A low-expansion-rate silicon-oxygen anode material based on porous carbon support and its preparation method

Abstract

This invention relates to the field of silicon-oxygen anode material technology, and in particular to a low-expansion-rate silicon-oxygen anode material based on a porous carbon support and its preparation method, comprising: Step 1, obtaining a low-condensation-degree carbon-rich precursor by pretreating the feed oil; Step 2, obtaining a porous carbon support by sequentially subjecting the low-condensation-degree carbon-rich precursor to oxidative crosslinking, molecular cleavage, pre-oxidation, and activation treatments; Step 3, obtaining the low-expansion-rate silicon-oxygen anode material by using the porous carbon support as a substrate and performing vapor phase deposition and pyrolysis treatment. This invention uses a porous carbon support as a substrate and obtains a silicon-oxygen anode material through vapor phase deposition and pyrolysis treatment, which exhibits characteristics such as low expansion rate and good cycle stability.

Description

Technical Field

[0001] This invention relates to the field of silicon-oxygen anode material technology, and in particular to a low expansion rate silicon-oxygen anode material based on a porous carbon support and its preparation method. Background Technology

[0002] In recent years, with the rapid development of new energy vehicles, portable electronic devices, and large-scale energy storage systems, lithium-ion batteries have faced higher requirements for cycle performance, energy density, and safety. However, the currently widely used full batteries composed of graphite anodes and nickel-cobalt-manganese oxides have an energy density as low as 250 Wh / kg, which is insufficient to meet the demands. To achieve the target of 400-500 Wh / kg, the development of high-energy-density electrode materials has become crucial.

[0003] Among various anode materials, silicon-based materials are significant for improving battery energy density due to their high specific capacity of 4200 mAh / g (10 times higher than graphite anodes). Adding 5-10 wt% silicon anode material to graphite can achieve a power battery energy density of 300 Wh / kg. Furthermore, silicon has a slightly higher lithium intercalation potential than graphite, which can suppress lithium dendrite growth and reduce safety risks. Silicon is also abundant and environmentally friendly. However, silicon experiences significant volume changes (300%-400%) during lithium intercalation / deintercalation, and suffers from problems such as continuous SEI film growth, low intrinsic conductivity, and low lithium-ion diffusion rate, hindering its commercial application.

[0004] Silicon suboxide (SiOx, 0≤x≤2) is considered one of the most promising anode materials for next-generation lithium-ion batteries due to its suitable operating potential and high theoretical capacity. However, it undergoes volume expansion during charge and discharge, leading to rapid capacity decay and poor charge-discharge cycle performance.

[0005] Therefore, this invention studies a low expansion rate silicon-oxygen anode material based on a porous carbon support and its preparation method. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the technical problem solved by the present invention is to provide a low expansion rate silicon-oxygen anode material based on a porous carbon support and its preparation method. The present invention uses a porous carbon support as a substrate and obtains a silicon-oxygen anode material through vapor deposition and pyrolysis treatment. The material has the characteristics of low expansion rate and good cycle stability.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] A method for preparing a low-expansion-rate silicon-oxygen anode material based on a porous carbon support, comprising:

[0009] Step 1: A low-condensation-degree carbon-rich precursor is obtained by pre-treating the feedstock oil.

[0010] Step 2: The low-condensation-degree carbon-rich precursor is sequentially subjected to oxidative crosslinking, molecular cleavage, pre-oxidation, and activation treatments to obtain a porous carbon support.

[0011] Step 3: Using a porous carbon support as a substrate, a low expansion rate silicon-oxygen anode material is obtained through vapor deposition and pyrolysis treatment.

[0012] In step one, the feedstock oil is one or more of the following: medium-low temperature coal tar, catalytic cracking slurry oil, ethylene tar, vacuum residue, and viscosity-reducing cracking residue; the low condensation degree carbon-rich precursor index is as follows: saturated content ≤10wt%, aromatic content ≥60wt%, gum content ≥18wt%, asphaltenes ≤1wt%, ash content ≤0.05wt%, H / C atomic ratio of (0.1~0.15):1, S ≥6wt%, N ≥7wt%.

[0013] In step one, the pretreatment is one or more of the following: solid-liquid separation, solvent sedimentation, solvent extraction and purification, solvent deasphalting, furfural solvent purification, supercritical fluid extraction, catalytic hydrogenation, and short-process molecular cutting.

[0014] In step two, the crosslinking agent for oxidative crosslinking treatment is one or more solvents selected from methylbenzenesulfonic acid, paraformaldehyde, benzaldehyde alkylbenzenesulfonic acid, unsaturated fatty acids, and petroleum naphthenic acid compounds, or a combination of the above solvents. The mass ratio of the crosslinking agent to the low-condensation-degree carbon-rich precursor is (1~10):100. The vacuum degree is 0.01~0.09MPa, the heating rate is 5~15℃ / min, the reaction temperature is 280~420℃, and the treatment time is 0.5~4h.

[0015] In step two, molecular slicing is performed in one or more stages according to the molecular weight requirements of the components to be removed from the oxidative crosslinking product. Multi-stage processing is carried out step-by-step. The extractants used are any one or a mixture of two or more of the following: acetone, benzene, toluene, xylene, pyridine, quinoline, furfural, N-methylpyrrolidone, medium-quality wash oil, and kerosene. The reaction conditions are as follows: reaction temperature: 30~150℃, time: 0.5~8h, vacuum degree: 0.01~0.09MPa, sieve mesh size: 300~1200 mesh. For molecular weights 5000≤<50000, one-stage molecular slicing is used; for molecular weights 2600≤<5000, two-stage molecular slicing is used; and for molecular weights 200≤<2600, three or more stages of molecular slicing are used.

[0016] In step two, the oxidant used for pre-oxidation is one of HNO3, H2SO4, KMnO4, and H2O2. The oxidation reaction temperature is 150~350℃, the oxidation residence time is 1~6h, and the mass ratio of oxidant to molecular cleavage product is (0.5~2):1.

[0017] In step two, depending on the requirements of the porous carbon support structure, the activation process can be a single-stage or multi-stage activation treatment. Multi-stage activation is performed step-by-step. The single-stage activation is surface modification, with reaction conditions of 500-800℃, oxygen, air, or carbon dioxide atmosphere, flow rate of 60-300 L / h, and reaction time of 0.5-15 h. The second-stage activation is etching, with reaction conditions of 600-1200℃, reaction time of 2-10 h, and reaction medium of one of KOH, NaOH, CO2, water vapor, NaHCO3, KHCO3, or H3PO4. Three-stage and higher activation treatments use the same conditions as the two-stage activation treatment.

[0018] 600m 2 / g≤ Porous carbon support specific surface area<1000m² 2 / g, when the micropore content is ≥10% and the mesopore content is ≥30%, a single-stage activation treatment is adopted; 1000m 2 / g≤ Porous carbon support specific surface area<1600m² 2 / g, when the micropore content is ≥20% and the mesopore content is ≥40%, a two-stage activation treatment is adopted; 1600m 2 / g≤ Porous carbon support specific surface area<2200m² 2 / g, when the micropore ratio is ≥30% and the mesopore ratio is ≥50%, three or more activation treatments are used.

[0019] In step three, the silicon source gas for vapor deposition is silane (SiH4), silane (Si2H6), or a silicon hydride (Si). n H 2n+2 One of the following is used: gas flow rate is 2~30L / h, carrier gas is Ar or N2 with a gas flow rate of 10~60L / h, oxygen concentration is <0.5ppm, vacuum degree is 0.01~0.09Mpa, reaction temperature is 600~1400℃, heating rate is 2~15℃ / min, and isothermal time is 0.5~8h.

[0020] In step three, the pyrolysis reaction conditions are as follows: the carbon coating agent is one or more of citric acid, glucose, sucrose, phenolic resin, polyvinyl chloride, polyacrylic acid, and polyvinyl alcohol; under nitrogen protection, the reaction temperature is 600~1200℃; the reaction time is 1~8h; and the mass ratio of carbon coating agent to vapor deposition product is (0.2~4):1.

[0021] A method for preparing low-expansion-rate silicon-oxygen anode material based on porous carbon support reveals a three-layer structure: an inner porous carbon support, a middle SiOx deposited phase, and an outer pyrolytic carbon coating layer. The porous carbon support has a specific surface area of ​​800–2000 m². 2 / g, with a micropore content of 10-30% and a mesopore content of 30-50%, and a carbon content ≥90%; SiOx deposition phase, with a SiOx content ≥60wt%; pyrolytic carbon coating layer, which is an amorphous structure, with a carbon content ≥92% and a graphitization degree ≤70%; the particle size distribution of the silicon-oxygen anode material is D 10 : 6~12μm, D 50 15~24μm, D 90 : 28~45μm, true density ≥2.24g / cm³ 3 Tap density ≥ 0.9 g / cm³ 3 The compacted density of the powder is ≥1.55 g / cm³. 3 Ash content ≤0.01%, specific surface area ≤1.8m² 2 / g, interlayer spacing (d) 002 The wavelength ranges from 0.34 nm to 0.375 nm, and the thickness of the carbon layer ranges from 5 to 20 nm.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1) The present invention uses a porous carbon support as a substrate, and after vapor deposition and pyrolysis, the obtained silicon-oxygen anode material has good specific capacity, rate performance and cycle stability, which meets the requirements of high specific capacity and low expansion rate lithium-ion battery silicon-oxygen anode material.

[0024] 2) This invention prepares a carbon support with a three-dimensional porous network structure through processes such as raw oil pretreatment, oxidative crosslinking, molecular cleavage, pre-oxidation, and activation. This support is composed of interconnected amorphous carbon atoms and possesses high specific surface area, a controllable coefficient of thermal expansion, excellent thermal conductivity, and low density. Its continuous three-dimensional porous structure provides an ideal buffer space for the silicon-oxygen anode material, significantly suppressing the volume expansion effect during charge and discharge, thereby greatly improving the cycle stability of the battery.

[0025] 3) The carbon coating layer formed by the pyrolysis treatment of this invention forms a conductive network, which improves the conductivity and structural stability of the material, promotes the rapid transport of lithium ions, and enhances the rate performance.

[0026] 4) The method for preparing low expansion rate silicon-oxygen anode materials provided by the present invention is simple, the process flow is easy to control, and it is suitable for large-scale production. Attached Figure Description

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0028] Figure 1 This is the charge-discharge curve of the low expansion rate silicon-oxygen anode material of the present invention.

[0029] Figure 2 This is the cycling curve of the low expansion rate silicon-oxygen anode material of the present invention. Detailed Implementation

[0030] The specific embodiments of the present invention will be further described below:

[0031] This invention provides a method for preparing a low-expansion-rate silicon-oxygen anode material based on a porous carbon support, comprising:

[0032] Step 1: A low-condensation-degree carbon-rich precursor is obtained by pre-treating the feedstock oil.

[0033] Step 2: The low-condensation-degree carbon-rich precursor is sequentially subjected to oxidative crosslinking, molecular cleavage, pre-oxidation, and activation treatments to obtain a porous carbon support.

[0034] Step 3: Using a porous carbon support as a substrate, a low expansion rate silicon-oxygen anode material is obtained through vapor deposition and pyrolysis treatment.

[0035] In step one, the feedstock oil is one or more of the following: medium-low temperature coal tar, catalytic cracking slurry oil, ethylene tar, vacuum residue, and viscosity-reducing cracking residue; the low condensation degree carbon-rich precursor index is as follows: saturated content ≤10wt%, aromatic content ≥60wt%, gum content ≥18wt%, asphaltenes ≤1wt%, ash content ≤0.05wt%, H / C atomic ratio of (0.1~0.15):1, S ≥6wt%, N ≥7wt%.

[0036] In step one, the pretreatment is one or more of the following: solid-liquid separation, solvent sedimentation, solvent extraction and purification, solvent deasphalting, furfural solvent purification, supercritical fluid extraction, catalytic hydrogenation, and short-process molecular cutting.

[0037] In step two, the crosslinking agent for oxidative crosslinking treatment is one or more solvents selected from methylbenzenesulfonic acid, paraformaldehyde, benzaldehyde alkylbenzenesulfonic acid, unsaturated fatty acids, and petroleum naphthenic acid compounds, or a combination of the above solvents. The mass ratio of the crosslinking agent to the low-condensation-degree carbon-rich precursor is (1~10):100. The vacuum degree is 0.01~0.09MPa, the heating rate is 5~15℃ / min, the reaction temperature is 280~420℃, and the treatment time is 0.5~4h.

[0038] In step two, molecular cleavage is performed in one or more stages based on the molecular weight requirements of the components to be removed from the oxidative crosslinking product. Multi-stage cleavage involves sequential processing. The extractants used are any one or a mixture of two or more of the following: acetone, benzene, toluene, xylene, pyridine, quinoline, furfural, N-methylpyrrolidone, medium-quality wash oil, and kerosene. The reaction conditions are as follows: reaction temperature: 30~150℃, time: 0.5~8h, vacuum degree: 0.01~0.09MPa, sieve mesh size: 300~1200 mesh. For molecular weights 5000≤<50000, one-stage molecular cleavage is used; for molecular weights 2600≤<5000, two-stage molecular cleavage is used; and for molecular weights 200≤<2600, three or more stages of molecular cleavage are used. When using three-stage molecular cleavage, the first stage is performed first, followed by the second stage, and finally the third stage.

[0039] In step two, the oxidant used for pre-oxidation is one of HNO3, H2SO4, KMnO4, and H2O2. The oxidation reaction temperature is 150~350℃, the oxidation residence time is 1~6h, and the mass ratio of oxidant to molecular cleavage product is (0.5~2):1.

[0040] In step two, depending on the requirements of the porous carbon support structure, the activation process can be a single-stage or multi-stage activation treatment. Multi-stage activation is performed step-by-step. The single-stage activation is surface modification, with reaction conditions of 500-800℃, oxygen, air, or carbon dioxide atmosphere, flow rate of 60-300 L / h, and reaction time of 0.5-15 h. The second-stage activation is etching, with reaction conditions of 600-1200℃, reaction time of 2-10 h, and reaction medium of one of KOH, NaOH, CO2, water vapor, NaHCO3, KHCO3, or H3PO4. Three-stage and higher activation treatments use the same conditions as the two-stage activation treatment.

[0041] 600m 2 / g≤ Porous carbon support specific surface area<1000m² 2 / g, when the micropore content is ≥10% and the mesopore content is ≥30%, a single-stage activation treatment is adopted; 1000m 2 / g≤ Porous carbon support specific surface area<1600m² 2 / g, when the micropore content is ≥20% and the mesopore content is ≥40%, a two-stage activation treatment is adopted; 1600m 2 / g≤ Porous carbon support specific surface area<2200m² 2 When the micropore content is ≥30% and the mesopore content is ≥50%, a three-stage or higher activation treatment is adopted. When adopting a three-stage activation treatment, a first-stage treatment is performed first, followed by a second-stage treatment, and finally a third-stage treatment.

[0042] In step three, the silicon source gas for vapor deposition is silane (SiH4), silane (Si2H6), or a silicon hydride (Si). n H 2n+2 One of the following is used: gas flow rate is 2~30L / h, carrier gas is Ar or N2 with a flow rate of 10~60L / h, oxygen concentration is <0.5ppm, vacuum degree is 0.01~0.09Mpa, reaction temperature is 600~1400℃, heating rate is 2~15℃ / min, and isothermal time is 0.5~8h.

[0043] In step three, the pyrolysis reaction conditions are as follows: the carbon coating agent is one or more of citric acid, glucose, sucrose, phenolic resin, polyvinyl chloride, polyacrylic acid, and polyvinyl alcohol; under nitrogen protection, the reaction temperature is 600~1200℃; the reaction time is 1~8h; and the mass ratio of carbon coating agent to vapor deposition product is (0.2~4):1.

[0044] A method for preparing low-expansion-rate silicon-oxygen anode material based on porous carbon support reveals a three-layer structure: an inner porous carbon support, a middle SiOx deposited phase, and an outer pyrolytic carbon coating layer. The porous carbon support has a specific surface area of ​​800–2000 m². 2 / g, with a micropore content of 10-30% and a mesopore content of 30-50%, and a carbon content ≥90%; SiOx deposition phase, with a SiOx content ≥60wt%; pyrolytic carbon coating layer, which is an amorphous structure, with a carbon content ≥92% and a graphitization degree ≤70%; the particle size distribution of the silicon-oxygen anode material is D 10 : 6~12μm, D 50 15~24μm, D 90 : 28~45μm, true density ≥2.24g / cm³ 3 Tap density ≥ 0.9 g / cm³ 3 The compacted density of the powder is ≥1.55 g / cm³. 3 Ash content ≤0.01%, specific surface area ≤1.8m² 2 / g, interlayer spacing (d) 002 The wavelength ranges from 0.34 nm to 0.375 nm, and the thickness of the carbon layer ranges from 5 to 20 nm.

[0045] Example:

[0046] Table 1 shows the preparation process parameters for the low expansion ratio silicon-oxygen anode materials in each embodiment. Table 2 shows the performance indicators of the low expansion ratio silicon-oxygen anode materials prepared in each embodiment.

[0047] Table 1. Preparation process parameters for low expansion ratio silicon-oxygen anode materials

[0048]

[0049]

[0050] Table 2 shows the performance indicators of the low expansion rate silicon-oxygen anode materials prepared in each embodiment.

[0051]

[0052] Therefore, and in combination Figure 1 and Figure 2 It is known that the low expansion rate silicon-oxygen anode material based on porous carbon support and its preparation method provided by the present invention have the following advantages: initial coulombic efficiency ≥90%, initial discharge specific capacity ≥450mAh / g, capacity retention ≥80% after 400 0.5C cycles, cycle performance ≥800 cycles, and rate performance (2C / 0.2C) ≥80%. It has advantages such as low expansion rate, long safe service life, and good cycle stability.

[0053] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention. Furthermore, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. In addition, various different embodiments of the present invention can also be arbitrarily combined, as long as they do not violate the spirit of the present invention, they should also be considered as the content disclosed by the present invention.

Claims

1. A method for preparing a low-expansion-rate silicon-oxygen anode material based on a porous carbon support, characterized in that, Includes the following steps: Step 1: A low-condensation-degree carbon-rich precursor is obtained by pre-treating the feedstock oil. Step 2: The low-condensation-degree carbon-rich precursor is sequentially subjected to oxidative crosslinking, molecular cleavage, pre-oxidation, and activation treatments to obtain a porous carbon support. Step 3: Using a porous carbon support as a substrate, a low expansion rate silicon-oxygen anode material is obtained through vapor deposition and pyrolysis treatment. In step one, the feedstock oil is one or more of the following: low-temperature coal tar, catalytic cracking slurry oil, ethylene tar, vacuum residue, and viscosity-reducing cracking residue; the low-condensation-degree carbon-rich precursor index is as follows: saturated content ≤10wt%, aromatic content ≥60wt%, resin ≥18wt%, asphaltenes ≤1wt%, ash content ≤0.05wt%, H / C atomic ratio of (0.1~0.15):1, S ≥6wt%, N ≥7wt%. In step one, the pretreatment is one or more of the following: solid-liquid separation, solvent sedimentation, solvent extraction and purification, solvent deasphalting, furfural solvent purification, supercritical fluid extraction, catalytic hydrogenation, and short-process molecular cutting. In step two, molecular slicing is performed in one or more stages according to the molecular weight requirements of the components to be removed from the oxidative crosslinking product. Multi-stage processing is carried out step-by-step. The extractants used are any one or a mixture of two or more of the following: acetone, benzene, toluene, xylene, pyridine, quinoline, furfural, N-methylpyrrolidone, medium-quality wash oil, and kerosene. The reaction conditions are as follows: reaction temperature: 30~150℃, time: 0.5~8h, vacuum degree: 0.01~0.09MPa, sieve mesh size: 300~1200 mesh. For molecular weights 5000≤<50000, one-stage molecular slicing is used; for molecular weights 2600≤<5000, two-stage molecular slicing is used; for molecular weights 200≤<2600, three or more stages of molecular slicing are used. The low expansion coefficient silicon-oxygen anode material has a three-layer structure: an inner porous carbon support, a middle SiOx deposited phase, and an outer pyrolytic carbon coating layer; the porous carbon support has a specific surface area of ​​800~2000 m². 2 / g, with a micropore content of 10-30% and a mesopore content of 30-50%, and a carbon content ≥90%; SiOx deposition phase, with a SiOx content ≥60wt%; pyrolytic carbon coating layer, which is an amorphous structure, with a carbon content ≥92% and a graphitization degree ≤70%; the particle size distribution of the silicon-oxygen anode material is D 10 6~12μm, D 50 15~24μm, D 90 : 28~45μm, true density ≥2.24g / cm³ 3 Tap density ≥ 0.9 g / cm³ 3 The compacted density of the powder is ≥1.55 g / cm³. 3 Ash content ≤0.01%, specific surface area ≤1.8m² 2 / g, interlayer spacing (d002) is 0.34nm~0.375nm, and carbon layer thickness is 5~20nm.

2. The method for preparing a low-expansion-rate silicon-oxygen anode material based on a porous carbon support according to claim 1, characterized in that, In step two, the crosslinking agent for oxidative crosslinking treatment is one or more solvents selected from methylbenzenesulfonic acid, paraformaldehyde, benzaldehyde alkylbenzenesulfonic acid, unsaturated fatty acids, and petroleum naphthenic acid compounds, or a combination of the above solvents. The mass ratio of the crosslinking agent to the low-condensation-degree carbon-rich precursor is (1~10):

100. The vacuum degree is 0.01~0.09MPa, the heating rate is 5~15℃ / min, the reaction temperature is 280~420℃, and the treatment time is 0.5~4h.

3. The method for preparing a low-expansion-rate silicon-oxygen anode material based on a porous carbon support according to claim 1, characterized in that, In step two, the oxidant used for pre-oxidation is one of HNO3, H2SO4, KMnO4, and H2O2. The oxidation reaction temperature is 150~350℃, the oxidation residence time is 1~6h, and the mass ratio of oxidant to molecular cleavage product is (0.5~2):

1.

4. The method for preparing a low-expansion-rate silicon-oxygen anode material based on a porous carbon support according to claim 1, characterized in that, In step two, depending on the requirements of the porous carbon support structure, the activation process can be a single-stage or multi-stage activation treatment. Multi-stage activation is performed step-by-step. The single-stage activation is surface modification, with reaction conditions of 500-800℃, oxygen, air, or carbon dioxide atmosphere, flow rate of 60-300 L / h, and reaction time of 0.5-15 h. The second-stage activation is etching, with reaction conditions of 600-1200℃, reaction time of 2-10 h, and reaction medium of one of KOH, NaOH, CO2, water vapor, NaHCO3, KHCO3, or H3PO4. Three-stage and higher activation treatments use the same conditions as the two-stage activation treatment. 600m 2 / g≤ Porous carbon support specific surface area<1000m² 2 / g, when the micropore content is ≥10% and the mesopore content is ≥30%, a single-stage activation treatment is adopted; 1000m 2 / g≤ Porous carbon support specific surface area<1600m² 2 / g, when the micropore content is ≥20% and the mesopore content is ≥40%, a two-stage activation treatment is adopted; 1600m 2 / g≤ Porous carbon support specific surface area<2200m² 2 / g, when the micropore ratio is ≥30% and the mesopore ratio is ≥50%, three or more activation treatments are used.

5. The method for preparing a low-expansion-rate silicon-oxygen anode material based on a porous carbon support according to claim 1, characterized in that, In step three, the silicon source gas for vapor deposition is a silicon hydride (Si). n H 2n+2 The gas flow rate is 2~30L / h, the carrier gas is Ar or N2 with a flow rate of 10~60L / h, the oxygen concentration is <0.5ppm, the vacuum degree is 0.01~0.09Mpa, the reaction temperature is 600~1400℃, the heating rate is 2~15℃ / min, and the isothermal time is 0.5~8h.

6. The method for preparing a low-expansion-rate silicon-oxygen anode material based on a porous carbon support according to claim 1, characterized in that, In step three, the pyrolysis reaction conditions are as follows: the carbon coating agent is one or more of citric acid, glucose, sucrose, phenolic resin, polyvinyl chloride, polyacrylic acid, and polyvinyl alcohol; under nitrogen protection, the reaction temperature is 600~1200℃; the reaction time is 1~8h; and the mass ratio of carbon coating agent to vapor deposition product is (0.2~4):1.

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