Preparation method of silicon-carbon composite negative electrode material capable of being quickly charged and lithium ion battery containing silicon-carbon composite negative electrode material

Abstract

The invention belongs to the technical field of lithium batteries, and particularly relates to a preparation method of a fast-charging silicon-carbon negative electrode material and a lithium ion battery containing the fast-charging silicon-carbon negative electrode material. The negative electrode material is prepared by the following method: placing a micro-mesoporous composite porous carbon substrate in a reactor for in-situ silicon deposition, firstly controlling silicon to preferentially and uniformly deposit into micropores of the porous carbon substrate under a first deposition condition, and stopping introducing silicon source gas when the micropores of the porous carbon substrate are filled; then the materials are subjected to aging treatment at a higher temperature, so that the deposited silicon is more tightly combined with the carbon substrate; depositing the aged material under a second deposition condition to enable the silicon to be continuously deposited in the residual mesoporous structure, and stopping introducing the silicon source gas after the residual mesoporous structure is filled with the deposited silicon; and then passivating and coating the obtained material to finally obtain the silicon-carbon composite material of which the dynamic performance, the pressure resistance and the safety are remarkably improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium batteries, and particularly relates to a preparation method of a silicon-carbon negative electrode material capable of fast charging and a lithium ion battery comprising the same. BACKGROUND

[0002] Silicon-based negative electrodes have very high specific capacity, and can significantly improve the energy density of lithium ion batteries when applied to the lithium ion batteries. However, silicon itself is not conductive, and after lithium intercalation, it will undergo very serious volume change, leading to the breakage and differentiation of silicon particles, and ultimately resulting in poor cycle stability, which is difficult to meet the actual application. It has been proved that filling elemental silicon into a porous carbon substrate with high microporous structure by chemical vapor deposition is a very effective solution. On the one hand, the porous carbon substrate has a developed microporous void structure, so that the deposited elemental silicon mainly exists in a nano state (<2 nm), which to some extent alleviates the volume expansion of silicon. In addition, the porous carbon substrate has good electrical conductivity, so that ions and electrons can shuttle and meet to occur electrochemical reactions. The silicon-carbon material obtained by depositing silicon into a high microporous porous carbon substrate exhibits good cycle stability.

[0003] However, the porous carbon material with a high micropore ratio has some problems: 1) the huge specific surface area (>1700 m 2 / g) of the high microporous porous carbon after depositing silicon forms a large number of interfaces, so that the silicon-carbon material has insufficient rate performance and cannot meet the demand of fast charging; 2) in addition, the silicon-carbon material prepared by using the high microporous porous carbon as a substrate has insufficient pressure resistance. Under the condition of high compaction (>1.65 g / cm 3 ), the silicon-carbon particles are cracked, the internal nano-scale high-activity silicon is exposed, and reacts with oxygen or moisture in the air, resulting in obvious capacity loss and reduction of the first coulombic efficiency; 3) the nano-silicon formed in the deposition process has very high activity, so that the formed silicon-carbon material will burn violently under high temperature conditions, bringing safety risks.

[0004] There are many reports on the preparation of silicon-carbon composite materials by using microporous-mesoporous composite porous carbon as a substrate for silicon deposition, such as CN119263273A, which reports the use of porous carbon with a mesopore ratio of 1.86-4.69%; CN118954506A reports the use of porous carbon with a mesopore ratio of 10-20%; CN117790701A reports a composite negative electrode material, the inner core of which comprises a porous carbon material and Si (silicon) particles, and the composite negative electrode material comprises micropores and mesopores, wherein the ratio of the pore volume of the micropores to the pore volume of the mesopores is (50-80):(20-50); and CN120261548A discloses the use of biomass activated carbon with a specific surface area of ≥2150 m 2 / g, a micropore volume ratio of more than 62%, and a mesopore volume ratio of less than 38%.

[0005] The prior art uses micro-mesoporous composite porous carbon as a substrate to prepare silicon-carbon composite materials by silicon deposition, but the silicon deposition process is still a conventional control method, and the silane is deposited into the porous carbon at one time: on the one hand, the micro-pore filling rate is insufficient, and there is a micro-pore dead volume; on the other hand, the deposited silicon is in an amorphous state, and the combination with carbon is physical filling. When charging and discharging, lithium ions need to pass through the carbon interface and then reach the silicon particles. The combination of silicon and carbon is insufficient, which reduces the interface transmission efficiency, thereby leading to poor rate performance, and the combination of silicon and carbon is insufficient, so that the material still exhibits poor rate performance. SUMMARY

[0006] The purpose of the present application is to solve the technical problem that the rate performance of the silicon-carbon material prepared by the silane vapor deposition method in the preparation process of the existing silicon-carbon composite negative electrode material needs to be improved and cannot meet the actual fast charging requirements. The present application uses micro-mesoporous composite porous carbon with a certain mesopore rate (2-10 nm accounts for 30-50%) as a carbon substrate to perform two-stage silane vapor silicon deposition. First, the first deposition conditions are controlled to make elemental silicon preferentially deposit into the micro-pore structure, and aging treatment is performed at high temperature to obtain a silicon-carbon semi-finished product with close combination of silicon and carbon. Then, silicon deposition is performed under conventional conditions, at which time silicon is deposited into the remaining mesopores and macropores to form larger particles of elemental silicon. Finally, the above silicon-carbon composite product is passivated and carbon-coated to obtain a final silicon-carbon composite material product. The present application uses micro-mesoporous composite porous carbon with a certain mesopore structure as a substrate, which can avoid the safety problem of easy combustion of nano-silicon caused by using high-microporous carbon substrates. For example, the deposited silicon mainly exists in the form of <2 nm, which has very high activity, resulting in a decrease in the safety of the material. In addition, the specific surface area of high-microporous carbon is very high, resulting in a large silicon-carbon interface in the finished silicon-carbon material and slow interface ion and electron transmission, thereby leading to poor rate performance and failing to meet the actual fast charging requirements. In addition, the walls between the pores of the micro-mesoporous porous carbon are thicker, resulting in higher pressure resistance of the material compared to high-microporous porous carbon. Moreover, even after fracturing, the silicon-carbon material obtained from the micro-mesoporous porous carbon has less exposed silicon than the high-microporous porous carbon silicon-carbon composite material, so it exhibits lower capacity loss and first coulombic efficiency loss after rolling.

[0007] In order to achieve the above effects, the present application provides a preparation method of a fast-charging silicon-carbon negative electrode material, comprising the following steps: (S1) depositing silicon on the micro-mesoporous composite porous carbon under first deposition conditions to obtain a precursor I; the first deposition conditions are that silicon deposition mainly occurs in micropores; specifically, the first deposition conditions are that the deposition temperature is 250-300 DEG C, the first silane gas and the carrier gas are introduced, the system pressure is 4-10 MPa, and the ratio of V1 / M satisfies 0.24-0.31, M=M1*V0*A, wherein V1 is the total volume of the first silane gas introduced, M1 is the mass of the micro-mesoporous composite porous carbon, V0 is the total pore volume of the micro-mesoporous composite porous carbon, and A is the micropore ratio of the micro-mesoporous composite porous carbon; (S2) under an inert atmosphere, the precursor is subjected to high-temperature aging treatment to obtain a precursor II; (S3) depositing silicon on the precursor II under second deposition conditions to obtain a precursor III; the second deposition conditions are conventional silicon deposition conditions; specifically, the second deposition conditions are that the deposition temperature is 500-650 DEG C, the second silane gas and the carrier gas are introduced, the system pressure is normal pressure, and the ratio of V2 / N satisfies 0.24-0.31, N=M1*V0*B, V2 is the total amount of the second silane gas introduced, M1 is the mass of the micro-mesoporous composite porous carbon, V0 is the total pore volume of the micro-mesoporous composite porous carbon, and B is the mesopore ratio of the micro-mesoporous composite porous carbon; (S4) carbon-coated precursor III to obtain a product silicon-carbon negative electrode material.

[0008] Further, in step (S1), the mesopore volume ratio of the micro-mesoporous composite porous carbon is 30-50%, the micropore ratio is 50-70%, and the >10 nm pore ratio is ≤5%; preferably, the mesopore ratio is 31-41%, the micropore ratio is 57-69%, and the >10 nm pore ratio is ≤2%; the micro-mesoporous composite porous carbon is selected from at least one of coconut-based porous carbon, bamboo-based porous carbon, coal-based porous carbon, petroleum coke-based porous carbon, and artificial synthetic resin-based porous carbon.

[0009] Further, in step (S1), the micro-mesoporous composite porous carbon is artificial synthetic resin-based porous carbon, preferably phenolic resin obtained by pyrolysis and activation to form pores. The preparation of phenolic resin is well known in the art, which is obtained by condensation of phenolic monomers and aldehyde monomers, the phenolic monomers are selected from phenol and resorcinol, and the aldehyde is an aqueous formaldehyde solution. The micropore ratio of the micro-mesoporous composite porous carbon can be adjusted by adjusting the ratio of phenolic monomers and aldehyde monomers.

[0010] The present application needs to select a suitable porous carbon with a proper mesopore ratio and micropore ratio for the first silicon deposition, and the first silicon deposition is a silicon deposition by controlling the conditions of silane deposition, mainly low-temperature and high-pressure conditions, at which the temperature is lower than the normal silane decomposition temperature, but the silane can be deposited normally under high-pressure conditions. The adsorption potential of micropores is higher, so the silane is preferentially deposited in the micropores of the porous carbon under low-temperature and high-pressure conditions. By controlling the first deposition conditions and the total amount of silane gas, the silane deposition in step S1 can be basically in micropores, and the mesopores are basically not deposited.

[0011] Further, in step (S1), the ratio of V1 / M is 0.27-0.29; in step (S3), the ratio of V2 / N is 0.27-0.29.

[0012] Further, in step (S1), the first silicon source gas is selected from at least one of monosilane and disilane, and the carrier gas is selected from at least one of nitrogen and argon; the volume ratio of the first silicon source gas to the carrier gas is 4-10:1. The first silicon source gas is selected because monosilane and disilane are more easily deposited under low-temperature and high-pressure conditions. If silicon tetrachloride, trichlorosilane, dichlorosilane, chloromethylsilane, or other chlorine-containing silanes are selected, the deposition is not complete under low-temperature and high-pressure conditions, and the utilization rate of silane gas is not high, resulting in waste.

[0013] Further, in step (S2), the aging treatment temperature is 650-950℃, the treatment time is 1-5h, and the inert atmosphere is at least one of nitrogen and argon. The purpose of the aging treatment is to improve the bonding degree of the deposited silicon and carbon.

[0014] Further, in step (S3), the second silicon source gas is selected from at least one of monosilane, disilane, silicon tetrachloride, trichlorosilane, dichlorosilane, and chloromethylsilane.

[0015] Further, in step (S4), the carbon coating is a liquid phase method coating or a gas phase deposition method coating. The liquid phase method coating refers to: uniformly mixing the precursor III and a coating agent solution, then distilling the solvent, and treating the remaining solid at 600-900℃ for 1-3h to obtain a carbon-coated silicon-carbon composite material. The coating agent is selected from at least one of pitch, tar, and polycyclic aromatic hydrocarbon; the solvent is selected from at least one of tetrahydrofuran, cyclohexane, benzene, toluene, xylene, N,N-dimethylformamide, N-methylpyrrolidone, and ethyl acetate; and the gas phase method coating is to place the precursor III in a gas phase deposition furnace, then heat to 500-950℃ under an inert atmosphere, then introduce a carbon source gas to perform gas phase deposition coating for 1-5h. The carbon source gas can be one or a combination of two or more of methane, acetylene, ethylene, propane, butane, benzene vapor, toluene vapor, and natural gas. After carbon coating, a carbon coating layer with a thickness of 5-30nm is formed on the surface of the precursor III; preferably, the thickness of the carbon coating layer is 5-15nm.

[0016] The application also provides a fast-charging silicon-carbon negative electrode material prepared by the above preparation method.

[0017] The application also provides a lithium ion battery, the negative electrode of which comprises the fast-charging silicon-carbon negative electrode material prepared by the above preparation method.

[0018] Compared with the prior art, the application prepares a silicon-carbon composite negative electrode material by adopting a micro-mesoporous composite porous carbon with a certain mesopore ratio to perform two-step silicon deposition. In the two-step silicon deposition, the first silicon deposition is under low-temperature high-pressure conditions, and in this condition, silicon deposition basically occurs in micropores, while mesopores and macropores have basically no deposition. After the first silicon deposition, there is a high-temperature aging step, followed by the second conventional silicon deposition, which deposits silicon in the remaining mesopores and macropores. The preparation method of the application makes the silicon-carbon combination more compact, and finally makes the material exhibit better rate performance, pressure resistance, and stability. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is the XRD curve comparison of Examples 1-4 and Comparative Example 1; Figure 2 is the SEM photograph of the silicon-carbon material obtained in Example 1. DETAILED DESCRIPTION

[0020] The application will be further described below in conjunction with specific examples, but the application is not limited to the following examples.

[0021] In the following examples, the experimental methods are conventional methods unless otherwise specified; and the reagents and materials are commercially available unless otherwise specified.

[0022] Different porous carbons with micro-mesopores were used for silicon deposition, wherein the porous carbons 1-4 were obtained by condensation of resorcinol and formaldehyde to obtain a phenolic resin, and then pyrolysis carbonization, pore activation, and airflow crushing were sequentially performed. For example, the preparation method of the porous carbon 1 is as follows: Preparation of the porous carbon 1 4 kg of resorcinol was dissolved in 10 L of water, and then 5 kg of formaldehyde solution with a concentration of 37% was added under stirring conditions, followed by the addition of 40 g of glacial acetic acid, and stirring at room temperature for 20 min; then the above mixture was incubated at 45 ℃ for 12 h, and then heated to 90 ℃ for 12 h to obtain a solidified phenolic resin; the above resin was coarsely broken and then placed in a freeze dryer for freeze-drying for 48 h to obtain a dried phenolic resin precursor; then the above phenolic resin was heated to 700 ℃ in a rotary furnace under a nitrogen atmosphere for pyrolysis carbonization treatment for 3 h; then the carbonized material was introduced into carbon dioxide gas at 950 ℃ for activation treatment for 10 h; finally, the obtained activated material was crushed by airflow powder to obtain a micro-mesoporous porous carbon 1 with a D50 of 7.5 μm.

[0023] By adjusting the proportions of resorcinol and formaldehyde, porous carbons 2-4 with different pore structures were obtained.

[0024] Preparation of the porous carbon 5 10 kg of thermoplastic phenolic resin was placed in a rotary furnace and heated to 700 ℃ under a nitrogen atmosphere for pyrolysis carbonization treatment for 3 h; then the carbonized material was introduced into carbon dioxide gas at 950 ℃ for activation treatment for 18 h; finally, the obtained activated material was crushed by airflow powder to obtain a high-microporous porous carbon 5 with a D50 of 7.5 μm.

[0025] Table 1 Comparison of pore BET parameters of different porous carbons .

[0026] Example 1 (S1) 12.5 kg of the porous carbon 1 obtained in the preparation example 1 was placed in a fluidized bed, and a first silicon deposition was performed under first deposition conditions to obtain a precursor I; the first deposition conditions were as follows: the deposition temperature was 300 ℃, a mixed gas of methylsilane and argon with a volume ratio of 5:1 was introduced, the system pressure was maintained at 4 MPa, and the total amount of methylsilane introduced was 1965 L; it was calculated that V1 / M = 0.276; (S2) The precursor I was heated to 650 ℃ in the reactor for high-temperature aging treatment for 2 h to obtain a precursor II; (S3) The reactor temperature is reduced to 550℃, and a mixed gas of silane and argon in a volume ratio of 5:1 is introduced to carry out a second silicon deposition under a second deposition condition to obtain precursor III. The second deposition condition is as follows: the temperature is 550℃, the system pressure is normal pressure, and the total amount of silane introduced is 925L. It is calculated that V2 / N = 0.276. (S4) The reactor temperature is increased to 650℃, and a mixed gas of acetylene and argon in a volume ratio of 10:1 is introduced to carry out a carbon coating on the surface of the material by vapor deposition. After coating for 3h, the introduction of acetylene gas is stopped, the flow rate of acetylene gas is 2L / min, and the temperature is reduced to room temperature to discharge the product silicon-carbon composite negative electrode material.

[0027] In order to verify that step S1 only occurs microporous silicon deposition under the first deposition condition of low temperature and high pressure, BET tests are performed on samples obtained at different steps, and the results are shown in Table 2.

[0028] Table 2 BET test results of samples obtained at different steps in Example 1 .

[0029] As can be seen from the results in Table 2, after step S1, the precursor I still has a large specific surface area, and the BET test result shows that the micropores are filled, and the existing pores are mainly mesopores; after step S3, the overall specific surface area and pore volume become very small, indicating that the mesopores are also filled; after step S4, the surface is coated with carbon, and the specific surface area and pore volume become very small, and the residual pores on the surface are filled with deposited carbon.

[0030] Example 2 Preparation is carried out according to the conditions of Example 1, except that the aging temperature of step S2 is 750℃.

[0031] Example 3 Preparation is carried out according to the conditions of Example 1, except that the aging temperature of step S2 is 850℃.

[0032] Example 4 Preparation is carried out according to the conditions of Example 1, except that the aging temperature of step S2 is 950℃.

[0033] Example 5 Preparation is carried out according to the conditions of Example 3, except that in step (S1), porous carbon 2 is used for the preparation of silicon-carbon material. In step S1, the amount of silane introduced is adjusted so that V1 / M = 0.285; in step S3, the amount of silane introduced is adjusted so that V2 / N = 0.288.

[0034] Example 6 Prepared according to the conditions of Example 3, except that in step (S1), porous carbon 3 was used for the preparation of the silicon-carbon material. In step S1, the amount of silane was adjusted so that V1 / M = 0.246; in step S3, the amount of silane was adjusted so that V2 / N = 0.244.

[0035] Example 7 Prepared according to the conditions of Example 3, except that in step (S1), porous carbon 4 was used for the preparation of the silicon-carbon material. In step S1, the amount of silane was adjusted so that V1 / M = 0.305; in step S3, the amount of silane was adjusted so that V2 / N = 0.302.

[0036] Comparative Example 1 Prepared according to Example 1, except that the high-temperature aging treatment of step (S2) was not performed.

[0037] Figure 1 are the XRD patterns of the silicon-carbon composite materials obtained in Examples 1-4 and Comparative Example 1. As can be seen, with increasing treatment temperature in step S2, the silicon-carbon peak around 34 degrees gradually increases in Examples 1-4, meaning that the combination of silicon-carbon is more compact. However, the peak around 34 degrees in the XRD curve of the sample obtained in Example 4 becomes very obvious, resulting in the significant generation of silicon carbide, which in turn leads to a significant decrease in the specific capacity of the material. In Comparative Example 1, which was not subjected to the high-temperature treatment of S2, there is no signal around 34 degrees. In addition, the silicon peak at 28 degrees in Comparative Example 1 is relatively flat, indicating that the deposited silicon is more amorphous. However, after the treatment of step S2 in Examples 1-4, the silicon peak at 28 degrees becomes sharp, indicating that the crystallinity of the silicon is enhanced, which is also helpful to improve the kinetics.

[0038] Comparative Example 2 Prepared according to the conditions of Example 3, except that in step (S1), porous carbon 5 with high microporosity was used for the preparation of the silicon-carbon material. In step S1, the total amount of silane was 2616 L to satisfy V1 / M = 0.276; in step S3, the total amount of silane was 273 L to satisfy V2 / N = 0.276.

[0039] Comparative Example 3 (S1) 12.5 Kg of porous carbon 1 obtained in Preparation Example 1 was placed in a fluidized bed, and a mixed gas of silane and argon at a volume ratio of 5:1 was introduced at 550°C, with the system pressure maintained at atmospheric pressure. The flow rate of silane was 3 L / min, and the total amount of silane introduced was 2890 L, to obtain a precursor I after the deposition of silicon; (S2) The precursor I was heated to 850°C in the reactor for high-temperature aging treatment for 2 h to obtain a precursor II; (S3) The reactor temperature is raised to 650°C, and acetylene and argon gas are introduced as a mixed gas with a volume ratio of 10:1 to perform gas-phase deposition carbon coating on the material surface. After coating for 3 h, the acetylene gas is stopped, and the temperature is lowered to room temperature to discharge the product silicon-carbon composite negative electrode material.

[0040] That is, compared with Example 3, Comparative Example 3 is a one-step deposition under conventional silicon deposition conditions, rather than a two-step deposition.

[0041] Comparative Example 4 Preparation is performed according to the conditions of Example 3, except that in step S1, the amount of silane introduced is adjusted to V1 / M = 0.224; and in step S3, the amount of silane introduced is adjusted to V2 / N = 0.226.

[0042] Comparative Example 5 Preparation is performed according to the conditions of Example 3, except that in step S1, the amount of silane introduced is adjusted to V1 / M = 0.330; and in step S3, the amount of silane introduced is adjusted to V2 / N = 0.246.

[0043] Test Example The silicon-carbon composite materials obtained in the above examples and comparative examples are tested for electrochemical performance by the following method: the silicon-carbon composite material, Super P, and a binder polytetrafluoroethylene are mixed in a mass ratio of 8:1:1 to prepare a slurry, which is uniformly coated on a copper foil using a doctor blade. After drying, the silicon-carbon negative electrode sheet is placed in a vacuum oven at 80°C for 24 h to obtain a silicon-carbon negative electrode sheet, which is cut into a sheet with a diameter of 1 cm for battery assembly. A lithium metal sheet is used as the counter electrode for half-cell testing, a polyolefin separator, and 1 mol / L LiPF6 (a mixed solution of ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1) is used as the electrolyte, with the addition of 2% VC and 5% FEC by volume fraction. The 2032 button cell is assembled in an argon atmosphere. The above assembled battery is tested for charge and discharge using a LAND charge and discharge tester, with a charge and discharge interval of 50 mV-1.5V, and reversible capacity testing at 0.1 C rate and rate performance testing at 2C. The pressure resistance of the material is characterized by reversible capacity and initial coulombic efficiency testing after rolling the sheet under a pressure of 5t. The test results are shown in Table 3.

[0044] Table 3 Performance comparison of silicon-carbon composite materials obtained in examples and comparative examples .

[0045] Table 3 is the electrochemical performance and stability test results of different embodiments and comparative examples of the silicon-carbon composite material, embodiments 1-7 use micro-mesoporous composite porous carbon as the carbon substrate and are prepared by using the deposition preparation process provided by the present application, and the silicon-carbon composite material obtained has significantly improved rate performance, initial efficiency and pressure resistance compared with comparative examples 1-5, thereby better meeting the demand of high energy density lithium ion batteries for silicon-carbon negative electrode materials.

Claims

1. A method for preparing a fast-charging silicon-carbon anode material, characterized in that, Includes the following steps: (S1) Silicon deposition is performed on the micro-mesoporous composite porous carbon under the first deposition conditions to obtain precursor I; the first deposition conditions are that silicon deposition mainly occurs in the micropores; specifically, the first deposition conditions are a deposition temperature of 250-300℃, the introduction of first silane gas and carrier gas, a system pressure of 4-10MPa, and the V1 / M ratio of 0.24-0.31, M=M1×V0×A, where V1 is the total volume of first silane gas introduced, M1 is the mass of micro-mesoporous composite porous carbon, V0 is the total pore volume of micro-mesoporous composite porous carbon, and A is the micropore ratio of micro-mesoporous composite porous carbon; (S2) Under an inert atmosphere, the precursor is subjected to high-temperature aging treatment to obtain precursor II; (S3) Precursor II is subjected to silicon deposition under the second deposition conditions to obtain precursor III; The second deposition conditions are conventional silicon deposition conditions; specifically, the second deposition conditions are a deposition temperature of 500-650℃, the introduction of second silane gas and carrier gas, a system pressure of atmospheric pressure, and the satisfaction of a V2 / N ratio of 0.24-0.31, where N=M1×V0×B, V2 is the total amount of second silane gas introduced, M1 is the mass of micro-mesoporous composite porous carbon, V0 is the total pore volume of micro-mesoporous composite porous carbon, and B is the mesopore ratio of micro-mesoporous composite porous carbon. (S4) Precursor III is carbon coated to obtain the silicon-carbon anode material.

2. The preparation method according to claim 1, characterized in that, In step (S1), the mesopore volume of the micro-mesoporous composite porous carbon is 30-50%, the micropore volume is 50-70%, and the pore volume >10nm is ≤5%; the micro-mesoporous composite porous carbon is selected from at least one of coconut shell-based porous carbon, bamboo-based porous carbon, coal-based porous carbon, petroleum coke-based porous carbon, and artificially synthesized resin-based porous carbon.

3. The preparation method according to claim 1, characterized in that, In step (S1), the mesoporous composite porous carbon has a mesoporous content of 31-41%, a microporous content of 57-69%, and a pore size >10nm of ≤2%.

4. The preparation method according to claim 1, characterized in that, In step (S1), the ratio of V1 / M is 0.27-0.29; and / or, in step (S3), the ratio of V2 / N is 0.27-0.

29.

5. The preparation method according to claim 1, characterized in that, In step (S1), the first silicon source gas is selected from at least one of silane and silane, and the carrier gas is selected from at least one of nitrogen and argon; the volume ratio of the first silicon source gas to the carrier gas is 4-10:

1.

6. The preparation method according to claim 1, characterized in that, In step (S2), the aging treatment temperature is 650-950℃, the treatment time is 1-5h, and the inert atmosphere is at least one of nitrogen and argon.

7. The preparation method according to claim 1, characterized in that, In step (S3), the second silicon source gas is selected from at least one of silane, silane, silicon tetrachloride, trichlorosilane, dichlorosilane, and monochlorosilane.

8. The preparation method according to claim 1, characterized in that, In step (S4), the carbon coating is performed by liquid phase coating or vapor phase deposition coating; after carbon coating, a carbon coating layer with a thickness of 5-30 nm is formed on the surface of precursor III.

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

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

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