Silicon-carbon material, method of making the same, porous carbon substrate, negative electrode material, and battery
By combining phenolic resin with biomass carbon precursors to form a spherical porous carbon substrate and then doping it with elements, the conductivity and adhesion problems of silicon-carbon anode materials are solved, achieving high efficiency in cycle performance and low-cost production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WANXIANG 123 CO LTD
- Filing Date
- 2025-02-28
- Publication Date
- 2026-08-04
AI Technical Summary
Existing silicon-carbon anode materials suffer from problems such as smooth particle surfaces leading to poor contact between conductive agents and binders, poor doping uniformity, high production costs, and difficulty in scaling up production.
A spherical porous carbon substrate is formed by combining phenolic resin with biomass carbon precursor and using catalysts and dispersants. During the synthesis process, elements are homogeneously doped and combined with blocky biomass carbon precursor to form a complementary structure, which enhances conductivity and adhesion while reducing production costs.
This improved the cycle performance and conductivity of silicon-carbon materials, reduced production costs, and achieved long cycle life and efficient lithium-ion diffusion.
Smart Images
Figure CN119812286B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of battery materials technology, and in particular to silicon-carbon materials and their preparation methods, porous carbon substrates, anode materials, and batteries. Background Technology
[0002] Silicon-based anodes are considered the most promising next-generation anode material to replace graphite due to their high theoretical capacity, low lithium intercalation potential, and abundant resources. With the booming development of semi-solid-state batteries and the low-altitude economy, silicon-based anodes will usher in more opportunities. From the development history of silicon anodes, they have generally gone through several stages, from traditional milled silicon-carbon anodes and silicon-oxygen anodes to novel deposition-based silicon-carbon anodes. Among them, novel deposition-based silicon-carbon anodes, due to their unique structure and technology, have alleviated the expansion problem of silicon-based anodes to the greatest extent and have become the mainstream development direction, gaining widespread recognition from academia and industry.
[0003] The design concept of novel silicon-carbon anodes involves first preparing a porous carbon substrate, then decomposing a silicon source within the pores of the porous carbon to form nano-silicon particles. By controlling the size of the silicon particles and ensuring their amorphous structure, and by reserving a certain expansion space in the porous carbon substrate, the volume effect of silicon-carbon materials is effectively mitigated, resulting in a significant improvement in the material's cycle performance. The selection of raw materials for the carbon substrate and the control of the activation and pore-forming structure are crucial, determining the overall performance of the novel silicon-carbon material. Resin-based carbon substrates have become a research hotspot due to their advantages such as low impurities and high compaction density. Researchers tend to synthesize spherical porous carbon substrates because they offer advantages such as high filling density, good fluidity, and uniform stress during lithium intercalation expansion. However, perfectly spherical particles, due to their smooth surface, also pose a risk of insufficient contact with conductive agents and binders.
[0004] Patent CN 118908209A uses phenol source, dispersant, formaldehyde, stabilizer, activator and catalyst as the main raw materials to synthesize phenolic resin-based microspheres at room temperature, and then carbonizes and activates them to obtain phenolic resin-based porous carbon spheres. The products have the characteristics of high monodispersity, no adhesion and high specific surface area, but there may also be risks due to the smooth surface of the particles and insufficient contact between the conductive agent and the binder.
[0005] Patent CN 118754119B discloses a method for preparing heterogeneous element-doped carbon materials. By doping non-metallic and metallic heterogeneous elements in a specific order, the mechanical properties of lithium-ion and electron motion are improved, while the breakage of composite material particles during charging and discharging is suppressed and the interface stability is improved. However, there are also problems such as poor doping uniformity, limited improvement in kinetic performance, and problems such as many added components, high synthesis difficulty, and difficulty in large-scale production. Summary of the Invention
[0006] Addressing the shortcomings of existing technologies, this invention provides silicon-carbon materials and their preparation methods, porous carbon substrates, negative electrode materials, and batteries. The core aspect lies in the controllable synthesis of the porous carbon substrate. Phenolic monomers and aldehyde monomers are polymerized in the presence of a catalyst and dispersant. Simultaneously, dopants and pre-carbonized biomass carbon precursors are added to the solution. The resulting phenolic resin has a spherical structure, and homogeneous elemental doping is achieved during the synthesis process. The added biomass carbon precursor has a blocky structure. The combination of carbon-based particles with different structures can better leverage their respective beneficial effects, compensating for each other's weaknesses and comprehensively improving performance. Furthermore, the biomass carbon precursor can also provide reactive groups, partially replacing the amount of phenolic and aldehyde monomers, thereby improving resource utilization and significantly reducing production costs.
[0007] In a first aspect, this application provides a porous carbon substrate:
[0008] A porous carbon substrate includes a phenolic resin, a biomass carbon precursor after pre-carbonization of biomass carbon material, and a dopant dispersed in the porous carbon substrate.
[0009] The phenolic resin is spherical;
[0010] The pre-carbonized biomass carbon precursor has a blocky structure and a specific surface area ranging from 200 to 500 m². 2 / g;
[0011] The dopant includes one or more combinations of elements N, B, P, S, F, and O.
[0012] Thirdly, this application provides a silicon-carbon material:
[0013] A silicon-carbon material, comprising
[0014] Porous carbon substrates containing dopants,
[0015] The porous carbon substrate includes phenolic resin and a biomass carbon precursor after pre-carbonization of biomass carbon materials.
[0016] The specific surface area of the pre-carbonized biomass carbon precursor ranges from 200 to 500 m². 2 / g;
[0017] The dopant includes one or more combinations of elements N, B, P, S, F, and O;
[0018] Silicon particles deposited in the carbon pores of a porous carbon substrate;
[0019] And carbon layers deposited on porous carbon substrates and / or silicon particle surfaces;
[0020] The phenolic resin is spherical; the pre-carbonized biomass carbon precursor has a blocky structure.
[0021] Thirdly, this application provides a method for preparing silicon-carbon materials:
[0022] A method for preparing a silicon-carbon material includes the following steps:
[0023] 1) Disperse phenolic monomers, aldehyde monomers, and catalysts in water to form solution A; dissolve pre-carbonized biomass carbon precursors, dispersants, and dopants in an organic solvent to form solution B;
[0024] 2) Slowly pour solution A into solution B and mix, then heat to 60 °C, react for 3 h, and dry to obtain solid precursor powder C;
[0025] 3) The solid precursor powder C obtained in step 2) is activated to create pores, resulting in a porous carbon substrate;
[0026] 4) The porous carbon substrate obtained in step 3) is subjected to silicon deposition in an atmosphere of carrier gas and silicon source gas to obtain a composite material;
[0027] 5) The composite material obtained in step 4) is heated, and a carrier gas and a carbon source gas are introduced to perform surface carbon coating to obtain the finished silicon-carbon material.
[0028] The pre-carbonized porous carbon precursor, dispersant, and dopant account for 20-50%, 1-10%, and 1-5% of the total mass of phenolic monomers and aldehyde monomers, respectively.
[0029] This application discloses a controllable synthesis of porous carbon substrates in silicon-carbon materials. Phenolic monomers and aldehyde monomers are polymerized in the presence of a catalyst and a dispersant. Simultaneously, dopants and pre-carbonized biomass carbon precursors are added to the solution. The resulting phenolic resin has a spherical structure, and homogeneous elemental doping is achieved during the synthesis process. The added biomass carbon precursor has a blocky structure. The combination of carbon-based particles with different structures can better exert their respective beneficial effects, complementing each other's strengths and weaknesses, and comprehensively improving battery performance, resulting in excellent cycle performance and conductivity. In addition, the biomass carbon precursor can also provide reactive groups, partially replacing the amount of phenolic and aldehyde monomers, thereby improving resource utilization and significantly reducing production costs.
[0030] Further, in step 1), the phenolic monomers include one or at least two combinations of phenol, cresol, xylenol, and resorcinol; the aldehyde monomers include one or at least two combinations of formaldehyde, acetaldehyde, propionaldehyde, furfural, and acrolein; the catalyst includes one or at least two combinations of sodium hydroxide, potassium hydroxide, barium hydroxide, ammonia, and sodium carbonate; the molar ratio of the phenolic monomers to the aldehyde monomers is 1:0.5~3, and the mass of the catalyst accounts for 1~10% of the total mass of the phenolic monomers and the aldehyde monomers.
[0031] Furthermore, in step 1), the pre-carbonized biomass carbon precursor is obtained by heat treatment of biomass carbon material in an inert atmosphere; the biomass carbon material is one or at least two combinations of coconut shell, fruit shell, straw, bamboo, and lignin; the heat treatment temperature is 200~400℃, and the heat treatment time is 1~4h.
[0032] Furthermore, the dispersant is one or a combination of at least two of Span 80, cetyltrimethylammonium bromide, polyvinylpyrrolidone, and polyvinyl alcohol;
[0033] The dopant is one or at least two of the following: urea, melamine, boron oxide, boric acid, boron nitride, ammonium dihydrogen phosphate, sodium sulfate, thiourea, polytetrafluoroethylene, silicon tetrafluoride, and hydrogen peroxide.
[0034] The organic solvent is one or a combination of at least two of ethanol, propanol, N-methylpyrrolidone, acetone, and benzene.
[0035] Furthermore, in step 3), the activation of pore formation is either chemical activation or physical activation;
[0036] The chemically activated activator is one or a combination of potassium hydroxide, sodium hydroxide, zinc chloride, and potassium carbonate; the mass ratio of the precursor powder to the activator is 1:1~5, the activation temperature is 800~1000 ℃, and the time is 1~4h.
[0037] The activator for physical activation is water vapor or carbon dioxide. The specific process involves heating the precursor powder to 800~1000 ℃ and introducing water vapor or carbon dioxide.
[0038] The novel silicon-carbon material structure involves first preparing a porous carbon substrate, and then depositing carbon particles in the pores. If the porous silicon particles are not activated, they will accumulate on the material surface, resulting in a decrease in the battery's electrical performance.
[0039] Adding dopants can improve the strength of the carbon framework structure, enhance ionic conductivity, and reduce impedance.
[0040] Furthermore, the carrier gas is one or a combination of at least two of nitrogen, argon, and helium; the silicon source gas is one or a combination of at least two of silane, silane, dichlorosilane, and trichlorosilane; the ratio of the carrier gas to the silane gas is 1 to 5:1; and the silicon deposition temperature is 400 to 600°C, and the time is 1 to 6 hours.
[0041] The carbon source gas is one or a combination of at least two of acetylene, methane, propylene, acetone, and natural gas;
[0042] The ratio of carrier gas to carbon source gas is 1~5:1, and the surface carbon coating temperature is 800~1000 ℃ for 2~6 hours.
[0043] Fourthly, this application provides a battery negative electrode material:
[0044] A battery negative electrode material comprising the porous carbon substrate of this application, the silicon-carbon material described in this application, or the silicon-carbon material obtained by the preparation method described in this application.
[0045] Fifthly, this application provides a lithium-ion battery:
[0046] A lithium-ion battery comprising the porous carbon substrate of this application, or the silicon-carbon material described in this application, or the silicon-carbon material obtained by the preparation method described in this application.
[0047] Beneficial effects:
[0048] 1) By combining blocky biomass carbon substrates with spherical resin-based carbon substrates, a complementary effect is formed. This ensures that the spherical carbon substrates have high filling density, good fluidity, and uniform stress during lithium intercalation expansion, while also improving the bonding force with conductive agents and binders, thus better leveraging the long-cycle performance of the material; 2) Element doping is completed during the synthesis of resin carbon. In-situ homogeneous doping enhances the structural strength of the carbon skeleton, while increasing the lithium-ion diffusion coefficient and reducing impedance; 3) Biomass carbon precursors can also provide reactive groups, partially replacing the amount of phenolic and aldehyde monomers, thereby improving resource utilization and significantly reducing production costs. Attached Figure Description
[0049] Figure 1 This is a flowchart of the porous carbon substrate and silicon-carbon preparation process of the present invention;
[0050] Figure 2 SEM image of the silicon-carbon material prepared in Example 1 of this invention;
[0051] Figure 3 Here is a SEM image of the silicon-carbon material prepared in Comparative Example 1 of this invention;
[0052] Figure 4The graphs show the powder conductivity properties of silicon-carbon materials prepared in Examples 1 and 2 and Comparative Examples 1 and 2 of the present invention under different pressures.
[0053] Figure 5 The high-temperature cycling performance diagrams are for the silicon-carbon materials prepared in Examples 1 and 2 and Comparative Examples 1 and 2 of this invention. Detailed Implementation
[0054] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0055] Example 1: A method for preparing silicon-carbon material, the specific process flow diagram is as follows. Figure 1 This includes the following steps:
[0056] 1) Phenol, formaldehyde, and ammonia (25% by mass) are dispersed in deionized water to form solution A; wherein the molar ratio of phenol to formaldehyde is 1:1.2, and the mass of ammonia added is 3% of the total mass of phenol and formaldehyde.
[0057] Lignin pre-carbonized in an inert atmosphere (heat treatment temperature 300-500 ℃, heat treatment time 2 h, specific surface area 200~500 m²) 2 The lignin, Span 80 dispersant, and melamine dopant are dispersed in ethanol to form solution B, wherein the amounts of lignin, Span 80, and melamine added account for 25%, 2%, and 2% of the total mass of phenol and formaldehyde, respectively.
[0058] 2) Place solution A in a reaction vessel, slowly pour in solution B while stirring, heat to 60°C, react for 3 hours, dry the solution, and obtain solid precursor powder C.
[0059] 3) Mix the powder C obtained in step 2) with the activator KOH at a mass ratio of 1:1.2, heat treat at 950℃ for 3 hours, acid wash, and dry to obtain a porous carbon substrate.
[0060] 4) Place the porous carbon substrate obtained in step 3) in a fluidized bed deposition furnace, introduce N2, heat to 500°C, and introduce silane gas, wherein the flow ratio of silane to N2 is 1:3. After deposition for 6 hours, the composite material is obtained.
[0061] 5) Place the composite material obtained in step 4) in a rotary kiln, introduce N2, heat to 500℃, and then introduce acetylene, wherein the acetylene to N2 flow rate ratio is 1:1. After deposition for 4 hours, the finished silicon-carbon material is obtained. The SEM image of the silicon-carbon material is shown below. Figure 2 .
[0062] Example 2, a method for preparing a silicon-carbon material, comprising the following steps:
[0063] 1) Disperse resorcinol, formaldehyde, and sodium carbonate catalyst in deionized water to form solution A, wherein the molar ratio of resorcinol to formaldehyde is 1:1.5, and the mass of sodium carbonate added is 5% of the total mass of resorcinol and formaldehyde.
[0064] Coconut shell charcoal pre-carbonized in an inert atmosphere (heat treatment temperature 300-500 ℃, heat treatment time 2 h, specific surface area 200~500 m²) 2 The pre-carbonized coconut shell carbon, hexadecyltrimethylammonium bromide dispersant, and boric acid dopant are dispersed in ethanol to form solution B, wherein the amounts of pre-carbonized coconut shell carbon, hexadecyltrimethylammonium bromide, and boric acid added account for 30%, 3%, and 5% of the total mass of resorcinol and formaldehyde, respectively.
[0065] 2) Place solution A in a reaction vessel, slowly pour in solution B while stirring, heat to 60°C, react for 3 hours, dry the solution, and obtain solid precursor powder C.
[0066] 3) Place the powder C obtained in step 2) in a rotary kiln, introduce nitrogen gas, heat to 950°C, introduce water vapor, and continue the reaction for 4 hours to obtain a porous carbon substrate.
[0067] 4) Place the porous carbon substrate obtained in step 3) in a fluidized bed deposition furnace, introduce N2, heat to 550°C, and introduce silane gas, wherein the flow ratio of silane to N2 is 1:2. After deposition for 5 hours, the composite material is obtained.
[0068] 5) Place the composite material obtained in step 4) in a rotary kiln, introduce N2, heat to 500°C, introduce acetylene, wherein the flow ratio of acetylene to N2 is 1:1, and after deposition for 4 hours, the finished silicon-carbon material is obtained.
[0069] Comparative Example 1
[0070] The material preparation process is the same as in Example 1, except that in step 1), pre-carbonized lignin was not added to solution B. The SEM image of the silicon-carbon material is shown below. Figure 3 .
[0071] Comparative Example 2
[0072] The material preparation process is the same as in Example 1, except that in step 1), melamine, a dopant, was not added to solution B.
[0073] A battery negative electrode material:
[0074] The silicon-based anode materials prepared in Examples 1 and 2 and Comparative Examples 1 and 2 were mixed with commercial artificial graphite with an average particle size of 15 μm at a mass ratio of 7:93 to form a battery anode material with a capacity of 450 mAh / g.
[0075] A type of battery:
[0076] Active material, binder PAA, conductive agent 1 single-arm CNT, and conductive agent 2 carbon black were dispersed and slurried in a ratio of 95.35%:4.05%:0.06%:0.54%. The aforementioned battery negative electrode material (the silicon-based negative electrode material prepared in Examples 1 and 2 and Comparative Examples 1 and 2 in sequence) was used. Then, the battery cell was prepared by coating, rolling, slitting and other cell preparation processes, and then combined with NCM811 positive electrode to make a small soft pack battery.
[0077] The conductivity of the finished powder materials prepared in Examples 1 and 2 and Comparative Examples 1 and 2 was tested, and the results are as follows: Figure 4 .
[0078] The test assessed the high-temperature cycling performance of the relevant materials in a full-cell battery. Specific test conditions included 1C constant current / constant voltage charging to 4.25V, followed by 1C constant current discharging to 2.8V. The initial capacity was used as a baseline, and cycling was terminated when the capacity decreased to 80%. The test results are as follows: Figure 5 .
[0079] The test results show that without the addition of pre-carbonized lignin (Comparative Example 1), the finished silicon-carbon product did not have a combination of particles with different structures. Because the perfectly spherical particle structure has the problem of poor contact with conductive agents and binders, the cycle decay is fast. Without element doping (Comparative Example 2), the impedance of the finished silicon-carbon product was not effectively reduced, which affected the lithium-ion migration efficiency and also reduced the cycle life.
[0080] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.
Claims
1. A porous carbon substrate, characterized in that, Includes phenolic resin, biomass carbon precursors after pre-carbonization of biomass carbon materials, and dopants dispersed in a porous carbon substrate; The phenolic resin is spherical; the pre-carbonized biomass carbon precursor has a blocky structure, and the specific surface area of the pre-carbonized biomass carbon precursor ranges from 200 to 500 m². 2 / g; The dopant includes one or more combinations of elements N, B, P, S, F, and O; A method for preparing a porous carbon substrate includes the following steps: 1) Disperse phenolic monomers, aldehyde monomers, and catalysts in water to form solution A; dissolve pre-carbonized biomass carbon precursors, dispersants, and dopants in an organic solvent to form solution B; 2) Slowly pour solution A into solution B and mix, then heat to 60 °C, react for 3 h, and dry to obtain solid precursor powder C; 3) The solid precursor powder C obtained in step 2) is activated to create pores, resulting in a porous carbon substrate; The pre-carbonized biomass carbon precursor, dispersant, and dopant account for 20-50%, 1-10%, and 1-5% of the total mass of phenolic monomers and aldehyde monomers, respectively.
2. A silicon-carbon material, characterized in that, Including porous carbon substrates containing dopants, The porous carbon substrate includes phenolic resin and a biomass carbon precursor after pre-carbonization of biomass carbon materials. The phenolic resin is spherical, the pre-carbonized biomass carbon precursor is blocky, and the specific surface area of the pre-carbonized biomass carbon precursor ranges from 200 to 500 m². 2 / g; Wherein, the dopant includes one or more combinations of elements N, B, P, S, F, and O; silicon particles deposited in the carbon pores of a porous carbon substrate; and a carbon layer deposited on the surface of the porous carbon substrate and / or silicon particles; A method for preparing a porous carbon substrate includes the following steps: 1) Disperse phenolic monomers, aldehyde monomers, and catalysts in water to form solution A; dissolve pre-carbonized biomass carbon precursors, dispersants, and dopants in an organic solvent to form solution B; 2) Slowly pour solution A into solution B and mix, then heat to 60 °C, react for 3 h, and dry to obtain solid precursor powder C; 3) The solid precursor powder C obtained in step 2) is activated to create pores, resulting in a porous carbon substrate; The pre-carbonized biomass carbon precursor, dispersant, and dopant account for 20-50%, 1-10%, and 1-5% of the total mass of phenolic monomers and aldehyde monomers, respectively.
3. A method for preparing a silicon-carbon material, characterized in that, Includes the following steps: 1) Disperse phenolic monomers, aldehyde monomers, and catalysts in water to form solution A; The pre-carbonized biomass carbon precursor, dispersant, and dopant are dissolved in an organic solvent to form solution B; 2) Slowly pour solution A into solution B and mix, then heat to 60 °C, react for 3 h, and dry to obtain solid precursor powder C; 3) The solid precursor powder C obtained in step 2) is activated to create pores, resulting in a porous carbon substrate; 4) The porous carbon substrate obtained in step 3) is subjected to silicon deposition in an atmosphere of carrier gas and silicon source gas to obtain a composite material; 5) The composite material obtained in step 4) is heated, and a carrier gas and a carbon source gas are introduced to perform surface carbon coating to obtain the finished silicon-carbon material. The pre-carbonized biomass carbon precursor, dispersant, and dopant account for 20-50%, 1-10%, and 1-5% of the total mass of phenolic monomers and aldehyde monomers, respectively. The pre-carbonized biomass carbon precursor has a blocky structure.
4. The method for preparing a silicon-carbon material according to claim 3, characterized in that, In step 1), the phenolic monomers include one or at least two combinations of phenol, cresol, xylenol, and resorcinol; the aldehyde monomers include one or at least two combinations of formaldehyde, acetaldehyde, propionaldehyde, furfural, and acrolein; the catalyst includes one or at least two combinations of sodium hydroxide, potassium hydroxide, barium hydroxide, ammonia, and sodium carbonate; the molar ratio of the phenolic monomers to the aldehyde monomers is 1:0.5~3; and the mass of the catalyst accounts for 1~10% of the total mass of the phenolic monomers and the aldehyde monomers.
5. The method for preparing a silicon-carbon material according to claim 3, characterized in that, In step 1), the pre-carbonized biomass carbon precursor is obtained by heat treatment of biomass carbon material in an inert atmosphere; the biomass carbon material is one or at least two combinations of coconut shell, fruit shell, straw, bamboo, and lignin; the heat treatment temperature is 200~400℃, and the heat treatment time is 1~4h.
6. The method for preparing a silicon-carbon material according to claim 3, characterized in that, The dispersant is one or a combination of at least two of Span 80, cetyltrimethylammonium bromide, polyvinylpyrrolidone, and polyvinyl alcohol. The dopant is one or at least two of the following: urea, melamine, boron oxide, boric acid, boron nitride, ammonium dihydrogen phosphate, sodium sulfate, thiourea, polytetrafluoroethylene, silicon tetrafluoride, and hydrogen peroxide. The organic solvent is one or a combination of at least two of ethanol, propanol, N-methylpyrrolidone, acetone, and benzene.
7. The method for preparing a silicon-carbon material according to claim 3, characterized in that, In step 3), the activation of pore formation is either chemical activation or physical activation; The chemically activated activator is one or a combination of potassium hydroxide, sodium hydroxide, zinc chloride, and potassium carbonate; the mass ratio of the solid precursor powder C to the activator is 1:1~5, the activation temperature is 800~1000 ℃, and the time is 1~4h. The activator for physical activation is water vapor or carbon dioxide. The specific process involves heating the solid precursor powder C to 800~1000 ℃ and introducing water vapor or carbon dioxide.
8. The method for preparing porous carbon substrates and silicon-carbon materials according to claim 3, characterized in that, The carrier gas is one or a combination of at least two of nitrogen, argon, and helium; the silicon source gas is one or a combination of at least two of silane, dichlorosilane, dichlorosilane, and trichlorosilane; the ratio of the carrier gas to the silicon source gas is 1 to 5:1; the silicon deposition temperature is 400 to 600°C, and the time is 1 to 6 hours. The carbon source gas is one or a combination of at least two of acetylene, methane, propylene, acetone, and natural gas; The ratio of carrier gas to carbon source gas is 1~5:1, and the surface carbon coating temperature is 800~1000 ℃ for 2~6 hours.
9. A battery negative electrode material, characterized in that, It comprises a porous carbon substrate as described in claim 1, a silicon-carbon material as described in claim 2, or a silicon-carbon material obtained by the preparation method described in any one of claims 3-8.
10. A lithium-ion battery, characterized in that, It comprises a porous carbon substrate as described in claim 1, a silicon-carbon material as described in claim 2, or a silicon-carbon material obtained by the preparation method described in any one of claims 3-8.