Method for preparing silicon-carbon composite negative electrode material by using porous graphite and application thereof

Abstract

This invention discloses a method for preparing silicon-carbon composite anode materials using porous graphite. First, a porous carbon material with a large number of uniformly distributed nano- to micron-sized pores is prepared using a physical foaming method, and then graphitized at high temperature to obtain porous graphite. Next, the porous graphite is pulverized to obtain graphite powder with a cratered surface structure, and then mixed with a certain proportion of nano-silicon and ball-milled to embed the nano-silicon into the cratered structure on the graphite powder surface. Finally, the mixed material is carbon-coated to obtain a silicon-carbon composite anode material for lithium-ion batteries. Applications of this composite material are also provided. In this invention, nano-silicon and graphite have good electrical contact, greatly improving the electrochemical performance of the silicon-carbon composite anode material. Simultaneously, graphite can buffer the volume expansion of the silicon material. The cratered structure on the graphite surface improves the lithium intercalation reaction of the silicon-carbon composite anode material, improving the rate capability and low-temperature performance of lithium-ion batteries.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion batteries, specifically a method for preparing silicon-carbon composite anode materials using porous graphite. Background Technology

[0002] Currently, commercial lithium-ion batteries primarily use graphite-based anode materials, which offer advantages such as low plateau potential, good cycle stability, high conductivity, and low irreversible capacity. However, their theoretical specific capacity limit of 372 mAh / g is insufficient to meet the growing demands of users. Therefore, developing anode material systems with higher specific capacity to further improve the energy density of lithium-ion batteries is urgently needed.

[0003] Silicon (Si) has a theoretical specific capacity of 4200 mAh / g, more than ten times that of graphite. Furthermore, silicon constitutes approximately 26.3% of the Earth's crust, second only to oxygen, making it abundant and relatively inexpensive. Silicon-based anode materials offer advantages such as low operating voltage, abundant resources, and low cost. Their lithium intercalation potential is similar to that of graphite, making them a preferred alternative to carbon-based anode materials and attracting considerable attention from academia and industry for many years.

[0004] However, the low electronic conductivity of silicon-based anode materials and the 100-400% volume expansion and contraction during charging and discharging make the electrode materials extremely easy to break and detach from the current collector and electrode conductive network. The resulting new surface requires the formation of a new solid electrolyte interface (SEI), which leads to a large consumption of electrolyte and seriously affects the cycle stability of the material itself. This has prevented silicon-based anode materials from achieving large-scale commercial application for a long time.

[0005] To address this issue, existing technologies employ physical or chemical methods, such as surface coating and loading, to composite silicon-based materials with carbon-based materials. This effectively mitigates the breakage of silicon-based materials during charging and discharging, improves their conductivity, and avoids direct contact between the silicon-based materials and the electrolyte, thereby reducing side reactions between them. Patent CN110098380A proposes a method for preparing silicon-based anode materials for lithium-ion batteries, using a pore-forming agent to etch multiple nanometer- to micrometer-scale pores onto the surface of carbon materials and embed nano-silicon particles. However, this method suffers from drawbacks such as pore-forming agent residue, difficulty in uniform pore distribution, and low pore formation rate, making the process complex and hindering industrial application. Therefore, developing a high-performance silicon-carbon composite anode material with a simple process and no byproduct residue is of great significance. Summary of the Invention

[0006] Therefore, in order to overcome the defects of the prior art, the technical problem to be solved by the present invention is to provide a method for preparing silicon-carbon composite anode materials with better dispersion and cycle performance using porous graphite, so as to solve the problem of poor dispersion and cycle performance of silicon-carbon anode materials in the prior art.

[0007] The technical solution of this invention is a method for preparing silicon-carbon composite anode materials using porous graphite, comprising the following steps:

[0008] (1) Porous graphite is prepared by physical foaming method; high softening point asphalt is placed in a high pressure container, and foaming agent is added at a volume ratio of asphalt: foaming agent = 1:5-1:200. The temperature is then raised to above the critical temperature of the foaming agent at a rate of 1-30℃ / min, and held at the temperature for 0.5-5h. The pressure is then rapidly released to atmospheric pressure at a rate of 1-100MPa / s to obtain porous asphalt. The asphalt is then heated to 2500-3000℃ and graphitized at high temperature to obtain porous graphite. The foaming agent is a gaseous or liquid foaming agent without residual components.

[0009] (2) The porous graphite obtained in step (1) is crushed to obtain graphite powder with a certain size and a crater structure on the surface.

[0010] (3) The graphite powder obtained in step (2) is mixed with nano-silicon material and ball-milled to embed the nano-silicon into the crater structure on the surface of the graphite powder; or, the obtained graphite powder, intermediate medium and nano-silicon material are mixed and ball-milled, the intermediate medium is filled into the crater and the nano-silicon is embedded in the crater through the intermediate medium; the intermediate medium includes but is not limited to carbon, metal, organic polymer and inorganic salt.

[0011] (4) The graphite material embedded with nano-silicon obtained in step (3) is subjected to carbon coating treatment to obtain silicon-carbon composite anode material; the carbon coating treatment is one of gas phase coating, liquid phase coating and solid phase coating.

[0012] In step (1), the foaming agent is a foaming agent without residual components, meaning that there is no residual foaming agent or its byproducts after the foaming process is completed. In step (2), because a porous structure is formed inside the material, the pores on the surface after crushing are craters. In step (3), nano-silicon refers to elemental silicon at the nanoscale.

[0013] According to a method for preparing silicon-carbon composite anode material using porous graphite according to the present invention, preferably, the container in step (1) is a high-pressure constant-volume container; and the softening point of the asphalt is 200-350℃.

[0014] According to a method for preparing silicon-carbon composite anode material using porous graphite according to the present invention, preferably, the foaming agent in step (1) is one of carbon dioxide, nitrogen and toluene.

[0015] According to a method for preparing silicon-carbon composite anode material using porous graphite according to the present invention, preferably, the pore size range of the porous graphite in step (1) is 1 nm to 30 μm.

[0016] According to a method for preparing silicon-carbon composite anode material using porous graphite according to the present invention, the pore size range of the porous graphite in step (1) is 0.2μm-5μm.

[0017] According to a method for preparing silicon-carbon composite anode material using porous graphite according to the present invention, preferably, in step (1), the ratio of asphalt to foaming agent is 1:8-1:150; the heating rate is 3-15℃ / minute; the isothermal time is 1-3h; and the pressure relief rate is 5-50MPa / second.

[0018] According to a method for preparing silicon-carbon composite anode material using porous graphite according to the present invention, preferably, the size range of the graphite powder with crater structure on the surface is 10μm-200μm.

[0019] According to a method for preparing silicon-carbon composite anode material using porous graphite according to the present invention, preferably, the particle size range of the nano-silicon is 30nm-200nm.

[0020] According to a method for preparing silicon-carbon composite anode materials using porous graphite according to the present invention, preferably, the mass ratio of nano-silicon to graphite powder is 0.1%-10%. Further, the mass ratio of nano-silicon to graphite powder is 1%-7%.

[0021] According to a method for preparing silicon-carbon composite anode material using porous graphite according to the present invention, preferably, the nano-silicon is located in the crater structure on the surface of the graphite powder, and the silicon is in direct contact with the graphite.

[0022] Alternatively, in the presence of an intermediate medium, the nano-silicon is located within the crater structure on the surface of the graphite powder, with the silicon in contact with the intermediate medium. That is, the silicon and graphite do not directly contact each other.

[0023] According to a method for preparing silicon-carbon composite anode material using porous graphite according to the present invention, preferably, the solid phase coating in step (4) includes: fully mixing graphite material embedded with nano-silicon and low-temperature pitch in a ratio of (7-12):1 and placing it in a rotary tube furnace, introducing nitrogen gas at high temperature, fully removing coke at 280-600℃ for 0.5-5h, and then carbonizing at 700-1200℃ for 0.5-5h, and cooling to room temperature after the reaction is completed;

[0024] The gas phase coating includes: using one or more of ethylene, acetylene, methane, ethane, and propane as carbon sources, and employing chemical vapor deposition to carbon coat graphite materials embedded with nano-silicon, with a gas flow rate of 0.1-5 L / min, and treating at 500-1000℃ for 0.5-3 h to form a carbon coating layer.

[0025] The liquid phase coating is as follows: using one or more of glucose, sucrose, citric acid, and water-based phenolic resin as carbon sources, the graphite material embedded with nano-silicon, the above carbon sources, and deionized water are stirred and mixed evenly in a ratio of (1-10):1:(1-10), dried in a vacuum oven at 40-80℃, and then carbonized at 700-1200℃ for 0.5-4h to form a carbon coating layer.

[0026] The present invention also provides the application of the silicon-carbon composite anode material prepared by the above-mentioned method of preparing silicon-carbon composite anode material using porous graphite in the field of lithium-ion battery anode materials.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] (1) Under the supercritical conditions of the foaming agent, the foaming agent and the high softening point asphalt form a homogeneous system. By rapidly depressurizing, the supercritical fluid is in a supersaturated state in the high softening point asphalt and nucleates and foams. The porous graphite produced by high-temperature graphitization has a small average pore size, controllable pore size, narrow pore size distribution, high pore density, and no by-product residue.

[0029] (2) Nano-silicon is embedded in the crater on the surface of graphite powder and maintains good electrical contact with graphite, which greatly improves the electrochemical performance of silicon-based anode materials. While giving full play to the high theoretical specific capacity of silicon-based materials, it alleviates the volume expansion effect and improves the charge-discharge performance, cycle performance and stability of silicon-carbon composite anode materials.

[0030] This invention uses a gaseous or liquid foaming agent with no residual components for supercritical physical foaming, instead of the etching method in CN110098380A. In this invention, the foaming agent (pore-forming agent) is completely separated from the material system during the supercritical foaming process, so there are no residues. The supercritical physical foaming method controls the foam size to be highly consistent through processes such as temperature and pressure, so the final pores are uniform. High pore formation rate is also one of the characteristics of physical foaming. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of the graphite powder embedded with silicon nanoparticles prepared in Example 1 of the present invention.

[0032] Figure 2 This is a schematic diagram of the structure of the silicon-carbon composite anode material prepared in Example 1 of the present invention.

[0033] Figure 3 This is a cycle capacity diagram of the silicon-carbon composite anode material prepared in Example 1 of the present invention. Detailed Implementation

[0034] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. 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. These all fall within the scope of protection of the present invention.

[0035] Example 1:

[0036] A method for preparing silicon-carbon composite anode materials using porous graphite comprises the following steps:

[0037] (1) Weigh 200g of mesophase asphalt (softening point 275℃) and place it in a high-pressure reactor. The volume of the mesophase asphalt should not exceed one-twentieth of the volume of the high-pressure reactor to ensure that the asphalt has enough space to foam and form. Fill the reactor with low-pressure carbon dioxide to completely replace the air, and then fill it with high-pressure carbon dioxide. Heat the reactor to 300℃ at a heating rate of 5℃ / min, and control the pressure at 15MPa. Allow it to swell and penetrate for 1 hour. Then, depressurize the reactor to atmospheric pressure at a rate of 10MPa / second and cool the reactor to room temperature to obtain porous asphalt.

[0038] (2) The porous pitch obtained in step (1) is heated to 2800℃ and graphitized at high temperature to obtain porous graphite, which is then crushed and sieved to obtain graphite powder with an average particle size D50 of 10μm. The surface of the graphite powder has uniformly distributed pores with a diameter of about 1μm.

[0039] (3) Weigh 90g of graphite powder obtained in step (2) and 5g of silicon nanomaterial with an average particle size D50 of 81nm and place them in a planetary ball mill jar. Add an appropriate amount of zirconium balls and mill for 1 hour.

[0040] (4) Weigh 90g of the graphite material embedded with nano-silicon obtained in step (3), mix it thoroughly with 10g of low-temperature asphalt, place it in a rotary tube furnace, introduce nitrogen gas at high temperature, perform full coking at 400℃ for 1h, and then perform carbonization at 1000℃ for 1h. After the reaction is completed, cool to room temperature to obtain a high-performance silicon-carbon composite anode material for lithium-ion batteries.

[0041] The prepared high-performance silicon-carbon composite anode material, conductive carbon black, and sodium carboxymethyl cellulose were mixed uniformly in a weight ratio of 80:10:10 to form a slurry. This slurry was then uniformly coated onto copper foil, vacuum dried, and stamped into circular electrode sheets. Lithium metal was used as the counter electrode, 1 mol / L LiPF6 / DMC+DEC+EC (volume ratio 1:1:1) was used as the electrolyte, and Celgard 2400 was used as the separator to form an experimental battery. Constant current charge-discharge tests were conducted on the battery, with a charge-discharge voltage range of 0.01–1.5 V. The results showed that it exhibited good electrochemical performance. At a current density of 0.1 A / g, the initial charge specific capacity was 458.5 mAh / g, the initial coulombic efficiency was 93.2%, and the capacity retention after 60 cycles was greater than 97%, indicating that the material has good cycle stability.

[0042] Example 2:

[0043] A method for preparing silicon-carbon composite anode materials using porous graphite comprises the following steps:

[0044] (1) Weigh 20g of mesophase asphalt (softening point 275℃) and 240mL of toluene into a high-pressure reactor. The volume of the mesophase asphalt should not exceed one-twentieth of the volume of the high-pressure reactor to ensure that the asphalt has sufficient space to foam and form. After sealing, heat to 320℃ at a heating rate of 4℃ / min, and control the pressure at 9MPa for swelling and penetration for 2h. Then, rapidly depressurize to atmospheric pressure at a rate of 12MPa / s and cool the high-pressure reactor to room temperature to obtain porous asphalt.

[0045] (2) The porous pitch obtained in step (1) is heated to 2900℃ and graphitized at high temperature to obtain porous graphite, which is then crushed and sieved to obtain graphite powder with an average particle size D50 of 20μm. The surface of the graphite powder has uniformly distributed pores with a diameter of about 3μm.

[0046] (3) Weigh 9g of graphite powder obtained in step (2) and 0.25g of silicon nanomaterial with an average particle size D50 of 164nm and place them in a planetary ball mill jar. Add an appropriate amount of zirconium balls and ball mill for 1 hour.

[0047] (4) Weigh 9g of the graphite material embedded with nano-silicon obtained in step (3), mix it thoroughly with 1g of low-temperature asphalt, place it in a rotary tube furnace, introduce nitrogen gas at high temperature, perform full coking at 450℃ for 2h, and then perform carbonization at 950℃ for 1h. After the reaction is completed, cool to room temperature to obtain a high-performance silicon-carbon composite anode material for lithium-ion batteries.

[0048] The prepared high-performance silicon-carbon composite anode material, conductive carbon black, and sodium carboxymethyl cellulose were mixed uniformly in a weight ratio of 80:10:10 to form a slurry, which was then uniformly coated onto copper foil. After vacuum drying, the slurry was stamped into circular electrode sheets. Lithium metal was used as the counter electrode, 1 mol / L LiPF6 / DMC+DEC+EC (volume ratio 1:1:1) was used as the electrolyte, and Celgard 2400 was used as the separator to form an experimental battery. Constant current charge-discharge tests were conducted on the battery, with a charge-discharge voltage range of 0.01–1.5 V. The results showed that the battery exhibited good electrochemical performance. At a current density of 0.1 A / g, the initial charge specific capacity was 406.7 mAh / g, the initial coulombic efficiency was 94.1%, and the capacity retention after 60 cycles was greater than 97%, indicating that the material has good cycle stability.

[0049] Example 3:

[0050] A method for preparing silicon-carbon composite anode materials using porous graphite comprises the following steps:

[0051] (1) Weigh 50g of mesophase asphalt (softening point 275℃) and place it in a high-pressure reactor. The volume of the mesophase asphalt should not exceed one-twentieth of the volume of the high-pressure reactor to ensure that the asphalt has enough space to foam and form. Fill the reactor with low-pressure nitrogen to completely replace the air, and then fill it with high-pressure nitrogen. Heat the reactor to 290℃ at a heating rate of 10℃ / min, and control the pressure at 12MPa. Allow it to swell and penetrate for 3 hours. Then, rapidly depressurize the reactor to atmospheric pressure at a rate of 15MPa / second and cool the reactor to room temperature to obtain porous asphalt.

[0052] (2) The porous pitch obtained in step (1) is heated to 2850℃ and graphitized at high temperature to obtain porous graphite, which is then crushed and sieved to obtain graphite powder with an average particle size D50 of 15μm. The surface of the graphite powder has uniformly distributed pores with a diameter of about 1.5μm.

[0053] (3) Weigh 20g of graphite powder obtained in step (2) and 0.5g of silicon nanomaterial with an average particle size D50 of 65nm and place them in a planetary ball mill jar. Add an appropriate amount of zirconium balls and mill for 1 hour.

[0054] (4) Weigh 20g of the graphite material embedded with nano-silicon obtained in step (3) and place it in a tube furnace. Introduce nitrogen and heat it. When the temperature reaches 800℃, introduce ethylene at a flow rate of 0.5L / min and continue for 2 hours for chemical vapor deposition. After the reaction is completed, cool it to room temperature to obtain a high-performance silicon-carbon composite anode material for lithium-ion batteries.

[0055] The prepared high-performance silicon-carbon composite anode material, conductive carbon black, and sodium carboxymethyl cellulose were mixed uniformly in a weight ratio of 80:10:10 to form a slurry. This slurry was then uniformly coated onto copper foil, vacuum dried, and stamped into circular electrode sheets. Lithium metal was used as the counter electrode, 1 mol / L LiPF6 / DMC+DEC+EC (volume ratio 1:1:1) was used as the electrolyte, and Celgard 2400 was used as the separator to form an experimental battery. Constant current charge-discharge tests were conducted on the battery, with a charge-discharge voltage range of 0.01–1.5 V. The results showed that it exhibited good electrochemical performance. At a current density of 0.1 A / g, the initial charge specific capacity was 394.5 mAh / g, the initial coulombic efficiency was 93.8%, and the capacity retention after 60 cycles was greater than 97%, indicating that the material has good cycle stability.

[0056] Example 4:

[0057] A method for preparing silicon-carbon composite anode materials using porous graphite comprises the following steps:

[0058] (1) Weigh 50g of mesophase asphalt (softening point 275℃) and place it in a high-pressure reactor. The volume of the mesophase asphalt should not exceed one-twentieth of the volume of the high-pressure reactor to ensure that the asphalt has enough space to foam and form. Fill the reactor with low-pressure nitrogen to completely replace the air, and then fill it with high-pressure nitrogen. Heat the reactor to 290℃ at a heating rate of 15℃ / min, and control the pressure at 11MPa. Allow it to swell and penetrate for 3 hours. Then, depressurize the reactor to atmospheric pressure at a rate of 14MPa / second and cool it to room temperature to obtain porous asphalt.

[0059] (2) The porous pitch obtained in step (1) is heated to 2800℃ and graphitized at high temperature to obtain porous graphite, which is then crushed and sieved to obtain graphite powder with an average particle size D50 of 15μm. The surface of the graphite powder has uniformly distributed pores with a diameter of about 1.8μm.

[0060] (3) Weigh 20g of graphite powder obtained in step (2) and 0.5g of silicon nanomaterial with an average particle size D50 of 65nm and place them in a planetary ball mill jar. Add an appropriate amount of zirconium balls and mill for 1 hour.

[0061] (4) Weigh 20g of the graphite material embedded with nano-silicon obtained in step (3), 5g of glucose and 30g of deionized water, mix them evenly, dry them in a vacuum oven at 60℃, and then carbonize them at 1000℃ for 2h. After the reaction is completed, cool them to room temperature to obtain a high-performance silicon-carbon composite anode material for lithium-ion batteries.

[0062] The prepared high-performance silicon-carbon composite anode material, conductive carbon black, and sodium carboxymethyl cellulose were mixed uniformly in a weight ratio of 80:10:10 to form a slurry. This slurry was then uniformly coated onto copper foil, vacuum dried, and stamped into circular electrode sheets. Lithium metal was used as the counter electrode, 1 mol / L LiPF6 / DMC+DEC+EC (volume ratio 1:1:1) was used as the electrolyte, and Celgard 2400 was used as the separator to form an experimental battery. Constant current charge-discharge tests were conducted on the battery, with a charge-discharge voltage range of 0.01–1.5 V. The results showed that it exhibited good electrochemical performance. At a current density of 0.1 A / g, the initial charge specific capacity was 403.8 mAh / g, the initial coulombic efficiency was 93.4%, and the capacity retention after 60 cycles was greater than 97%, indicating that the material has good cycle stability.

[0063] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a silicon-carbon composite negative electrode material using porous graphite, characterized by: Includes the following steps: (1) Porous graphite is prepared by physical foaming method; high softening point asphalt is placed in a high pressure container, and foaming agent is added at a volume ratio of asphalt: foaming agent = 1:5-1:

200. The temperature is then raised to above the critical temperature of the foaming agent at a rate of 1-30℃ / min, and held at the temperature for 0.5-5h. The pressure is then rapidly released to normal pressure at a rate of 1-100MPa / second to obtain porous asphalt. The temperature is then raised to 2500-3000℃ and graphitized at high temperature to obtain porous graphite. The foaming agent is a gaseous or liquid foaming agent without residual components. (2) The porous graphite obtained in step (1) is pulverized to obtain graphite powder with a certain size and a crater structure on the surface; the size range of the graphite powder with a crater structure on the surface is 10μm-200μm. (3) The graphite powder obtained in step (2) is mixed and ball-milled with nano-silicon material so that the nano-silicon is embedded in the crater structure on the surface of the graphite powder; or, the obtained graphite powder, intermediate medium and nano-silicon material are mixed and ball-milled, the intermediate medium is filled into the crater and the nano-silicon is embedded in the crater through the intermediate medium; the intermediate medium includes but is not limited to carbon, metal, organic polymer and inorganic salt. (4) The graphite material embedded with nano-silicon obtained in step (3) is subjected to carbon coating treatment to obtain silicon-carbon composite anode material; the carbon coating treatment is one of gas phase coating, liquid phase coating, and solid phase coating. 2.The method for preparing a silicon-carbon composite negative material by using porous graphite according to claim 1, characterized in that: The container in step (1) is a high-pressure constant-volume container; the softening point of the asphalt is 200-350℃.

3. The method for preparing silicon-carbon composite anode material using porous graphite according to claim 1, characterized in that: The foaming agent mentioned in step (1) is one of carbon dioxide, nitrogen, or toluene.

4. The method for preparing silicon-carbon composite anode material using porous graphite according to claim 1, characterized in that: The pore size range of the porous graphite in step (1) is 1 nm to 30 μm.

5. The method for preparing silicon-carbon composite anode material using porous graphite according to claim 1, characterized in that: In step (1), the ratio of asphalt to foaming agent is 1:8 to 1:150; the heating rate is 3-15℃ / minute; the constant temperature time is 1-3h; and the depressurization rate is 5-50MPa / second.

6. The method for preparing silicon-carbon composite anode material using porous graphite according to claim 1, characterized in that: The particle size range of the nano-silicon is 30nm-200nm.

7. The method for preparing silicon-carbon composite anode material using porous graphite according to claim 1, characterized in that: The mass ratio of the nano-silicon to graphite powder is 0.1%–10%.

8. The method for preparing silicon-carbon composite anode material using porous graphite according to claim 1, characterized in that: Nano-silicon is located in the crater structure on the surface of graphite powder, and silicon is in direct contact with graphite; Alternatively, in the presence of an intermediate medium, the nano-silicon is located within the crater structure on the surface of the graphite powder, and the nano-silicon is in contact with the intermediate medium.

9. The method for preparing silicon-carbon composite anode material using porous graphite according to claim 1, characterized in that: The solid coating in step (4) includes: fully mixing graphite material embedded with nano-silicon and low-temperature pitch in a ratio of (7~12):1 and placing it in a rotary tube furnace, introducing nitrogen gas at high temperature, fully removing coke at 280-600℃ for 0.5-5h, and then carbonizing at 700-1200℃ for 0.5-5h. After the reaction is completed, the temperature is lowered to room temperature. The gas phase coating includes: using one or more of ethylene, acetylene, methane, ethane, and propane as carbon sources, and employing chemical vapor deposition to carbon coat graphite materials embedded with nano-silicon, with a gas flow rate of 0.1-5 L / min, and treating at 500-1000℃ for 0.5-3 h to form a carbon coating layer. The liquid phase coating process includes: using one or more of glucose, sucrose, citric acid, and water-based phenolic resin as carbon sources, mixing graphite material embedded with nano-silicon, the above-mentioned carbon sources, and deionized water in a ratio of (1~10):1:(1~10) until homogeneous, drying in a vacuum oven at 40-80℃, and then carbonizing at 700-1200℃ for 0.5-4h to form a carbon coating layer.

10. The application of the silicon-carbon composite anode material prepared by the method of preparing silicon-carbon composite anode material using porous graphite as described in claim 1 in the field of lithium-ion battery anode materials.

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