Preparation method of fast-charging silicon-carbon composite material and lithium ion battery

Abstract

The application provides a preparation method of a fast-charging silicon-carbon composite material and a lithium ion battery, and comprises the following steps: obtaining a second mixture by carbonizing a first mixture, performing graphitization on the second mixture to obtain porous graphite, wherein the first mixture comprises coke raw materials, a pore forming agent and a first catalyst; depositing nano-silicon on the surface of the porous graphite by using silane and a second catalyst to obtain a third mixture; and growing carbon nanotubes on the surface of the third mixture to obtain the fast-charging silicon-carbon composite material. Compared with the prior art, the application can deposit nano-silicon on the surface of the porous graphite, utilize the advantages of high specific capacity and small expansion of the nano-silicon to improve the deficiency of the graphite in the energy density aspect, and further deposit carbon nanotubes outside the nano-silicon, utilize the high electronic conductivity and specific surface area of the carbon nanotubes, so that the fast-charging silicon-carbon composite material has good energy density, and the fast-charging performance and cycle performance of the fast-charging silicon-carbon composite material are improved.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery materials, specifically to a method for preparing fast-charging silicon-carbon composite materials and lithium-ion batteries. Background Technology

[0002] As users increasingly demand higher energy density and faster charging performance from lithium-ion batteries, the anode materials used in these batteries must possess both high energy density and excellent fast charging capabilities. While single graphite anode materials can achieve excellent fast charging and cycle performance, their energy density is relatively low due to the inherent limitations of graphite. Silicon-based materials, although possessing higher energy density, exhibit significant expansion, resulting in poor fast charging and cycle performance. Therefore, researchers are exploring the possibility of combining graphite and silicon-based materials to create anode materials with superior performance.

[0003] However, commonly used composite materials often suffer from problems such as excessively large silicon grains and poor electronic conductivity, which cannot adequately meet the needs of users. Summary of the Invention

[0004] This application mainly provides a method for preparing fast-charging silicon-carbon composite materials and a lithium-ion battery, which enables the material to have good energy density while improving its fast-charging performance and cycle performance.

[0005] To solve the above-mentioned technical problems, one technical solution adopted in this application is: to provide a method for preparing fast-charging silicon-carbon composite material, including carbonizing a first mixture to obtain a second mixture, graphitizing the second mixture to obtain porous graphite, wherein the first mixture includes coke-based raw materials, a pore-forming agent and a first catalyst; depositing nano-silicon on the surface of porous graphite using silane and a second catalyst to obtain a third mixture; and growing carbon nanotubes on the surface of the third mixture to obtain the fast-charging silicon-carbon composite material.

[0006] In one specific embodiment, the first mixture further includes lithium carboxymethyl cellulose; the carbonization of the first mixture yields a second mixture, and the graphitization of the second mixture includes uniformly mixing the coke raw material, the pore-forming agent, the first catalyst, and the lithium carboxymethyl cellulose to obtain the first mixture; heating the first mixture to 500-800°C and carbonizing it for 1-6 hours to obtain the second mixture; pressing the second mixture into blocks at 10-20 MPa; and then graphitizing the pressed second mixture at 2800-3200°C for 24-72 hours.

[0007] In one specific embodiment, the mass ratio of the coke raw material, the pore-forming agent, the first catalyst, and the lithium carboxymethyl cellulose is 100:1-5:1-5:1-5.

[0008] In one specific embodiment, the pore-forming agent includes at least one of potassium carbonate, sodium carbonate, calcium carbonate, magnesium carbonate, and aluminum carbonate.

[0009] In one specific embodiment, the first catalyst includes at least one of nickel chloride, nickel carbonate, nickel sulfate, nickel acetate, cobalt acetate, cobalt nitrate, cobalt chloride, copper acetate, copper chloride, copper sulfate, copper carbonate, ferric acetate, and ferric chloride.

[0010] In one specific embodiment, the second catalyst includes at least one of ferrocene, nickel acetylacetonate, cobalt(II) acetate, and cobalt acetylacetonate.

[0011] In one specific embodiment, the mass ratio of the silane, the second catalyst, and the porous graphite is 10–30:1–5:100.

[0012] In one specific embodiment, the deposition of nano-silicon on the surface of porous graphite using silane and a second catalyst includes adding the silane and the second catalyst to an organic solvent to prepare a 0.5-5 wt% solution, adding the porous graphite to the solution and dispersing it evenly, and heating until the silane decomposes to deposit nano-silicon on the silane surface.

[0013] In one specific embodiment, the silane includes at least one of liquid silane, dimethylsilane, trichloroethylsilane, methyltrimethoxysilane, propyltrichlorosilane, and propyltrimethoxysilane, and the organic solvent includes at least one of benzene, diethyl ether, methanol, xylene, and carbon tetrachloride.

[0014] To solve the above-mentioned technical problems, another technical solution adopted in this application is: to provide a lithium-ion battery, the lithium-ion battery including a negative electrode sheet, the negative electrode sheet including a fast-charging silicon-carbon composite material prepared by the above-mentioned preparation method.

[0015] The beneficial effects of this application are as follows: Unlike the prior art, the embodiments of this application provide a method for preparing fast-charging silicon-carbon composite materials and a lithium-ion battery. Porous graphite is obtained by adding pore-forming agents and catalysts to treat coke-like raw materials. Nano-silicon is deposited on the surface of the porous graphite, thereby utilizing the advantages of high specific capacity and small expansion of nano-silicon to improve the shortcomings of graphite in terms of energy density. At the same time, carbon nanotubes are also deposited on the nano-silicon, utilizing the high electronic conductivity and specific surface area of ​​carbon nanotubes to improve the fast-charging performance and cycle performance of the material. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a SEM image of an embodiment of the fast-charging silicon-carbon composite material provided in this application;

[0018] Figure 2 This is a schematic flowchart of an embodiment of the preparation method of the fast-charging silicon-carbon composite material provided in this application. Detailed Implementation

[0019] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are for illustrative purposes only and do not limit the scope of the application. Similarly, the following embodiments are only some, not all, embodiments of the present application, and all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0020] The terms "first," "second," and "third" in this application are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first," "second," or "third" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationships and movements between components in a specific orientation (as shown in the figures). If the specific orientation changes, the directional indications also change accordingly. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. A process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices.

[0021] In this document, the term "implementation" means that a specific feature, structure, or characteristic described in connection with an implementation may be included in at least one implementation of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same implementation, nor is it a separate or alternative implementation mutually exclusive with other implementations. It will be explicitly and implicitly understood by those skilled in the art that the implementations described herein can be combined with other implementations.

[0022] Please see Figure 2 , Figure 2 This is a schematic flowchart of an embodiment of the preparation method of the fast-charging silicon-carbon composite material provided in this application. It should be noted that if substantially the same result is obtained, this embodiment is not necessarily identical. Figure 2 The illustrated process sequence is limited. For example... Figure 2 As shown, this embodiment includes:

[0023] S100: Carbonize the first mixture to obtain the second mixture, and graphitize the second mixture to obtain porous graphite. The first mixture includes coke-based raw materials, pore-forming agent and first catalyst.

[0024] A first mixture is provided, comprising a coke-based feedstock, a pore-forming agent, and a first catalyst. The first mixture is carbonized to obtain a second mixture, which is then subjected to a graphitization process to obtain porous graphite.

[0025] In this process, the gasification of the first catalyst can form nano- and micro-sized pores on the surface of porous graphite, while the pore-forming agent can promote the formation of millimeter-sized large pores on the surface of porous graphite. The two work together to form a loose and porous structure on the surface of porous graphite, which can increase the specific surface area and facilitate the uniform deposition of materials such as nano-silicon and carbon nanotubes in subsequent processes.

[0026] Specifically, lithium carboxymethyl cellulose can be added during the carbonization process of coking raw materials.

[0027] Step S100 can be specifically as follows: a first mixture is obtained by uniformly mixing coke raw materials, pore-forming agent, first catalyst and lithium carboxymethyl cellulose; the first mixture is heated to 500-800°C and carbonized for 1-6 hours to obtain a second mixture; the second mixture is briquetteed at 10-20 MPa; and then the briquetteed second mixture is heated to 2800-3200°C for a high-temperature graphitization process of 24-72 hours.

[0028] Heating to 500–800℃ to obtain the second mixture allows for preliminary carbonization of the coke-based raw materials, thereby removing some impurities and moisture from the first mixture and improving the quality of porous graphite to a certain extent. The addition of lithium carboxymethyl cellulose can dope the porous graphite with lithium and amorphous carbon, thus reducing material defects and improving material performance.

[0029] The briquetting step agglomerates the second mixture into denser lumps, increasing the loading capacity of the graphitization process and making the temperature distribution more uniform, thereby improving the graphitization effect. Lithium carboxymethyl cellulose also acts as a binder during briquetting, helping to maintain the shape of the briquetted blocks and further enhancing the briquetting effect.

[0030] In one embodiment, the mass ratio of coke-based raw material, pore-forming agent, first catalyst, and lithium carboxymethyl cellulose is 100:1-5:1-5:1-5. According to this mass ratio, the pore-forming agent and the first catalyst can work efficiently in the formation of porous graphite, and the amorphous carbon and lithium doped into the porous graphite can effectively improve its properties, thereby ensuring that all components are fully utilized.

[0031] Optionally, the pore-forming agent may include at least one of potassium carbonate, sodium carbonate, calcium carbonate, magnesium carbonate, and aluminum carbonate. By using an active metal salt as the pore-forming agent, the agent decomposes and vaporizes at high temperatures, releasing gas that escapes through the graphite surface, thereby achieving the purpose of creating pores on the graphite surface to form porous graphite.

[0032] Optionally, the first catalyst may include at least one of nickel chloride, nickel carbonate, nickel sulfate, nickel acetate, cobalt acetate, cobalt nitrate, cobalt chloride, copper acetate, copper chloride, copper sulfate, copper carbonate, ferric acetate, and ferric chloride. Using a transition metal compound as the first catalyst, the high-temperature reaction releases gas, thereby forming a porous structure on the graphite surface. Furthermore, the chemically reactive transition metal element produced by the reaction is more readily combined with carbon to undergo heterogeneous catalytic reactions compared to ordinary elemental metal catalysts, thus significantly improving the efficiency of the graphitization process.

[0033] S200: Nano-silicon is deposited on the surface of porous graphite using silane and a second catalyst to obtain a third mixture.

[0034] Nano-silicon is deposited on the porous graphite surface obtained in step S100 using silane and a second catalyst to obtain a third mixture.

[0035] Under suitable conditions, silane undergoes cracking, and the resulting silicon adheres to the pores and surface of porous graphite, depositing nanoscale silicon in these pores and on the surface. This nanoscale silicon deposited on the porous graphite surface enhances the material's specific capacity. Furthermore, the expansion of nanoscale silicon is less than that of ordinary silicon crystals, thus balancing the material's expansion performance.

[0036] Optionally, the second catalyst may include at least one of ferrocene, nickel acetylacetonate, cobalt(II) acetate, and cobalt acetylacetonate. Compared with inorganic transition metal catalysts, these organic transition metal catalysts possess the catalytic performance of transition metals while also offering advantages such as low impurity content, low boiling point, and good catalytic effect. Furthermore, the metal catalyst formed by the second catalyst can serve as a matrix for the subsequent growth of carbon nanotubes, thereby utilizing the carbon nanotube layer to coat the nano-silicon, reducing its expansion, and improving the material's cycling performance.

[0037] In one embodiment, the mass ratio of silane, the second catalyst, and porous graphite is 10–30:1–5:100. According to this mass ratio, the second catalyst can effectively catalyze the deposition process of nano-silicon on the surface of porous graphite, and can deposit sufficient but not excessive amounts of nano-silicon on the porous graphite surface. Simultaneously, the metal catalyst generated by the second catalyst is sufficient to serve as a matrix for carbon nanotube growth, thereby enabling the obtained fast-charging silicon-carbon composite material to possess excellent performance.

[0038] Specifically, the process of silane cracking leading to nano-silicon deposition can be carried out in a system of silane solution mixed with porous graphite. For example, silane and a second catalyst are added to an organic solvent to prepare a solution with a mass concentration of 0.5–5 wt%, and porous graphite is added to the solution and dispersed evenly. The system is then heated until the silane decomposes, thereby depositing nano-silicon on the surface of the porous graphite.

[0039] Optionally, the heating system can be simultaneously evacuated to reduce the temperature requirement of the reaction, which is beneficial to the efficiency of the silane pyrolysis and nano-silicon deposition process. For example, the system can be evacuated to 0.1–1 torr and heated to 200–400°C to deposit nano-silicon on the surface of porous graphite using the silane pyrolysis method.

[0040] The silane may include at least one of liquid silane, dimethylsilane, trichloroethylsilane, methyltrimethoxysilane, propyltrichlorosilane, and propyltrimethoxysilane. Common and readily available silanes are selected to reduce the cost of preparing fast-charging silicon-carbon composite materials.

[0041] Organic solvents may include at least one of benzene, diethyl ether, methanol, xylene, and carbon tetrachloride. Depending on the choice of silane, the organic solvent can be selected that can effectively dissolve the silane and the second catalyst, thereby helping the silane and catalyst to be uniformly dispersed in the reaction system, which is beneficial to improving the efficiency of the reaction and can also make the nano-silicon layer deposited on the porous graphite surface more uniform.

[0042] S300: Carbon nanotubes are grown on the surface of the third mixture to obtain a fast-charging silicon-carbon composite material.

[0043] Carbon nanotubes are grown on the surface of the third mixture obtained in step S200, thereby preparing the desired silicon-carbon composite material.

[0044] Specifically, the process of growing carbon nanotubes can be as follows: a third mixture is heated to 700–1200°C under normal pressure, thereby coating a layer of carbon nanotubes onto a nano-silicon layer deposited on the porous graphite surface. The carbon source for the carbon nanotubes can be the organic solvent and carbon-containing substances generated by the cracking of silanes in the system. These two substances gradually carbonize during the heating process, and carbon nanotubes are grown using a metal catalyst generated by a second catalyst as a matrix, thus coating the nano-silicon.

[0045] Carbon nanotubes coated on the surface of nano-silicon can reduce material expansion and improve cycle performance. Furthermore, due to the high electronic conductivity and specific surface area of ​​carbon nanotubes, they can effectively improve the fast-charging performance of fast-charging silicon-carbon composite materials.

[0046] Using the method provided in this embodiment, coke-like raw materials can be treated with pore-forming agents and catalysts to obtain porous graphite with a better pore structure that is conducive to uniform deposition. This allows for the uniform deposition of nano-silicon layers and carbon nanotube layers in the pores and on the surface of the porous graphite. The high specific capacity of nano-silicon improves the energy density of graphite, while the high electronic conductivity and specific surface area of ​​carbon nanotubes enhance the fast-charging and cycling performance of the material. Through multi-faceted synergy, the material achieves both good energy density and excellent fast-charging and cycling performance.

[0047] This application also provides a lithium-ion battery. The battery includes a negative electrode, which may comprise a fast-charging silicon-carbon composite material prepared using the above-described method. This fast-charging silicon-carbon composite material exhibits good energy density, as well as excellent fast-charging performance and cycle performance.

[0048] Fast-charging silicon-carbon composite materials were prepared in Examples 1, 2, and 3 below, which can be applied to lithium-ion batteries.

[0049] Example 1

[0050] Step S1: In this embodiment, petroleum coke is used as a coke raw material to participate in the reaction. 100g of petroleum coke, 3g of potassium carbonate, 3g of nickel chloride and 3g of lithium carboxymethyl cellulose are added to a ball mill and mixed evenly. Then, the temperature is raised to 600℃ for pre-carbonization for 3h. After carbonization, the temperature is lowered to room temperature. The resulting material is then pressed into briquettes at 15MPa and heated to 3000℃ for graphitization for 48h to obtain porous graphite.

[0051] Step S2: Add 20g of dimethylsilane and 3g of ferrocene to 300g of diethyl ether organic solution to prepare a 1wt% solution, and ultrasonically disperse it evenly. Then add 100g of porous graphite and disperse it evenly. Then transfer it to a vacuum reactor, evacuate to 0.5 torr and heat to 300℃ to deposit nano-silicon in porous graphite. Then heat to 900℃ under normal pressure to grow carbon nanotubes on the surface of nano-silicon, thereby obtaining fast-charging silicon-carbon composite material.

[0052] Example 2

[0053] Step S1: In this embodiment, needle coke is used as a coke raw material to participate in the reaction. 100g of needle coke, 1g of sodium carbonate, 1g of nickel carbonate and 1g of lithium carboxymethyl cellulose are added to a ball mill and mixed evenly. Then, the temperature is raised to 500℃ for pre-carbonization for 6h. After the carbonization process is completed, the temperature is lowered to room temperature. Then, the obtained material is pressed into briquettes at 10MPa and then heated to 2800℃ for graphitization for 72h to obtain porous graphite.

[0054] Step S2: Add 10g of trichloroethylsilane and 1g of nickel acetylacetonate to 200g of xylene to prepare a 0.5wt% solution, and ultrasonically disperse it evenly. Then add 100g of porous graphite and disperse it evenly. Then transfer it to a vacuum reactor, evacuate to 0.1 torr and heat to 200℃ to deposit nano-silicon in its porous graphite. Then heat to 700℃ under normal pressure to grow carbon nanotubes on its surface to obtain fast-charging silicon-carbon composite material.

[0055] Example 3

[0056] Step S1: In this embodiment, isotropic coke is used as the coke raw material to participate in the reaction. 100g of isotropic coke, 5g of calcium carbonate, 5g of nickel sulfate and 5g of lithium carboxymethyl cellulose are added to a ball mill and mixed evenly. Then, the temperature is raised to 800℃ for pre-carbonization for 1h. After the carbonization process is completed, the temperature is lowered to room temperature. Then, the resulting material is pressed into briquettes at 20MPa and heated to 3200℃ for graphitization for 24h to obtain porous graphite.

[0057] Step S2: Add 30g of trichloroethylsilane and 5g of cobalt acetylacetonate to 100g of organic solution to prepare a 5wt% solution, and ultrasonically disperse it evenly. Then add 100g of porous graphite and disperse it evenly. Then transfer it to a vacuum reactor, evacuate to 1 torr and heat to 400℃ to deposit nano-silicon in its porous graphite. Then heat to 71200℃ under normal pressure to grow carbon nanotubes on its surface to obtain fast-charging silicon-carbon composite material.

[0058] Two comparative examples are provided below for comparison with the preparation method of the fast-charging silicon-carbon composite material described in this application.

[0059] Comparative Example 1: Unlike Example 1, potassium carbonate, nickel chloride and its carboxymethyl cellulose lithium were not added in step S1, while other conditions and operations were the same as in Example 1.

[0060] Comparative Example 2: Unlike Example 1, dimethylsilane was not added in step S2, but the other conditions and operations were the same as in Example 1.

[0061] The materials prepared in the above embodiments and comparative examples were subjected to the following performance tests.

[0062] The tests include:

[0063] (1) SEM (Scanning Electron Microscopy) test

[0064] The fast-charging silicon-carbon composite material prepared in Example 1 was subjected to SEM testing, and the test results are as follows: Figure 1 As shown. By Figure 1 As can be seen from the above, the fast-charging silicon-carbon composite material prepared in Example 1 is granular with a secondary granulation structure and a particle size between 8 and 15 μm.

[0065] (2) Physical and chemical properties and button cell testing

[0066] Physical and chemical performance testing:

[0067] The powder OI value and specific surface area of ​​the fast-charging silicon-carbon composite materials prepared in Examples 1-3 and the graphite composite materials prepared in Comparative Examples 1-2 were tested according to the methods specified in GB / T-24533-2019 "Graphite Anode Materials for Lithium-ion Batteries". The test results are shown in Table 1.

[0068] Button cell battery testing:

[0069] The fast-charging silicon-carbon composite materials in Examples 1-3 and the graphite composite materials in Comparative Examples 1-2 were used as negative electrode materials for lithium-ion batteries and assembled into button cells.

[0070] The specific preparation method of the negative electrode material is as follows: Fast-charging silicon-carbon composite material (graphite composite material), CMC, SBR, SP, and H2O are mixed in a mass ratio of 95:2.5:1.5:1:150 to obtain the negative electrode sheet. Lithium foil is used as the positive electrode, and the electrolyte is LiPF6 / EC+DEC (LiPF6 is the electrolyte, and a 1:1 volume ratio mixture of EC and DEC is used as the solvent, with an electrolyte concentration of 1.3 mol / L). The separator is a composite membrane of polyethylene (PE), polypropylene (PP), and polyethylene propylene (PEP). The coin cell assembly is carried out in an argon-filled glove box.

[0071] The electrochemical performance of the coin cells was tested using a Wuhan Landian CT2001A battery tester. The charge / discharge voltage range was 0.005V to 2.0V, and the charge / discharge rate was 0.1C. The initial discharge capacity, initial efficiency, and rate performance (2C / 0.1C) of the coin cells were tested. The test results are shown in Table 1.

[0072] Table 1

[0073]

[0074] As can be seen from Example 1, the material in Example 1 is superior to the comparative example in terms of specific capacity, first-pass efficiency and OI value. This is because the doping of nano-silicon improves the specific capacity of the material and the doping of lithium improves the first-pass efficiency.

[0075] (3) Pouch Battery Testing

[0076] Pouch cell manufacturing:

[0077] The fast-charging silicon-carbon composite materials from Examples 1-3 and the graphite composite materials from Comparative Examples 1-2 were slurried and coated to prepare negative electrode sheets. NCM622 was used as the positive electrode, LiPF6 / EC+DEC+PC was used as the electrolyte (LiPF6 as the solute, with a concentration of 1.2 mol / L and a solvent volume ratio of EC:DEC:PC = 1:1:1), and Celgard 2400 membrane was used as the separator to prepare a 5Ah soft-pack battery.

[0078] Electrochemical performance testing:

[0079] Liquid absorption capacity of the negative electrode: Using a 1 mL burette, take V mL of electrolyte, add one drop to the surface of the negative electrode, and time the process until the electrolyte is completely absorbed, then record the time t.

[0080] Cycling performance: charge / discharge current 1.0C / 1.0C, voltage range 2.8-4.2V, number of cycles 500.

[0081] Rate performance: The constant current ratio under 2C charging conditions, i.e., constant current capacity / (constant current capacity + constant voltage capacity).

[0082] The test results are shown in Table 2.

[0083] Table 2

[0084] Example 1 89 93.7 96.1 Example 2 98 94.9 96.9 Example 3 77 95.8 95.6 Comparative Example 1 121 90.9 92.3 Comparative Example 2 107 96.3 90.2

[0085] As can be seen from Table 2, the material of the embodiment is superior to the comparative example in terms of liquid absorption rate and circulation. This is because the material of the embodiment has a high specific surface area, which increases the liquid absorption rate and improves the circulation performance. At the same time, the material of the embodiment has a low OI value, which can reduce expansion, improve kinetic performance, and increase the constant flow ratio.

[0086] The above description is only a partial embodiment of this application and does not limit the scope of protection of this application. Any equivalent device or equivalent process transformation made based on the content of this application specification and drawings, or directly or indirectly applied to other related technical fields, are similarly included within the scope of patent protection of this application.

Claims

1. A method for preparing a fast-charging silicon-carbon composite material, characterized in that, include: Carbonizing the first mixture yields a second mixture, which is then graphitized to obtain porous graphite. The first mixture comprises coke-based raw materials, a pore-forming agent, and a first catalyst. The first catalyst comprises at least one of nickel chloride, nickel carbonate, nickel sulfate, nickel acetate, cobalt acetate, cobalt nitrate, cobalt chloride, copper acetate, copper chloride, copper sulfate, copper carbonate, ferric acetate, and ferric chloride. A third mixture is obtained by depositing nano-silicon on the surface of the porous graphite using silane and a second catalyst. The specific method is as follows: The silane and the second catalyst are added to an organic solvent to prepare a solution of 0.5-5 wt%, and the porous graphite is added to the solution and dispersed evenly. Heating until the silane decomposes to deposit nano-silicon on the porous graphite surface; The second catalyst includes at least one of ferrocene, nickel acetylacetonate, cobalt(II) acetate, and cobalt acetylacetonate. Carbon nanotubes are grown on the surface of the third mixture to obtain the fast-charging silicon-carbon composite material. In this process, the metal catalyst formed after the deposition of nano-silicon is used as a substrate for growing the carbon nanotubes, so that the carbon nanotubes coat the nano-silicon.

2. The method for preparing the fast-charging silicon-carbon composite material according to claim 1, characterized in that, The first mixture also includes lithium carboxymethyl cellulose; The carbonization of the first mixture yields a second mixture, and the graphitization of the second mixture includes: The coke raw material, the pore-forming agent, the first catalyst, and the lithium carboxymethyl cellulose are mixed evenly to obtain the first mixture; The first mixture is heated to 500-800°C and carbonized for 1-6 hours to obtain the second mixture; The second mixture is pressed into blocks at 10-20 MPa, and the pressed second mixture is then graphitized at 2800-3200°C for 24-72 hours.

3. The method for preparing the fast-charging silicon-carbon composite material according to claim 2, characterized in that, The mass ratio of the coke raw material, the pore-forming agent, the first catalyst, and the lithium carboxymethyl cellulose is 100:1~5:1~5:1~5.

4. The method for preparing the fast-charging silicon-carbon composite material according to claim 1, characterized in that, The pore-forming agent includes at least one of potassium carbonate, sodium carbonate, calcium carbonate, magnesium carbonate, and aluminum carbonate.

5. The method for preparing the fast-charging silicon-carbon composite material according to claim 1, characterized in that, The mass ratio of the silane, the second catalyst, and the porous graphite is 10~30:1~5:

100.

6. The method for preparing the fast-charging silicon-carbon composite material according to claim 1, characterized in that, The silane includes at least one of liquid silane, dimethylsilane, trichloroethylsilane, methyltrimethoxysilane, propyltrichlorosilane, and propyltrimethoxysilane, and the organic solvent includes at least one of benzene, diethyl ether, methanol, xylene, and carbon tetrachloride.

7. A lithium-ion battery, characterized in that, Includes a negative electrode, said negative electrode comprising a fast-charging silicon-carbon composite material prepared using the method of any one of claims 1 to 6.

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