Silicon-carbon negative electrode material, preparation method and application thereof

Abstract

This invention relates to an anode material, its preparation method, and its applications. The silicon-carbon anode material has a multi-layered core-shell structure, comprising, from the inside out: a graphite core; an induction layer covering the surface of the graphite core; a silicon layer deposited on the induction layer; and a carbon coating layer covering the outside of the silicon layer. The induction layer is amorphous carbon with oxygen-containing functional groups on its surface, and the silicon in the silicon layer covers the surface of the induction layer in a continuous or semi-continuous thin layer form. The silicon-carbon anode material provided by this invention, by adding an induction layer to the graphite surface, improves the reactivity of graphite, induces uniform silicon deposition and coating on the graphite surface, reduces silicon size, suppresses silicon expansion, and improves the high-rate performance and first-cycle coulombic efficiency of the silicon-carbon anode material.

Description

Technical Field

[0001] This invention relates to the field of lithium battery anode material technology, and in particular to a silicon-carbon anode material, its preparation method, and its application. Background Technology

[0002] The performance of lithium-ion batteries is highly dependent on the anode material. Silicon is an ideal choice due to its extremely high theoretical specific capacity, but it undergoes huge volume changes during charging and discharging, which can easily lead to material structure damage and instability of the solid electrolyte interface film, resulting in rapid capacity decay.

[0003] To address these challenges, silicon-carbon composite materials have become the mainstream solution, but existing preparation technologies each have their limitations: While physical polishing is a simple process, it results in uneven silicon particle dispersion and larger particle size, which can lead to stress concentration and poor first-cycle performance and cycling stability. Compared to physical polishing, chemical vapor deposition (CVD) can improve silicon distribution, but it often uses porous carbon substrates with poor order, low conductivity, and high defects as the substrate. This results in weak silicon adhesion, making it difficult to effectively suppress volume expansion, and ultimately, rate performance and cycle life remain unsatisfactory. It is worth noting that using graphite, with its high structural order, few defects, and excellent conductivity, as the deposition substrate is theoretically a more ideal choice. However, due to the high chemical inertness of graphite surfaces, silicon source gas molecules cannot effectively nucleate on its surface. This often leads to uneven distribution of silicon in isolated "island" morphology or localized agglomerations, failing to achieve uniform coating to synergistically suppress volume effects and resulting in unstable long-cycle performance. Existing technologies have also attempted to optimize the technology through element doping and microstructure design, such as the hydrothermal doping method in Chinese patent CN112670479A and the core-shell structure design in CN116885144A. However, due to the complexity of the process, low efficiency, poor uniformity, or the scattered distribution of doped elements and low interface contact efficiency, these technologies have failed to fundamentally solve the problem.

[0004] In summary, current technologies have failed to achieve uniform and robust loading of nano-silicon on graphite substrates, which possess ordered structure, few defects, and excellent conductivity. Therefore, overcoming the technical bottleneck of optimized silicon deposition on graphite surfaces has become a key research direction for developing high-performance silicon-carbon anode materials. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a silicon-carbon anode material, its preparation method, and its applications. The silicon-carbon anode material provided by this invention improves the reactivity of graphite by adding an induction layer to the graphite surface, induces uniform silicon deposition and coating on the graphite surface, reduces silicon size, suppresses silicon expansion, and improves the high-rate performance and first-cycle coulombic efficiency of the silicon-carbon anode material.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a silicon-carbon anode material, which has a multilayer core-shell structure and comprises, from the inside to the outside: Graphite core; An induction layer covering the surface of the graphite core; A silicon layer deposited on the induced layer; and, A carbon coating layer covering the outside of the silicon layer; The induction layer is an amorphous carbon with oxygen-containing functional groups on its surface, and the silicon in the silicon layer covers the surface of the induction layer in a continuous or semi-continuous thin layer form.

[0007] Preferably, the graphite core has a particle size D50 of 5μm-12μm and a specific surface area of ​​1m³. 2 / g-10m 2 / g; The graphite core and the inducing layer together form a functionalized graphite precursor, the specific surface area of ​​which is 15 m². 2 / g-50m 2 / g; The silicon-carbon anode material has a particle size D50 of 6μm-13μm and a specific surface area of ​​1m². 2 / g-5 m 2 / g.

[0008] Preferably, the silicon content in the silicon-carbon anode material accounts for 5wt%-25wt% of the total mass of the silicon-carbon anode material, and the carbon content in the silicon-carbon anode material accounts for 75wt%-95wt% of the total mass of the silicon-carbon anode material.

[0009] In a second aspect, the present invention provides a method for preparing a silicon-carbon anode material as described in the first aspect above, the method comprising the following steps: After uniformly mixing graphite, dispersant, inducing layer carbon source and solvent in a mass ratio of 100:[0.5-2]:[5-20]:[150-400], spray drying is performed to coat the graphite surface with the inducing layer carbon source. Then, under a protective atmosphere, the temperature is raised to 500℃-800℃ for 1h-4h for heat treatment to carbonize the inducing layer carbon source to form amorphous carbon with oxygen-containing functional groups on the surface, forming an inducing layer on the graphite surface. Subsequently, the temperature is lowered to room temperature under a protective atmosphere to form a functionalized graphite precursor. The functionalized graphite precursor is placed in a chemical vapor deposition apparatus and heated to a first deposition temperature under a protective atmosphere. A mixture of inert carrier gas and silicon source gas is introduced to perform silicon chemical vapor deposition. During the silicon chemical vapor deposition process, the oxygen-containing functional groups act as active sites, adsorbing and catalyzing the thermal decomposition of the silicon source gas. This induces the generated silicon atoms to undergo heterogeneous nucleation on the surface of the induced layer and grow along the surface to form a continuous or semi-continuous silicon layer. Subsequently, the introduction of the silicon source gas is stopped, and the inert carrier gas is continuously introduced at the first deposition temperature for purging treatment to remove residual silicon source gas and byproducts generated by thermal decomposition, while stabilizing the silicon layer structure to obtain a silicon / graphite composite matrix. The temperature is further increased to the second deposition temperature, and a mixture of inert carrier gas and carbon source gas is introduced to perform carbon layer chemical vapor deposition. The carbon source gas undergoes thermal decomposition and is deposited on the surface of the silicon / graphite composite matrix to form a carbon coating layer. Then, the temperature is lowered to room temperature under a protective atmosphere to obtain silicon-carbon anode material.

[0010] Preferably, the dispersant is one or more of hexadecyltrimethylammonium bromide or polyvinylpyrrolidone; The carbon source for the induction layer includes one or more of glucose, starch, or phenolic resin; the solvent is one or more of water or ethanol. The silicon source gas includes one or more of silane, silane, or dichlorosilane; The carbon source gas includes one or more of methane, acetylene, ethylene, or propylene. The inert carrier gas is one or more of nitrogen or argon; The protective atmosphere is one or more of nitrogen or argon.

[0011] Preferably, the mass ratio of the graphite, the dispersant, the carbon source of the induction layer, and the solvent is 100:[1-2]:[10-15]:[200-300].

[0012] Preferably, the equipment used for spray drying is selected from either an open spray dryer or a closed spray dryer.

[0013] Preferably, the inlet temperature of the spray dryer is 200℃-240℃, and the outlet temperature is 90℃-110℃; The first deposition temperature is 480℃-510℃, the time for silicon layer chemical phase deposition is 0.5h-6h, and the purging treatment time is 0.5h-1h; The second deposition temperature is 520℃-600℃, and the time for the carbon layer chemical vapor deposition is 0.5h-3h.

[0014] Thirdly, the present invention provides a negative electrode sheet comprising the silicon-carbon negative electrode material described in the first aspect above, or comprising the silicon-carbon negative electrode material prepared by the preparation method described in the second aspect above.

[0015] Fourthly, the present invention provides an energy storage device, the energy storage device comprising: for a lithium-ion battery or a lithium-ion capacitor; The energy storage device includes the silicon-carbon anode material described in the first aspect above, or the silicon-carbon anode material prepared by the preparation method described in the second aspect above, or the anode sheet described in the third aspect above.

[0016] The silicon-carbon anode material provided in this invention has a multi-layer core-shell structure. The graphite core provides a high-speed electron conduction channel, laying the foundation for high first-cycle efficiency and high rate capability. The silicon layer, in a continuous / semi-continuous thin-layer morphology, fundamentally and uniformly disperses charge and discharge stress, giving the material extremely low volume expansion rate and ultra-long cycle life. The induced layer on the surface, rich in oxygen-containing functional groups, promotes the uniform distribution of silicon, significantly improving the lithium-ion diffusion rate of the material and giving it high rate performance. The outermost carbon coating layer effectively stabilizes the electrode / electrolyte interface and suppresses side reactions. This synergistic effect of the structure enables the material to inherently exhibit excellent comprehensive performance with high first-cycle coulombic efficiency, high rate capability, low expansion, and long cycle life. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the silicon-carbon anode material structure provided in an embodiment of the present invention; Figure 2 This is a flowchart illustrating the preparation method of silicon-carbon anode material provided in an embodiment of the present invention. Figure 3 A scanning electron microscope (SEM) image of graphite raw materials; Figure 4 SEM image of the functionalized graphite precursor prepared in Example 1; Figure 5 SEM image of the silicon-carbon anode material prepared in Comparative Example 1; Figure 6 SEM image of the cross-section of the silicon-carbon anode material prepared in Comparative Example 1; Figure 7 SEM image of the silicon-carbon anode material prepared in Example 1; Figure 8 SEM image of the cross-section of the silicon-carbon anode material prepared in Example 1; Figure 9 The graph shows a comparison of the rate performance of the silicon-carbon anode materials prepared in Examples 1-5 and Comparative Examples 1-3. Detailed Implementation

[0018] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0019] The reagents and materials used in the following examples and comparative examples are all commercially available conventional reagent products, or can be prepared by conventional methods. Where specific experimental steps or conditions are not specified in the examples, they were performed according to conventional experimental steps and conditions in the art. Unless otherwise specified, all equipment used is conventional equipment currently available in the art.

[0020] This invention provides a silicon-carbon anode material, such as... Figure 1 As shown, the silicon-carbon anode material has a multi-layered core-shell structure, which includes, from the inside out: Graphite core; An induction layer coating the surface of the graphite core; A silicon layer deposited on top of the induced layer; and, A carbon coating layer covering the outside of a silicon layer; The induction layer is an amorphous carbon with oxygen-containing functional groups on its surface, and the silicon in the silicon layer covers the surface of the induction layer in the form of a continuous or semi-continuous thin layer.

[0021] In this context, the silicon layer covering the surface of the induction layer in a continuous or semi-continuous thin film form means that some silicon layers are like a complete, undamaged thin film, completely covering the induction layer below without any exposed areas, while other silicon layers basically cover the surface, but may contain some tiny pores, channels, or areas of uneven thickness. Overall, they still present a thin film form rather than independent particles.

[0022] The graphite core particle size D50 is 5μm-12μm, and the specific surface area is 1m². 2 / g-10m 2 / g.

[0023] The graphite core and the induced layer together form a functionalized graphite precursor with a specific surface area of ​​15 m². 2 / g-50m 2 / g.

[0024] The silicon-carbon anode material has a particle size D50 of 6μm-13μm and a specific surface area of ​​1m². 2 / g-5 m 2 / g.

[0025] The silicon content in silicon-carbon anode materials accounts for 5wt%-25wt% of the total mass of silicon-carbon anode materials, and the carbon content accounts for 75wt%-95wt% of the total mass of silicon-carbon anode materials.

[0026] The silicon-carbon anode material provided in this invention has a multi-layer core-shell structure. The graphite core provides a high-speed electron conduction channel, laying the foundation for high first-cycle efficiency and high rate capability. The continuous / semi-continuous thin-layer morphology of the silicon layer fundamentally and uniformly disperses charge and discharge stress, giving the material extremely low volume expansion rate and ultra-long cycle life. The induced layer rich in oxygen-containing functional groups on the surface promotes the uniform distribution of silicon, significantly improving the lithium-ion diffusion rate of the material and giving it high rate performance. The outermost carbon coating layer effectively stabilizes the electrode / electrolyte interface and suppresses side reactions. This synergistic effect of the structure enables the material to inherently exhibit excellent comprehensive performance with high first-cycle coulombic efficiency, high rate capability, low expansion, and long cycle life.

[0027] Therefore, when the silicon-carbon anode material provided by this invention is applied to lithium-ion batteries or capacitors, its advantages are specifically manifested in that it can more effectively alleviate volume expansion during cycling, thereby significantly improving the cycle life and safety of the product.

[0028] In addition, the present invention also provides a method for preparing the above-mentioned silicon-carbon anode material, the main steps of which are as follows: Figure 2 As shown, it includes the following steps: Step 110: After uniformly mixing graphite, dispersant, inducing layer carbon source and solvent in a mass ratio of 100:[0.5-2]:[5-20]:[150-400], spray drying is performed to coat the graphite surface with the inducing layer carbon source. Then, heat treatment is performed at 500℃-800℃ under a protective atmosphere to carbonize the inducing layer carbon source into amorphous carbon with oxygen-containing functional groups on the surface. This forms an inducing layer by coating the graphite surface. Subsequently, the temperature is lowered to room temperature under a protective atmosphere to form a functionalized graphite precursor.

[0029] The purpose of this step is to construct an amorphous carbon-induced layer rich in oxygen-containing functional groups on the graphite surface. Graphite serves as the conductive framework and main active material of the silicon-carbon anode material, providing high conductivity and structural support. Furthermore, graphite exhibits superior electrical conductivity and first-cycle coulombic efficiency compared to common porous materials. Introducing graphite as a core effectively improves the electronic conduction efficiency of the silicon-carbon anode material, while also significantly mitigating irreversible lithium intercalation compared to porous carbon. This lays the foundation for the high rate capability, cycle stability, and first-cycle coulombic efficiency of the silicon-carbon anode material.

[0030] This step involves optimizing the carbon source for the inducing layer and controlling the temperature during carbonization to construct an active inducing layer on the graphite surface. Specifically: The carbon source for the inducing layer includes one or more of glucose, starch, or phenolic resin. These polysaccharides or resins are rich in hydroxyl groups and cannot be completely graphitized at low temperatures. They exist in amorphous carbon form and retain a large number of oxygen-containing groups such as hydroxyl or carboxyl groups, which serve as "active sites" for catalyzing the decomposition of silanes in subsequent steps and are key to inducing uniform silicon deposition.

[0031] The solvent is one or more of water or ethanol. Compared with organic solvents, water or ethanol is more environmentally friendly, less expensive, and easier to dry, enabling water-based system processing and reducing costs and environmental burden.

[0032] The role of the dispersant is to prevent graphite particles from agglomerating in the solvent and to ensure that the carbon source of the inducing layer can be uniformly coated on the surface of the graphite particles. A uniform slurry is a prerequisite for achieving uniform coating on the graphite surface. Preferably, the dispersant is one or more of hexadecyltrimethylammonium bromide or polyvinylpyrrolidone. If the dispersant content is too high, the dispersion effect will be poor, and if it is too high, it will affect the subsequent carbonization. Preferably, the mass ratio of graphite, dispersant, carbon source of the inducing layer and solvent is 100:[0.5-2]:[5-20]:[150-400]. More preferably, the mass ratio of graphite, dispersant, carbon source of the inducing layer and solvent is 100:[1-2]:[10-15]:[200-300].

[0033] In this step, the spray drying equipment is selected from either an open-type spray dryer or a closed-type spray dryer. The purpose of spray drying is to rapidly remove the solvent and uniformly coat the carbon source onto the graphite surface in the form of tiny droplets, forming precursor microspheres. Excessive temperature will cause premature charring of the carbon source and uneven coating, while excessively low temperature will result in incomplete drying. To ensure rapid solvent evaporation without damaging the carbon source structure, the preferred process parameters during spray drying are: an inlet temperature of 200℃-240℃ and an outlet temperature of 90℃-110℃. Further, the feed inlet temperature is 210℃-230℃, and the outlet temperature is 100℃-110℃.

[0034] After spray drying is completed, the material is discharged into a coating reactor (such as a coating furnace) for low-temperature heat treatment. If the heat treatment temperature is too low, carbonization will be incomplete; if it is too high, the functional groups will decompose, easily causing the carbon source in the inducing layer to graphitize and lose its activity. Specifically, the temperature is increased to 500℃-800℃ at a heating rate of 1℃ / min-5℃ / min under a protective atmosphere for 1h-4h, and then cooled to obtain graphite material coated with an inducing layer.

[0035] This heat treatment process is actually a carbonization and activation process. The carbon source in the induced layer decomposes and carbonizes at high temperature, forming an amorphous carbon layer whose surface retains a large number of oxygen-containing functional groups such as hydroxyl and carboxyl groups. More preferably, the heat treatment temperature is 600℃-700℃.

[0036] During heat treatment, the furnace tube rotates at 3Hz-6Hz to ensure the material tumbles within the tube, resulting in uniform heating, preventing localized overheating or sintering, and ensuring consistent properties of the induced layer on the graphite surface. This leads to the production of functionalized graphite precursors with high stability and consistent performance. Functionalized graphite precursors have a core-shell structure, consisting of a graphite core and an induced layer covering the surface of the graphite core. In other words, functionalized graphite precursors are composite nuclei formed by graphite and the induced layer.

[0037] In this application, the graphite has a particle size D50 of 5 μm - 12 μm and a specific surface area of ​​1 m². 2 / g-10m 2 / g. The specific surface area of ​​the functionalized graphite precursor is 15m². 2 / g-50m 2 / g.

[0038] The protective atmosphere is one or more of nitrogen or argon.

[0039] The graphite surface is a stable, passivated carbon layer with few active sites when in contact with silanes. Silanes tend to grow in the same phase as silicon particles, or continue to grow only on the graphite surface where silicon has already been deposited. This results in only a portion of the graphite surface being able to deposit silicon, accompanied by a large number of isolated silicon particles. This application aims to improve the reactivity of the graphite surface and promote uniform silicon deposition by introducing an inducible layer on the graphite surface. Specifically, an inducible layer carbon source is uniformly coated onto the graphite surface via a drying spray. After heat treatment, the carbon source carbonizes to form an inducible layer covering the graphite. The surface of the inducible layer is rich in oxygen-containing groups such as hydroxyl and carboxyl groups, which can serve as sites for binding with silanes during subsequent vapor phase deposition, promoting heterogeneous nucleation, enhancing the substrate's adsorption capacity for silane molecules, and increasing the reactivity of silane decomposition. Ultimately, the silicon generated from the thermal decomposition of silanes covers the surface of the inducible layer in a continuous or semi-continuous thin layer. That is, silicon is uniformly distributed on the graphite surface in a thin layer. Therefore, during lithium intercalation during charging, silicon can expand outward uniformly, dispersing stress and giving silicon-carbon anode materials extremely low volume expansion rate and ultra-long cycle life.

[0040] In addition, graphite has better electrical conductivity and first-cycle coulombic efficiency than common porous materials. Introducing graphite as a core can effectively improve the electronic conduction efficiency of silicon-carbon anode materials. At the same time, irreversible lithium intercalation is also significantly improved by porous carbon. Therefore, the silicon-carbon anode materials prepared have high rate performance and first-cycle coulombic efficiency.

[0041] Step 120: The functionalized graphite precursor is placed in a reaction apparatus capable of chemical vapor deposition (CVD). Under a protective atmosphere, the temperature is raised to the first deposition temperature. A mixture of inert carrier gas and silicon source gas is introduced to perform CVD of the silicon layer. During CVD of the silicon layer, oxygen-containing functional groups act as active sites, adsorbing and catalyzing the thermal decomposition of the silicon source gas. The generated silicon atoms are induced to nucleate heterogeneously on the surface of the induced layer and grow along the surface to form a continuous or semi-continuous silicon layer. Subsequently, the introduction of silicon source gas is stopped, and inert carrier gas is continuously introduced at the first deposition temperature for purging treatment to remove residual silicon source gas and byproducts generated by thermal decomposition, while stabilizing the silicon layer structure to obtain a silicon / graphite composite matrix. The purpose of this step is to grow a continuous or semi-continuous silicon layer on the induced layer by chemical deposition.

[0042] In this step, the reaction apparatus for vapor deposition is either a vapor deposition furnace or a fluidized bed, wherein the vapor deposition furnace is either a tube furnace or a rotary furnace. The protective atmosphere is one or more of nitrogen or argon. The silicon source gas includes one or more of silane, disilane, or dichlorosilane. The inert carrier gas is one or more of nitrogen or argon.

[0043] Specifically, the first deposition temperature is 480℃-510℃, and the time for silicon chemical vapor deposition is 0.5h-6h. The suitable temperature for the decomposition of silicon source gases such as silane is 480℃-510℃. If the temperature is too low, the decomposition will be insufficient, resulting in a slow deposition rate; if the temperature is too high, the silicon source will decompose prematurely in the gas phase, producing silicon powder, which cannot be deposited uniformly. Preferably, silicon chemical vapor deposition is performed at 500℃-510℃. In this step, the heating rate is 1℃ / min-5℃ / min.

[0044] By adjusting the volumetric flow rate ratio of silicon source gas to inert carrier gas (1:1-10:1) and the mixed gas flow rate (1L / min-100L / min), the silicon deposition rate and the silicon content in the silicon-carbon anode material (5wt%-25wt%) can be precisely controlled. If the mixed gas flow rate is slow and the volumetric flow rate ratio is low, silicon deposition will be slow and the silicon layer will be thin; conversely, deposition will be fast and the silicon layer will be thick.

[0045] After silicon deposition is stopped, a purging process is performed at the first deposition temperature by continuously introducing an inert carrier gas (flow rate of 30 L / min-50 L / min). The purpose is twofold: firstly, to purge and purify the reaction chamber, removing residual silicon source gas and byproducts, creating an inert atmosphere to prevent unnecessary side reactions during subsequent heating or introduction of carbon source gas; secondly, to stabilize the structure, using a thermally insulated environment to thermally relax the silicon layer, thereby relaxing its internal stress and maintaining the continuous and uniform film morphology achieved by the induced layer, and stabilizing its metastable structure.

[0046] Step 130: Continue heating to the second deposition temperature, introduce a mixture of inert carrier gas and carbon source gas to perform carbon layer chemical vapor deposition, causing the carbon source gas to thermally decompose and deposit on the surface of the silicon / graphite composite substrate to form a carbon coating layer, and then cool down to room temperature in a protective atmosphere to obtain silicon-carbon anode material.

[0047] The purpose of this step is to coat the surface of the silicon / graphite composite matrix with carbon.

[0048] In this step, the carbon source gas includes one or more of methane, acetylene, ethylene, or propylene. Because acetylene has a high hydrocarbon ratio, resulting in high deposition efficiency and a high-quality carbon coating, acetylene is preferably used as the carbon source gas. The silicon source gas includes one or more of silane, disilane, or dichlorosilane; the inert carrier gas is one or more of nitrogen or argon.

[0049] Specifically, the second deposition temperature is 520℃-600℃. Preferably, the temperature is further increased to 520℃-600℃ at a heating rate of 1℃ / min-5℃ / min, and a mixed gas of carbon source gas and inert carrier gas is introduced at a volume flow rate ratio of 1:1-4:1 for carbon layer chemical vapor deposition for 0.5h-3h, uniformly coating a layer of carbon onto the surface of the silicon / graphite composite substrate. The substrate is then cooled to room temperature under a protective atmosphere, and after dispersing, sieving, and demagnetizing, a silicon-carbon anode material is obtained. Preferably, the second deposition temperature is 520℃-530℃.

[0050] The carbon deposition rate can be precisely controlled by adjusting the volumetric flow rate ratio of the carbon source gas to the inert carrier gas (1:1-4:1) and the mixed gas flow rate (2L / min-50L / min). If the mixed gas flow rate is slow and the volumetric flow rate ratio is low, carbon deposition is slow and the carbon coating layer is thin; conversely, deposition is fast and the carbon coating layer is thick.

[0051] This method provides a low-cost, industrially producible method for preparing silicon-carbon anode materials. By constructing an induced layer on the graphite surface using a simplified process, this method effectively controls the vapor deposition behavior of silicon, achieving a stable structure with adjustable and uniform silicon content, and significantly mitigating volume expansion during lithium intercalation. The final material exhibits excellent electrochemical performance, with an initial coulombic efficiency exceeding 88.3% and a charge capacity retention rate exceeding 93.6% at 1C, demonstrating a significant improvement in overall performance.

[0052] Therefore, when this silicon-carbon anode material is applied to lithium-ion batteries or lithium-ion capacitors, its advantages are specifically manifested in that it can more effectively alleviate volume expansion during cycling, thereby significantly improving the cycle life and safety of the product.

[0053] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0054] Example 1 (1) After stirring graphite, hexadecyltrimethylammonium bromide, starch and water in a mass ratio of 1:0.02:0.1:2 evenly, the mixture was spray-dried using a closed spray dryer with an inlet temperature of 220°C and an outlet temperature of 100°C. After discharge, the mixture was placed in a coating furnace and heated to 700°C for 2 hours under a nitrogen atmosphere at a heating rate of 3°C / min. The furnace tube rotation speed was 6 Hz. The mixture was then cooled to room temperature under a nitrogen atmosphere to obtain a functionalized graphite precursor.

[0055] (2) The functionalized graphite precursor was placed in a fluidized bed and heated to 500°C at a heating rate of 2°C / min under a nitrogen atmosphere. A mixture of argon and silane was introduced at a volume flow rate of 10L / min:1L / min. Silicon was deposited on the functionalized graphite precursor after holding the temperature for 3 hours. Then, only argon was introduced at a rate of 50L / min and the temperature was held for another 0.5 hours to purge the material and obtain a silicon / graphite composite matrix.

[0056] (3) Continue to heat the fluidized bed to 540°C at a heating rate of 2°C / min. Introduce a mixture of argon and acetylene at a volume flow rate of 40L / min:10L / min. Hold the mixture at 540°C for 1 hour to uniformly coat the silicon / graphite composite matrix with a carbon layer. Cool the mixture under a protective atmosphere. After breaking it up, sieving and demagnetizing, the silicon-carbon anode material is obtained.

[0057] The specific surface areas of graphite raw material, functionalized graphite precursor, and silicon-carbon anode material were measured using the BET method and were 5m², respectively. 2 / g、30m 2 / g、2m 2 / g. This indicates that the specific surface area of ​​the material exhibits a "first increase and then decrease" change during the preparation process. This suggests that the introduction of the inducing layer forms a rough active surface, providing a substrate for the continuous and uniform deposition of silicon, while the outer carbon coating achieves a tight seal and greatly suppresses side reactions.

[0058] Example 2 (1) After stirring graphite, hexadecyltrimethylammonium bromide, starch and water in a mass ratio of 1:0.01:0.2:1.5 evenly, the mixture was spray-dried using a closed spray dryer with an inlet temperature of 230°C and an outlet temperature of 100°C. After discharge, the mixture was placed in a coating furnace and heated to 700°C for 2 hours under a nitrogen atmosphere at a heating rate of 1°C / min. The furnace tube rotation speed was 6 Hz. The mixture was then cooled to room temperature under a nitrogen atmosphere to obtain a functionalized graphite precursor.

[0059] (2) The functionalized graphite precursor was placed in a fluidized bed and heated to 480°C at a heating rate of 1°C / min under a nitrogen atmosphere. A mixture of argon and silane was introduced at a volume flow rate of 30L / min:1L / min. Silicon was deposited on the functionalized graphite precursor after holding the temperature for 5 hours. Then, only argon was introduced at a rate of 40L / min and the temperature was held for another 0.5 hours to purge the material and obtain a silicon / graphite composite matrix.

[0060] (3) Continue to heat the fluidized bed to 520°C at a heating rate of 4°C / min. Introduce a mixture of argon and acetylene at a volume flow rate of 40L / min:10L / min. Hold the mixture at 520°C for 3 hours to uniformly coat the surface of the silicon / graphite composite matrix with a carbon layer. Cool the mixture under a protective atmosphere. After breaking it up, sieving and demagnetizing, the silicon-carbon anode material is obtained.

[0061] Example 3 (1) After mixing graphite, polyvinylpyrrolidone, starch and water in a mass ratio of 1:0.005:0.05:3 evenly, the mixture was spray-dried using a closed spray dryer with an inlet temperature of 210°C and an outlet temperature of 110°C. After discharge, the mixture was placed in a coating furnace and heated to 500°C for 4 hours under a nitrogen atmosphere at a heating rate of 1°C / min. The furnace tube rotation speed was 5 Hz. The mixture was then cooled to room temperature under a nitrogen atmosphere to obtain a functionalized graphite precursor.

[0062] (2) The functionalized graphite precursor was placed in a fluidized bed and heated to 510°C at a heating rate of 5°C / min under a nitrogen atmosphere. A mixture of argon and silane was introduced at a volume flow rate of 10L / min:1L / min. Silicon was deposited on the functionalized graphite precursor after holding the temperature for 0.5h. Then, only argon was introduced at a rate of 50L / min and the temperature was held for another 0.5h to purge the material and obtain a silicon / graphite composite matrix.

[0063] (3) Continue to heat the fluidized bed to 540°C at a heating rate of 2°C / min. Introduce a mixture of argon and acetylene at a volume flow rate of 40L / min:10L / min. Hold the mixture at 540°C for 2 hours to uniformly coat the surface of the silicon / graphite composite matrix with a carbon layer. Cool the mixture under a protective atmosphere. After breaking it up, sieving and demagnetizing, the silicon-carbon anode material is obtained.

[0064] Example 4 (1) After stirring graphite, hexadecyltrimethylammonium bromide, starch and water in a mass ratio of 1:0.02:0.1:2 evenly, the mixture was spray-dried using a closed spray dryer with an inlet temperature of 220°C and an outlet temperature of 100°C. After discharge, the mixture was placed in a coating furnace and heated to 700°C for 2 hours under a nitrogen atmosphere at a heating rate of 3°C / min. The furnace tube rotation speed was 6 Hz. The mixture was then cooled to room temperature under a nitrogen atmosphere to obtain a functionalized graphite precursor.

[0065] (2) The functionalized graphite precursor was placed in a rotary furnace and heated to 500°C at a heating rate of 1°C / min under a nitrogen atmosphere. A mixture of argon and silane was introduced at a volume flow rate of 1L / min:0.51L / min. Silicon was deposited on the functionalized graphite precursor after holding the temperature for 6 hours. Then, only argon was introduced at a rate of 2L / min, and the temperature was held for another 1 hour to purge the material and obtain a silicon / graphite composite matrix.

[0066] (3) Continue heating in the rotary kiln to 540℃ at a heating rate of 1℃ / min, and introduce a mixed gas of argon and acetylene at a volume flow rate of 1L / min:1L / min. Hold at 540℃ for 0.5h to uniformly coat the silicon / graphite composite matrix with a carbon layer. Cool down under a protective atmosphere, and obtain silicon-carbon anode material after dispersing, sieving, and demagnetizing. The silicon content in the material was measured to be 12.99%.

[0067] Example 5 (1) After stirring graphite, hexadecyltrimethylammonium bromide, glucose and water in a mass ratio of 1:0.02:0.15:4 evenly, the mixture was spray-dried using a closed spray dryer with an inlet temperature of 200°C and an outlet temperature of 90°C. After discharge, the mixture was placed in a coating furnace and heated to 600°C for 2 hours under a nitrogen atmosphere at a heating rate of 5°C / min. The furnace tube rotation speed was 3Hz. The mixture was then cooled to room temperature under a nitrogen atmosphere to obtain a functionalized graphite precursor.

[0068] (2) The functionalized graphite precursor was placed in a fluidized bed and heated to 510°C at a heating rate of 3°C / min under a nitrogen atmosphere. A mixture of argon and silane was introduced at a volume flow rate of 10L / min:1L / min. The temperature was maintained for 2 hours to deposit silicon on the functionalized graphite precursor. Then, only 50L / min of argon was introduced and the temperature was maintained for 0.5 hours to purge the material and obtain a silicon / graphite composite matrix.

[0069] (3) Continue to heat the fluidized bed to 600℃ at a heating rate of 5℃ / min, introduce a mixed gas of argon and acetylene at a volume flow rate of 40L / min:10L / min, keep at 600℃ for 0.5h, uniformly coat a carbon layer on the surface of the silicon / graphite composite matrix, cool down in a protective atmosphere, and obtain silicon-carbon anode material after dispersing, sieving and demagnetizing.

[0070] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that step (1) is omitted.

[0071] Comparative Example 2 Comparative Example 2 uses a grinding method to prepare silicon-carbon anode materials. The specific operation is as follows: (1) After the nano-silicon particles, graphite, hexadecyltrimethylammonium bromide, asphalt and ethanol in a mass ratio of 1:2:0.05:1:5 are mixed evenly by sand milling, the mixture is heated and spray-dried in a spray drying device with an inlet temperature of 220°C and an outlet temperature of 100°C.

[0072] (2) The material is heated to 900°C in a rotary kiln and kept at that temperature for 2 hours. Then, a mixture of argon and acetylene is introduced at a volume flow rate of 5L / min: 5L / min and kept at that temperature for 2 hours. A carbon layer is uniformly coated on the surface of the material. The material is cooled in a protective atmosphere and then broken up, sieved and demagnetized to obtain silicon-carbon anode material.

[0073] Comparative Example 3 Comparative Example 3 replaced graphite with a porous carbon material (pore volume 0.40 cm³). 3 / g, specific surface area 920m² 2 / g) is used to prepare silicon-carbon anode materials by chemical vapor deposition of silicon, the specific operation is as follows: (1) Place the porous carbon in a rotary furnace and heat it to 500°C under a nitrogen atmosphere. Then, introduce a mixture of argon and silane at a volume flow rate of 100 L / min: 10 L / min and keep it at the temperature for 3.5 h to deposit silicon on the porous carbon material. Then, only introduce argon at a flow rate of 50 L / min and keep it at the temperature for 0.5 h to purge the material. (2) Continue to heat the material in the rotary kiln to 540°C, and introduce a mixture of argon and acetylene at a volume flow rate of 40 L / min: 10 L / min. Keep the material at this temperature for 1 hour to uniformly coat it with a carbon layer. Cool the material under a protective atmosphere, and obtain silicon-carbon anode material after breaking it up, sieving and demagnetizing it.

[0074] Next, the intermediate materials or silicon-carbon anode materials prepared in the above embodiments and comparative examples were tested.

[0075] 1. The graphite used in the above raw materials, the functionalized graphite precursor prepared in Example 1, the silicon-carbon anode material prepared in Example 1, and the silicon-carbon anode material prepared in Comparative Example 1 were characterized by scanning electron microscopy (HITACHI SU8600). The test results are shown in the figure. Figures 3-8 .

[0076] in, Figure 3 These are scanning electron microscope (SEM) images of graphite raw materials. Figure 4 This is a SEM image of the functionalized graphite precursor prepared in Example 1. Figure 3 The graphite particles show a relatively smooth and dense surface with a typical layered structure and sharp, clear edges. Figure 4 The image shows a SEM image of graphite after coating with an induction layer. It shows that after spray drying and heat treatment, the graphite surface becomes rough and covered with an uneven layer of granular or flocculent material, blurring the original smoothness and sharp edges. Figure 3 and Figure 4 By comparing the SEM images with the clear surface, this invention successfully constructed a rough, irregular amorphous carbon-induced layer on a smooth and dense graphite surface. This transformation of surface morphology from smooth to rough leads to an increase in the specific surface area of ​​the material, providing abundant active sites for the subsequent heterogeneous nucleation of silane gas. This lays a key structural foundation for the eventual uniform deposition of silicon and the achievement of excellent electrochemical performance with low expansion and high rate capability.

[0077] Figure 5 This is a SEM image of the silicon-carbon anode material prepared in Comparative Example 1. Figure 6 The image shows a cross-sectional SEM image of the silicon-carbon anode material prepared for Comparative Example 1. Figure 5 and Figure 6 The results show that, without an induction layer, silicon deposition is uneven, with obvious silicon particle agglomeration on the surface. Figure 5 The white portion), and silicon is visible in the interface as isolated islands or blocks. Figure 6 (The white part) indicates that the silicon failed to form a uniform coating layer.

[0078] Figure 7 This is a SEM image of the silicon-carbon anode material prepared in Example 1. Figure 8 The image shows a cross-sectional SEM image of the silicon-carbon anode material prepared in Example 1. Figure 7 and Figure 8 The results show that after the introduction of the inducing layer, silicon forms a continuous and dense coating layer on the material surface, with a smooth and uniform surface. Figure 7 The interface shows that the silicon layer (bright white ring) is completely and uniformly wrapped around the outside of the substrate. Figure 8 This indicates that the present invention induces silicon to be uniformly distributed in a thin layer on the graphite surface by introducing an induction layer on the graphite surface.

[0079] 2. Prepare negative electrode sheets from the silicon-carbon negative electrode materials obtained in Examples 1-5 and Comparative Examples 1-3, assemble them into half-cells, and conduct electrochemical tests on the half-cells.

[0080] A water-based anode slurry was prepared by mixing silicon-carbon anode material with Super P conductive agent, sodium carboxymethyl cellulose, and styrene-butadiene rubber at a mass ratio of 16:2:1:1. The solid content of the slurry was controlled at approximately 45 wt%, and the slurry was homogenized using a homogenizer. The slurry was coated onto copper foil to a thickness of 100 μm, and after drying at 80 °C, rolling, cutting, and vacuum drying at 110 °C for 24 h, silicon-carbon anode sheets were obtained. Using lithium metal sheets as the counter electrode and reference electrode, and with a CR2032 battery case, a Celgard 2500 separator, and a 1 mol / L LiPF6 / ethylene carbonate + dimethyl carbonate (v / v = 1:1) electrolyte (with 5.0 vol% fluorocarbonate and 1.0 vol% ethylene carbonate added), the anode half-cell was assembled in a glove box.

[0081] First, discharge to 0.005V at 0.1C (1C = 1000mAh / g), let stand for 5 minutes, then charge to 2V at 0.1C, let stand for 5 minutes, then discharge to 0.005V at 0.1C (1C = 1000mAh / g). Then, sequentially adjust the current density to 1C, 0.75C, 0.5C, 0.3C, and 0.2C, charging to 1V each time (with a 5-minute interval after each charge), and finally charge to 2V at 0.1C. Record the specific capacity of each charge and discharge cycle, and calculate the percentage of the capacity charged at the 1C current density in the next cycle (a higher percentage indicates better rate performance). The test results are shown in [link to test results]. Figure 9 .

[0082] Figure 9 The rate performance comparison shows that all embodiments of the present invention have significantly higher capacity retention rates at high rates (1C), representing fast charging capability, than all comparative examples. This indicates that the material of the present invention has a faster "charge and discharge response speed". The reason why the material prepared by the present invention has the above advantages is that the graphite core provides a fast electron conduction channel, and the continuous silicon thin film morphology facilitated by the induction layer greatly optimizes the interface transport path of lithium ions and shortens the diffusion distance. In contrast, comparative example 1 has increased ion transport impedance due to uneven silicon distribution caused by the lack of an induction layer, while comparative examples 2 (grinding method) and 3 (porous carbon-based) have severely deteriorated charge and discharge response speeds due to problems such as slow diffusion inside silicon particles and poor conductivity of carbon substrate, respectively.

[0083] 3. Prepare negative electrode sheets from the silicon-carbon negative electrode materials obtained in Examples 1-5 and Comparative Examples 1-3 and assemble them into half-cells. Test their discharge specific capacity and charge specific capacity, and calculate the first-cycle coulombic efficiency.

[0084] The method for preparing the negative electrode and assembling it into a half-cell is the same as above. Six cells were assembled for each embodiment and comparative example, and constant current charge-discharge tests were simultaneously conducted on the LAND test system at different current densities. The test voltage range was 0.005-2V, and the tests were performed at 25℃. First, the cells were discharged to 0.005V at 0.1C (1C = 1000mAh / g), allowed to stand for 5 minutes, and then charged to 2V at 0.1C. The discharge and charge specific capacities were recorded for each cycle, and the first-cycle coulombic efficiency was calculated and recorded in Table 1. The first-cycle coulombic efficiency is the ratio of the charge specific capacity to the discharge specific capacity in the first week.

[0085] 4. Prepare negative electrode sheets from the silicon-carbon negative electrode materials obtained in Examples 1-5 and Comparative Examples 1-3 and assemble them into half cells, and then conduct chemical tests on the half cells.

[0086] The method for preparing the negative electrode and assembling it into a half-cell is the same as above.

[0087] During electrode preparation, three pre-cut electrodes were reserved for each sample. For half-cell electrochemical testing, the electrodes were discharged at 0.1C (1C = 1000 mAh / g) to 0.005V. The battery was then removed, and the electrode thickness was measured using a micrometer. This measurement was compared with the thickness of the pre-cut electrodes not yet assembled into a battery. The expansion rate of the electrode was calculated and recorded in Table 1.

[0088] 5. The silicon content in the silicon-carbon anode materials prepared in Examples 1-5 and Comparative Examples 1-3 was measured using the ignition method and recorded in Table 1.

[0089] Table 1 According to the data in Table 1, comparing Examples 1-5 with Comparative Examples 1-3, it can be seen that in terms of first-cycle coulombic efficiency, the examples of the present invention (93.8%-95.0%) are significantly higher than those of the comparative examples (88.1%-90.3%). This indicates that the silicon-carbon anode material prepared by the present invention has a higher first-cycle coulombic efficiency when the charge-discharge specific capacity is close to or much lower than that of the comparative examples. This shows that the present invention achieves extremely high first-cycle coulombic efficiency under moderate charge-discharge specific capacity. In terms of volume expansion rate, the examples of the present invention (27.9%-38.4%) are much lower than those of the comparative examples (75.0%-94.5%), showing that the material prepared by the present invention has an absolute advantage in structural stability.

[0090] In addition, based on the data in Table 1 and Figure 9Data shows that, comparing Example 1 (with an inducing layer, silicon content 12.99%) and Comparative Example 1 (without an inducing layer, silicon content 12.24%), with similar silicon content, Example 1 achieved continuous / semi-continuous thin film deposition of silicon thanks to the inducing layer. Its first-week coulombic efficiency (95.0% vs 90.3%) and rate performance (94.7% vs 93.7%) were both superior to those of Comparative Example 1, where silicon was distributed in an island-like, non-uniform manner. This indicates that the inducing layer promotes uniform silicon film formation by providing active sites, thereby achieving high first-week coulombic efficiency and high rate performance.

[0091] A comparison of Example 4 (silicon content 21.45%) and Comparative Example 3 (silicon content 22.87%) shows that, with similar silicon content, the first-cycle coulombic efficiency of Example 4 (93.9%) is significantly higher than that of Comparative Example 3 (88.7%), while the expansion rate of Example 4 (38.45%) is significantly lower than that of Comparative Example 3 (75.0%). This indicates that, with similar silicon content, the present invention achieves a balance between high capacity, high first-cycle coulombic efficiency, and low expansion rate, solving the problem of poor cycle stability of high-capacity silicon-carbon materials.

[0092] The above comparative results fully demonstrate that the multi-core-shell structure of "graphite core-inducing layer-silicon layer-carbon coating layer" adopted in this invention fundamentally solves the inherent contradiction between first-cycle coulombic efficiency and expansion in traditional silicon-carbon materials. The essence of this invention is that the graphite core provides a highly efficient electron conduction channel, the inducing layer achieves uniform silicon film formation, and the continuous silicon film structure achieves overall stress dispersion, thereby inherently achieving a synergistic improvement in high first-cycle coulombic efficiency, low expansion, and long lifetime at the material level.

[0093] This invention addresses the shortcomings of existing silicon-carbon materials in terms of first-cycle coulombic efficiency, high-rate performance, and expansion performance by innovatively proposing a silicon-carbon anode material with a multi-layered core-shell structure. This approach uses structurally ordered graphite as its core, and by constructing an induced layer rich in oxygen-containing functional groups on its surface, heterogeneous nucleation and growth of silicon source gas on the graphite surface are achieved. This results in a uniform, continuous silicon thin film layer, rather than discrete silicon particles, with a dense carbon layer covering the outermost layer. The multi-layer core-shell structure of "graphite core-inducing layer-silicon layer-carbon coating layer" synergistically leverages the high conductivity of graphite, the film-forming induction properties of the inducing layer, the low stress characteristics of the silicon film, and the interface protection of the carbon layer. Ultimately, this results in the material exhibiting comprehensive superior performance, including high initial efficiency (>90%), excellent rate performance (1C capacity retention >90%), low expansion (<40%), and long lifespan. This provides a practical solution to key obstacles in the commercial application of high-capacity silicon-carbon anode materials (such as the difficulty in balancing initial coulombic efficiency, fast charging, and lifespan), and promotes the development of next-generation high-energy-density power battery technology.

[0094] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. 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 silicon-carbon anode material, characterized in that, The silicon-carbon anode material has a multi-layered core-shell structure, comprising, from the inside out: Graphite core; An induction layer covering the surface of the graphite core; A silicon layer deposited on the induced layer; and, A carbon coating layer covering the outside of the silicon layer; The induction layer is an amorphous carbon with oxygen-containing functional groups on its surface, and the silicon in the silicon layer covers the surface of the induction layer in a continuous or semi-continuous thin layer form. The silicon-carbon anode material is prepared by the following method: After uniformly mixing graphite, dispersant, inducing layer carbon source and solvent in a mass ratio of 100:[0.5-2]:[5-20]:[150-400], spray drying is performed to coat the graphite surface with the inducing layer carbon source. Then, under a protective atmosphere, the temperature is raised to 500℃-800℃ for 1h-4h for heat treatment to carbonize the inducing layer carbon source to form amorphous carbon with oxygen-containing functional groups on the surface, forming an inducing layer on the graphite surface. Subsequently, the temperature is lowered to room temperature under a protective atmosphere to form a functionalized graphite precursor. The functionalized graphite precursor is placed in a chemical vapor deposition apparatus and heated to a first deposition temperature under a protective atmosphere. A mixture of inert carrier gas and silicon source gas is introduced to perform silicon chemical vapor deposition. During the silicon chemical vapor deposition process, the oxygen-containing functional groups act as active sites, adsorbing and catalyzing the thermal decomposition of the silicon source gas. This induces the generated silicon atoms to undergo heterogeneous nucleation on the surface of the induced layer and grow along the surface to form a continuous or semi-continuous silicon layer. Subsequently, the introduction of the silicon source gas is stopped, and the inert carrier gas is continuously introduced at the first deposition temperature for purging treatment to remove residual silicon source gas and byproducts generated by thermal decomposition, while stabilizing the silicon layer structure to obtain a silicon / graphite composite matrix. The temperature is further increased to the second deposition temperature, and a mixture of inert carrier gas and carbon source gas is introduced to perform carbon layer chemical vapor deposition. The carbon source gas undergoes thermal decomposition and is deposited on the surface of the silicon / graphite composite matrix to form a carbon coating layer. Then, the temperature is lowered to room temperature under a protective atmosphere to obtain silicon-carbon anode material.

2. The silicon-carbon anode material according to claim 1, characterized in that, The graphite core has a particle size D50 of 5-12 μm, a specific surface area of 1-10 m 2 / g-10 m 2 / g; The graphite inner core and the induction layer together form a functionalized graphite precursor, the specific surface area of the functionalized graphite precursor is 15 m 2 / g-50 m 2 / g; The silicon-carbon anode material has a particle size D50 of 6μm-13μm and a specific surface area of ​​1m². 2 / g-5 m 2 / g.

3. The silicon-carbon anode material according to claim 1, characterized in that, The silicon content in the silicon-carbon anode material accounts for 5wt%-25wt% of the total mass of the silicon-carbon anode material, and the carbon content in the silicon-carbon anode material accounts for 75wt%-95wt% of the total mass of the silicon-carbon anode material.

4. A method for preparing a silicon-carbon anode material as described in any one of claims 1-3, characterized in that, The preparation method includes the following steps: After uniformly mixing graphite, dispersant, inducing layer carbon source and solvent in a mass ratio of 100:[0.5-2]:[5-20]:[150-400], spray drying is performed to coat the graphite surface with the inducing layer carbon source. Then, under a protective atmosphere, the temperature is raised to 500℃-800℃ for 1h-4h for heat treatment to carbonize the inducing layer carbon source to form amorphous carbon with oxygen-containing functional groups on the surface, forming an inducing layer on the graphite surface. Subsequently, the temperature is lowered to room temperature under a protective atmosphere to form a functionalized graphite precursor. The functionalized graphite precursor is placed in a chemical vapor deposition apparatus and heated to a first deposition temperature under a protective atmosphere. A mixture of inert carrier gas and silicon source gas is introduced to perform silicon chemical vapor deposition. During the silicon chemical vapor deposition process, the oxygen-containing functional groups act as active sites, adsorbing and catalyzing the thermal decomposition of the silicon source gas. This induces the generated silicon atoms to undergo heterogeneous nucleation on the surface of the induced layer and grow along the surface to form a continuous or semi-continuous silicon layer. Subsequently, the introduction of the silicon source gas is stopped, and the inert carrier gas is continuously introduced at the first deposition temperature for purging treatment to remove residual silicon source gas and byproducts generated by thermal decomposition, while stabilizing the silicon layer structure to obtain a silicon / graphite composite matrix. The temperature is further increased to the second deposition temperature, and a mixture of inert carrier gas and carbon source gas is introduced to perform carbon layer chemical vapor deposition. The carbon source gas undergoes thermal decomposition and is deposited on the surface of the silicon / graphite composite matrix to form a carbon coating layer. Then, the temperature is lowered to room temperature under a protective atmosphere to obtain silicon-carbon anode material.

5. The preparation method according to claim 4, characterized in that, The dispersant is one or more of hexadecyltrimethylammonium bromide or polyvinylpyrrolidone; The carbon source for the induction layer includes one or more of glucose, starch, or phenolic resin. The solvent is one or more of water or ethanol; The silicon source gas includes one or more of silane, silane, or dichlorosilane; The carbon source gas includes one or more of methane, acetylene, ethylene, or propylene. The inert carrier gas is one or more of nitrogen or argon; The protective atmosphere is one or more of nitrogen or argon.

6. The preparation method according to claim 4, characterized in that, The mass ratio of the graphite, the dispersant, the carbon source of the induction layer, and the solvent is 100:[1-2]:[10-15]:[200-300].

7. The preparation method according to claim 4, characterized in that, The equipment used for spray drying is selected from either an open spray dryer or a closed spray dryer.

8. The preparation method according to claim 4, characterized in that, The inlet temperature of the spray dryer is 200℃-240℃, and the outlet temperature is 90℃-110℃. The first deposition temperature is 480℃-510℃, the time for silicon layer chemical phase deposition is 0.5h-6h, and the purging treatment time is 0.5h-1h; The second deposition temperature is 520℃-600℃, and the time for the carbon layer chemical vapor deposition is 0.5h-3h.

9. A negative electrode sheet, characterized in that, Includes the silicon-carbon anode material according to any one of claims 1-3, or includes the silicon-carbon anode material prepared by the preparation method according to any one of claims 4-8.

10. An energy storage device, characterized in that, The energy storage device includes: for lithium-ion batteries or lithium-ion capacitors; The energy storage device includes the silicon-carbon anode material according to any one of claims 1-3, or the silicon-carbon anode material prepared by any one of claims 4-8, or the anode sheet according to claim 9.

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