Preparation method for heteroatom-doped carbon material

Abstract

Disclosed is a preparation method for a heteroatom-doped carbon material, comprising the following steps: (S1) uniformly mixing a phenolic monomer, an aldehyde monomer and a non-metal doping source, then pre-polymerizing same to obtain a liquid phenolic resin oligomer, then adding a metal doping source and uniformly mixing same, and then curing same to obtain a solid precursor; (S2) sequentially subjecting the solid precursor to crushing, pyrolysis and carbonization, and then an activation process for pore forming, to obtain a carbon material having a porous structure; (S3) pulverizing the carbon material having the porous structure, placing same into a reactor and introducing a silicon-containing gas, performing silicon deposition, and then subjecting same to stabilization treatment to obtain a silicon-carbon composite material; and (S4) performing carbon coating on a surface of the silicon-carbon composite material to obtain a product heteroatom-doped carbon material. By doping with non-metal and metal heteroatoms in a specific order, the present invention improves the kinetic properties of lithium ions and electrons, inhibits composite material particle breakdown during charging and discharging, and improves interface stability.

Description

Preparation method of a hetero-element doped carbon material TECHNICAL FIELD

[0001] The present application belongs to the technical field of batteries, and particularly relates to a preparation method of a hetero-element doped carbon material. BACKGROUND

[0002] The energy density of traditional lithium-ion batteries with layered oxides as positive electrodes and graphite as negative electrodes has gradually approached its theoretical limit. Developing new positive and negative electrode material systems is an important means to further improve the energy density of lithium-ion batteries. For negative electrode materials, silicon is the most powerful candidate for the next generation of lithium-ion battery negative electrode materials because it has a specific capacity about an order of magnitude higher than graphite (4200 mAh / g), a suitable working potential (0.4 V vs. Li+ / Li), abundant reserves, and environmental friendliness. However, during the lithium intercalation / deintercalation process, silicon undergoes more than 300% volume change, which leads to a series of negative effects such as particle breakage, electrode delamination, electrolyte consumption, and repeated SEI formation, which seriously hinders the practical application of silicon.

[0003] The electrochemical-mechanical properties of silicon have a significant size effect. Specifically, nano-sized silicon negative electrodes can withstand the huge mechanical stress during the lithium intercalation / deintercalation process, thereby inhibiting the structural damage of silicon and improving the cycle stability of silicon. However, the decrease in particle size leads to an increase in interfacial side reactions, a decrease in compaction density, a decrease in processing performance, and an increase in production cost, making it difficult to achieve large-scale application. Micron-sized materials have more advantages in terms of volumetric energy density, processing performance, and cost. Therefore, the practical application of silicon-based negative electrodes needs to combine the advantages of nano-scale and micron-scale to build nanometer-micrometer composite materials to comprehensively improve the overall performance. Specifically, on the one hand, the active silicon needs to be reduced to nano-size to play the size effect of silicon and improve the structural stability, and on the other hand, the nano-sized silicon needs to be combined together to form micron-sized particles to improve its practicality in actual battery systems. Therefore, a silicon-carbon composite material in which silicon is filled into the pores of a carbon material with a nanoporous structure through a chemical vapor infiltration method is a solution for silicon-based negative electrodes. However, due to the poor mechanical properties of the carbon material itself, during the lithium intercalation / deintercalation process, the structure is easily damaged under the action of silicon volume change, leading to a decrease in cycle stability. In addition, the low diffusion coefficient of lithium ions in the carbon material also limits the ability of the material to intercalate / deintercalate at high current density. Therefore, the mechanical properties and ion transport ability of the carbon material need to be improved to further improve the electrochemical performance of the silicon-carbon composite material. SUMMARY

[0004] The application aims to improve the mechanical properties and ion transmission capacity of porous carbon materials, and provides a porous carbon material with improved mechanical properties and lithium ion transport capacity by hetero-element doping and a corresponding silicon-carbon material. In the process of preparing the porous carbon skeleton, a hetero-doping element is introduced into the carbon skeleton, so that the structural strength of the whole carbon skeleton is enhanced, the lithium ion diffusion coefficient is increased, the structural stability and cycle stability during the electrochemical process of the silicon-carbon composite material are maintained, and the rate performance of the silicon-carbon composite material is improved. The application achieves the above-mentioned purposes by providing the following technical solutions.

[0005] A preparation method of a hetero-element doped carbon material, comprising the following steps:

[0006] (S1) mixing a phenolic monomer, an aldehyde monomer and a non-metallic doping source uniformly, pre-polymerizing to obtain a liquid phenolic aldehyde resin oligomer, then adding a metallic doping source, mixing uniformly, and solidifying to obtain a solid precursor;

[0007] (S2) sequentially crushing, pyrolyzing and carbonizing, and activating and pore-forming the solid precursor to obtain a carbon material with a pore structure;

[0008] (S3) crushing the carbon material with a pore structure, putting it into a reactor and introducing a silicon-containing gas to deposit silicon, then performing a stabilization treatment to obtain a silicon-carbon composite material;

[0009] (S4) performing carbon coating on the surface of the silicon-carbon composite material to obtain a product hetero-element doped carbon material.

[0010] Further, in step (S1), the phenolic monomer includes but is not limited to phenol, o-cresol, m-cresol, p-cresol, 2,3-dimethylphenol, 2,4-dimethylphenol, 2,5-dimethylphenol, 2,6-dimethylphenol, 3,4-dimethylphenol, 3,5-dimethylphenol, resorcinol, t-butyl phenol, t-octyl phenol, t-amyl phenol, sec-butyl phenol, cyclohexyl phenol, nonyl phenol, benzyl phenol, bisphenol A, etc.; the aldehyde monomer includes but is not limited to formaldehyde, paraformaldehyde, trioxane, acetaldehyde, triacetaldehyde, sugar aldehyde, propyl aldehyde, butyl aldehyde, propylene aldehyde, benzaldehyde, cinnamaldehyde, 2-furfuraldehyde, glycerol aldehyde, ethanol aldehyde, malondialdehyde, succinic aldehyde, benzene dicarboxaldehyde, etc.; the molar ratio of the phenolic monomer and the aldehyde monomer is 1:0.5-1.5, and preferably 1:0.7-1.

[0011] Further, in step (S1), the non-metallic doping source contains non-metallic elements such as boron, nitrogen, phosphorus, oxygen, sulfur, selenium, fluorine, chlorine, bromine, etc., and is specifically at least one selected from urea, pyridine, pyrrole, acrylamide, melamine, polyvinylpyrrolidone, phosphoric acid, methyl phosphate, dimethyl phosphate, trimethyl phosphate, phosphorous acid, hypophosphorous acid, phenylphosphonic acid, triphenylphosphine, boric acid, isopropyl borate, triphenyl borate, thiourea, ethyl mercaptan, benzyl sulfide, methyl sulfide, thiophenol, thiophene. The amount of non-metallic doping source is 7-12wt% of the total mass of phenolic monomers and aldehyde monomers.

[0012] Further, in step (S1), the process parameters for curing the phenolic monomers and aldehyde monomers to prepare the liquid phenolic resin are well known in the art, such as, in the presence of an alkaline catalyst, under stirring and heating conditions for a certain period of time, the alkaline catalyst includes but is not limited to sodium hydroxide, ammonia, barium hydroxide, calcium hydroxide, magnesium hydroxide, sodium carbonate, etc.; the amount of alkaline catalyst is such that the pH of the system is >9. The prepolymerization is carried out at 40-50℃ for 5-10h to obtain the liquid phenolic resin oligomer.

[0013] Further, in step (S1), the metallic doping source is a salt of lithium, potassium, magnesium, aluminum, calcium, tin, titanium, vanadium, chromium, zirconium, molybdenum, germanium, and the salt is selected from acetate, halide (fluoride, chloride, bromide), nitrate. Specifically, the metallic doping source includes but is not limited to lithium acetate, sodium acetate, potassium acetate, magnesium acetate, calcium acetate, aluminum acetate, titanium acetate, vanadium acetate, chromium acetate, zirconium acetate, niobium acetate, molybdenum acetate, germanium acetate, tin acetate, lithium nitrate, sodium nitrate, potassium nitrate, magnesium nitrate, calcium nitrate, aluminum nitrate, titanium nitrate, vanadium nitrate, chromium nitrate, zirconium nitrate, niobium nitrate, molybdenum nitrate, germanium nitrate, tin nitrate, lithium chloride, sodium chloride, potassium chloride, magnesium chloride, calcium chloride, aluminum chloride, titanium chloride, vanadium chloride, chromium chloride, zirconium chloride, niobium chloride, molybdenum chloride, germanium chloride, tin chloride. The amount of metallic doping source is 1-5wt%, preferably 2-4wt% of the total mass of phenolic and aldehyde monomers. The way of mixing the metallic doping source and the liquid phenolic resin oligomer uniformly is not particularly limited, such as stirring.

[0014] Further, in step (S1), the curing is carried out at 80-110℃ for 3-6h to obtain the solid precursor.

[0015] In step (S1), the preparation process of the solid precursor can be divided into two stages of preliminary polymerization and curing. The preliminary polymerization stage forms a polymer with a lower molecular weight, and after curing, a high molecular weight phenolic resin is formed. The present application carries out two-step doping, non-metallic element doping in the preliminary polymerization stage, and metal element doping in the curing stage. Metal elements cannot effectively bond with carbon under the conditions of resin preliminary polymerization, and cannot achieve effective atomic doping, but can effectively bond with non-metallic elements such as boron, nitrogen, phosphorus, sulfur, selenium, fluorine, chlorine, bromine, etc. through coordination bonds, so it is necessary to first dope non-metallic elements in the preliminary polymerization stage, and then dope metal elements in the curing stage. Through the doping of non-metallic elements, the structural strength of the material is improved by using the stronger bond energy between non-metallic elements and carbon elements, thereby inhibiting the particle breakage and pulverization caused by the low mechanical strength of the material during the charging and discharging process, and improving the structural stability and cycle stability. Through the doping of metal elements, by taking advantage of the characteristic that metal elements can only combine with non-metallic doping elements, "end groups" not combined with carbon atoms are generated in the carbon skeleton, breaking the continuous network structure of carbon-carbon bonds, and constructing diffusion channels for lithium ions in the silicon-carbon composite material, thereby improving the kinetic performance and charging and discharging rate of the material.

[0016] Further, in step (S2), the crushing is crushed into particles of 10-70 mesh; the pyrolysis carbonization is heat treated at 400-700℃ for 4-10h under an inert atmosphere; the activation pore forming is carried out in an activation furnace, including physical activation, and the physical activation includes but is not limited to oxygen, water vapor, carbon dioxide, etc. The activation temperature is 700-1050℃, and the activation time is 10-20h. The pore size of the carbon material with a pore structure after activation and pore forming is 0.4-50nm, and the specific surface area is 1300-2700m 2 / g.

[0017] Further, in step (S3), the median particle size of the crushed carbon material is 1-20um, preferably 5-15um; the silicon-containing gas includes but is not limited to monosilane, disilane, trisilane, monochlorohydrosilane, dichlorohydrosilane, trichlorohydrosilane, silicon tetrachloride; and the stabilization treatment process is heat treated at 350-420℃ for 1-5h in an oxygen, carbon dioxide, acetylene, ethylene, propylene, propyne, methane, ethane, propane, etc. atmosphere. The silicon content of the silicon-carbon composite material is 30-70wt%, preferably 50-60wt%. The silicon is uniformly filled in the pores of the above-mentioned carbon material, and part of the silicon can also exist on the surface of the carbon material.

[0018] Further, in step (S4), the carbon coating is carried out by introducing carbon source process gas and inert gas into the reactor under the exclusion of air at 500-700℃, and the thickness of the carbon coating layer is 2-20nm, preferably 5-10nm.

[0019] The present application realizes the synergistic effect of non-metallic element doping and metallic element doping by introducing non-metallic doping elements and metallic doping elements respectively in the pre-polymerization and curing stages of phenolic resin, which greatly improves the electrochemical performance of silicon-carbon composite materials. First, in the synthesis of phenolic resin, a non-metallic doping source is added during the mixing stage of phenolic and aldehyde monomers to achieve uniform dispersion of the non-metallic doping source. The reaction conditions are controlled to obtain a liquid phenolic resin oligomer solution doped with non-metallic elements. Then, a metallic doping source is added to realize the combined effect of metallic doping elements and non-metallic elements to improve the structural stability and cycle stability of silicon-carbon composite materials. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a scanning electron microscope photograph of the silicon-carbon composite material prepared in Example 1;

[0021] Figure 2 is a transmission electron microscope photograph of the silicon-carbon composite material prepared in Example 1;

[0022] Figure 3 is the first charge-discharge curve of the silicon-carbon composite material prepared in Example 1. DETAILED DESCRIPTION

[0023] The present application will be further described below in conjunction with specific examples, but the present application is not limited to the following examples.

[0024] In the following examples, the experimental methods are conventional methods unless otherwise specified; the reagents and materials can be obtained commercially unless otherwise specified.

[0025] The scanning electron microscope (SEM) is Regulus 8100, and the transmission electron microscope (TEM) is JEM-2100F.

[0026] Example 1

[0027] (S1). Preparation of carbon material precursor: First, 7.1 kg of m-diphenol was added to a reactor, followed by the addition of 7.2 kg of 37% formaldehyde solution and 1 kg of melamine. After stirring uniformly, the temperature was raised to 50°C and kept constant for 12 h to obtain a liquid phenolic resin oligomer. Then, 0.20 kg of molybdenum acetate was added, followed by heating to 110°C and keeping constant for 6 h to obtain a solid nitrogen-doped phenolic resin, i.e. a solid precursor;

[0028] (S2). Preparation of carbon material: The solid precursor obtained in step (S1) was crushed into 10-mesh particles and heated to 700°C under nitrogen protection for 4 h to obtain a carbonized doped carbon material. The carbonized material was loaded into an activation furnace and kept at 900°C for 6 h under a carbon dioxide atmosphere to obtain a porous doped carbon material with a pore size of 0.4-5 nm and a specific surface area of 1800 m2 / g.2 / g;

[0029] (S3). Preparation of silicon-carbon composite material: 10 kg of porous doped carbon material was crushed to a median particle size of about 10 μm, and was put into a vertical fluidized bed reactor. After air was excluded, 15 L / min of silane gas was introduced at 420°C for 6 h, and then 10 L / min of acetylene gas was introduced for 1 h before being cooled to room temperature for discharge, to obtain a doped silicon-carbon composite negative electrode material with a silicon content of 48.2 wt%;

[0030] (S4). Coating of silicon-carbon composite material: 20 kg of doped silicon-carbon composite negative electrode material was put into a coating furnace. After air was excluded, 13 L / min of methane gas and 13 L / min of nitrogen gas as protective gas were introduced at 530°C for 4 h, to obtain a doped silicon-carbon composite negative electrode material coated with a surface carbon shell, i.e., the product hetero-element doped carbon material.

[0031] Figure 1 is a scanning electron microscope photograph of the silicon-carbon composite material prepared in Example 1, with a particle size of about 6.5 μm. Figure 2 is a transmission electron microscope photograph of the silicon-carbon composite material prepared in Example 1, which shows that the coating layer has a thickness of about 6 nm.

[0032] Figure 3 is a first charge-discharge curve of the silicon-carbon composite material prepared in Example 1.

[0033] Example 2

[0034] The other conditions and operations were the same as in Example 1, except that in step (S1), 1 kg of melamine was replaced by 0.7 kg of urea, and 0.20 kg of molybdenum acetate was replaced by 0.28 kg of tin acetate.

[0035] Example 3

[0036] The other conditions and operations were the same as in Example 1, except that in step (S1), 1 kg of melamine was replaced by 1.4 kg of polyvinylpyrrolidone, and 0.20 kg of molybdenum acetate was replaced by 0.39 kg of zirconium chloride.

[0037] Example 4

[0038] The other conditions and operations were the same as in Example 1, except that in step (S1), 1 kg of melamine was replaced by 0.8 kg of thiourea.

[0039] Example 5

[0040] The other conditions and operations were the same as in Example 1, except that in step (S1), 1 kg of melamine was replaced by 0.7 kg of phosphoric acid.

[0041] Example 6

[0042] Other conditions and operations are the same as Example 1, except that in step (S1), 1 kg of melamine is replaced by 0.6 kg of isopropyl borate.

[0043] Comparative Example 1

[0044] Other operations are the same as Example 1, except that in step (S1), 7.1 kg of m-phenol is added to the reactor, 7.2 kg of 37% formaldehyde solution, 1 kg of melamine and 0.20 kg of molybdenum acetate are added, and after stirring, the temperature is raised to 50°C and kept constant for 12 h, to preliminarily obtain liquid phenolic resin oligomers, and then heated to 110°C and kept constant for 6 h, to obtain solid doped phenolic resin, i.e. solid precursor.

[0045] Comparative Example 2

[0046] Other operations are the same as Example 1, except that in step (S1), 7.1 kg of m-phenol is added to the reactor, 7.2 kg of 37% formaldehyde solution is added, and after stirring, the temperature is raised to 50°C and kept constant for 12 h, to preliminarily obtain liquid phenolic resin oligomers, 1 kg of melamine and 0.20 kg of molybdenum acetate are added, and after mixing, the temperature is then raised to 110°C and kept constant for 6 h, to obtain solid doped phenolic resin, i.e. solid precursor.

[0047] Comparative Example 3

[0048] Other operations are the same as Example 1, except that in step (S1), 7.1 kg of m-phenol is added to the reactor, 7.2 kg of 37% formaldehyde solution and 1 kg of melamine are added, and after stirring, the temperature is raised to 50°C and kept constant for 12 h, to preliminarily obtain liquid phenolic resin oligomers, and then heated to 110°C and kept constant for 6 h, to obtain solid doped phenolic resin, i.e. solid precursor.

[0049] Comparative Example 4

[0050] Other operations are the same as Example 1, except that in step (S1), 7.1 kg of m-phenol is added to the reactor, 7.2 kg of 37% formaldehyde solution is added, and after stirring, the temperature is raised to 50°C and kept constant for 12 h, to preliminarily obtain liquid phenolic resin oligomers, 0.20 kg of molybdenum acetate is then added, and the temperature is then raised to 110°C and kept constant for 6 h, to obtain solid doped phenolic resin, i.e. solid precursor.

[0051] Application Example

[0052] The electrochemical performance of the silicon-based negative electrode material prepared in the above examples and comparative examples was tested according to the following method: the silicon-carbon composite material, carbon black and carboxymethyl cellulose (CMC) prepared were mixed with a mass ratio of 80:10:10 to form a slurry (the mass ratio of CMC and SBR was 1:1), the slurry was uniformly coated on a copper foil current collector, and after vacuum drying for 12 h, a working electrode was prepared; lithium flake was used as a counter electrode, a glass fiber membrane (purchased from the British Whatman Company) was used as a separator, 1 mol / L LiPF6 (solvent was a mixture of ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1) was used as an electrolyte, 1% VC and 5% FEC were added to the electrolyte, and a button cell was assembled in an argon atmosphere in a German Braun inert gas glove box.

[0053] The silicon-carbon composite material prepared in Example 1 was subjected to electrochemical analysis test, and the results are shown in Figure 3. The charge-discharge interval was 0-1.5 V, the material capacity could reach 1925.4 mAh / g at a current density of 0.2 C, the first cycle coulombic efficiency was 91.5%, the specific capacity at 1 C was 88.7% of the specific capacity under the condition of 0.2 C, i.e. the 1 C capacity retention rate; the capacity of the battery at 1 C was as high as 97.2% after 100 cycles, which proved that the silicon-carbon composite material obtained by the application had good cycle stability and rate performance.

[0054] The negative electrode materials of other examples and comparative examples were subjected to charge-discharge test according to the above method, and the results are shown in Table 1 below:

[0055] Table 1 Electrochemical performance test

[0056] In summary, the silicon-carbon composite material prepared by the element-doped porous carbon provided by the application has good structural stability and kinetic performance, so that the battery has stable cycle and excellent rate performance, the preparation method provided by the application is simple and easy to operate, and is suitable for industrialized scale production. Comparative examples 1-4 cannot effectively form co-doping of metal elements and non-metals, so the electrochemical performance is poor.

Claims

1. A method for producing a hetero-element doped carbon material, characterized by, The method comprises the following steps: (S1) mixing phenolic monomers, aldehyde monomers and non-metallic doping sources uniformly, pre-polymerizing to obtain liquid phenolic resin oligomers, then adding metallic doping sources, mixing uniformly, and solidifying to obtain solid precursors; The pre-polymerization is carried out at 40-50℃ for 5-10h to obtain liquid phenolic resin oligomers; the solidification is carried out at 80-110℃ for 3-6h to obtain solid precursors; (S2) the solid precursors are sequentially subjected to crushing, pyrolysis carbonization and activation pore forming to obtain carbon materials with pore structures; (S3) the carbon materials with pore structures are crushed, then put into a reactor and fed with silicon-containing gas to deposit silicon, then subjected to stabilization treatment to obtain silicon-carbon composite materials; (S4) carbon coating is carried out on the surface of the silicon-carbon composite materials to obtain the product hetero-element doped carbon materials.

2. The production method according to claim 1, characterized by, In step (S1), the phenolic monomers include phenol, o-cresol, m-cresol, p-cresol, 2,3-dimethylphenol, 2,4-dimethylphenol, 2,5-dimethylphenol, 2,6-dimethylphenol, 3,4-dimethylphenol, 3,5-dimethylphenol, resorcinol, t-butyl phenol, t-octyl phenol, t-amyl phenol, sec-butyl phenol, cyclohexyl phenol, nonyl phenol, benzyl phenol or bisphenol A; the aldehyde monomers include formaldehyde, paraformaldehyde, trioxane, acetaldehyde, triacetaldehyde, sugar aldehyde, propyl aldehyde, butyl aldehyde, propylene aldehyde, benzaldehyde, cinnamaldehyde, 2-furfuraldehyde, glycerol aldehyde, ethanol aldehyde, malondialdehyde, succinic aldehyde or benzaldehyde; the molar ratio of the phenolic monomers and the aldehyde monomers is 1:0.5-1.

5.

3. The preparation method according to claim 1, characterized in that, In step (S1), the non-metallic doping source contains boron, nitrogen, phosphorus, oxygen, sulfur, selenium, fluorine, chlorine or bromine; the metallic doping source is a salt of metallic lithium, potassium, magnesium, aluminum, calcium, tin, titanium, vanadium, chromium, zirconium, molybdenum or germanium, and the salt is selected from acetate, halide, nitrate.

4. The production method according to claim 3, characterized by, In step (S1), the non-metallic doping source is selected from at least one of urea, pyridine, pyrrole, acrylamide, melamine, polyvinylpyrrolidone, phosphoric acid, methyl phosphate, dimethyl phosphate, trimethyl phosphate, phosphorous acid, hypophosphorous acid, phenylphosphonic acid, triphenylphosphine, boric acid, isopropyl borate, triphenyl borate, thiourea, ethyl mercaptan, benzyl sulfide, methyl sulfide, thiophenol, thiophene; the amount of the non-metallic doping source is 7-12wt% of the total mass of the phenolic monomers and the aldehyde monomers.

5. The preparation method according to claim 3, characterized in that, In step (S1), the metallic doping source is selected from at least one of lithium acetate, sodium acetate, potassium acetate, magnesium acetate, calcium acetate, aluminum acetate, titanium acetate, vanadium acetate, chromium acetate, zirconium acetate, niobium acetate, molybdenum acetate, germanium acetate, tin acetate, lithium nitrate, sodium nitrate, potassium nitrate, magnesium nitrate, calcium nitrate, aluminum nitrate, titanium nitrate, vanadium nitrate, chromium nitrate, zirconium nitrate, niobium nitrate, molybdenum nitrate, germanium nitrate, tin nitrate, lithium chloride, sodium chloride, potassium chloride, magnesium chloride, calcium chloride, aluminum chloride, titanium chloride, vanadium chloride, chromium chloride, zirconium chloride, niobium chloride, molybdenum chloride, germanium chloride, tin chloride; the amount of the metallic doping source is 2-4wt% of the total mass of the phenolic monomers and the aldehyde monomers.

6. The method of claim 1, wherein, In step (S1), the phenolic monomer and aldehyde monomer are solidified to prepare a liquid phenolic resin in the presence of a basic catalyst, including sodium hydroxide, ammonia, barium hydroxide, calcium hydroxide, magnesium hydroxide or sodium carbonate, under stirring and heating conditions for a certain period of time; the amount of the basic catalyst is such that the pH of the system is > 9.

7. The preparation method according to claim 1, characterized in that, In step (S2), the crushing is into particles of 10-70 mesh; the pyrolytic carbonization is under an inert atmosphere, at 400-700℃ for 4-10h; the pore structure of the activated pore-structured carbon material has a pore diameter of 0.4-50nm and a specific surface area of 1300-2700m 2 / g.

8. The method of claim 1, wherein, In step (S3), the median particle size of the crushed carbon material is 5-15 μm; the silicon-containing gas includes but is not limited to monosilane, disilane, trisilane, monochlorohydrosilane, dichlorohydrosilane, trichlorohydrosilane and silicon tetrachloride; the stabilization treatment process is a heat treatment at 300-420 ℃ for 1-5 h in an atmosphere of oxygen, carbon dioxide, acetylene, ethylene, propylene, propyne, methane, ethane or propane; the silicon content of the silicon-carbon composite material is 50-60 wt%; and / or in step (S4), the carbon coating is performed at 500-700 ℃ in the presence of a carbon source process gas and an inert gas after excluding air, and the thickness of the carbon coating layer is 5-10 nm.

9. A heteroelement-doped carbon material, characterized by, is prepared by the preparation method of any one of claims 1-8.

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