as in Example 1.

[0167] Example 4

[0168] 1) Preparation of silicon negative electrode sheet:

[0169] S1. Weigh 60g of D 50 =4.1μm first silicon-carbon, 11.9g D 50 =10.5μm second silicon-carbon and 3g D 50 =150nm nano-silicon was mixed in a pulverizer for 1 minute to obtain silicon anode premix;

[0170] S2, Weigh 18.4g of D 50 =0.3μm Li6PS5Cl 0.5 Br 0.5 The silicon anode premix was ground in a high-energy ball mill at 300 rpm for 40 min to obtain the silicon anode composite material.

[0171] S3. Weigh 1.5g of SWCNT, 4.5g of VGCF and silicon anode composite material and mix them in a planetary ball mill at 400rpm for 40min to obtain silicon anode mixture.

[0172] S4. Weigh 1.75g ​​of SEBS and 0.25g of PVDF as binders, use toluene and ethyl butyrate (ratio 1:1) as solvents to prepare the adhesive solution, mix it with the silicon anode mixture, and homogenize it in a planetary ball mill at 360rpm for 60min with a solid content of 45% to obtain a uniform silicon anode slurry.

[0173] S5. The slurry is applied to carbon-coated copper foil and pre-dried in a forced-air oven at 55°C for 60 minutes. Then, it is transferred to a vacuum oven and dried at 80°C for 10 hours to obtain a silicon negative electrode sheet.

[0174] 2) Preparation of electrolyte layer: Same as in Example 1.

[0175] 3) Solid-state battery assembly: Same as in Example 1.

[0176] Example 5

[0177] 1) Preparation of silicon negative electrode sheet:

[0178] S1. Weigh 36.5g of D 50 =5μm first silicon-carbon, 30g D 50 =10μm of second silicon-carbon and 10g of D 50 =80nm nano-silicon was mixed in a pulverizer for 10 minutes to obtain silicon anode premix;

[0179] S2, Weigh 13.5g of D 50 Li7P2S8I with a particle size of 1 μm and silicon anode premix were ground in a high-energy ball mill at a speed of 250 rpm for 50 min to obtain silicon anode composite material.

[0180] S3. Weigh 2g of conductive carbon black, 5g of VGCF and silicon anode composite material and mix them in a planetary ball mill at 400rpm for 40min to obtain silicon anode mixture.

[0181] S4. Weigh 3g of SEBSF as a binder, and use xylene, ethyl butyrate and anisole (ratio 1:2:1) as solvents to prepare the adhesive solution. Mix it with the silicon anode mixture, and homogenize it in a planetary ball mill at 360 rpm for 80 minutes with a solid content of 45% to obtain a uniform silicon anode slurry.

[0182] S5. The slurry is applied to carbon-coated copper foil and pre-dried in a forced-air oven at 55°C for 60 minutes. Then, it is transferred to a vacuum oven and dried at 80°C for 10 hours to obtain a silicon negative electrode sheet.

[0183] 2) Preparation of electrolyte layer: Same as in Example 1.

[0184] 3) Solid-state battery assembly: Same as in Example 1.

[0185] Comparative Example 1

[0186] The difference from Example 1 is that the average particle size D of the first silicon-carbon and the second silicon-carbon is... 50 All are 8.2 μm; no electrolyte is added.

[0187] Comparative Example 2

[0188] The difference from Example 1 is that the electrolyte (Li7P2S8Br) 0.5 I 0.5 The average particle size D 50 =2μm.

[0189] Comparative Example 3

[0190] The difference from Example 1 is that the mass of the first silicon carbon is 51.4 g, the mass of the second silicon carbon is 25.7 g, and the mass of the nano-silicon is 8.4 g; the electrolyte (Li7P2S8Br) 0.5 I 0.5 The weight of ) is 9.5g.

[0191] Comparative Example 4

[0192] The difference from Example 1 is that the mass of the first silicon carbon is 20g and the mass of the second silicon carbon is 40g.

[0193] Comparative Example 5

[0194] The difference from Example 1 is that the particle size distribution D of the first silicon-carbon is... 50 =10.0μm, the particle size distribution D of the second silicon-carbon 50 =15.0μm.

[0195] The electrochemical performance of the solid-state batteries prepared in the above embodiments and comparative examples was tested, and the test results are shown in Table 1. The specific test contents are as follows:

[0196] 1. Test of the expansion rate of the full electrode sheet:

[0197] Specifically, the initial thickness of the silicon anode sheet is tested; after the solid-state battery is fully charged, the second thickness of the silicon anode sheet is tested; based on the initial thickness and the second thickness of the silicon anode sheet, the full-charge sheet expansion rate is calculated.

[0198] 2. Ratio performance testing:

[0199] Test conditions: Test temperature was 25℃, and the equivalent pressure was 2MPa. Test procedure: First, the battery was discharged at a constant current of 0.1C to 1.5V, then discharged at a current of 0.1C to 0.05V to obtain the 0.1C charging capacity. After resting for 5 minutes, one cycle was completed. This charge-discharge cycle was repeated 2 times. Then, a charge-discharge cycle test was performed at a current of 1C to obtain the battery's initial 1C capacity and 1C capacity retention rate.

[0200] Table 1. Electrochemical performance test results of solid-state batteries

[0201]

[0202] Based on the test results in Table 1 above, it can be seen that compared with Comparative Example 1, the full-load electrode expansion rate of the solid-state battery containing silicon carbon with different particle sizes and solid electrolyte in the silicon anode slurry is significantly lower, and the 0.1C charging capacity, 1C charging capacity and 1C capacity retention rate are significantly higher. It can be seen that silicon carbon with different particle sizes and solid electrolyte can effectively improve the expansion problem and rate performance of silicon anode sheets.

[0203] Furthermore, based on the test data from Examples 1, 2, and 3, an excessively large particle size distribution of the solid electrolyte or an excessive proportion of solid electrolyte will lead to a decrease in both the rate performance and expansion performance of the silicon anode sheet. It is evident that both the particle size and proportion of the solid electrolyte affect the uniformity of the solid electrolyte distribution in the silicon anode slurry. Therefore, selecting a suitable particle size of solid electrolyte and determining a suitable proportion of solid electrolyte can further improve the rate performance and expansion performance of the silicon anode sheet provided by this invention.

[0204] Furthermore, based on the test data from Examples 1, 4, and 5, the mixed silicon-carbon material showed a significantly higher proportion of larger particle sizes than smaller particle sizes, or all silicon-carbon particles in the mixed silicon-carbon material were excessively large. This resulted in a decrease in both the rate performance and expansion performance of the silicon anode electrode. Therefore, the mixing ratio of silicon-carbon particles of different sizes and the particle size of each type of silicon-carbon material also affect the rate performance and expansion performance of the silicon anode electrode. Thus, selecting silicon-carbon particles of appropriate sizes and determining the mixing ratio of silicon-carbon particles of different sizes can further improve the rate performance and expansion performance of the silicon anode electrode provided by this invention.

[0205] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A silicon negative electrode sheet, characterized in that, The silicon anode electrode includes: an anode current collector and a silicon anode slurry coated on the surface of the anode current collector; The silicon anode slurry includes a solid electrolyte, nano-silicon, mixed silicon carbon, conductive agent, binder, and solvent. The mixed silicon carbon includes first silicon carbon and second silicon carbon with different particle sizes. Wherein, the particle size distribution D of the solid electrolyte 50 The particle size distribution D is smaller than that of the first silicon-carbon. 50 And the particle size distribution D of the first silicon-carbon 50 The particle size distribution D is smaller than that of the second silicon-carbon. 50 ; The particle size distribution D of the first silicon-carbon 50 =3~6μm; and / or, the particle size distribution D of the second silicon carbide 50 =6~12μm; The mass ratio of the first silicon carbon to the second silicon carbon in the mixed silicon carbon is 50:50 to 85:

15. The mass ratio of the mixture of the mixed silicon-carbon and the nano-silicon to the solid electrolyte is 60:40 to 90:

10. The particle size distribution D of the solid electrolyte 50 =0.3~1μm.

2. The silicon negative electrode sheet according to claim 1, characterized in that, The mass ratio of the mixed silicon-carbon to the nano-silicon is 80:20 to 97:

3.

3. The silicon negative electrode sheet according to claim 1 or 2, characterized in that, The first silicon-carbon and / or the second silicon-carbon are silicon-carbon materials with porous carbon as the framework.

4. The silicon negative electrode sheet according to claim 1 or 2, characterized in that, The solid electrolyte is a sulfide electrolyte.

5. The silicon negative electrode sheet according to claim 4, characterized in that, The sulfide electrolyte includes at least one of the following: binary Li2S-P2S5 system sulfide solid electrolyte, sulfide solid electrolyte of silver-germanium ore type, and lithium-phosphorus-sulfide-iodine type sulfide solid electrolyte.

6. The silicon negative electrode sheet according to claim 5, characterized in that, The expressions for both the binary Li₂S-P₂S₅ system sulfide solid electrolyte and the sulfide solid electrolyte of the argillium sulfide type are xLi₂S·(100-xz)A. y S n ·zB; Among them, 0 < x < 100, y is 0, 1 or 2, n is 2y or 2y + 1, 0 ≤ z < 100 - x, and A is B 3+ 、Si 4+ 、P 3+ 、P 5+ or Ge 4+ , and B is LiCl, LiBr, LiI, Li3PO4, GeS2, P2O5, Li4SiO4 or P2S3; And / or, When the S-site dopant element in the lithium-phosphorus-sulfur-iodine type sulfide solid electrolyte is a +5 valence element, the expression for the lithium-phosphorus-sulfur-iodine type sulfide solid electrolyte is: ; When the S-site dopant element is a +4 valence element, the expression for the lithium-phosphorus-sulfur-iodine type sulfide solid electrolyte is: Where 0.01≤a≤2, 0.01≤b≤1, 0.01≤c≤1, A is the P-site dopant element, B is the S-site dopant element, and C is the I-site dopant element.

7. The silicon negative electrode sheet according to claim 1 or 2, characterized in that, The particle size distribution D of the nano-silicon 50 =20~200nm.

8. The silicon negative electrode sheet according to claim 1 or 2, characterized in that, The conductive agent is at least one of conductive carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, vapor-grown carbon fibers, and graphene. And / or, The adhesive is at least one of polytetrafluoroethylene, styrene-butadiene rubber, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, nitrile rubber, styrene-ethylene-butene-styrene copolymer, polyacrylic acid, and styrene-butadiene-styrene copolymer.

9. The silicon negative electrode sheet according to claim 1 or 2, characterized in that, The mass ratio of the solid electrolyte, the nano-silicon, and the mixed silicon-carbon substance to the conductive agent is 98.5:1.5 to 85:

15.

10. The silicon negative electrode sheet according to claim 1 or 2, characterized in that, The binder accounts for 0.25% to 5% of the mass fraction of the silicon anode sheet.

11. A method for preparing a silicon negative electrode sheet according to any one of claims 1 to 10, characterized in that, The method includes: Mixed silicon-carbon and nano-silicon are combined in a mixer to obtain a silicon anode premix. The mixed silicon-carbon comprises a first silicon-carbon and a second silicon-carbon with different particle sizes. The particle size distribution D of the first silicon-carbon is... 50 The particle size distribution D is smaller than that of the second silicon-carbon. 50 ; The silicon anode premix and solid electrolyte are ground in a high-energy mixer to obtain a silicon anode composite material. The particle size distribution D of the solid electrolyte is... 50 The particle size distribution D is smaller than that of the first silicon-carbon. 50 ; The silicon anode composite material and the conductive agent are mixed in a mixer to obtain a silicon anode mixture. The silicon anode mixture, binder, and solvent are homogenized using a homogenizing device to obtain a silicon anode slurry with a preset solid content. The silicon anode slurry is coated onto the anode current collector to obtain the silicon anode sheet.

12. A solid-state battery, characterized in that, Includes the silicon anode sheet according to any one of claims 1 to 10.

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