Negative electrode material and preparation method thereof, and solid-state battery

Abstract

The embodiment of the application provides a kind of negative electrode material and its preparation method, solid-state battery, relating to solid-state battery technical field.The negative electrode material includes graphite material and the porous carbon intermediate layer and amorphous carbon coating layer successively coated on the surface of graphite material, wherein the porous carbon intermediate layer includes porous carbon, and silicon nanoparticles and sulfide solid-state electrolyte material are dispersed in the pore of porous carbon;The amorphous carbon coating layer includes amorphous carbon.The present scheme at least solves the problem that the existing technology is not complete, not uniform, which leads to serious silicon and solid-state electrolyte interface side reaction and interface stress concentration, structure failure in the process of volume expansion.

Description

Technical Field

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

[0002] The rapid development of electric vehicles and the large-scale energy storage market has placed unprecedented demands on the energy density and safety of lithium-ion batteries, making all-solid-state batteries the core development direction for next-generation power batteries. However, the commercial application of all-solid-state batteries still faces many severe challenges, one of which stems from the anode material system. Currently, the theoretical capacity of commercial graphite anodes is low (~372 mAh / g), making it difficult to meet the high energy density requirements of all-solid-state batteries. Silicon materials, due to their extremely high theoretical specific capacity (~4200 mAh / g), have become one of the most promising alternatives. However, the dramatic volume expansion (>300%) of silicon materials during cycling can lead to electrode structure damage and rapid capacity decay. This problem is particularly prominent in all-solid-state batteries: First, in liquid batteries, the electrolyte can penetrate cracks and repair the unstable SEI film; however, in all-solid-state batteries, the solid-solid interface is prone to peeling when the silicon volume changes repeatedly, forming gaps, significantly increasing interfacial impedance and blocking ion transport, leading to battery failure. Second, to maintain good solid-solid contact, a large external pressure is usually required, which hinders the practical application of all-solid-state batteries.

[0003] Currently, a common improvement method is to combine silicon with graphite. However, simple physical mixing makes it difficult to achieve uniform dispersion and strong bonding. Silicon is prone to detaching from graphite during cycling, exposing its surface and undergoing side reactions with the solid electrolyte. In addition, traditional coating techniques (such as liquid phase coating and mechanical mixing) are not easy to form a complete, dense coating layer with controllable thickness, which cannot effectively limit the volume expansion of silicon or isolate it from contact with the solid electrolyte.

[0004] There is currently no good solution to the above problems. Summary of the Invention

[0005] This application provides an anode material and its preparation method, as well as a solid-state battery, to at least solve the problems in the prior art where incomplete or uneven coating of the anode material leads to severe side reactions at the interface between silicon and the solid electrolyte, as well as interface stress concentration and structural failure during volume expansion.

[0006] According to one aspect of the embodiments of this application, a negative electrode material is provided, comprising a graphite material and a porous carbon intermediate layer and an amorphous carbon coating layer sequentially coated on the surface of the graphite material, wherein the porous carbon intermediate layer comprises porous carbon, and silicon nanoparticles and sulfide solid electrolyte material are dispersed in the pores of the porous carbon; the amorphous carbon coating layer comprises amorphous carbon.

[0007] Furthermore, by mass percentage, the aforementioned anode material comprises: 10%-50% graphite material, 20%-69% porous carbon, 0.1%-10% sulfide solid electrolyte material, 20%-69% silicon nanoparticles, and 0.1%-10% amorphous carbon; and / or, the porous carbon has a pore size of (0.1~80) nm and a specific surface area of ​​100 m². 2 / g~3000m 2 / g, with a porosity of 30~80%; and / or, the ratio of the thickness of the amorphous carbon coating layer to the thickness of the porous carbon interlayer is (0.1~50) nm : (0.1~10) nm; and / or, the sulfide solid electrolyte material is Li 6-x P 1+y S 5-x Cl 1+x At least one of the following, wherein 0 ≤ x ≤ 0.5 and 0 ≤ y ≤ 0.5.

[0008] Furthermore, the ratio of the median particle size of the silicon-carbon composite material to the median particle size of the graphite material is (10~100) μm: (10~20) μm; and / or, the graphite is artificial graphite particles or natural graphite secondary particles.

[0009] To achieve the above objectives, according to another aspect of the present invention, a method for preparing the above-mentioned negative electrode material is provided, the method comprising: step S1, heat-treating raw materials including graphite material and coating agent under an inert atmosphere to obtain carbon-coated graphite material; step S2, using an activator to perform activation and pore-forming treatment on the carbon-coated graphite material, and washing and drying the material obtained by the activation and pore-forming treatment sequentially to obtain porous carbon-coated graphite material; step S3, dispersing the porous carbon-coated graphite material and solid electrolyte powder in a solvent under an inert atmosphere to obtain a mixture; step S4, subjecting the mixture to pressure spray drying and then sintering to obtain a graphite / porous carbon / solid electrolyte intermediate material; step S5, performing vapor deposition of the intermediate material and a silicon-containing compound to obtain a silicon-carbon composite material precursor; and step S6, performing carbon coating treatment on the silicon-carbon composite material precursor to obtain the negative electrode material.

[0010] Further, in step S1 above, the mass ratio of the coating agent to the graphite material is (3~8):(2~7), preferably the coating agent is one or more of phenolic resin and asphalt; and / or, the flow rate of the inert atmosphere is 2L / min-20L / min, preferably the inert atmosphere is one or more of nitrogen atmosphere and argon atmosphere; the heat treatment temperature is 500-1200℃; and the heat treatment heating time is 2-6h.

[0011] Further, in step S2 above, the mass ratio of porous carbon to the activator is 1:(0.5-10), and the activator is preferably one or more of water vapor, carbon dioxide, potassium hydroxide, sodium hydroxide, zinc chloride, and phosphoric acid; the activation temperature is 600-800℃; the activation time is 2-4h; and / or, the washing process includes a first-stage washing and a second-stage washing. The first-stage washing process includes: performing a first cleaning on the material obtained from the activated pore-forming treatment with a 2mol / L hydrochloric acid solution to obtain a cleaned product, wherein the first cleaning time is 6-12h; the second-stage washing process includes: performing a second cleaning on the cleaned product with deionized water until the pH of the cleaned product is neutral.

[0012] Further, in step S3 above, the mass ratio of the porous carbon-coated graphite material to the solid electrolyte is (50-90):(10-50); the total mass ratio of the porous carbon-coated graphite material and the solid electrolyte to the volume ratio of the solvent is (1:10~50) g / mL; the solvent is one or more of methanol, ethanol, acetonitrile, benzyl alcohol, tetrahydrofuran, anisole, dimethylformamide and ethylene glycol.

[0013] Furthermore, in step S4 above, the pressure of pressure spray drying is 5-25 MPa, the flow rate of pressure spray drying is 10-50 mL / min, and the temperature of pressure spray drying is 80-250℃; and / or, the sintering temperature is 500-800℃, and the sintering time is 1-12 h.

[0014] Further, in step S5 above, the silicon-containing compound and the intermediate material are vapor-deposited using a carrier gas. The carrier gas is one or more of nitrogen and argon, and the flow rate of the carrier gas is 2L / min-20L / min. The silicon-containing compound includes one or more of metallic silicon vapor, silane, propane, dichlorosilane, trichlorosilane, and tetrachlorosilane. The vapor-phase deposition temperature is 400-1600℃, and the vapor-phase deposition time is 1-24h.

[0015] According to another aspect of the embodiments of this application, a solid-state battery is also provided. The solid-state battery includes a positive electrode and a negative electrode. The negative electrode includes the negative electrode material described above, or a negative electrode material prepared by the preparation method described above.

[0016] In this embodiment, the porous carbon interlayer formed on the graphite surface provides space for in-situ confined deposition of silicon nanoparticles, limiting their radial expansion during lithiation / delithiation. Simultaneously, the sulfide solid electrolyte material embedded in the pores actively introduces ion conductors into the interior of the negative electrode material, achieving three-dimensional interconnection of solid-solid ion channels at the electrode particle scale. This shortens the lithium-ion transport path within the electrode, reduces interfacial charge transfer resistance, and alleviates localized current density unevenness and interfacial passivation caused by poor solid-solid contact. The outermost carbon coating layer acts as a physical isolation layer, effectively preventing excessive mixing or interfacial structural instability between the internal porous carbon-silicon-electrolyte composite structure and the external solid electrolyte layer due to mechanical stress during long-term cycling. Thanks to the pre-constructed three-dimensional ion transport network, the transphase transport of lithium ions no longer entirely depends on the outer carbon / solid electrolyte interface, improving ion conductivity while minimizing harmful interfacial side reactions. Therefore, this structural design can achieve long-term stable contact between the negative electrode and the electrolyte interface in an all-solid-state battery without relying on external high voltage. Detailed Implementation

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0018] As analyzed in the background section, the existing technology has the technical problem that incomplete or uneven coating of the negative electrode material leads to poor contact between silicon and the solid electrolyte. To solve this problem, the present invention provides a negative electrode material, its preparation method, and a solid-state battery.

[0019] According to an embodiment of this application, a negative electrode material is provided, comprising a graphite material and a porous carbon intermediate layer and an amorphous carbon coating layer sequentially coated on the surface of the graphite material. The porous carbon intermediate layer comprises porous carbon, and silicon nanoparticles and sulfide solid electrolyte material are dispersed in the pores of the porous carbon. The amorphous carbon coating layer comprises amorphous carbon.

[0020] The porous carbon interlayer formed on the graphite surface provides in-situ confined deposition space for silicon nanoparticles, limiting their radial expansion during lithiation / delithiation. Simultaneously, the sulfide solid electrolyte material embedded within the pores actively introduces ion conductors into the interior of the negative electrode material, achieving three-dimensional solid-solid ion channel connectivity at the electrode particle scale. This shortens the lithium-ion transport path within the electrode, reduces interfacial charge transfer resistance, and alleviates localized current density unevenness and interfacial passivation caused by poor solid-solid contact. The outermost carbon coating layer acts as a physical isolation layer, effectively preventing excessive mixing or interfacial structural instability between the internal porous carbon-silicon-electrolyte composite structure and the external solid electrolyte layer due to mechanical stress during long-term cycling. Thanks to the pre-constructed three-dimensional ion transport network, lithium-ion transphase transport no longer entirely depends on the outer carbon / solid electrolyte interface, improving ionic conductivity while minimizing harmful interfacial side reactions. Therefore, this structural design can achieve long-term stable contact between the negative electrode and the electrolyte interface in an all-solid-state battery without relying on external high voltage.

[0021] In one embodiment of this application, the negative electrode material comprises, by mass percentage, 10%-50% graphite material, 20%-69% porous carbon, 0.1%-10% sulfide solid electrolyte material, 20%-69% silicon nanoparticles, and 0.1%-10% amorphous carbon; and / or, the porous carbon has a pore size of (0.1~80) nm and a specific surface area of ​​100 m². 2 / g~3000m 2 / g, with a porosity of 30~80%; and / or, the ratio of the thickness of the amorphous carbon coating layer to the thickness of the porous carbon interlayer is (0.1~50) nm : (0.1~10) nm; and / or, the sulfide solid electrolyte material is Li 6-x P 1+y S 5-x Cl 1+x At least one of the following, wherein 0 ≤ x ≤ 0.5 and 0 ≤ y ≤ 0.5.

[0022] By compounding graphite materials, porous carbon, silicon nanoparticles, sulfide solid electrolyte materials and amorphous carbon in a specific mass ratio, a layered structure is constructed in which a porous carbon intermediate layer and an amorphous carbon coating layer are sequentially coated on the surface of the graphite matrix, thus buffering the volume expansion during its cycling process.

[0023] Anode materials that control the size, specific surface area, porosity of porous carbon, and the size of the amorphous carbon coating layer within the above-mentioned ranges exhibit structural integrity, low interfacial impedance, and high ion conductivity during cycling, which can suppress capacity decay and improve the cycle stability and rate performance of the battery.

[0024] In one embodiment of this application, the ratio of the median particle size of the silicon-carbon composite material to the median particle size of the graphite material is (10~100) μm: (10~20) μm; and / or, the graphite is artificial graphite particles or natural graphite secondary particles.

[0025] In the all-solid-state system, the electrode is directly cold-pressed from dry powder, and the particle size directly affects the tablet density and the number of contact points. By controlling the particle size of the composite particles within the aforementioned range, the size range of the solid electrolyte particles can be matched, allowing the graphite-based multilayer structure to fully leverage its structural advantages during the pressing process: the inner graphite layer provides stable mechanical support and an electronic conduction core, while the silicon deposited in the confined space of the outer porous carbon framework, together with the pre-filled solid electrolyte, constructs a three-dimensional interconnected ion / electron hybrid conduction network. The synergistic effect of these two elements significantly improves the uniformity of interfacial contact and charge transport efficiency while ensuring the overall structural integrity of the electrode, thereby achieving a high-density, low-impedance electrode structure without the assistance of a liquid medium.

[0026] In another typical embodiment of this application, a method for preparing the aforementioned negative electrode material is provided. The method includes: step S1, heat-treating raw materials including graphite material and coating agent in an inert atmosphere to obtain carbon-coated graphite material; step S2, using an activator to activate and create pores in the carbon-coated graphite material, and washing and drying the material obtained from the activation and pore-creating treatment to obtain porous carbon-coated graphite material; step S3, dispersing the porous carbon-coated graphite material and solid electrolyte powder in a solvent in an inert atmosphere to obtain a mixture; step S4, subjecting the mixture to pressure spray drying and then sintering to obtain a graphite / porous carbon / solid electrolyte intermediate material; step S5, performing vapor deposition of the intermediate material and a silicon-containing compound to obtain a silicon-carbon composite material precursor; and step S6, performing carbon coating treatment on the silicon-carbon composite material precursor to obtain the negative electrode material.

[0027] The surface of graphite material is pyrolyzed and carbonized under an inert atmosphere using a coating agent, forming a dense but non-porous amorphous carbon shell. At this point, the graphite transforms from exposed crystalline particles into carbon-coated graphite. Selective etching of the carbon coating layer using a strong activator opens up the disordered carbon structure within the carbon layer, forming a large network of micro-mesopores, increasing the specific surface area and porosity. The porous carbon-coated graphite is co-dispersed with sulfide solid electrolyte powder in a solvent and pressure-spray dried to form micron-sized droplets. These droplets are then instantaneously dried and sintered at high temperature, causing the solid electrolyte particles to form on the pore surface or inner wall of the porous carbon. Through vapor deposition, the silicon-containing precursor is pyrolyzed at high temperature, and silicon atoms nucleate and grow into nanoscale silicon particles within the pores of the porous carbon. The entire process achieves stable construction of the solid-solid interface within the anode material without relying on external pressure, improving the material's structural integrity and electrochemical kinetic performance.

[0028] To construct a uniform, dense, structurally controllable, and thermally stable initial carbon coating layer, laying a high-quality foundation for subsequent porous carbon formation, confined silicon deposition, and overall structural stability, in step S1, the preferred mass ratio of coating agent to graphite material is (3~8):(2~7), and the preferred coating agent is one or more of phenolic resin and asphalt; and / or, the flow rate of the inert atmosphere is 2L / min-20L / min, and the preferred inert atmosphere is one or more of nitrogen atmosphere and argon atmosphere; the heat treatment temperature is 500-1200℃; and the heat treatment heating time is 2-6h.

[0029] By controlling the proportion and type of coating agent, the flow rate of inert atmosphere, and the heat treatment temperature and time within the above range, a uniform, continuous, and strongly supportive carbon coating layer can be formed.

[0030] To construct a porous carbon shell with high specific surface area, uniform micro-mesoporous structure, and extremely low impurity content based on carbon-coated graphite through controllable activation pore formation and precise acid washing purification, in step S2, the preferred mass ratio of porous carbon to activator is 1:(0.5-10), and the preferred activator is one or more of water vapor, carbon dioxide, potassium hydroxide, sodium hydroxide, zinc chloride, and phosphoric acid; the activation temperature is 600-800℃; the activation time is 2-4h; and / or, the washing process includes a first-stage washing and a second-stage washing. The first-stage washing process includes: first washing the material obtained from the activation pore formation treatment with a 2mol / L hydrochloric acid solution to obtain a cleaned product, wherein the first washing time is 6-12h; the second-stage washing process includes: second washing the cleaned product with deionized water until the pH of the cleaned product is neutral.

[0031] By controlling the proportion and type of activator, activation temperature, and the number of two-stage washing chambers within the above range, a porous carbon carrier with high specific surface area, stable structure, and chemical purity can be constructed, enabling deep embedding of solid electrolytes and precise confined deposition of silicon nanoparticles, thereby improving the ion transport efficiency, volume buffering capacity, and interface stability of the anode material.

[0032] To control the solid-solid mixing ratio and solvent system, and to achieve uniform, deep, and non-agglomerated embedding of sulfide solid electrolyte in the porous carbon-coated graphite material pore structure, thereby constructing an integrated electrode-electrolyte three-dimensional ion-conducting network, in step S3, the preferred ratio of the mass of the porous carbon-coated graphite material to the mass of the solid electrolyte is (50-90):(10-50); the ratio of the total mass of the porous carbon-coated graphite material and the solid electrolyte to the volume of the solvent is (1:10~50) g / mL; and the solvent is one or more of methanol, ethanol, acetonitrile, benzyl alcohol, tetrahydrofuran, anisole, dimethylformamide, and ethylene glycol.

[0033] To efficiently transform solid-solid mixed slurry into a structurally complete and uniformly composed integrated graphite / porous carbon / solid electrolyte intermediate, and to achieve stable anchoring and preliminary bonding of the electrolyte in the porous carbon pores, in step S4, the pressure of pressure spray drying is preferably 5-25 MPa, the flow rate of pressure spray drying is 10-50 mL / min, and the temperature of pressure spray drying is 80-250℃; and / or, the sintering temperature is 500-800℃, and the sintering time is 1-12 h.

[0034] By controlling the pressure, flow rate, temperature, sintering temperature, and time of pressure spray drying within the aforementioned range, uniform loading and stable anchoring of solid electrolyte particles on the porous carbon-coated graphite surface are achieved. This avoids droplet splashing, particle agglomeration, or solvent residue caused by excessively fast drying rates, as well as electrolyte decomposition and interfacial loosening caused by excessively high sintering temperatures or excessively long sintering times.

[0035] To achieve in-situ, confined, and uniform deposition of silicon nanoparticles in the porous structure of carbon-coated graphite / solid electrolyte intermediates, and to construct a composite structure of "silicon synergistically confined by carbon shell and electrolyte", in preferred step S5, silicon-containing compounds and intermediate materials are vapor-deposited using a carrier gas. The carrier gas is one or more of nitrogen and argon, and the flow rate of the carrier gas is 2 L / min-20 L / min. The silicon-containing compound includes one or more of metallic silicon vapor, silane, propane, dichlorosilane, trichlorosilane, and tetrachlorosilane. The vapor-phase deposition temperature is 400-1600℃, and the vapor-phase deposition time is 1-24 h.

[0036] By using one or more of nitrogen and argon as carrier gases and controlling the flow rate within the range of 2L / min-20L / min, the delivery rate of silicon-containing compounds can be effectively stabilized, ensuring that they enter the deposition reaction zone uniformly and controllably. This avoids uneven distribution of precursors due to excessively low airflow or turbulent disturbances that damage the pore structure due to excessively high airflow. Combined with a deposition temperature of 400-1600℃ and a reaction time of 1-24h, the nucleation density, growth rate, and particle size of silicon nanoparticles can be controlled, promoting in-situ, uniform, and confined deposition of silicon within the pores of porous carbon-coated graphite materials. This avoids excessive silicon growth that could lead to pore blockage or particle agglomeration.

[0037] In another typical embodiment of this application, a solid-state battery is provided, which includes a positive electrode and a negative electrode. The negative electrode includes the negative electrode material described above, or a negative electrode material prepared by the preparation method described above.

[0038] The negative electrode employs a composite material with a multi-level coating structure. The graphite core in the composite material provides mechanical support, while the outer amorphous carbon coating layer synergistically strengthens the constraint on silicon volume expansion, maintaining the integrity of the electrode structure. The porous carbon support in the middle layer enables efficient confinement of silicon nanoparticles and in-situ loading of solid electrolyte, constructing a continuous and interconnected three-dimensional ion transport channel, shortening the lithium-ion transport path, optimizing the interface contact state, and maximizing the interface regulation advantages of the multi-level structure. Ultimately, this ensures the formation of a stable, low-resistance continuous solid-solid interface between the electrode and the solid electrolyte, avoiding interface delamination failure during cycling. The multi-level coating structure endows the electrode with excellent structural stability and cycle reversibility, thereby achieving synergistic optimization of high capacity and long cycle life.

[0039] The beneficial effects of this application will be explained below with reference to specific embodiments and comparative examples.

[0040] Example 1

[0041] Artificial graphite particles and phenolic resin coating agent were mixed evenly (the phenolic resin coating agent accounted for 60% of the total mass of the two). The mixture was placed in a tube furnace and carbonized at 600°C for 2 hours under nitrogen protection at a heating rate of 2°C / min to obtain carbon-coated graphite material. Subsequently, it was mixed with potassium hydroxide (the mass ratio of carbon coating layer to potassium hydroxide was 1:2) and activated at 800°C for 2 hours under nitrogen atmosphere. It was then acid-washed with 2 mol / L hydrochloric acid solution for 6 hours, washed with deionized water until neutral, and dried to obtain porous carbon-coated graphite material with graphite as the core and porous carbon as the shell.

[0042] Porous carbon-coated graphite material and Li6PS5Cl powder were uniformly dispersed in ethanol solvent under a nitrogen atmosphere (the mass ratio of porous carbon-coated graphite material to Li6PS5Cl was 60:40), with a solid-liquid ratio of 1:20 g / mL. The mixture was pressure spray dried at a pressure of 5 MPa, a flow rate of 20 mL / min, and a temperature of 100 °C, and then sintered at 600 °C for 3 h to obtain a graphite / porous carbon / solid electrolyte intermediate.

[0043] The intermediate was placed in the deposition chamber of a vapor deposition furnace, and silane was introduced into the deposition chamber by nitrogen carrier gas at a flow rate of 2 L / min. The reaction was carried out at 800℃ for 10 h at a heating rate of 5℃ / min to perform vapor deposition, so that silicon nanoparticles were deposited in the pores of the intermediate material to form a silicon-containing coating layer. After natural cooling to room temperature, the silicon-carbon composite material precursor was obtained.

[0044] The precursor material and liquid phenolic resin were transferred to a fusion machine and fused at 500 r / min for 20 min (the mass ratio of precursor material to liquid phenolic resin was 95:5). Then, the mixture was placed in a tube furnace and heated to 600℃ and held for 2 h for carbon coating, finally obtaining a multi-level coated silicon-carbon composite material.

[0045] Example 2

[0046] Artificial graphite particles and phenolic resin coating agent were mixed evenly (the phenolic resin coating agent accounted for 65% of the total mass of the two). The mixture was placed in a tube furnace and carbonized at 600°C for 2 hours under nitrogen protection at a heating rate of 2°C / min to obtain carbon-coated graphite material. Subsequently, it was mixed with potassium hydroxide (the mass ratio of carbon coating layer to potassium hydroxide was 1:3) and activated at 800°C for 2 hours under nitrogen atmosphere. It was then acid-washed with 2 mol / L hydrochloric acid solution for 6 hours, washed with deionized water until neutral, and dried to obtain porous carbon-coated graphite material with graphite as the core and porous carbon as the shell.

[0047] Porous carbon-coated graphite material and Li6PS5Cl powder were uniformly dispersed in ethanol solvent under a nitrogen atmosphere (the mass ratio of porous carbon-coated graphite material to Li6PS5Cl was 60:40), with a solid-liquid ratio of 1:30 g / mL. The mixture was pressure spray dried at a pressure of 15 MPa, a flow rate of 15 mL / min, and a temperature of 100 °C, and then sintered at 600 °C for 3 h to obtain a graphite / porous carbon / solid electrolyte intermediate.

[0048] The intermediate was placed in the deposition chamber of a vapor deposition furnace, and silane was introduced into the deposition chamber by nitrogen carrier gas at a flow rate of 2 L / min. The reaction was carried out at 800℃ for 12 h at a heating rate of 5℃ / min to perform vapor deposition, so that silicon nanoparticles were deposited in the pores of the intermediate material to form a silicon-containing coating layer. After natural cooling to room temperature, the silicon-carbon composite material precursor was obtained.

[0049] The precursor material and liquid phenolic resin were transferred to a fusion machine and fused at 500 r / min for 20 min (the mass ratio of precursor material to liquid phenolic resin was 95:5). Then, the mixture was placed in a tube furnace and heated to 600℃ and held for 2 h for carbon coating, finally obtaining a multi-level coated silicon-carbon composite material.

[0050] Example 3

[0051] Artificial graphite particles and asphalt coating agent were mixed evenly (the mass of the asphalt coating agent accounted for 70% of the total mass of the two). The mixture was placed in a tube furnace and carbonized at 600°C for 2 hours under nitrogen protection at a heating rate of 2°C / min to obtain carbon-coated graphite material. Then, water vapor was added (the mass ratio of carbon coating layer to water vapor was 1:3), and the mixture was activated at 800°C for 4 hours under nitrogen atmosphere. It was then acid-washed with 2 mol / L hydrochloric acid solution for 6 hours, washed with deionized water until neutral, and dried to obtain porous carbon-coated graphite material with graphite as the core and porous carbon as the shell.

[0052] Porous carbon-coated graphite material and Li6PS5Cl powder were uniformly dispersed in ethylene glycol solvent under a nitrogen atmosphere (the mass ratio of porous carbon-coated graphite material to Li6PS5Cl was 50:50), with a solid-liquid ratio of 1:30 g / mL. The mixture was pressure spray dried at a pressure of 10 MPa, a flow rate of 15 mL / min, and a temperature of 100 °C, and then sintered at 600 °C for 4 h to obtain a graphite / porous carbon / solid electrolyte intermediate.

[0053] The intermediate was placed in the deposition chamber of a vapor deposition furnace, and propane was introduced into the deposition chamber by nitrogen carrier gas at a flow rate of 5 L / min. The reaction was carried out at 1000℃ for 6 h at a heating rate of 5℃ / min to perform vapor deposition, so that silicon nanoparticles were deposited in the pores of the intermediate material to form a silicon-containing coating layer. After natural cooling to room temperature, the silicon-carbon composite material precursor was obtained.

[0054] The precursor material and liquid phenolic resin were transferred to a fusion machine and fused at 500 r / min for 20 min (the mass ratio of precursor material to liquid phenolic resin was 98:2). Then, the mixture was placed in a tube furnace and heated to 800℃ and held for 1 h for carbon coating, finally obtaining a multi-level coated silicon-carbon composite material.

[0055] Example 4

[0056] Artificial graphite particles and asphalt coating agent were mixed evenly (the mass of the asphalt coating agent accounted for 75% of the total mass of the two). The mixture was placed in a tube furnace and carbonized at 600℃ for 2 hours under nitrogen protection at a heating rate of 2℃ / min to obtain carbon-coated graphite material. Then, water vapor was added (the mass ratio of carbon coating layer to water vapor was 1:5), and the mixture was activated at 850℃ for 3 hours under nitrogen atmosphere. It was then acid-washed with 2 mol / L hydrochloric acid solution for 6 hours, washed with deionized water until neutral, and dried to obtain porous carbon-coated graphite material with graphite as the core and porous carbon as the shell.

[0057] Porous carbon-coated graphite material and Li6PS5Cl powder were uniformly dispersed in ethanol solvent under a nitrogen atmosphere (the mass ratio of porous carbon-coated graphite material to Li6PS5Cl was 50:50), with a solid-liquid ratio of 1:30 g / mL. The mixture was pressure spray dried at a pressure of 10 MPa, a flow rate of 20 mL / min, and a temperature of 80 °C, and then sintered at 500 °C for 5 h to obtain a graphite / porous carbon / solid electrolyte intermediate.

[0058] The intermediate was placed in the deposition chamber of a vapor deposition furnace, and silane was introduced into the deposition chamber by nitrogen carrier gas at a flow rate of 2 L / min. The reaction was carried out at 1000℃ for 6 h at a heating rate of 5℃ / min to perform vapor deposition, so that silicon nanoparticles were deposited in the pores of the intermediate material to form a silicon-containing coating layer. After natural cooling to room temperature, the silicon-carbon composite material precursor was obtained.

[0059] The precursor material and liquid phenolic resin were transferred to a fusion machine and fused at 500 r / min for 20 min (the mass ratio of precursor material to liquid phenolic resin was 95:5). Then, the mixture was placed in a tube furnace and heated to 700℃ and held for 3 h for carbon coating, finally obtaining a multi-level coated silicon-carbon composite material.

[0060] Example 5

[0061] Artificial graphite particles and phenolic resin coating agent were mixed evenly (the phenolic resin coating agent accounted for 40% of the total mass of the two). The mixture was placed in a tube furnace and carbonized at 600°C for 2 hours under nitrogen protection at a heating rate of 2°C / min to obtain carbon-coated graphite material. Then carbon dioxide was added (the mass ratio of carbon coating layer to carbon dioxide was 1:4), and the mixture was activated at 900°C for 5 hours under nitrogen atmosphere. It was then acid-washed with 2 mol / L hydrochloric acid solution for 6 hours, washed with deionized water until neutral, and dried to obtain porous carbon-coated graphite material with graphite as the core and porous carbon as the shell.

[0062] Porous carbon-coated graphite material and Li6PS5Cl powder were uniformly dispersed in methanol solvent under a nitrogen atmosphere (the mass ratio of porous carbon-coated graphite material to Li6PS5Cl was 65:35), with a solid-liquid ratio of 1:10 g / mL. The mixture was pressure spray dried at a pressure of 20 MPa, a flow rate of 15 mL / min, and a temperature of 80 °C, and then sintered at 650 °C for 6 h to obtain a graphite / porous carbon / solid electrolyte intermediate.

[0063] The intermediate was placed in the deposition chamber of a vapor deposition furnace, and dichlorosilane was introduced into the deposition chamber by nitrogen carrier gas at a flow rate of 2 L / min. The reaction was carried out at 1200℃ for 10 h with a heating rate of 5℃ / min to perform vapor deposition, so that silicon nanoparticles were deposited in the pores of the intermediate material to form a silicon-containing coating layer. After natural cooling to room temperature, the silicon-carbon composite material precursor was obtained.

[0064] The precursor material and liquid phenolic resin were transferred to a fusion machine and fused at 500 r / min for 10 min (the mass ratio of precursor material to liquid phenolic resin was 95:5). Then, the mixture was placed in a tube furnace and heated to 500℃ and held for 2 h for carbon coating, finally obtaining a multi-level coated silicon-carbon composite material.

[0065] Example 6

[0066] Artificial graphite particles and phenolic resin coating agent were mixed evenly (the phenolic resin coating agent accounted for 50% of the total mass of the two). The mixture was placed in a tube furnace and carbonized at 600°C for 2 hours under nitrogen protection at a heating rate of 2°C / min to obtain carbon-coated graphite material. Then carbon dioxide was added (the mass ratio of carbon coating layer to carbon dioxide was 1:1), and the mixture was activated at 900°C for 5 hours under nitrogen atmosphere. It was then acid-washed with 2 mol / L hydrochloric acid solution for 6 hours, washed with deionized water until neutral, and dried to obtain porous carbon-coated graphite material with graphite as the core and porous carbon as the shell.

[0067] Porous carbon-coated graphite material and Li6PS5Cl powder were uniformly dispersed in acetonitrile solvent under a nitrogen atmosphere (the mass ratio of porous carbon-coated graphite material to Li6PS5Cl was 50:50), with a solid-liquid ratio of 1:20 g / mL. The mixture was pressure spray dried at a pressure of 5 MPa, a flow rate of 15 mL / min, and a temperature of 80 °C, and then sintered at 650 °C for 4 h to obtain a graphite / porous carbon / solid electrolyte intermediate.

[0068] The intermediate was placed in the deposition chamber of a vapor deposition furnace, and dichlorosilane was introduced into the deposition chamber by nitrogen carrier gas at a flow rate of 2 L / min. The reaction was carried out at 1200℃ for 12 h with a heating rate of 5℃ / min to perform vapor deposition, so that silicon nanoparticles were deposited in the pores of the intermediate material to form a silicon-containing coating layer. After natural cooling to room temperature, the silicon-carbon composite material precursor was obtained.

[0069] The precursor material and liquid phenolic resin were transferred to a fusion machine and fused at 500 r / min for 10 min (the mass ratio of precursor material to liquid phenolic resin was 95:5). Then, the mixture was placed in a tube furnace and heated to 600℃ and held for 4 h for carbon coating, finally obtaining a multi-level coated silicon-carbon composite material.

[0070] Example 7

[0071] Artificial graphite particles and phenolic resin coating agent were mixed evenly (the phenolic resin coating agent accounted for 70% of the total mass of the two). The mixture was placed in a tube furnace and carbonized at 600°C for 2 hours under nitrogen protection at a heating rate of 2°C / min to obtain carbon-coated graphite material. Then, potassium hydroxide was added (the mass ratio of carbon coating layer to potassium hydroxide was 1:1), and the mixture was activated at 800°C for 2 hours under nitrogen atmosphere. It was then acid-washed with 2 mol / L hydrochloric acid solution for 6 hours, washed with deionized water until neutral, and dried to obtain porous carbon-coated graphite material with graphite as the core and porous carbon as the shell.

[0072] Porous carbon-coated graphite material and Li6PS5Cl powder were uniformly dispersed in acetonitrile solvent under a nitrogen atmosphere (the mass ratio of porous carbon-coated graphite material to Li6PS5Cl was 50:50), with a solid-liquid ratio of 1:30 g / mL. The mixture was pressure spray dried at a pressure of 15 MPa, a flow rate of 15 mL / min, and a temperature of 100 °C, and then sintered at 500 °C for 8 h to obtain a graphite / porous carbon / solid electrolyte intermediate.

[0073] The intermediate was placed in the deposition chamber of a vapor deposition furnace, and silane was introduced into the deposition chamber by carrying nitrogen gas at a flow rate of 2 L / min. The reaction was carried out at 1400℃ for 4 h at a heating rate of 5℃ / min to perform vapor deposition, so that silicon nanoparticles were deposited in the pores of the intermediate material to form a silicon-containing coating layer. After natural cooling to room temperature, a silicon-carbon composite material precursor was obtained. It was then transferred to a carbon coating device, and the temperature was increased to 600℃ by carrying nitrogen gas at a flow rate of 10 L / min and at a rate of 5℃ / min. Acetylene was then introduced at a flow rate of 2 L / min for 2 h. After stopping the introduction of acetylene, the material was allowed to cool naturally to room temperature to finally obtain a multi-stage coated silicon-carbon composite material.

[0074] Example 8

[0075] Artificial graphite particles and asphalt coating agent were mixed evenly (the mass of the asphalt coating agent accounted for 70% of the total mass of the two). The mixture was placed in a tube furnace and carbonized at 600°C for 2 hours under nitrogen protection at a heating rate of 2°C / min to obtain carbon-coated graphite material. Then, water vapor was added (the mass ratio of carbon coating layer to water vapor was 1:6), and the mixture was activated at 800°C for 4 hours under nitrogen atmosphere. It was then acid-washed with 2 mol / L hydrochloric acid solution for 6 hours, washed with deionized water until neutral, and dried to obtain porous carbon-coated graphite material with graphite as the core and porous carbon as the shell.

[0076] Porous carbon-coated graphite material and Li6PS5Cl powder were uniformly dispersed in methanol solvent under a nitrogen atmosphere (the mass ratio of porous carbon-coated graphite material to Li6PS5Cl was 60:40), with a solid-liquid ratio of 1:20 g / mL. The mixture was pressure spray dried at a pressure of 10 MPa, a flow rate of 16 mL / min, and a temperature of 80 °C, and then sintered at 650 °C for 6 h to obtain a graphite / porous carbon / solid electrolyte intermediate.

[0077] The intermediate was placed in the deposition chamber of a vapor deposition furnace, and propane was introduced into the deposition chamber by carrying nitrogen gas at a flow rate of 2 L / min. The reaction was carried out at 1600℃ for 1 h at a heating rate of 5℃ / min to perform vapor deposition, so that silicon nanoparticles were deposited in the pores of the intermediate material to form a silicon-containing coating layer. After natural cooling to room temperature, a silicon-carbon composite material precursor was obtained. It was then transferred to a carbon coating device, and heated to 600℃ by carrying nitrogen gas at a flow rate of 10 L / min at a rate of 5℃ / min. Acetylene was then introduced at a flow rate of 2.5 L / min for 1.5 h. After stopping the introduction of acetylene, the material was allowed to cool naturally to room temperature to finally obtain a multi-stage coated silicon-carbon composite material.

[0078] Comparative Example 1

[0079] Phenolic resin and potassium hydroxide were mixed and placed in a tube furnace (the mass ratio of phenolic resin to potassium hydroxide was 1:2). The mixture was activated at 800℃ for 2 hours under a nitrogen atmosphere at a heating rate of 2℃ / min. The mixture was then acid-washed with a 2 mol / L hydrochloric acid solution for 6 hours, washed with deionized water until neutral, and dried to obtain porous carbon material.

[0080] Porous carbon material and Li6PS5Cl powder were uniformly dispersed in ethanol solvent under nitrogen atmosphere (the mass ratio of porous carbon material to Li6PS5Cl was 60:40), and the solid-liquid ratio was 1:20 g / mL. The mixture was pressure spray dried at a pressure of 5 MPa, a flow rate of 20 mL / min, and a temperature of 100 °C, and then sintered at 600 °C for 3 h to obtain a porous carbon / solid electrolyte intermediate.

[0081] The intermediate was placed in the deposition chamber of a vapor deposition furnace, and silane was introduced into the deposition chamber by nitrogen carrier gas at a flow rate of 2 L / min. The reaction was carried out at 800℃ for 10 h at a heating rate of 5℃ / min to perform vapor deposition, so that silicon nanoparticles were deposited in the pores of the intermediate material to form a silicon-containing coating layer. After natural cooling to room temperature, the silicon-carbon composite material precursor was obtained.

[0082] The precursor material and liquid phenolic resin were transferred to a fusion machine and fused at 500 r / min for 20 min (the mass ratio of precursor material to liquid phenolic resin was 95:5). Then, the mixture was placed in a tube furnace and heated to 600℃ and held for 2 h for carbon coating, finally obtaining a multi-level coated silicon-carbon composite material.

[0083] Comparative Example 2

[0084] Phenolic resin was placed in a tube furnace and carbonized at 600°C for 2 hours under nitrogen protection at a heating rate of 2°C / min. Then it was mixed with potassium hydroxide (the mass ratio of carbon coating layer to potassium hydroxide was 1:2) and activated at 800°C for 2 hours under nitrogen atmosphere. It was then acid-washed with 2 mol / L hydrochloric acid solution for 6 hours, washed with deionized water until neutral, and dried to obtain porous carbon material.

[0085] Porous carbon material and Li6PS5Cl powder were uniformly dispersed in ethanol solvent under a nitrogen atmosphere (the mass ratio of porous carbon to Li6PS5Cl was 60:40), with a solid-liquid ratio of 1:20 g / mL. The mixture was pressure spray dried at a pressure of 5 MPa, a flow rate of 20 mL / min, and a temperature of 100 °C, and then sintered at 600 °C for 3 h to obtain a porous carbon / solid electrolyte intermediate.

[0086] The intermediate was placed in the deposition chamber of a vapor deposition furnace, and silane was introduced into the deposition chamber by nitrogen carrier gas at a flow rate of 2 L / min. The reaction was carried out at 800℃ for 10 h at a heating rate of 5℃ / min to perform vapor deposition, so that silicon nanoparticles were deposited in the pores of the intermediate material to form a silicon-containing coating layer. After natural cooling to room temperature, the silicon-carbon composite material precursor was obtained.

[0087] The precursor material and liquid phenolic resin were transferred to a fusion machine and fused at 500 r / min for 20 min (the mass ratio of precursor material to liquid phenolic resin was 95:5). Then, the mixture was placed in a tube furnace and heated to 600℃ and held for 2 h to obtain carbon-coated CVD silicon-carbon material.

[0088] Carbon-coated CVD silicon-carbon composite material was added to graphite and mixed evenly to obtain graphite / carbon-coated CVD silicon-carbon composite material, wherein the carbon-coated CVD silicon-carbon material accounted for 60% of the mass percentage of the composite material.

[0089] Comparative Example 3

[0090] Artificial graphite particles were placed in the deposition chamber of a vapor deposition furnace. Silane was introduced into the deposition chamber by nitrogen carrier gas at a flow rate of 2 L / min. The mixture was heated at 800℃ for 10 h at a heating rate of 5℃ / min to perform vapor deposition, which deposited silicon nanoparticles on the surface of the graphite material to form a silicon-containing coating layer. The mixture was then naturally cooled to room temperature to obtain a silicon / graphite composite material precursor.

[0091] The precursor material and liquid phenolic resin were transferred to a fusion machine and fused at 500 r / min for 20 min (the mass ratio of precursor material to liquid phenolic resin was 95:5). Then, the mixture was placed in a tube furnace and heated to 600℃ and held for 2 h for carbon coating to obtain carbon-coated silicon / graphite composite material.

[0092] Carbon-coated silicon / graphite composite material and Li6PS5Cl powder were uniformly dispersed in ethanol solvent (mass ratio of carbon-coated silicon / graphite composite material to Li6PS5Cl was 60:40), with a solid-liquid ratio of 1:20 g / mL. The mixture was pressure spray dried at a pressure of 5 MPa, a flow rate of 20 mL / min, and a temperature of 100 °C, and then sintered at 600 °C for 3 h to obtain the final silicon-carbon composite material.

[0093] Comparative Example 4

[0094] Artificial graphite particles and phenolic resin coating agent were mixed evenly (the phenolic resin coating agent accounted for 60% of the total mass of the two). The mixture was placed in a tube furnace and carbonized at 600°C for 2 hours under nitrogen protection at a heating rate of 2°C / min to obtain carbon-coated graphite material. Subsequently, it was mixed with potassium hydroxide (the mass ratio of carbon coating layer to potassium hydroxide was 1:2) and activated at 800°C for 2 hours under nitrogen atmosphere. It was then acid-washed with 2 mol / L hydrochloric acid solution for 6 hours, washed with deionized water until neutral, and dried to obtain porous carbon-coated graphite material with graphite as the core and porous carbon as the shell.

[0095] Porous carbon-coated graphite material was placed in the deposition chamber of a vapor deposition furnace. Silane was introduced into the deposition chamber by nitrogen carrier gas at a flow rate of 2 L / min. The material was heated at 800℃ for 10 h at a heating rate of 5℃ / min to perform vapor deposition, which allowed silicon nanoparticles to be deposited in the pores of the porous carbon material to form a silicon-containing coating layer. The material was then naturally cooled to room temperature to obtain a silicon-carbon composite material precursor.

[0096] The precursor material and liquid phenolic resin were transferred to a fusion machine and fused at 500 r / min for 20 min (the mass ratio of precursor material to liquid phenolic resin was 95:5). Then, the mixture was placed in a tube furnace and heated to 600℃ and held for 2 h for carbon coating, finally obtaining a multi-level coated silicon-carbon composite material.

[0097] Comparative Example 5

[0098] Artificial graphite particles and phenolic resin coating agent were mixed evenly (the phenolic resin coating agent accounted for 60% of the total mass of the two). The mixture was placed in a tube furnace and carbonized at 600°C for 2 hours under nitrogen protection at a heating rate of 2°C / min to obtain carbon-coated graphite material. Subsequently, it was mixed with potassium hydroxide (the mass ratio of carbon coating layer to potassium hydroxide was 1:2) and activated at 800°C for 2 hours under nitrogen atmosphere. It was then acid-washed with 2 mol / L hydrochloric acid solution for 6 hours, washed with deionized water until neutral, and dried to obtain porous carbon-coated graphite material with graphite as the core and porous carbon as the shell.

[0099] Porous carbon-coated graphite material and Li6PS5Cl powder were uniformly dispersed in ethanol solvent under a nitrogen atmosphere (the mass ratio of porous carbon-coated graphite material to Li6PS5Cl was 60:40), with a solid-liquid ratio of 1:20 g / mL. The mixture was pressure spray dried at a pressure of 5 MPa, a flow rate of 20 mL / min, and a temperature of 100 °C, and then sintered at 600 °C for 3 h to obtain a graphite / porous carbon / solid electrolyte intermediate.

[0100] The intermediate was placed in the deposition chamber of a vapor deposition furnace, and silane was introduced into the deposition chamber by nitrogen at a flow rate of 2 L / min. The reaction was carried out at 800℃ for 10 h at a heating rate of 5℃ / min to perform vapor deposition, so that silicon nanoparticles were deposited in the pores of the intermediate material to form a silicon-containing coating layer. After natural cooling to room temperature, a silicon-carbon composite material was obtained.

[0101] Fabrication of all-solid-state lithium batteries:

[0102] Li6PS5C1 solid electrolyte powder with a median particle size of 5 μm was used to prepare a solid electrolyte sheet with a thickness of 1 mm under 150 MPa. The composite negative electrode materials provided in the above examples and comparative examples were pressed onto one side of the electrolyte sheet under a pressure of 100 MPa. Indium foil (10 mm in diameter and 100 μm in thickness) and lithium foil (8 mm in diameter and 100 μm in thickness) were placed on the other side in sequence and then pressed under 100 MPa to obtain an all-solid-state mold half-cell.

[0103] Performance testing:

[0104] The prepared solid-state mold half-cell was subjected to one charge-discharge cycle at a rate of 0.1C under the conditions of room temperature, charge-discharge voltage range of 0.900V to -0.595V, and pressure of 100MPa. The initial charge-discharge efficiency (initial charge specific capacity / initial discharge specific capacity) was tested. Subsequently, the cell was cycled at a rate of 1C, and the rate retention rate (1C discharge capacity / 0.1C discharge capacity) and the capacity retention rate after 200 cycles (specific capacity of the 200th charge cycle at 1C rate / specific capacity of the first charge cycle at 1C rate) were tested. The test results are shown in Table 1.

[0105] Table 1

[0106]

[0107] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0108] 1) The multi-level buffer structure effectively solves the problem of silicon volume expansion and significantly improves cycling stability. The progressive structure of "graphite core - porous carbon intermediate layer - silicon nanoparticles - amorphous carbon shell" constructed in the above embodiments achieves multiple buffering and constraints from macroscopic to microscopic levels. The graphite material provides mechanical support as a matrix; the porous carbon intermediate layer not only confines the subsequently deposited silicon nanoparticles, but also absorbs and disperses the stress generated by silicon during lithium insertion / extraction; the outermost amorphous carbon shell provides final constraint on the entire internal composite unit, preventing the particles from breaking and pulverizing during cycling.

[0109] 2) The integrated design optimizes the solid-solid interface contact and improves ion transport efficiency. Before constructing the silicon-carbon host structure, the solid electrolyte and porous carbon-coated graphite composite are uniformly mixed by spray drying, allowing the solid electrolyte particles to be pre-embedded deeply into the secondary particles of the negative electrode material and the surface of the porous carbon layer. In the final composite material, a three-dimensional interpenetrating ion-conducting network is formed between the solid electrolyte and the active material, greatly reducing interfacial impedance.

[0110] 3) The dense outer carbon shell enhances interfacial stability and improves cycle reversibility. The outermost layer, an amorphous carbon shell, acts as a high-strength physical protective layer, providing solid support for the entire composite particle and directly suppressing the outward transmission of volume expansion of the internal silicon nanoparticles during cycling. By improving the overall structural strength and integrity of the material, it effectively resists the cyclic stress generated during battery charging and discharging, thereby ensuring that the negative electrode sheet made of this material has an extremely low expansion rate.

[0111] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A negative electrode material, characterized in that, The negative electrode material includes graphite material and a porous carbon intermediate layer and an amorphous carbon coating layer sequentially coated on the surface of the graphite material. The porous carbon intermediate layer includes porous carbon, and silicon nanoparticles and sulfide solid electrolyte material are dispersed in the pores of the porous carbon. The amorphous carbon coating layer includes amorphous carbon.

2. The negative electrode material according to claim 1, characterized in that, The negative electrode material comprises, by weight percentage: 10%-50% of the graphite material, 20%-69% of the porous carbon, 0.1%-10% of the sulfide solid electrolyte material, 20%-69% of the silicon nanoparticles, and 0.1%-10% of the amorphous carbon. And / or, the porous carbon has a pore size of (0.1~80) nm and a specific surface area of ​​100 m². 2 / g~3000m 2 / g, porosity 30~80%; And / or, the thickness ratio of the amorphous carbon coating layer to the thickness of the porous carbon interlayer is (0.1~50) nm : (0.1~10) nm; And / or, the sulfide solid electrolyte material is Li 6-x P 1+y S 5-x Cl 1+x At least one of the following, wherein 0 ≤ x ≤ 0.5 and 0 ≤ y ≤ 0.

5.

3. The negative electrode material according to claim 1, characterized in that, The ratio of the median particle size of the silicon-carbon composite material to the median particle size of the graphite material is (10~100) μm : (10~20) μm; And / or, the graphite is artificial graphite particles or natural graphite secondary particles.

4. A method for preparing the negative electrode material according to any one of claims 1-3, characterized in that, The preparation method includes: Step S1: In an inert atmosphere, the raw materials including graphite material and coating agent are heat-treated to obtain carbon-coated graphite material. Step S2: The carbon-coated graphite material is activated and pore-forming using an activator. The material obtained from the activation and pore-forming treatment is then washed and dried sequentially to obtain a porous carbon-coated graphite material. Step S3: In the inert atmosphere, the porous carbon-coated graphite material and solid electrolyte powder are dispersed in a solvent to obtain a mixture. Step S4: The mixture is subjected to pressure spray drying and then sintered to obtain a graphite / porous carbon / solid electrolyte intermediate material. Step S5: The intermediate material is vapor-deposited with a silicon-containing compound to obtain a silicon-carbon composite material precursor. Step S6: The silicon-carbon composite material precursor is subjected to carbon coating treatment to obtain the negative electrode material.

5. The preparation method according to claim 4, characterized in that, In step S1, the mass ratio of the coating agent to the graphite material is (3~8):(2~7), preferably the coating agent is one or more of phenolic resin and asphalt; and / or, the flow rate of the inert atmosphere is 2L / min-20L / min, preferably the inert atmosphere is one or more of nitrogen atmosphere and argon atmosphere; the temperature of the heat treatment is 500-1200℃; and the heating time of the heat treatment is 2-6h.

6. The preparation method according to claim 4, characterized in that, In step S2, the mass ratio of the porous carbon to the activator is 1:(0.5-10), and preferably the activator is one or more of water vapor, carbon dioxide, potassium hydroxide, sodium hydroxide, zinc chloride, and phosphoric acid; the activation temperature is 600-800℃; and the activation time is 2-4 hours. And / or, the washing process includes a first-stage washing and a second-stage washing. The first-stage washing process includes: performing a first cleaning on the material obtained from the activated pore-forming treatment with a hydrochloric acid solution with a concentration of 2 mol / L to obtain a cleaned product, wherein the first cleaning time is 6-12 hours. The second-stage washing process includes: performing a second wash on the item with deionized water until the pH of the item is neutral.

7. The preparation method according to claim 4, characterized in that, In step S3, the mass ratio of the porous carbon-coated graphite material to the solid electrolyte is (50-90):(10-50); the total mass ratio of the porous carbon-coated graphite material and the solid electrolyte to the volume ratio of the solvent is (1:10~50) g / mL; the solvent is one or more of methanol, ethanol, acetonitrile, benzyl alcohol, tetrahydrofuran, anisole, dimethylformamide, and ethylene glycol.

8. The preparation method according to claim 4, characterized in that, In step S4, the pressure of the pressure spray drying is 5-25 MPa, the flow rate of the pressure spray drying is 10-50 mL / min, and the temperature of the pressure spray drying is 80-250℃; and / or, the sintering temperature is 500-800℃, and the sintering time is 1-12 h.

9. The preparation method according to claim 4, characterized in that, In step S5, the silicon-containing compound and the intermediate material are vapor-deposited using a carrier gas. The carrier gas is one or more of nitrogen and argon, and the flow rate of the carrier gas is 2 L / min-20 L / min. The silicon-containing compound includes one or more of metallic silicon vapor, silane, propane, dichlorosilane, trichlorosilane, and tetrachlorosilane. The vapor-deposit temperature is 400-1600℃, and the vapor-deposit time is 1-24 h.

10. A solid-state battery, the solid-state battery comprising a positive electrode and a negative electrode, characterized in that, The negative electrode comprises the negative electrode material according to any one of claims 1-3, or the negative electrode material prepared by the preparation method according to any one of claims 4-9.

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