Metal and silicon-doped hard carbon composite material and preparation method thereof

Abstract

This invention belongs to the field of lithium-ion battery material preparation technology, specifically relating to a metal- and silicon-doped hard carbon composite material and its preparation method. By mass, the raw materials for preparing the metal- and silicon-doped hard carbon composite material include: 1-10 parts of a silane coupling agent, 100 parts of a nitrogen-containing hydrocarbon compound, and 1-5 parts of a metal. The silane coupling agent is one of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldiethoxysilane, and γ-aminopropylmethyldimethoxysilane. The nitrogen-containing hydrocarbon compound is one of methylamine, dimethylamine, trimethylamine (TMA), triethylamine, aniline, and pyridine. The metal is one of nano-copper, nano-silver, and nano-nickel. This invention enables the mixing of a silane coupling agent and its metal into a hard carbon precursor via a liquid-phase method, carbonizing to form silicon and its metal doping, and doping amorphous carbon with boron in its outer shell to improve the power performance and initial efficiency of the material.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material preparation technology, specifically relating to a metal and silicon-doped hard carbon composite material and its preparation method. Background Technology

[0002] Hard carbon materials are used in lithium-ion and sodium-ion batteries due to their high low-temperature performance, zero expansion, and wide availability. However, they suffer from low initial efficiency, low specific capacity (300 mAh / g), and poor electronic conductivity, which reduces the rate performance of batteries at room temperature. Silicon-oxygen materials, on the other hand, are used in high-energy-density lithium-ion batteries due to their high specific capacity (1700 mAh / g) and wide availability. However, their high expansion limits their application areas.

[0003] To address the inherent defects of the aforementioned materials, it is necessary to mix two or more materials to leverage their respective advantages, thereby increasing the material's energy density, reducing expansion, and improving power performance. Summary of the Invention

[0004] The purpose of this invention is to provide a metal and silicon doped hard carbon composite material and its preparation method, which can mix silane coupling agent and its metal into a hard carbon precursor by liquid phase method, carbonize to form silicon and its metal doping, and dop boron doping amorphous carbon in its shell to improve the power performance and first efficiency of the material.

[0005] The specific technical solution adopted by this invention is as follows: A metal-silicon doped hard carbon composite material for use in lithium-ion batteries or sodium-ion batteries, wherein the raw materials for preparing the metal-silicon doped hard carbon composite material are, by mass parts: 1-10 parts of silane coupling agent, 100 parts of nitrogen-containing hydrocarbon compound, and 1-5 parts of metal; The silane coupling agent is one of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldiethoxysilane, and γ-aminopropylmethyldimethoxysilane. The nitrogen-containing hydrocarbon is one of methylamine, dimethylamine, trimethylamine (TMA), triethylamine, aniline, and pyridine; The metal is one of nano-copper, nano-silver, or nano-nickel.

[0006] A method for preparing a metal-silicon-doped hard carbon composite material, characterized by comprising the following steps: Step 1: Add the silane coupling agent to an aqueous solution containing nitrogen-containing hydrocarbons and disperse it evenly to prepare the first solution; Step 2: Add the metal to the first solution and transfer it to a ball mill for uniform dispersion to prepare the second solution; Step 3: Spray dry and pulverize the second solution to obtain the precursor material; Step 4: Transfer the precursor material to a tube furnace and sequentially introduce carbon source gas, borane gas and inert gas to obtain a hard carbon-metal-silicon composite material. Step 5: Transfer the hard carbon and metal-silicon composite material to a tube furnace and introduce carbon dioxide gas to obtain a metal-silicon doped hard carbon composite material.

[0007] In a preferred embodiment, in step one, the weight content of the nitrogen-containing hydrocarbon in the aqueous solution of the nitrogen-containing hydrocarbon is 1-10 wt%.

[0008] In a preferred embodiment, in step two, the particle size of the metal is 200-1000 nm.

[0009] In a preferred embodiment, in steps one and two, the mass ratio of the silane coupling agent: nitrogen-containing hydrocarbon compound: metal is 1-10:100:1-5.

[0010] In a preferred embodiment, in step four, when the carbon source gas is introduced, the tubular furnace is heated to 600-800°C, the gas flow rate is 10-100 ml / min, and the deposition time is 30-300 min; when the borane gas is introduced, the tubular furnace is heated to 800-1200°C, the gas flow rate is 1-10 ml / min, and the deposition time is 30-300 min; when the inert gas is introduced, the tubular furnace is cooled to room temperature.

[0011] In a preferred embodiment, in step five, when carbon dioxide gas is introduced, the gas flow rate is 50-200 ml / min, the temperature is 200-400℃, and the reaction time is 30-300 min.

[0012] In a preferred embodiment, in step four, the carbon source gas is one of methane, acetylene, and ethylene.

[0013] In a preferred embodiment, in step four, the inert gas is argon.

[0014] The technical effects achieved by this invention are as follows: This invention uses a silane coupling agent to couple and carbonize a nitrogen-containing hydrocarbon solution with a metal to obtain metal- and silicon-based materials doped with amorphous carbon. Furthermore, boron-doped amorphous carbon is deposited on the surface of the precursor material through gas deposition to improve the electronic conductivity and first-pass efficiency of the material. This invention expands the layers of a hard carbon-metal-silicon composite material using carbon dioxide gas, thereby increasing the interlayer spacing. This facilitates the insertion and extraction of lithium ions and sodium ions during charging and discharging, improving rate performance. At the same time, carbon dioxide treatment reduces surface defects in the material, improving the material's initial efficiency. Attached Figure Description

[0015] Figure 1 This is a SEM image of the metal and silicon-doped hard carbon composite material prepared in Example 1 of the present invention. Detailed Implementation

[0016] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0017] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0018] Secondly, the term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in a preferred embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that mutually excludes other embodiments.

[0019] Secondly, the present invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not according to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0020] A metal-silicon doped hard carbon composite material for use in lithium-ion batteries or sodium-ion batteries, wherein the raw materials for preparing the metal-silicon doped hard carbon composite material are, by mass parts: 1-10 parts of silane coupling agent, 100 parts of nitrogen-containing hydrocarbon compound, and 1-5 parts of metal; The silane coupling agent is one of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldiethoxysilane, and γ-aminopropylmethyldimethoxysilane. The nitrogen-containing hydrocarbon is one of methylamine, dimethylamine, trimethylamine (TMA), triethylamine, aniline, and pyridine; The metal is one of nano-copper, nano-silver, or nano-nickel.

[0021] A method for preparing a metal-silicon-doped hard carbon composite material, characterized by comprising the following steps: S1. Add the silane coupling agent to an aqueous solution containing nitrogen-containing hydrocarbons and disperse it evenly to prepare the first solution; S2. Add the metal to the first solution and transfer it to a ball mill for uniform dispersion to prepare the second solution; S3. The second solution is spray-dried and pulverized to obtain the precursor material; S4. The precursor material is transferred to a tube furnace, and carbon source gas, borane gas and inert gas are introduced in sequence to obtain a hard carbon, metal and silicon composite material. S5. Transfer the hard carbon and metal-silicon composite material to a tube furnace and introduce carbon dioxide gas to obtain a metal-silicon doped hard carbon composite material.

[0022] As described in steps S1-S5 above, a precursor material can be obtained by coupling a silane coupling agent with a metal to a nitrogen-containing hydrocarbon solution. The precursor material is then carbonized in a tube furnace to obtain metal and silicon-based doped amorphous carbon. The carbon source gas and borane gas introduced into the tube furnace can deposit boron-doped amorphous carbon in the precursor material. Finally, the inert gas introduced can prevent the precursor material from reacting with other substances during cooling, allowing the precursor material to return to room temperature to obtain a hard carbon and metal and silicon composite material. The hard carbon and metal and silicon composite material is then fed back into the tube furnace and carbon dioxide gas is introduced to form an extended layer on its surface, increasing the interlayer spacing of the material. This is beneficial for the insertion and extraction of lithium ions and sodium ions during charging and discharging, improving rate performance. At the same time, carbon dioxide treatment reduces surface defects in the material, improving the initial efficiency of the material.

[0023] In a preferred embodiment, in S1, the weight content of the nitrogen-containing hydrocarbon in the aqueous solution of the nitrogen-containing hydrocarbon is 1-10 wt%.

[0024] In a preferred embodiment, in S2, the particle size of the metal is 200-1000 nm.

[0025] In a preferred embodiment, in S1 and S2, the mass ratio of the silane coupling agent: nitrogen-containing hydrocarbon compound: metal is 1-10:100:1-5.

[0026] The above describes how the raw materials are obtained according to the mass ratio of silane coupling agent: nitrogen-containing hydrocarbon compound: metal, wherein the nitrogen-containing hydrocarbon compound is prepared into an aqueous solution according to its weight content. For example, to obtain 100g of nitrogen-containing hydrocarbons, you need to prepare an aqueous solution of 1000-10000g of nitrogen-containing hydrocarbons, and you also need to obtain 1-10g of silane coupling agent and 1-5g of metal.

[0027] In a preferred embodiment, in S4, when the carbon source gas is introduced, the tubular furnace is heated to 600-800°C, the gas flow rate is 10-100 ml / min, and the deposition time is 30-300 min; when the borane gas is introduced, the tubular furnace is heated to 800-1200°C, the gas flow rate is 1-10 ml / min, and the deposition time is 30-300 min; when the inert gas is introduced, the tubular furnace is cooled to room temperature.

[0028] The carbon source gas is one of methane, acetylene, and ethylene. The purpose of introducing carbon source gas and borane gas is to deposit boron-doped amorphous carbon on the surface of the precursor material, thereby improving the electronic conductivity and initial efficiency of the material.

[0029] In a preferred embodiment, during step S5, when carbon dioxide gas is introduced, the gas flow rate is 50-200 ml / min, the temperature is 200-400°C, and the reaction time is 30-300 min.

[0030] The purpose of introducing carbon dioxide gas is to expand the layers of the hard carbon-metal-silicon composite material, increase the interlayer spacing, which is beneficial for the insertion and extraction of lithium ions or sodium ions during charging and discharging, improve rate performance, and at the same time, carbon dioxide treats fewer surface defects in the material, thus improving the material's first efficiency.

[0031] In a preferred embodiment, in S4, the inert gas is argon.

[0032] As mentioned above, introducing argon gas as an inert gas during cooling can prevent the material from reacting with other substances during the cooling process.

[0033] Example 1 5g of γ-aminopropyltriethoxysilane was added to an aqueous solution of 2000g of methylamine, the weight content of methylamine in the aqueous solution being 5wt%. Then, 3g of nano-silver (particle size 500nm) was added and the mixture was transferred to a ball mill and dispersed evenly. After spray drying and pulverization, the precursor material was obtained. The precursor material was transferred into a tube furnace. First, methane gas was introduced and the temperature was raised to 700°C. The methane gas flow rate was 50 ml / min and the deposition time was 120 min. Then, borane gas was introduced and the temperature was raised to 950°C. The borane gas flow rate was 5 ml / min and the deposition time was 120 min. After that, argon inert gas was introduced to cool the temperature inside the tube furnace to room temperature, thus obtaining a hard carbon-metal-silicon composite material. The hard carbon and metal-silicon composite material was transferred to a tube furnace, and then carbon dioxide gas was introduced at a flow rate of 100 ml / min. The temperature was 300℃ and the reaction time was 120 min to carry out layer expansion, thereby obtaining the metal-silicon doped hard carbon composite material.

[0034] Example 2 1g of γ-aminopropyltrimethoxysilane was added to an aqueous solution of 10000g of dimethylamine, the weight content of dimethylamine in the aqueous solution being 1wt%. Then, 1g of nano-copper (particle size 500nm) was added and the mixture was transferred to a ball mill and dispersed evenly. After spray drying and pulverization, the precursor material was obtained. The precursor material was transferred into a tube furnace. First, acetylene gas was introduced, and the temperature was raised to 600°C. The acetylene gas flow rate was 10 ml / min, and the deposition time was 300 min. Then, borane gas was introduced, and the temperature was raised to 800°C. The borane gas flow rate was 1 ml / min, and the deposition time was 300 min. After that, argon inert gas was introduced to cool the temperature inside the tube furnace to room temperature, thus obtaining a hard carbon-metal-silicon composite material. The hard carbon and metal-silicon composite material was transferred to a tube furnace, and then carbon dioxide gas was introduced at a flow rate of 50 ml / min. The temperature was 200℃ and the reaction time was 300 min to carry out layer expansion, thereby obtaining the metal-silicon doped hard carbon composite material.

[0035] Example 3 10g of γ-aminopropylmethyldiethoxysilane was added to 1000g of methylamine solution, the weight content of methylamine in the aqueous solution was 10wt%, then 5g of nano nickel (particle size 1000nm) was added, and the mixture was transferred to a ball mill and dispersed evenly. After spray drying and pulverization, the precursor material was obtained. The precursor material was transferred into a tube furnace. First, ethylene gas was introduced, and the temperature was raised to 800°C. The gas flow rate of ethylene gas was 100 ml / min, and the deposition time was 30 min. Then, borane gas was introduced, and the temperature was raised to 1200°C. The gas flow rate of borane gas was 10 ml / min, and the deposition time was 30 min. After that, argon inert gas was introduced to cool the temperature inside the tube furnace to room temperature, thus obtaining a hard carbon-metal-silicon composite material. The hard carbon and metal-silicon composite material was transferred to a tube furnace, and then carbon dioxide gas was introduced at a flow rate of 200 ml / min. The temperature was 400℃ and the reaction time was 30 min to carry out layer expansion, thus obtaining the metal-silicon doped hard carbon composite material.

[0036] Comparative Example 1: 5g of γ-aminopropyltriethoxysilane was added to an aqueous solution of 2000g of methylamine, the methylamine content in the aqueous solution was 5wt%, and the solution was transferred to a ball mill to disperse evenly. Then, it was spray-dried and pulverized to obtain the precursor material. The precursor material was transferred into a tube furnace. First, methane gas was introduced and the temperature was raised to 700°C. The methane gas flow rate was 50 ml / min and the deposition time was 120 min. Then, borane gas was introduced and the temperature was raised to 950°C. The borane gas flow rate was 5 ml / min and the deposition time was 120 min. After that, argon inert gas was introduced to cool the temperature inside the tube furnace to room temperature, thus obtaining a hard carbon and silicon composite material. The hard carbon and silicon composite material was transferred to a tube furnace, and then carbon dioxide gas was introduced at a flow rate of 100 ml / min. The temperature was 300℃ and the reaction time was 120 min to carry out layer expansion and obtain silicon-doped hard carbon composite material.

[0037] The difference between Comparative Example 1 and Example 1 is that no nano-silver was added in Comparative Example 1, but otherwise it is the same as Example 1.

[0038] Comparative Example 2: 3g of nano-silver was added to an aqueous solution of 2000g of methylamine, the weight content of methylamine in the aqueous solution was 5wt%, and the mixture was transferred to a ball mill to disperse evenly. Then, it was spray-dried and pulverized to obtain the precursor material. The precursor material was transferred into a tube furnace. First, methane gas was introduced and the temperature was raised to 700°C. The methane gas flow rate was 50 ml / min and the deposition time was 120 min. Then, borane gas was introduced and the temperature was raised to 950°C. The borane gas flow rate was 5 ml / min and the deposition time was 120 min. After that, argon inert gas was introduced to cool the temperature inside the tube furnace to room temperature, thus obtaining a hard carbon-metal composite material. The hard carbon-metal-silicon composite material was transferred to a tube furnace, and then carbon dioxide gas was introduced at a flow rate of 100 ml / min. The temperature was 300℃, and the reaction time was 120 min to carry out layer expansion, thereby obtaining a metal-doped hard carbon composite material. The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 does not contain γ-aminopropyltriethoxysilane, but is otherwise the same as Example 1.

[0039] Comparative Example 3: 5g of γ-aminopropyltriethoxysilane was added to an aqueous solution of 2000g of methylamine, the weight content of methylamine in the aqueous solution being 5wt%. Then, 3g of nano-silver was added, and the mixture was transferred to a ball mill and dispersed evenly. After spray drying and pulverization, the precursor material was obtained. The precursor material was transferred into a tube furnace. First, methane gas was introduced, and the temperature was raised to 700°C. The methane gas flow rate was 50 ml / min, and the deposition time was 120 min. Then, borane gas was introduced, and the temperature was raised to 950°C. The borane gas flow rate was 5 ml / min, and the deposition time was 120 min. After that, argon inert gas was introduced to cool the temperature inside the tube furnace to room temperature, thus obtaining a hard carbon-metal-silicon composite material.

[0040] The difference between Comparative Example 3 and Example 1 is that Comparative Example 3 does not introduce carbon dioxide gas for layer expansion, but otherwise it is the same as Example 1.

[0041] Performance testing of the materials prepared in the above embodiments and comparative examples: SEM test: Figure 1 This is a SEM image of the metal and silicon-doped hard carbon composite material obtained in Example 1. Figure 1 It can be seen that the hard carbon composite material obtained in Example 1 has a granular structure with uniform size distribution and a particle size between 3-5 μm.

[0042] Physicochemical performance testing: The specific surface area, tap density, particle size, powder conductivity, initial discharge specific capacity, and initial charge / discharge efficiency of the hard carbon composite materials in Examples 1-3 and Comparative Examples 1-3 were tested according to the national standard GB / T-24533-2019 "Graphite Anode Materials for Lithium-ion Batteries". The test results are shown in Table 1. Table 1 ; As can be seen from Table 1, the hard carbon composite materials obtained in Examples 1-3 are significantly better than those in Comparative Examples 1-3 in terms of specific surface area and tap density. This is because the nitrogen-containing hydrocarbon solution is coupled and carbonized by a silane coupling agent and a metal to obtain metal and silicon-based doped amorphous carbon, and the electronic conductivity and first efficiency of the material are improved by depositing boron-doped amorphous carbon on its surface through gas deposition.

[0043] Button batteries: The metal and silicon-doped hard carbon composite materials obtained in Examples 1-3 and Comparative Examples 1-3 were used as negative electrodes (the mass ratio of the substances in the formula was hard carbon composite material: CMC: SBR: SP: H2O = 95:2.5:1.5:1:150), and lithium sheets were used as counter electrodes. The electrolyte was LiPF6 / EC+DEC (the volume ratio of electrolyte solvent EC:DEC = 1:1), and the separator was a composite membrane of polyethylene (PE), polypropylene (PP), and polyethylene propylene (PEP). The button cells were assembled in an argon-filled glove box to form button cells A1, A2, A3 and B1, B2, B3.

[0044] Electrochemical performance was tested using a Wuhan Landian CT2001A battery tester. The charge / discharge voltage range was controlled between 0.0-2V, and the charge / discharge rate was 0.1C / 0.1C. Simultaneously, the 2C and 0.1C lithium stripping capacities, the DCR of the coin cells, and the cycle performance (0.5C / 0.5C, 100 cycles) of the coin cells were tested. Detailed test results are shown in Table 2. Table 2 ; As can be seen from Table 2, the cycle performance and rate performance of the button batteries made with the hard carbon composite materials of Examples 1-3 are significantly higher than those of the comparative examples. This is because the doping of metals in the materials of the examples improves the conductivity of the powder and thus improves the rate performance. At the same time, carbon dioxide gas is used to expand the layers of the hard carbon, metal and silicon composite materials, thereby increasing the interlayer spacing of the materials. This is beneficial for the intercalation and deintercalation of lithium ions and sodium ions during charging and discharging, thus improving the rate performance and cycle performance.

[0045] Soft-pack batteries: The hard carbon composite materials prepared in Examples 1-3 and Comparative Examples 1-3 were used to prepare negative electrode sheets through slurry mixing and coating. Ternary material NCM811 was used as the positive electrode, and EC / DEC / PC (volume ratio, EC:DEC:PC = 1:1:1) was used as the electrolyte with LiPF6 (concentration 1.3 mol / L) as the solute and Celgard 2400 membrane as the separator. 2Ah soft-pack batteries C1, C2, C3 and D1, D2, D3 were prepared respectively. The results are shown in Tables 3 and 4.

[0046] Liquid absorption capacity: Using a 1 mL burette, a volume of electrolyte (V mL) was drawn and a drop was added to the electrode surface. Timing was maintained until the electrolyte was completely absorbed, and the time (t) was recorded. The absorption rate of the electrode (V / t) was then calculated. The test results are shown in Table 3.

[0047] Liquid retention rate test: The theoretical liquid absorption capacity m1 of the electrode was calculated based on the electrode parameters, and the weight m2 of the electrode was measured. The electrode was then immersed in the electrolyte for 24 hours, and its weight m3 was measured. The liquid absorption capacity m3-m2 was calculated, and the liquid retention rate was calculated using the following formula: Liquid retention rate = (m3-m2)*100% / m1. The test results are shown in Table 3. Table 3 ; As can be seen from Table 3, the liquid absorption and retention capabilities of the negative electrode prepared by the hard carbon composite materials obtained in Examples 1-3 are significantly better than those of Comparative Examples 1-3. The reason for this is that the hard carbon materials in the examples have a high specific surface area, which improves the liquid absorption and retention performance of the electrode.

[0048] Ratio performance test: The rate performance of the soft-pack battery was tested under the following conditions: charge / discharge voltage range of 2.8–4.2V, temperature of 25±3.0℃, charging at 1.0C, 3.0C, 5.0C, and 10.0C, and discharging at 1.0C. The test results are shown in Table 4. Table 4 ; As shown in Table 3, the rate charging performance of the soft-pack batteries in Examples 1-3 is significantly better than that of Comparative Examples 1-3, i.e., the charging time is shorter. The reason for this is that the materials in the examples have excellent powder conductivity and high specific surface area, which improves the rate performance of the materials.

[0049] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. A metal and silicon doped hard carbon composite material applied to a lithium ion battery or a sodium ion battery, characterized in that: By weight: the raw materials for preparing the metal and silicon-doped hard carbon composite material include; 1-10 parts of silane coupling agent, 100 parts of nitrogen-containing hydrocarbon compound, and 1-5 parts of metal; The silane coupling agent is one of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldiethoxysilane, and γ-aminopropylmethyldimethoxysilane. The nitrogen-containing hydrocarbon is one of methylamine, dimethylamine, trimethylamine (TMA), triethylamine, aniline, and pyridine; The metal is one of nano-copper, nano-silver, or nano-nickel.

2. A method for preparing a metal-silicon doped hard carbon composite material, used to prepare the metal-silicon doped hard carbon composite material as described in claim 1, characterized in that: Includes the following steps: Step 1: Add the silane coupling agent to an aqueous solution containing nitrogen-containing hydrocarbons and disperse it evenly to prepare the first solution; Step 2: Add the metal to the first solution and transfer it to a ball mill for uniform dispersion to prepare the second solution; Step 3: Spray dry and pulverize the second solution to obtain the precursor material; Step 4: Transfer the precursor material to a tube furnace and sequentially introduce carbon source gas, borane gas and inert gas to obtain a hard carbon-metal-silicon composite material. Step 5: Transfer the hard carbon and metal-silicon composite material to a tube furnace and introduce carbon dioxide gas to obtain a metal-silicon doped hard carbon composite material.

3. The method of claim 2, wherein the metal and silicon-doped hard carbon composite is prepared by the following steps: (1) mixing a carbon precursor, a metal source, and a silicon source to form a mixture; (2) heating the mixture to form a metal and silicon-doped hard carbon composite. In step one, the weight content of the nitrogen-containing hydrocarbon in the aqueous solution of the nitrogen-containing hydrocarbon is 1-10 wt%.

4. The method of claim 2, wherein the metal and silicon-doped hard carbon composite is prepared by the following steps: (1) mixing a carbon precursor, a metal source, and a silicon source to form a mixture; (2) heating the mixture to form a metal and silicon-doped hard carbon composite. In step two, the particle size of the metal is 200-1000 nm.

5. The method of claim 2, wherein the metal and silicon-doped hard carbon composite is prepared by the following steps: (a) mixing a metal salt and a silicon source with a carbon precursor; (b) heating the mixture to form a metal and silicon-doped hard carbon composite. In steps one and two, the mass ratio of the silane coupling agent, nitrogen-containing hydrocarbon compound, and metal is 1-10:100:1-5.

6. The method for preparing a metal-silicon doped hard carbon composite material according to claim 2, characterized in that: In step four, when the carbon source gas is introduced, the tubular furnace is heated to 600-800℃, the gas flow rate is 10-100ml / min, and the deposition time is 30-300min. When the borane gas is introduced, the tubular furnace is heated to 800-1200℃, the gas flow rate is 1-10ml / min, and the deposition time is 30-300min. When the inert gas is introduced, the tubular furnace is cooled to room temperature.

7. The method for preparing a metal-silicon doped hard carbon composite material according to claim 2, characterized in that: In step five, when carbon dioxide gas is introduced, the gas flow rate is 50-200 ml / min, the temperature is 200-400℃, and the reaction time is 30-300 min.

8. The method of claim 2, wherein the metal and silicon-doped hard carbon composite is prepared by the following steps: (1) mixing a carbon precursor, a metal source, and a silicon source to form a mixture; (2) heating the mixture to form a metal and silicon-doped hard carbon composite. In step four, the carbon source gas is one of methane, acetylene, and ethylene.

9. The method of claim 2, wherein the metal-doped silicon-doped hard carbon composite is prepared by the following steps: (a) mixing a metal salt and a silicon source to form a mixture; (b) heating the mixture to form a metal-doped silicon-doped hard carbon composite. In step four, the inert gas is argon.

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