A nanoscale silicon-based powder material surface modification material, a preparation method and application thereof
By constructing a multilayer structure on the surface of nano-silicon-based materials and using supercritical carbon dioxide fluid modification, the processing difficulty and volume expansion rate of nano-scale silicon-based materials were solved, thereby improving the performance and processing capabilities of lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 杭州星科源新材料科技有限公司
- Filing Date
- 2026-02-07
- Publication Date
- 2026-06-05
AI Technical Summary
Nanoscale silicon-based materials in lithium-ion batteries are difficult to process, have a high volume expansion rate, and are prone to side reactions, which affect battery performance.
Supercritical carbon dioxide fluid is used to modify nano-silicon-based materials to construct a multilayer structure, including nano-silicon, a first silicon oxide layer, a second silicon oxide layer, and a carbon coating layer or an oxide coating layer. The supercritical fluid diffuses and flows through the material surface to uniformly coat the material.
It improves the stability and conductivity of nano-silicon-based materials, reduces side reactions, enhances the cycle stability and initial coulombic efficiency of batteries, and promotes the processing performance of materials.
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Figure CN122158659A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of negative electrode material technology, specifically a surface modification material for nanoscale silicon-based powder materials, its preparation method, and its application. Background Technology
[0002] In recent years, with the booming development of new energy vehicles, consumer electronics, and the low-altitude economy, the demand for high-energy-density, high-rate batteries has been increasing year by year. The theoretical capacity of graphite materials used in commercial anodes is 372 mAh / g, which is insufficient to meet the needs of high-energy-density lithium-ion batteries. Silicon materials, due to their high specific capacity of 3579 mAh / g, are considered a promising anode material and are expected to be widely used in lithium-ion battery anode materials.
[0003] However, when silicon is used as the negative electrode in lithium-ion batteries, its large volume expansion rate leads to internal stress that can cause material breakage and pulverization. This results in continuous side reactions with the electrolyte, forming a solid electrolyte interphase (SEI) film, which in turn affects the battery's capacity, cycle life, and initial efficiency. Furthermore, nanoscale silicon-based materials exhibit high reactivity and are difficult to process, requiring modification. Modification methods for nanoscale silicon include surface passivation, surface coating, in-situ doping, and metal composites, each imparting different properties to the material.
[0004] Supercritical fluids are fluids that exist at temperatures and pressures greater than their critical temperatures and pressures. Supercritical fluids include, but are not limited to, carbon dioxide, water, ethane, ethylene, propane, ammonia, nitrous oxide, and sulfur hexafluoride. These fluids exhibit gas-like diffusion properties and liquid-like dissolving abilities, and have wide applications in the food, pharmaceutical, environmental, and chemical industries.
[0005] Among supercritical fluids, carbon dioxide is the most commonly used, partly because it can reach a supercritical state at relatively low temperatures and pressures. Specifically, carbon dioxide exhibits a supercritical state when the temperature is above 31.3℃ and the pressure is above 7.38MPa. Summary of the Invention
[0006] To address the challenges of processing nanoscale silicon-based materials in practical applications and to enhance their utilization, enabling them to perform better as anode materials in liquid and solid-state batteries, this invention provides a surface modification material for nanoscale silicon-based powders, its preparation method, and its application. Utilizing the diffusion and flow characteristics of supercritical carbon dioxide, the nanoscale silicon-based material is modified. This modification method allows for the control of the surface structure of ultrafine powder materials and enables uniform coating of the nanoscale silicon-based material surface.
[0007] To address the aforementioned technical problems, this invention provides the following technical solution: a surface modification material for nanoscale silicon-based powder materials, the structure comprising, from the inside out, nano-silicon, a first silicon oxide layer, a second silicon oxide layer, and a carbon coating layer or an oxide coating layer. The size of the nano-silicon is between 30-200 nm; The thickness of the first silicon oxide layer is 2-4 nm, and the oxygen content is 2-6 wt%. The thickness of the second silicon oxide layer is 1-3 nm, and the oxygen content is 1-4 wt%. The carbon content in the carbon coating layer is 1-5 wt%, and the oxide content in the oxide coating layer is 0.1-1 wt%.
[0008] Preferably, the size of the nano-silicon is 30-80 nm, and the oxide content in the oxide coating layer is 0.2-0.5 wt%.
[0009] A method for preparing a surface-modified nanoscale silicon-based powder material, characterized by comprising the following steps: S1. A first silicon oxide layer is obtained through nano-silicon pretreatment. The nano-silicon material is placed in a container designed with an air inlet and an air outlet. The air inlet is connected to the outlet of the gas mixing system, and the air outlet is connected to a one-way valve and a water seal device. The gas mixing system mixes inert gas and oxygen in a certain proportion. By precisely controlling the oxygen concentration and heat treatment temperature, the purpose of constructing the first silicon oxide layer is achieved. The oxygen concentration is 0.1%-10wt%, the temperature is 50℃-500℃, and the heating rate is 0.5-10℃ / min. S2. The nano-silicon material containing the first silicon oxide layer is mixed with a precursor solution using ethanol as a solvent, and a precursor for the second silicon oxide layer and the coating layer is obtained under the action of supercritical fluid. S3. Add the nano-silicon material containing the first silicon oxide layer to the ethanol solution, and then add the precursor with the carbon coating layer or oxide coating layer. Mix evenly by stirring, homogenizing, emulsifying and dispersing. S4. Heat treatment is performed on the nano-silicon material containing the second silicon oxide layer and the precursor of the coating layer under an inert atmosphere. The atmosphere is selected from one or more of nitrogen, argon and carbon dioxide, the gas flow rate is 0.5L / min-100L / min, the heating rate is 1℃ / min-10℃ / min, the temperature is 300℃-1200℃, and the holding time is 0.5h-12h. After heat treatment, the surface modification of silicon-based powder containing the first silicon oxide layer, the second silicon oxide layer and the carbon coating layer or oxide coating layer is achieved.
[0010] Preferably, in step S1, the oxygen concentration is 0.5-5 wt%, the temperature is 100℃-200℃, and the heating rate is 2℃-6℃ / min.
[0011] Preferably, the precursors for the carbon coating layer in step S2 include, but are not limited to, glucose, sucrose, fructose, dopamine, polyethylene glycol, glycerol, tannic acid, gallic acid, salicylic acid, citric acid, phenolic resin, epoxy resin, urea-formaldehyde resin, and combinations thereof.
[0012] Preferably, the precursor for the oxide coating layer in step S2 includes, but is not limited to, aluminum isopropoxide, aluminum sec-butoxide, lithium tert-butoxide, lithium methoxide, boric acid, borate ester, and combinations thereof.
[0013] Preferably, in step S3, the carbon dioxide pressure is adjusted to 7.5MPa-20MPa and the carbon dioxide temperature is adjusted to 40℃-100℃, respectively, above the critical pressure and critical temperature of carbon dioxide, and the reaction time is 0.5h-10h.
[0014] Preferably, in step S3, the second silicon oxide layer is constructed by interfacial reaction of ethanol solvent on the surface of the nano-silicon material under the supercritical state of carbon dioxide; at the same time, the characteristic of ethanol as a co-solvent for supercritical carbon dioxide is utilized to promote the binding of the precursor of the coating layer with the surface active sites of the nano-silicon oxide layer; thereby achieving the purpose of uniform coating of the precursor.
[0015] Preferably, in step S4, the gas flow rate is 2L-20L / min; the heating rate is 2℃-5℃ / min; the temperature is 450℃-850℃; and the holding time is 2h-6h.
[0016] Application of a surface modification material for nanoscale silicon-based powder materials, applied to the surface modification of nanoscale silicon-based powder materials.
[0017] The following benefits can be achieved by adopting the technical solution of the present invention: 1. It achieves the modification of nanoscale silicon-based powder materials, solving the problem of uneven carbon coating and oxide coating in the traditional sense; in terms of process implementation, the multi-layer structure of nano-silicon materials constructed by this method has lower energy consumption, can be coated with different substances as needed, has a simpler process, and is easier to achieve mass production. 2. In terms of structure, by constructing a multilayer structure, different carbon precursors or oxide precursors are coated on the surface of the nano-silicon material. By coating the carbon layer and oxide layer, a stable conductive network can be constructed to maintain the continuity of conductivity. At the same time, the multilayer structure can improve the stability of the nano-scale silicon-based powder material. Even if the material cracks, it can prevent side reactions from occurring, thereby improving cycle stability and first coulombic efficiency. 3. Regarding the surface properties of nano-silicon, due to the diffusivity of gas, the fluidity (low viscosity) of liquid, and good mass transfer characteristics of supercritical carbon dioxide fluid, it can better penetrate between nanoparticles and on the active sites on the surface when ethanol is used as a co-solvent. This promotes the densification process between particles, reduces the voids between particles, improves the water solubility of the material, and enhances the processing performance of the material. This allows the material to be better applied to downstream battery companies, thus promoting the development of battery materials and solid-state batteries. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of the multilayer structure of the present invention; Figure 2 This is a graph showing the electrochemical charge-discharge test results for Example 4; Figure 3 This is a transmission electron microscope image of Example 4; Figure 4 This is a graph showing the electrochemical charge-discharge test results for Example 8; Figure 5 This is a scanning electron microscope image of Example 8. Detailed Implementation
[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1
[0020] A method for preparing a surface-modified nanoscale silicon-based powder material. (1) Select nano-silicon of about 50nm, control the oxygen concentration to 1.0wt%, specifically the oxygen flow rate to 1ml / min and the nitrogen flow rate to 99ml / min, to obtain the first silicon oxide layer.
[0021] (2) A supercritical processing precursor was obtained by mixing nano-silicon containing the first silicon oxide layer with ethanol. The mixture was in a clay-like state after mixing; then it was placed in a supercritical carbon dioxide drying device to react and obtain the second silicon oxide layer.
[0022] (3) The pressure of carbon dioxide was adjusted to 9.0 MPa and the temperature of carbon dioxide was adjusted to 70 °C. The reaction time was 4 h. After the reaction was completed, the material was removed by depressurization and cooling to obtain nano-silicon material containing the second silicon oxide layer. Example 2
[0023] The nano-silicon material was prepared using a method that was essentially the same as in Example 1, except that the size of the nano-silicon was 30 nm in step (1). Example 3
[0024] The nano-silicon material was prepared in basically the same way as in Example 1, except that in step (1), the oxygen concentration was 2.0 wt%, the oxygen flow rate was 2 ml / min, the nitrogen flow rate was 98 ml / min, the carbon dioxide pressure was 15.0 MPa, the temperature was 90 °C, and the reaction time was 8 h. Example 4
[0025] (1) Select nano-silicon of about 50nm, control the oxygen concentration to 1.0wt%, specifically the oxygen flow rate to 5ml / min and the nitrogen flow rate to 495ml / min, to obtain the first silicon oxide layer.
[0026] (2) A supercritical carbon-coated precursor is obtained by mixing nano-silicon material containing the first silicon oxide layer with a carbon precursor solution. Glucose is selected as the carbon precursor with a carbon coating ratio of 3.5%. Glucose is dissolved in ethanol and the dissolution is accelerated by stirring and heating to obtain a glucose solution. Nano-silicon material containing the first silicon oxide layer is added to the glucose solution and mixed by stirring to form a clay-like state.
[0027] (3) The reaction was carried out in a supercritical carbon dioxide drying device to obtain a second silicon oxide layer and a carbon pre-coating layer. The pressure of carbon dioxide was adjusted to 9.0 MPa, the temperature of carbon dioxide was adjusted to 70 °C, and the reaction time was 4 h.
[0028] (4) Carbonize the material containing the carbon pre-coating layer to obtain the carbon coating layer. The carbonization parameters are as follows: put the supercritical carbon dioxide nano-silicon pre-carbon coated material into a tube atmosphere furnace, introduce nitrogen gas at a flow rate of 120 ml / min, heat it to 900°C at a heating rate of 5°C / min under nitrogen protection, maintain the target temperature for 4 hours, and take out the material after it is naturally cooled to room temperature. Example 5
[0029] Nano-silicon materials were prepared using a method that was basically the same as in Example 4, except that the carbon precursor in step (2) was tannic acid and the carbon coating ratio was 2.5%, the carbon dioxide pressure in step (3) was 15.0 MPa, the temperature was 90°C, the reaction time was 8 h, and the heat treatment temperature in step (4) was 750°C. Example 6
[0030] Nano-silicon materials were prepared using a method that was basically the same as in Example 4, except that in step (2), the carbon precursor was citric acid and the carbon coating ratio was 5%; in step (3), the carbon dioxide pressure was 18.0 MPa, the temperature was 60°C, the reaction time was 6 h, and in step (4), the heat treatment temperature was 1000°C. Example 7
[0031] Nano-silicon materials were prepared using a method that was basically the same as in Example 4, except that in step (2), the carbon precursor was salicylic acid and the carbon coating ratio was 1.5%; in step (3), the carbon dioxide pressure was 10.0 MPa, the temperature was 80°C, the reaction time was 2 h, and in step (4), the heat treatment temperature was 850°C. Example 8
[0032] (1) Select nano-silicon of about 50 nm, control the oxygen concentration to 1.0%, specifically the oxygen flow rate of 1 ml / min and the nitrogen flow rate of 99 ml / min, to obtain the first silicon oxide layer.
[0033] (2) A supercritical oxide-coated precursor is obtained by mixing nano-silicon material containing the first silicon oxide layer with an oxide precursor solution. Aluminum isopropoxide is selected as the oxide coating precursor with a coating ratio of 1%. The oxide precursor is dissolved in ethanol and added to the oxide precursor solution by homogenization emulsification. The nano-silicon material containing the first silicon oxide layer is added to the oxide precursor solution and mixed by stirring until it is in a clay-like state.
[0034] (3) The reaction was carried out in a supercritical carbon dioxide drying device to obtain a second silicon oxide layer and an oxide pre-coating layer. The carbon dioxide pressure was adjusted to 9.0 MPa, the carbon dioxide temperature was adjusted to 70 °C, and the reaction time was 4 h; (4) Heat treatment is performed on the material containing the oxide pre-coating layer to obtain the oxide coating layer. The main heat treatment process is as follows: the supercritical carbon dioxide nano-silicon pre-oxide coated material is put into a tube furnace, nitrogen is introduced at a flow rate of 100 ml / min, and the temperature is raised to 550°C at a heating rate of 5°C / min under the nitrogen atmosphere. The temperature is maintained at the target temperature for 3 hours, and the material is taken out after natural cooling to room temperature to obtain nano-silicon material containing the oxide coating layer. Example 9
[0035] Nano-silicon materials were prepared in basically the same way as in Example 8, except that the oxide precursor in step (2) was lithium methoxide with a coating ratio of 0.5%, the carbon dioxide pressure in step (3) was 15.0 MPa, the temperature was 90 °C, the reaction time was 8 h, and the heat treatment temperature in step (4) was 650 °C. Example 10
[0036] Nano-silicon materials were prepared in basically the same way as in Example 8, except that the oxide precursor in step (2) was borate ester with a coating ratio of 0.2%, the carbon dioxide pressure in step (3) was 18.0 MPa, the temperature was 60°C, the reaction time was 6 h, and the heat treatment temperature in step (4) was 700°C. Example 11
[0037] Nano-silicon materials were prepared in basically the same way as in Example 8, except that in step (2), the oxide precursor was a mixture of aluminum isopropoxide and lithium methoxide with a coating ratio of 0.1%, in step (3) the carbon dioxide pressure was 10.0 MPa, the temperature was 80 °C, the reaction time was 2 h, and in step (4) the heat treatment temperature was 600 °C.
[0038] We selected silicon nanometers of about 50nm and only performed the first silicon oxide coating layer treatment.
[0039] We selected silicon nanometers of around 30nm and performed only the first silicon oxide coating layer treatment.
[0040] The materials prepared in Examples 1 to 11 and Comparative Examples 1 to 2 were subjected to various performance tests under the following conditions, and the test results are shown in Tables 1 and 2.
[0041] The oxygen content was tested using a nitrogen-oxygen analyzer, and the carbon content was tested using a carbon-sulfur analyzer.
[0042] The specific surface area was measured using a specific surface area analyzer.
[0043] Elemental analysis was performed using EDS (energy dispersive spectroscopy) analysis with scanning electron microscopy.
[0044] Electrochemical testing of materials: The prepared silicon-carbon anode material was used as the active material and mixed with an aqueous dispersion of acrylonitrile copolymer binder (LA132, 15% solid content) and conductive agent (Super P) at a mass ratio of 92:6:2. A suitable amount of water was added as a solvent to adjust the slurry to a solid content of 55%. This slurry was coated onto copper foil and then vacuum dried and rolled to prepare the anode sheet. A lithium metal sheet was used as the counter electrode. An electrolyte was formed by mixing 1 mol / L LiPF6 with a three-component mixed solvent in EC:DMC:EMC = 1:1:1 (v / v / v). A polypropylene microporous membrane was used as the separator, and CR2032 coin cells were assembled in an inert gas-filled glove box. Charge-discharge tests of the coin cells were conducted on the LANHE battery testing system.
[0045] First charge-discharge performance test: Under normal temperature conditions, discharge at a constant current of 0.1C to a voltage of 0.01V, then discharge at a constant current of 0.02C to a voltage of 0.005V, and then charge at a constant current of 0.1C to a voltage of 1.5V to obtain the first reversible specific capacity and the first coulombic efficiency.
[0046] Cyclic performance test: Under normal temperature conditions, charge and discharge at 1C constant current to 0.01V, then discharge at 0.05C constant current to 0.005V, and finally charge at 1C constant current to 1.5V to obtain the delithiation specific capacity. This cycle is repeated 100 times, and the expansion rate after 100 cycles is calculated.
[0047] Table 1 shows the oxygen content tests for Examples 1 to 3. As shown in Table 1, the oxygen content of the nano-silicon materials prepared in Examples 1 and 3 is significantly higher than that in Comparative Example 1, and the oxygen content of the nano-silicon material prepared in Example 2 is significantly higher than that in Comparative Example 2. The mechanism of this reaction is that carbon dioxide decomposes under supercritical conditions to form interstitial oxygen molecules within the oxide. The oxidation rate and the thickness of the second silicon oxide layer can be adjusted by controlling the partial pressure of carbon dioxide. At the same time, the oxygen content of 30 nm nano-silicon is higher than that of 50 nm nano-silicon because 30 nm nano-silicon has a larger specific surface area. The chemical reaction mainly occurs on the surface of the material, and a larger specific surface area means more reaction sites that come into contact with interstitial oxygen molecules, thus resulting in a higher oxygen content.
[0048] Table 2 shows the performance tests for Examples 1 to 11 and Comparative Examples 1 to 2.
[0049] As shown in Table 2, compared with nano-silicon containing a first silicon oxide layer and nano-silicon containing a second silicon oxide layer, the nano-silicon material with a carbon coating layer exhibits a significantly improved initial coulombic efficiency. This is because the carbon precursor is coated onto the particle surface through diffusion, flow, and mass transfer via supercritical carbon dioxide fluid. After carbonization, a uniform carbon coating layer is formed. This carbon coating layer introduces a stable, conductive, and mechanically strong carbon layer as an interface, transferring the formation and growth of the solid electrolyte interphase (SEI) film from the drastically changing silicon surface to the relatively stable, uniform carbon layer surface. This greatly limits the continuous irreversible growth of the SEI film and blocks the direct side reactions between silicon and the electrolyte. Under these conditions, the consumption of lithium ions and electrolyte in the first cycle is significantly reduced, and the number of reversible lithium ions in the cycle is greater. Therefore, the initial coulombic efficiency is significantly improved.
[0050] As shown in Table 2, compared with nano-silicon containing a first silicon oxide layer and nano-silicon containing a second silicon oxide layer, the expansion rate of nano-silicon containing an oxide coating layer is significantly reduced. This is because, through the action of supercritical carbon dioxide fluid, a uniform oxide coating layer is deposited on the surface of the nano-silicon material. When the oxide, with its high Young's modulus, coats the soft silicon particles, it forms a hard outer shell. During silicon lithium intercalation expansion, this hard shell layer exerts a strong mechanical constraint, restricting the free outward expansion of the nano-silicon. Simultaneously, it distributes the enormous stress generated by the nano-silicon more evenly across the entire particle, avoiding localized stress concentration and thus maintaining the structural integrity of the nano-silicon particles. Therefore, the expansion rate of nano-silicon containing an oxide coating layer is significantly reduced. Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A surface-modifying material for nanoscale silicon-based powders, characterized in that: Its structure, from the inside out, includes nano-silicon, a first silicon oxide layer, a second silicon oxide layer, and a carbon coating layer or an oxide coating layer. The size of the nano-silicon is between 30-200 nm; The thickness of the first silicon oxide layer is 2-4 nm, and the oxygen content is 2-6 wt%. The thickness of the second silicon oxide layer is 1-3 nm, and the oxygen content is 1-4 wt%. The carbon content in the carbon coating layer is 1-5 wt%, and the oxide content in the oxide coating layer is 0.1-1 wt%.
2. The surface modification material for nanoscale silicon-based powder materials according to claim 1, characterized in that: The size of the nano-silicon is 30-80nm, and the oxide content in the oxide coating layer is 0.2-0.5wt%.
3. A method for preparing a surface-modified nanoscale silicon-based powder material as described in claim 1, characterized in that: Includes the following steps: S1. A first silicon oxide layer is obtained through nano-silicon pretreatment. The nano-silicon material is placed in a container designed with an air inlet and an air outlet. The air inlet is connected to the outlet of the gas mixing system, and the air outlet is connected to a one-way valve and a water seal device. The gas mixing system mixes inert gas and oxygen in a certain proportion. By precisely controlling the oxygen concentration and heat treatment temperature, the purpose of constructing the first silicon oxide layer is achieved. The oxygen concentration is 0.1%-10wt%, the temperature is 50℃-500℃, and the heating rate is 0.5-10℃ / min. S2. The nano-silicon material containing the first silicon oxide layer is mixed with a precursor solution using ethanol as a solvent, and a precursor for the second silicon oxide layer and the coating layer is obtained under the action of supercritical fluid. S3. Add the nano-silicon material containing the first silicon oxide layer to the ethanol solution, and then add the precursor with the carbon coating layer or oxide coating layer. Mix evenly by stirring, homogenizing, emulsifying and dispersing. S4. Heat treatment is performed on the nano-silicon material containing the second silicon oxide layer and the precursor of the coating layer under an inert atmosphere. The atmosphere is selected from one or more of nitrogen, argon and carbon dioxide, the gas flow rate is 0.5L / min-100L / min, the heating rate is 1℃ / min-10℃ / min, the temperature is 300℃-1200℃, and the holding time is 0.5h-12h. After heat treatment, the surface modification of silicon-based powder containing the first silicon oxide layer, the second silicon oxide layer and the carbon coating layer or oxide coating layer is achieved.
4. The method for preparing a surface-modified nanoscale silicon-based powder material according to claim 3, characterized in that: In step S1, the oxygen concentration is 0.5-5 wt%, the temperature is 100℃-200℃, and the heating rate is 2℃-6℃ / min.
5. The method for preparing a surface-modified nanoscale silicon-based powder material according to claim 3, characterized in that: In step S2, the precursors for the carbon coating layer include, but are not limited to, glucose, sucrose, fructose, dopamine, polyethylene glycol, glycerol, tannic acid, gallic acid, salicylic acid, citric acid, phenolic resin, epoxy resin, urea-formaldehyde resin, and combinations thereof.
6. The method for preparing a surface-modified nanoscale silicon-based powder material according to claim 3, characterized in that: In step S2, the precursors for the oxide coating layer include, but are not limited to, aluminum isopropoxide, aluminum sec-butoxide, lithium tert-butoxide, lithium methoxide, boric acid, borate ester, and combinations thereof.
7. The method for preparing a surface-modified nanoscale silicon-based powder material according to claim 3, characterized in that: In step S3, above the critical pressure and critical temperature of carbon dioxide, the pressure of carbon dioxide is adjusted to 7.5MPa-20MPa, the temperature of carbon dioxide is adjusted to 40℃-100℃, and the reaction time is 0.5h-10h.
8. The method for preparing a surface-modified nanoscale silicon-based powder material according to claim 3, characterized in that: In step S3, under the supercritical state of carbon dioxide, the surface of the nano-silicon material is treated by interfacial reaction with ethanol solvent to construct a second silicon oxide layer; at the same time, taking advantage of the fact that ethanol can be used as a co-solvent for supercritical carbon dioxide, the precursor of the coating layer is promoted to combine with the surface active sites of the nano-silicon oxide layer; thereby achieving the purpose of uniform coating of the precursor.
9. The method for preparing a surface-modified nanoscale silicon-based powder material according to claim 3, characterized in that: In step S4, the gas flow rate is 2L-20L / min; the heating rate is 2℃-5℃ / min; the temperature is 450℃-850℃; and the holding time is 2h-6h.
10. An application of the surface-modified material of nanoscale silicon-based powder as described in claim 1, characterized in that: It is applied to the surface modification of nanoscale silicon-based powder materials.