Preparation method of high-rate silicon-carbon composite negative electrode material

Abstract

The invention relates to the technical field of lithium ion battery negative electrode materials, in particular to a preparation method of a high-rate silicon-carbon composite negative electrode material. The silicon-carbon composite material takes a porous carbon material as a substrate, and is compounded by depositing a silicon source into the porous carbon substrate in a chemical vapor deposition manner; according to the excellent fast charging performance, the porous carbon substrate is prepared by adopting a tin source and potassium hydroxide synergistic activation strategy, and the limitation of a traditional single alkali activation (such as KOH) or metal auxiliary activation method is broken through. Through the synergistic effect of the two, a hierarchical pore structure with micropore-mesopore gradient distribution is realized, the silicon deposition bearing capacity and ion transport dynamics performance of porous carbon are remarkably improved, and a structural basis is provided for subsequent uniform deposition of silicon and rapid migration of lithium ions.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery anode material technology, specifically to a method for preparing a high-rate silicon-carbon composite anode material. Background Technology

[0002] With the transformation of the global energy structure and the rapid development of electric vehicles, portable electronic devices, and other fields, lithium-ion batteries, as core energy storage devices, face increasingly stringent performance requirements. Anode materials, as a key component of lithium-ion batteries, directly determine crucial indicators such as energy density, power density, cycle life, and fast-charging performance. Traditional graphite anode materials have long dominated the lithium-ion battery anode material market due to their abundant resources, low cost, and mature technology. However, graphite's theoretical specific capacity is only 372 mAh / g, which is insufficient to meet the development needs of high-energy-density batteries. Especially in the electric vehicle sector, to extend driving range, batteries require higher energy densities, making graphite anode materials increasingly unsuitable for industry development. Silicon-based anode materials, with their ultra-high theoretical specific capacity (4200 mAh / g), are considered ideal candidates for next-generation lithium-ion battery anode materials. However, silicon-based anode materials face many severe challenges in practical applications: large volume expansion, poor conductivity, and low initial coulombic efficiency.

[0003] Silicon-carbon composite anode materials combine silicon and carbon, utilizing the high conductivity, good mechanical properties, and stable chemical properties of carbon to buffer the volume expansion of silicon and improve the conductivity of the electrode, thereby improving the overall performance of silicon-based anode materials. However, for silicon-carbon composite anode materials, the lithium-ion diffusion path in silicon-based anode materials is relatively long, and the crystal structure of silicon hinders lithium-ion diffusion, resulting in a low lithium-ion diffusion rate. Silicon-based anode materials also have poor electronic conductivity, limiting electron transport within the electrode, leading to increased internal resistance and exacerbated polarization. Traditional carbon substrates primarily function as conductors and buffers for volume expansion, but their surface lacks active sites, making it difficult to form a strong interfacial bond with silicon. Furthermore, the silicon-carbon interface problem hinders lithium-ion transport, making it difficult to meet the requirements of high-speed charging performance. Summary of the Invention

[0004] In order to overcome the shortcomings of existing technologies where the rate performance of silicon-carbon composite anode materials based on porous carbon cannot meet the requirements, this invention proposes a method for preparing high-rate silicon-carbon composite anode materials and their application in the preparation of lithium-ion battery anodes.

[0005] The first objective of this invention is to provide a method for preparing a high-rate silicon-carbon composite anode material, comprising the following steps:

[0006] (S1) Phenolic monomers and aldehyde monomers are polycondensed in the presence of an alkaline catalyst to prepare a semi-solid resin, which is then transferred to a curing reactor and cured under an inert atmosphere to obtain phenolic resin. The resin is then crushed, sieved, and carbonized under an inert atmosphere to obtain pyrolytic carbon.

[0007] (S2) Pyrolytic carbon, a tin source, and a chemical activator are mixed at a mass ratio of 2:0.7-1:3-5 and activated under an inert atmosphere to obtain porous carbon; the tin source comprises 60%...

[0008] (S3) Porous carbon is successively deposited with silicon and coated with carbon to obtain silicon-carbon composite anode material.

[0009] Further, in step (S1), the phenol monomer is selected from at least one of phenol, resorcinol, catechol, o-cresol, m-cresol, p-cresol, and p-hydroxymethylphenol, and the aldehyde monomer is selected from at least one of formaldehyde, acetaldehyde, propionaldehyde, paraformaldehyde, trioxymethylene, and furfural. Preferably, the phenol monomer is resorcinol, and the aldehyde monomer is an aqueous solution of formaldehyde. More preferably, the molar ratio of the phenol monomer to the aldehyde monomer is 1:1-2.5, preferably 1:1.5-2. The alkaline catalyst is selected from at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide, and ammonia water. The amount of alkaline catalyst used is 2-10% of the mass of the phenol monomer.

[0010] Further, in step (S1), the polycondensation reaction is carried out at 70-90℃ for 1-3 hours; the curing process involves heating to 120-150℃ and holding for 1-2 hours, then further heating to 150-165℃ and holding for 1-2 hours, and finally heating to 170-190℃ and holding for 3-5 hours to achieve complete curing and obtain a fully cross-linked phenolic resin. The inert atmosphere is nitrogen and / or argon. The carbonization process involves heating to 700-800℃ and holding for 2-5 hours at a heating rate of 5-10℃ / min.

[0011] Furthermore, in step (S1), the crushing and sieving are not particularly limited and are well known in the art. For example, in one specific embodiment of the present invention, a jaw crusher or roller crusher is used to crush the particles to a particle size of <2 mm and then pass them through a 100-200 mesh sieve.

[0012] Further, in step (S2), the tin source is inorganic tin and / or organotin, the inorganic tin is tin chloride, and the organotin is selected from at least one of tetrabutyl stannate, tetrapropyl stannate, and N-containing organotin complexes. The N-containing organotin complex is a complex of 2,2'-bipyridine-4,4'-dicarboxylic acid and trialkyltin chloride. The 2,2'-bipyridine-4,4'-dicarboxylic acid is selected from at least one of 2,2'-bipyridine-4,4'-dicarboxylic acid and 2,2'-bipyridine-4,4'-diacetic acid. The trialkyltin chloride is selected from at least one of trimethyltin chloride, triethyltin chloride, tripropyltin chloride, tributyltin chloride, and triphenyltin chloride. The molar ratio of bipyridine-4,4'-dicarboxylic acid and trialkyltin chloride is 1:2-2.5, preferably 1:2-2.1.

[0013] Furthermore, the tin source is a mixture of inorganic tin and an organotin complex containing nitrogen in a mass ratio of 3-5:1. The inventors unexpectedly discovered that doping with the aforementioned compounded tin source could further improve the rate performance and initial coulombic efficiency of the silicon-carbon composite anode material. A possible reason is that during high-temperature activation, inorganic tin (such as SnCl4) readily decomposes to form nano-tin particles or SnO. x These highly dispersed conductive components effectively enhance the electronic conductivity of the carbon framework. Simultaneously, the bipyridine structure in the nitrogen-containing organotin complex introduces nitrogen doping in situ during pyrolysis, improving not only the surface wettability and ionic conductivity of the carbon material, but also allowing its nitrogen-containing functional groups to form stronger chemical bonds with subsequently deposited silicon (e.g., Si-NC), thus significantly enhancing silicon-carbon interface stability and reducing interfacial delamination during cycling. Furthermore, the carbonization of the organic portion in the organotin complex contributes to the formation of richer microporous structures. Inorganic tin enhances conductivity, while organotin complexes optimize the interface and microstructure; the two produce a synergistic effect of "enhanced conductive network" and "stable interface anchoring," which is the core of achieving high-rate, long-cycle performance in materials.

[0014] Further, the nitrogen-containing organotin complex is prepared by a method comprising the following steps: under an inert atmosphere, 2,2'-bipyridine-4,4'-dicarboxylic acid, trialkyltin chloride, sodium organoalkoxide, and a C1-2 alcohol are added to a reactor and reacted at 20-40°C for 10-20 h. After the reaction, the solvent is removed, and the mixture is recrystallized to obtain the nitrogen-containing organotin complex. More specifically, the molar ratio of 2,2'-bipyridine-4,4'-dicarboxylic acid, trialkyltin chloride, and sodium organoalkoxide is 1:2-2.5:2-2.5, and the C1-2 alcohol is selected from methanol or ethanol; the ratio of the C1-2 alcohol to 2,2'-bipyridine-4,4'-dicarboxylic acid is 20-50 mL:1 mmol. The solvent is removed by rotary evaporation under reduced pressure, and recrystallization is performed using diethyl ether, acetone, and tetrahydrofuran.

[0015] Further, in step (S2), pyrolytic carbon, tin source, and chemical activator are mixed in a mass ratio of 2:0.7-1:3-5.

[0016] Further, in step (S2), the chemical activator is selected from at least one of sodium hydroxide and potassium hydroxide; the activation treatment is to heat to 800-1000℃ at a rate of 5-10℃ / min and hold for 3-6 hours.

[0017] Furthermore, in step (S2), the obtained porous carbon has a pore volume of 0.7-1.3 cm³. 3 / g, preferably 0.8-1.2 cm 3 / g; micropore content 60-95%, preferably 70-90%;

[0018] Further, in step (S3), the silicon deposition and carbon coating processes are well known in the art. In one specific embodiment of the present invention, silicon deposition involves introducing a mixed gas of silane gas and a carrier gas, and performing silane deposition at 500-600°C; carbon coating involves introducing a carbon-containing gas and a carrier gas, and performing gas-phase carbon coating at 600-700°C. The silane gas is selected from at least one of methane, silane, and trimethylchlorosilane; the carbon-containing gas is selected from at least one of methane, ethane, propane, butane, ethylene, propylene, butene, acetylene, and propyne; the carrier gas is argon. After silicon deposition, the silicon content of the silicon-carbon composite material is 45-55%; after carbon coating, the thickness of the carbon coating layer is 2-10 nm, and the mass of the carbon coating layer accounts for 2-4% of the silicon-carbon composite material (measured by the weight gain method).

[0019] Existing technologies have reported methods for tin doping of porous carbon to improve its electrochemical performance. For example, tin doping is achieved by immersing porous carbon in a tin-containing impregnation solution via hydrothermal reaction; tin doping is also achieved by depositing tin using organotin alkanes; and tin doping is achieved by preparing a precursor from an organotin source using a sol-gel method. However, these methods have low tin utilization efficiency, resulting in tin waste and hindering the development of the electrochemical performance of silicon-carbon composite anode materials. Liquid-phase methods, such as the sol-gel method, cause tin species to be deeply embedded within the carbon matrix rather than preferentially enriched on the pore surface, making it difficult for them to exert their catalytic or interface modification effects on subsequent silicon deposition. This invention, after preparing pyrolytic carbon, directly mixes the pyrolytic carbon, tin source, and chemical activator together and then heat-treats, simultaneously completing activation and pore formation and tin doping. Through the combined action of the alkali metal-containing chemical activator and tin, a large number of micropores are efficiently constructed in the carbon framework, while Sn... 4+Reduction catalyzes carbon structural rearrangement, mitigating the pore collapse problem caused by pure KOH activation. This synergistic effect achieves a hierarchical porous structure with a micropore-mesopore gradient distribution, significantly enhancing the silicon deposition carrying capacity and ion transport kinetics of porous carbon. This provides a structural basis for subsequent uniform silicon deposition and rapid lithium-ion migration. In-situ doping of tin embeds it into the carbon framework, resulting in strong interactions with carbon atoms, improving the electronic conductivity of the carbon matrix. After silicon deposition, it forms a Sn-C-Si ternary interface structure, constructing efficient lithium-ion transport channels, reducing interfacial impedance, and significantly improving the material's fast-charging capability.

[0020] The second objective of this invention is to provide a high-rate silicon-carbon composite anode material, which is prepared by the above-described method.

[0021] The third objective of this invention is to provide a lithium-ion battery whose negative electrode comprises the aforementioned high-rate silicon-carbon composite negative electrode material.

[0022] This invention proposes a silicon-carbon composite anode material with excellent fast-charging performance, the innovations of which include:

[0023] 1. Synergistic Activation of Porous Carbon Substrates: A synergistic activation strategy using tin sources and potassium hydroxide was employed to prepare porous carbon substrates, overcoming the limitations of traditional single-base activation (such as KOH) or metal-assisted activation methods. This synergistic activation mechanism combines: the strong etching ability of potassium hydroxide, which efficiently constructs a large number of micropores in the carbon framework, forming a uniform microporous network with a high specific surface area, facilitating rapid lithium-ion diffusion; and the redox-aiding effect of tin ions, which, during the high-temperature activation process, promotes the redox reaction of tin ions. 4+ Partially reduced to metallic tin or low-valent tin compounds, the in-situ generated nanoscale metallic phase can catalyze carbon structure rearrangement, alleviating the pore collapse problem caused by pure KOH activation. The synergistic effect of these two factors achieves a hierarchical porous structure with a micropore-mesopore gradient distribution, significantly improving the porous carbon's ability to support silicon deposition and its ion transport kinetics, providing a structural basis for subsequent uniform silicon deposition and rapid lithium-ion migration.

[0024] 2. Pore structure control: By precisely controlling the activation conditions and the ratio of tin source to potassium hydroxide, the pore size distribution and pore volume (0.4–1.2 cm³) of the porous carbon substrate were controlled. 3 The precise control of porosity ( / g) ensures a high specific surface area to enhance interface stability while retaining sufficient mesoporous channels for electrolyte penetration and lithium-ion transport. The micropores in the porous structure effectively limit the size of silicon particles and inhibit their aggregation and growth, while the mesopores act as buffer spaces to alleviate volume expansion during charging and discharging.

[0025] 3. Element doping: In-situ doping of tin is achieved. During the activation process, tin is embedded in the carbon framework and interacts strongly with carbon atoms, acting as a "pillar" to prevent the porous structure from collapsing during high-temperature treatment or recycling, and maintaining the long-term integrity of the large-pore channels. Tin doping can improve the electronic conductivity of the carbon matrix and form a Sn-C-Si ternary interface structure after silicon deposition, constructing an efficient lithium-ion transport channel, reducing interface impedance, and significantly improving the fast-charging capability of the material. The residual metallic tin phase may catalyze the cracking reaction of silane during CVD, improving silicon deposition efficiency and uniformity, and reducing energy consumption and cost. Attached Figure Description

[0026] Figure 1 This is a scanning electron microscope image of the porous carbon material prepared in Example 1.

[0027] Figure 2 This is a scanning electron microscope image of the silicon-carbon composite material prepared in Example 1.

[0028] Figure 3 The pore size distribution curve is shown for the porous carbon material prepared in Example 1.

[0029] Figure 4 The rate performance curve of the silicon-carbon composite material prepared in Example 1 is shown. Detailed Implementation

[0030] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0031] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0032] The scanning electron microscope (SEM) used was a JEOL-6701F, and the transmission electron microscope (TEM) used was a JEM-2100F.

[0033] Preparation Example 1

[0034] Under a nitrogen atmosphere, 2,2'-bipyridine-4,4'-dicarboxylic acid (10 mmol), tributyltin chloride (21 mmol), sodium ethoxide (21 mmol), and methanol (200 mL) were added to a reactor and reacted at 30 °C for 12 h. After the reaction was completed, the solvent was removed by rotary evaporation under reduced pressure, and the product was recrystallized from tetrahydrofuran to obtain an organotin complex containing nitrogen.

[0035] Preparation Example 2

[0036] Under a nitrogen atmosphere, 2,2'-bipyridine-4,4'-dicarboxylic acid (10 mmol), triphenyltin chloride (21 mmol), sodium ethoxide (21 mmol), and methanol (200 mL) were added to a reactor and reacted at 30 °C for 12 h. After the reaction was completed, the solvent was removed by rotary evaporation under reduced pressure, and the product was recrystallized from tetrahydrofuran to obtain an organotin complex containing nitrogen.

[0037] Example 1

[0038] (S1) Resorcinol and formaldehyde were added to a reaction vessel at a molar ratio of 1:2. An appropriate amount of deionized water was added to prepare a 30% solution. Then, 0.2M ammonia water was added as a catalyst. The amount of ammonia water was 5% of the mass of resorcinol. The reaction vessel was heated to 90℃ and reacted for 2 hours to obtain a semi-solid resin with a viscosity of 800 mPa·s. The resin was then transferred to a curing reactor and cured at 150℃ for 2 hours. The temperature was then slowly increased to 165℃ and cured for another 2 hours. Finally, the temperature was increased to 180℃ and cured for 4 hours to obtain a fully cross-linked phenolic resin. The fully cross-linked phenolic resin was then crushed to a particle size of <2 mm using a jaw crusher and a roller crusher and passed through a 100-mesh sieve. The phenolic resin block was then heated to 800℃ at a heating rate of 5℃ / min and held for 2 hours to ensure complete carbonization and obtain pyrolytic carbon.

[0039] (S2) Pyrolytic carbon, tin source (tin chloride) and potassium hydroxide are mixed in a mass ratio of 2:1:5 and activated at 850 °C for 3 h under inert gas protection to obtain porous carbon;

[0040] (S3) The porous carbon substrate was pulverized to a suitable particle size, fed into a reactor, and silane was introduced. At 500°C, the silane was introduced to penetrate the pores of the porous carbon substrate and cause pyrolysis, yielding a silicon-carbon composite material. Subsequently, acetylene was introduced at 600°C using chemical vapor deposition to perform gaseous carbon coating, resulting in a silicon-carbon composite material with a carbon coating layer. The silicon-carbon composite material obtained in Example 1 had a Si content of 51.2 wt%, and the carbon coating layer accounted for 2.4% of the silicon-carbon composite material (measured by the weight gain method).

[0041] Example 2

[0042] The other conditions and operations are the same as in Example 1, except that in step (S2), pyrolytic carbon, tin source (tin chloride) and potassium hydroxide are mixed in a mass ratio of 2:1:3.

[0043] Example 3

[0044] The other conditions and operations are the same as in Example 1, except that in step (S2), pyrolytic carbon, tin source (tin chloride) and potassium hydroxide are mixed in a mass ratio of 2:1:8.

[0045] Example 4

[0046] The other conditions and operations are the same as in Example 1, except that in step (S2), pyrolytic carbon, tin source (tin chloride) and potassium hydroxide are mixed in a mass ratio of 2:0.7:5.

[0047] Example 5

[0048] The other conditions and operations are the same as in Example 1, except that in step (S2), the tin source is a mixture of tin chloride and tetrabutyl stannate in a mass ratio of 3:1.

[0049] Example 6

[0050] The other conditions and operations are the same as in Example 1, except that in step (S2), the tin source is a mixture of tin chloride and the N-containing organotin complex obtained in Preparation Example 1 in a mass ratio of 5:1.

[0051] Example 7

[0052] The other conditions and operations are the same as in Example 1, except that in step (S2), the tin source is a mixture of tin chloride and the N-containing organotin complex obtained in Preparation Example 2 in a mass ratio of 3:1.

[0053] Comparative Example 1

[0054] The other conditions and operations are the same as in Example 1, except that tin chloride is not added in step (S2).

[0055] Application examples

[0056] The electrochemical performance of the silicon-based anode materials prepared in the examples and comparative examples was tested according to the following method: The prepared silicon-carbon composite material, carbon black, and carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) composite binder were mixed in a mass ratio of 80:10:10 to form a slurry (where the mass ratio of CMC and SBR was 1:1). The slurry was uniformly coated onto a copper foil current collector and dried under vacuum for 12 h to form a working electrode. A lithium sheet was used as the counter electrode, a glass fiber membrane (purchased from Whatman, UK) was used as the separator, and 1 mol / L LiPF6 (the solvent was a mixture of ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1) was used as the electrolyte. 1% VC and 5% FEC were added to the electrolyte. The cells were assembled into coin cells in an argon-atmosphere inert gas glove box from Braun, Germany.

[0057] Electrochemical analysis was performed on the silicon-carbon composite material prepared in Example 1, and the results are as follows: Figure 4 As shown, the capacity utilization rate at 5C is 70.4% compared to that at 0.2C, proving that the silicon-carbon composite material obtained in this invention has excellent rate performance.

[0058] The negative electrode materials of the examples and comparative examples were tested according to the above method, and the results are shown in Table 1 below:

[0059] Table 1

[0060]

[0061] The test results show that the ratio of tin chloride to potassium hydroxide affects the pore size distribution of the material. A lower tin source content results in a higher proportion of micropores, while a higher tin source content results in a lower proportion of micropores. Excessive micropores lead to slow ion transport rates. When the proportion of micropores is too low and the proportion of macropores is too high, the silicon grains become too large, resulting in significant volume expansion and low capacity retention. Furthermore, the presence of macropores leads to excessive side reactions during electrolyte penetration, generating more SEI films, which hinder electron-ion transport and result in poor fast-charging performance. The inventors also found that when the tin source is a combination of tin chloride and an N-containing organotin complex, both the initial coulombic efficiency and high-rate electrochemical performance are improved. This synergistic effect was not observed when the tin source was tin chloride and stannate, possibly because the N element doping in the N-containing organotin complex also plays a role.

Claims

1. A method for preparing a high-rate silicon-carbon composite anode material, characterized in that, Includes the following steps: (S1) Phenolic monomers and aldehyde monomers are polycondensed in the presence of an alkaline catalyst to prepare a semi-solid resin, which is then transferred to a curing reactor and cured under an inert atmosphere to obtain phenolic resin. The resin is then crushed, sieved, and carbonized under an inert atmosphere to obtain pyrolytic carbon. (S2) Pyrolytic carbon, a tin source, and a chemical activator are mixed at a mass ratio of 2:0.7-1:3-5 and activated under an inert atmosphere to obtain porous carbon; the tin source comprises 60%... (S3) Porous carbon is successively deposited with silicon and coated with carbon to obtain silicon-carbon composite anode material.

2. The preparation method according to claim 1, characterized in that, In step (S1), the phenol monomer is selected from at least one of phenol, resorcinol, catechol, o-cresol, m-cresol, p-cresol, and p-hydroxymethylphenol, and the aldehyde monomer is selected from at least one of formaldehyde, acetaldehyde, propionaldehyde, paraformaldehyde, trioxyformaldehyde, and furfural; further, the molar ratio of the phenol monomer to the aldehyde monomer is 1:1-2.5, preferably 1:1.5-2.

3. The preparation method according to claim 1, characterized in that, In step (S1), the polycondensation reaction is carried out by heating to 70-90℃ for 1-3 hours; the curing process involves heating to 120-150℃ and holding for 1-2 hours, then heating to 150-165℃ and holding for 1-2 hours, and finally heating to 170-190℃ and holding for 3-5 hours to achieve complete curing and obtain fully cross-linked phenolic resin; the carbonization process involves heating to 700-800℃ and holding for 2-5 hours at a heating rate of 5-10℃ / min.

4. The preparation method according to claim 1, characterized in that, In step (S2), the tin source is inorganic tin and / or organotin, the inorganic tin is tin chloride, and the organotin is selected from at least one of tetrabutyl stannate, tetrapropyl stannate, and N-containing organotin complexes, wherein the N-containing organotin complex is a complex of 2,2'-bipyridine-4,4'-dicarboxylic acid and trialkyltin chloride.

5. The preparation method according to claim 4, characterized in that, The 2,2'-bipyridine-4,4'-dicarboxylic acid is selected from at least one of 2,2'-bipyridine-4,4'-dicarboxylic acid and 2,2'-bipyridine-4,4'-diacetic acid; the trialkyltin chloride is selected from at least one of trimethyltin chloride, triethyltin chloride, tripropyltin chloride, tributyltin chloride, and triphenyltin chloride; the molar ratio of bipyridine-4,4'-dicarboxylic acid and trialkyltin chloride is 1:2-2.5, preferably 1:2-2.

1.

6. The preparation method according to claim 4, characterized in that, The tin source is a mixture of inorganic tin and nitrogen-containing organic tin complex in a mass ratio of 3-5:

1.

7. The preparation method according to claim 4, characterized in that, The nitrogen-containing organotin complex is prepared by a method comprising the following steps: under an inert atmosphere, 2,2'-bipyridine-4,4'-dicarboxylic acid, trialkyltin chloride, sodium organoalkoxide, and a C1-2 alcohol are added to a reactor and reacted at 20-40°C for 10-20 h. After the reaction is completed, the solvent is removed, and the mixture is recrystallized to obtain the nitrogen-containing organotin complex. Further, the molar ratio of 2,2'-bipyridine-4,4'-dicarboxylic acid, trialkyltin chloride, and sodium organoalkoxide is 1:2-2.5:2-2.5, and the C1-2 alcohol is selected from methanol and ethanol. The ratio of the amount of C1-2 alcohol to 2,2'-bipyridine-4,4'-dicarboxylic acid is 20-50 mL:1 mmol.

8. The preparation method according to claim 1, characterized in that, In step (S2), the mass ratio of pyrolytic carbon, tin source, and chemical activator is 2:0.7-1:3-5; further, the chemical activator is selected from at least one of sodium hydroxide and potassium hydroxide; the activation treatment involves heating at 5-10℃ / min to 800-1000℃ and holding for 3-6 hours; and / or, In step (S3), silicon deposition involves introducing a mixture of silane gas and carrier gas at 500-600°C; carbon coating involves introducing a carbon-containing gas and carrier gas at 600-700°C for gas-phase carbon coating; further, the silane gas is selected from at least one of methane, ethyl silane, and trimethylchlorosilane, and the carbon-containing gas is selected from at least one of methane, ethane, propane, butane, ethylene, propylene, butene, acetylene, and propyne; the carrier gas is argon; even further, the silicon content of the silicon-carbon composite material after silicon deposition is 45-55%; after carbon coating, the thickness of the carbon coating layer is 2-10 nm, and the mass of the carbon coating layer accounts for 2-4% of the silicon-carbon composite material.

9. A high-rate silicon-carbon composite anode material, characterized in that, It is prepared by the preparation method described in any one of claims 1-8.

10. A lithium-ion battery, characterized in that, Its negative electrode includes the high-rate silicon-carbon composite negative electrode material prepared by the preparation method according to any one of claims 1-8.

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