Novel silicon-carbon composite negative electrode material and preparation method and application thereof

Abstract

The embodiment of the invention relates to a novel silicon-carbon composite negative electrode material and a preparation method and application thereof. The preparation method comprises the following steps: adding a niobium source and potassium citrate into deionized water to prepare a mixed solution, and uniformly stirring and dispersing; transferring the mixed solution into a sand mill, and grinding into a nano suspension; leading out the nano suspension from a sand mill, adding a carbon source, uniformly stirring, and carrying out spray drying to obtain precursor powder; sintering the precursor powder, heating and decomposing the potassium citrate to form potassium carbonate, carbon dioxide and water vapor, forming a carbon matrix with a porous structure through overflow of the carbon dioxide and the water vapor, and meanwhile, heating and decomposing or hydrolyzing a niobium source to convert into niobium oxide; washing the sintered and discharged material with deionized water, and drying to obtain a porous carbon substrate material with a niobium oxide lined porous structure; and carrying out vapor deposition by taking silicon-containing gas as a silicon source so as to deposit silicon particles in the hole structure with the niobium oxide lining, thereby obtaining the novel silicon-carbon composite negative electrode material.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and particularly to a novel silicon-carbon composite anode material, a preparation method thereof, and an application thereof. Background Art

[0002] With the continuous progress of technology and the rapid development of electric vehicles, aerospace, and new-generation portable electronic products, the energy on the earth has been significantly reduced. The continuous depletion of energy will hinder scientific development and cause damage to the environment. Therefore, the demand for new energy materials has become more urgent now. As an advanced electrochemical energy storage technology, lithium-ion batteries have the advantages of high Coulomb efficiency, recyclability, portability, environmental protection, etc. Since they were put into commercial use, they have occupied an important position in the transportation and electronics fields. Due to technological progress, the demand for high-performance lithium-ion batteries has gradually increased.

[0003] Among many factors, the anode active material, as an important part of lithium-ion batteries, has a particularly significant impact on the performance of lithium-ion batteries. It determines the energy density, electrochemical performance, safety, and reliability of lithium-ion batteries. Currently, the disadvantages of commercial graphite anodes for lithium-ion batteries, such as low capacity, poor cycle stability, and the generation of lithium dendrites, have gradually emerged. In order to obtain excellent anode materials, silicon materials with a high theoretical capacity have gradually attracted people's attention. Silicon is abundant in the earth's crust and has an extremely high theoretical specific capacity (about 4200 mAh g -1 ) and a low voltage plateau (about 0.2 - 0.3 V vs Li + / Li), and is considered to be the most promising material for lithium-ion batteries. However, there are also many problems, such as excessive volume expansion (about 300%) during the lithium insertion and extraction process, which causes the electrode sheet to easily powder and fall off, losing contact with the current collector. In addition, the continuously generated SEI film at the interface also leads to poor electrochemical stability, severely restricting its commercial development. Summary of the Invention

[0004] The purpose of the present invention is to provide a novel silicon-carbon composite anode material, a preparation method thereof, and an application thereof. By using this method, the volume expansion of silicon can be effectively alleviated, the agglomeration of silicon can be reduced, the interfacial stability can be enhanced, and the prepared silicon-carbon anode material has the characteristics of good cycle stability and high capacity.

[0005] To this end, in a first aspect, an embodiment of the present invention provides a preparation method of a novel silicon-carbon composite anode material, and the preparation method includes:

[0006] Adding a niobium source and potassium citrate into deionized water according to a molar ratio of 1:1 - 1.5:1 to form a mixed solution, and stirring to disperse them evenly;

[0007] Transfer the mixed solution to a sand mill for grinding into a nano-suspension;

[0008] Export the nano-suspension from the sand mill, add a carbon source, stir evenly and then spray dry to obtain a precursor powder;

[0009] Heat the precursor powder to 500 °C - 650 °C under a protective atmosphere and keep it warm for 1 - 5 h for sintering of the precursor powder. The potassium citrate decomposes by heat to form potassium carbonate, carbon dioxide and water vapor. The carbon matrix with a pore structure is formed by the overflow of carbon dioxide and water vapor. At the same time, the niobium source is decomposed by heat or hydrolyzed in water vapor to be converted into niobium oxide; among them, niobium oxide and potassium carbonate exist on the inner wall of the pore structure;

[0010] Wash the material after sintering with deionized water and dry it. Remove potassium carbonate by water washing to obtain a porous carbon substrate material with a pore structure lined with niobium oxide;

[0011] Using the porous carbon substrate material with a pore structure lined with niobium oxide as the substrate, use a silicon-containing gas as the silicon source for chemical vapor deposition, so as to deposit silicon particles in the pore structure lined with niobium oxide to obtain the novel silicon-carbon composite anode material.

[0012] Preferably, the niobium source includes any one of niobium oxalate, niobium chloride, and niobium nitrate;

[0013] The ratio of the total mass of the potassium citrate and the niobium source to the mass of the deionized water is 1:5 - 1:20;

[0014] The stirring speed of the stirring is 400 - 800 r / min, and the stirring and dispersion time is 20 - 60 min.

[0015] Preferably, the particle size range of the solid particles in the nano-suspension obtained after grinding is 50 - 90 nm.

[0016] Preferably, the grinding specifically includes taking the slurry for particle size testing during the grinding process and stopping the grinding until a nano-suspension is obtained.

[0017] Preferably, the carbon source includes any one of polyethylene glycol, polyvinyl alcohol, polypyrrole, phenolic resin, sucrose, glucose, and citric acid;

[0018] The ratio of the total mass of the potassium citrate and the niobium source to the mass of the added carbon source is 1:10 - 1:20;

[0019] The feed temperature of the spray drying is 120 °C - 180 °C, and the discharge temperature is 80 °C - 130 °C.

[0020] Preferably, the protective atmosphere is nitrogen or argon, the heating rate is 1-5 °C / min, the gas flow rate is 1-2 L / min, and the drying temperature is 80 °C - 100 °C.

[0021] Preferably, the chemical vapor deposition is carried out in a protective atmosphere of nitrogen and / or argon, the flow rate is 1-4 L / min, the temperature of the chemical vapor deposition is 500 °C - 1200 °C, and the time of the chemical vapor deposition is 0.5-20 h; the flow rate of the silicon-containing gas is 0.5-10 L / min.

[0022] The preparation method of the novel silicon-carbon composite anode material provided by the embodiment of the present invention can achieve the uniform mixing of the niobium source and potassium citrate by preparing a suspension by nano-grinding the niobium source and potassium citrate, increase the contact area between the material spray drying and the carbon source, and is beneficial to the subsequent formation of a uniform porous carbon structure. The gas generated by the high-temperature treatment of potassium citrate realizes the first etching and activation of the carbon material to form pores during the thermal decomposition process, and then the secondary pore formation is further realized by washing with water potassium carbonate. And due to the alkaline characteristic of the potassium carbonate solution, it further plays a role in etching the carbon matrix, which is beneficial to the formation of a large number of micropores on the macroporous carbon wall, and a porous carbon substrate with a high specific surface area is obtained. At the same time, niobium oxide remains in the pores as the inner lining of the carbon-based pores. Using niobium oxide as the inner lining of the carbon-based pores can, on the one hand, prevent the capacity decline caused by the reaction of deposited silicon and the porous carbon matrix to generate silicon carbide, and on the other hand, utilize the unique ReO 3 of the two-dimensional shear plane layered structure to realize the rapid insertion and extraction of lithium ions, which is beneficial to improving the overall rate performance of the material. The method proposed by the present invention is simple, easy to operate, environmentally friendly and pollution-free, and can be industrialized. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic diagram of the preparation method of the novel silicon-carbon composite anode material provided by the embodiment of the present invention;

[0024] Figure 2 is a schematic diagram of the structure of the novel silicon-carbon composite anode material provided by the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The technical solutions of the present invention will be further described in detail below with reference to the drawings and embodiments.

[0026] The embodiment of the present invention provides a preparation method of a novel silicon-carbon composite anode material, and the main steps are as Figure 1 shown, including:

[0027] Step 110, adding a niobium source and potassium citrate into deionized water according to a molar ratio of 1:1 - 1.5:1 to form a mixed solution, and stirring to disperse it evenly;

[0028] Among them, the niobium source includes any one of niobium oxalate, niobium chloride, and niobium nitrate; the ratio of the total mass of potassium citrate and the niobium source to the mass of deionized water is 1:5 - 1:20; the stirring speed of stirring is 400 - 800 r / min, and the stirring and dispersion time is 20 - 60 min.

[0029] Step 120, transfer the mixed solution to a sand mill for grinding into a nano-suspension;

[0030] Among them, the particle size range of the solid particles in the nano-suspension obtained after grinding is 50 - 90 nm.

[0031] During the grinding process, the slurry can be taken for particle size testing multiple times until the nano-suspension is obtained and then the grinding is stopped.

[0032] In a specific implementation of the present invention, the grinding time is 30 - 60 min.

[0033] Step 130, export the nano-suspension from the sand mill, add a carbon source, stir evenly and then spray dry to obtain a precursor powder;

[0034] The carbon source includes any one of polyethylene glycol, polyvinyl alcohol, polypyrrole, phenolic resin, sucrose, glucose, and citric acid;

[0035] The ratio of the total mass of potassium citrate and the niobium source to the mass of the added carbon source is 1:10 - 1:20;

[0036] The feed temperature of the spray drying is 120°C - 180°C, and the discharge temperature is 80°C - 130°C.

[0037] Step 140, heat the precursor powder to 500°C - 650°C under a protective atmosphere, and keep it warm for 1 - 5 hours for sintering of the precursor powder. Potassium citrate is thermally decomposed to form potassium carbonate, carbon dioxide and water vapor. The carbon dioxide and water vapor overflow to form a carbon matrix with a pore structure. At the same time, the niobium source is thermally decomposed or hydrolyzed under water vapor to be converted into niobium oxide;

[0038] Among them, the protective atmosphere is nitrogen or argon, the heating rate is 1 - 5°C / min, the gas flow rate is 1 - 2 L / min, and the drying temperature is 80°C - 100°C.

[0039] During the sintering process, potassium citrate is thermally decomposed to form potassium carbonate, carbon dioxide and water vapor.

[0040] When the niobium source is niobium oxalate, niobium oxalate is thermally decomposed to form niobium oxide; when the niobium source is niobium chloride or niobium nitrate, it is hydrolyzed under water vapor conditions and finally forms niobium oxide.

[0041] Niobium oxide and potassium carbonate exist on the inner wall of the cavity structure.

[0042] Step 150: Wash and dry the material after sintering and discharging with deionized water, and remove potassium carbonate by water washing to obtain a porous carbon substrate material with a pore structure lined with niobium oxide;

[0043] By water washing, potassium carbonate dissolves in water and is removed. The aqueous solution of potassium carbonate is alkaline, so it will further etch the carbon matrix, forming a large number of micropores on the macroporous carbon wall, so as to obtain a porous carbon substrate with a high specific surface area.

[0044] Step 160: Using the porous carbon substrate material with a pore structure lined with niobium oxide as the substrate, and using a silicon-containing gas as the silicon source, perform chemical vapor deposition, so as to deposit silicon particles in the pore structure lined with niobium oxide to obtain the novel silicon-carbon composite anode material.

[0045] Specifically, the chemical vapor deposition is carried out in a protective atmosphere of nitrogen and / or argon, with a flow rate of 1-4 L / min, the temperature of the chemical vapor deposition is 500°C-1200°C, and the time of the chemical vapor deposition is 0.5-20 h; the flow rate of the silicon-containing gas is 0.5-10 L / min. The silicon-containing gas can preferably be silane or disilane.

[0046] In the present invention, by nano-grinding niobium source and potassium citrate to prepare a suspension, the uniform mixing of niobium source and potassium citrate can be realized, the contact area between the material spray drying and the carbon source is increased, which is beneficial to the subsequent formation of a uniform porous carbon structure. By high-temperature treatment of potassium citrate to generate gas, the first etching and activation of the carbon material to form pores are realized during the thermal decomposition process. Then, secondary pore formation is further realized by washing potassium carbonate with water, and due to the alkaline characteristic of the potassium carbonate solution, it further plays a role in etching the carbon matrix, which is beneficial to the formation of a large number of micropores on the macroporous carbon wall, and a porous carbon substrate with a high specific surface area is obtained. At the same time, niobium oxide remains in the pores as the lining of the carbon-based pores. Using niobium oxide as the lining of the carbon-based pores can, on the one hand, prevent the capacity decline caused by the reaction between the deposited silicon and the porous carbon matrix to generate silicon carbide, and on the other hand, utilize the unique ReO 3 Two-dimensional shear plane layered structure to realize the rapid insertion and extraction of lithium ions, which is beneficial to improving the overall rate performance of the material. The method proposed by the present invention is simple and feasible, environmentally friendly and pollution-free, and can be applied industrially.

[0047] Figure 2 FIG. is a schematic structural diagram of a novel silicon-carbon composite anode material prepared by the above method of the present invention. It can be seen that the novel silicon-carbon composite anode material prepared by the present invention includes a porous carbon matrix, the porous carbon matrix has micropores or mesopores, niobium oxide is provided on the inner wall of the pores of the porous carbon matrix, and silicon particles are deposited in the pores.

[0048] To more clearly illustrate the purpose and advantages of the present invention, the present invention will be further described below in conjunction with embodiments. In addition, the embodiments described in the present invention are only partial embodiments. All other embodiments obtained by those skilled in the art without creative efforts based on the embodiments described in the present invention fall within the protection scope of the present invention. Additionally, it should be understood that these embodiments are only for more detailed description and should not be construed as limiting the present invention in any form, that is, it is not intended to limit the protection scope of the present invention.

[0049] Example 1

[0050] This example provides a novel silicon-carbon composite anode material, and the preparation method is as follows:

[0051] Weigh 200 g of niobium oxalate and potassium citrate in a molar ratio of 1.2:1, dissolve them in 2000 g of deionized water, stir at 600 r / min for 20 min, then transfer the mixed solution to the dispersion tank of a sand mill and grind for 60 min. Take the slurry to test the particle size, and the particle size is 69 nm. End the grinding, transfer the nano-suspension to a stirring tank, add 2000 g of sulfonated phenolic resin, fully stir, and then spray-dry the suspension. The feeding temperature is 160 °C and the discharging temperature is 80 °C to obtain the precursor powder. Heat the powder to 600 °C in a nitrogen atmosphere and hold for 3 h, where the heating rate is 3 °C / min and the nitrogen flow rate is 2 L / min. After discharging, wash with deionized water 3 times and dry at 80 °C. Using nitrogen as the protective gas with a flow rate of 2 L / min, take the sintered and discharged material as the substrate, use silane gas as the silicon source for chemical vapor deposition, and the gas flow rate is 0.5 L / min. The temperature of chemical vapor deposition is 500 °C and the time of chemical vapor deposition is 10 h, thus obtaining the novel silicon-carbon composite anode material prepared in this example.

[0052] Example 2

[0053] This example provides a novel silicon-carbon composite anode material, and the preparation method is as follows:

[0054] Weigh 50 g of niobium chloride and potassium citrate in a molar ratio of 1:1, dissolve them in 1000 g of deionized water, stir at 400 r / min for 40 min, then transfer the mixed solution to the dispersion tank of a sand mill and grind for 30 min. Take the slurry to measure the particle size, and the measured particle size is 80 nm. Export the suspension to a stirring tank, add 600 g of glucose, fully stir the suspension and then perform spray drying. The feeding temperature is 130 °C and the discharging temperature is 90 °C to obtain the precursor powder. Subsequently, heat it to 550 °C in a nitrogen atmosphere and hold for 2 h, where the heating rate is 2 °C / min and the nitrogen flow rate is 1 L / min. After discharging, wash it 3 times with deionized water and dry it at 100 °C. Using nitrogen as the protective gas with a flow rate of 2 L / min, take the sintered and discharged material as the substrate, use the silicon-containing gas silane as the silicon source for chemical vapor deposition, and the gas flow rate is 1 L / min. The temperature of chemical vapor deposition is 1000 °C and the time of chemical vapor deposition is 20 h, thus obtaining the novel silicon-carbon composite anode material prepared in this example.

[0055] Example 3

[0056] This example provides a novel silicon-carbon composite anode material, and the preparation method is as follows:

[0057] Weigh 150 g of niobium nitrate and potassium citrate in a molar ratio of 1.5:1, dissolve them in 2400 g of deionized water, stir at 500 r / min for 30 min, then transfer the mixed solution to the dispersion tank of a sand mill and grind for 40 min. Take the slurry to measure the particle size, and the measured particle size is 76 nm. Export the suspension to a stirring tank, add 2100 g of sucrose, fully stir the suspension and then perform spray drying. The feeding temperature is 180 °C and the discharging temperature is 100 °C to obtain the precursor powder. Subsequently, heat it to 650 °C in a nitrogen atmosphere and hold for 2 h, where the heating rate is 5 °C / min and the nitrogen flow rate is 2 L / min. After discharging, wash it 3 times with deionized water and dry it at 90 °C. Using nitrogen as the protective gas with a flow rate of 1 L / min, take the sintered and discharged material as the substrate, use the silicon-containing gas silane as the silicon source for chemical vapor deposition, and the gas flow rate is 0.5 L / min. The temperature of chemical vapor deposition is 500 °C and the time of chemical vapor deposition is 20 h, thus obtaining the novel silicon-carbon composite anode material prepared in this example.

[0058] Example 4

[0059] This example provides a novel silicon-carbon composite anode material, and the preparation method is as follows:

[0060] Weigh 200 g of niobium oxalate and potassium citrate in a molar ratio of 1.2:1, dissolve them in 2000 g of deionized water, stir at 600 r / min for 20 min, then transfer the mixed solution to the dispersion tank of a sand mill and grind for 60 min. Take the slurry to test the particle size, and the particle size is 69 nm. End the grinding, transfer the nano-suspension to a stirring tank, add 2000 g of polypyrrole, fully stir, and then spray-dry the suspension. The feeding temperature is 160 °C, and the discharging temperature is 80 °C to obtain the precursor powder. Heat the powder to 600 °C in a nitrogen atmosphere and keep it for 3 h, with a heating rate of 3 °C / min and a nitrogen flow rate of 2 L / min. After discharging, wash it 3 times with deionized water and dry it at 80 °C. Using nitrogen as the protective gas with a flow rate of 2 L / min, take the sintered and discharged material as the substrate, use the silicon-containing gas silane as the silicon source for chemical vapor deposition, and the gas flow rate is 0.5 L / min. The temperature of chemical vapor deposition is 500 °C, and the time of chemical vapor deposition is 10 h, thus obtaining the novel silicon-carbon composite anode material prepared in this example.

[0061] Example 5

[0062] This example provides a novel silicon-carbon composite anode material, and the preparation method is as follows:

[0063] Weigh 50 g of niobium chloride and potassium citrate in a molar ratio of 1:1, dissolve them in 1000 g of deionized water, stir at 400 r / min for 40 min, then transfer the mixed solution to the dispersion tank of a sand mill and grind for 30 min. Take the slurry to measure the particle size, and the measured particle size is 80 nm. Export the suspension to a stirring tank, add 600 g of polyvinyl alcohol, fully stir, and then spray-dry the suspension. The feeding temperature is 130 °C, and the discharging temperature is 90 °C to obtain the precursor powder. Subsequently, heat it to 550 °C in a nitrogen atmosphere and keep it for 2 h, with a heating rate of 2 °C / min and a nitrogen flow rate of 1 L / min. After discharging, wash it 3 times with deionized water and dry it at 100 °C. Using nitrogen as the protective gas with a flow rate of 2 L / min, take the sintered and discharged material as the substrate, use the silicon-containing gas silane as the silicon source for chemical vapor deposition, and the gas flow rate is 1 L / min. The temperature of chemical vapor deposition is 1000 °C, and the time of chemical vapor deposition is 20 h, thus obtaining the novel silicon-carbon composite anode material prepared in this example.

[0064] Example 6

[0065] This example provides a novel silicon-carbon composite anode material, and the preparation method is as follows:

[0066] Weigh 150 g of niobium nitrate and potassium citrate in a molar ratio of 1.5:1, dissolve them in 2400 g of deionized water, stir at 500 r / min for 30 min, then transfer the mixed solution to the dispersion tank of a sand mill and grind for 40 min. Measure the particle size of the slurry, and the measured particle size is 76 nm. Export the suspension to a stirring tank, add 2100 g of polyvinyl alcohol, fully stir, and then spray-dry the suspension. The feeding temperature is 180 °C, and the discharging temperature is 100 °C to obtain the precursor powder. Subsequently, heat it to 650 °C in a nitrogen atmosphere and hold for 2 h, where the heating rate is 5 °C / min and the nitrogen flow rate is 2 L / min. After discharging, wash it 3 times with deionized water and dry it at 90 °C. Using nitrogen as the protective gas with a flow rate of 1 L / min, take the sintered and discharged material as the substrate, use silane gas as the silicon source for chemical vapor deposition, and the gas flow rate is 0.5 L / min. The temperature of chemical vapor deposition is 500 °C, and the time of chemical vapor deposition is 20 h, thus obtaining the novel silicon-carbon composite anode material prepared in this example.

[0067] Weigh the anode materials obtained in the above Examples 1-3, conductive additive carbon black, and binder (sodium carboxymethyl cellulose and styrene-butadiene rubber with a volume ratio of 1:1) according to a mass ratio of 95:2:3. Prepare the slurry in a pulper at room temperature. Coating the prepared slurry evenly on the copper foil. After drying in a forced-air drying oven at 50 °C for 2 hours, cut it into 8×8 mm electrode sheets, and vacuum-dry them at 100 °C in a vacuum drying oven for 10 hours. Immediately transfer the dried electrode sheets into a glove box for standby to assemble the battery.

[0068] The assembly of the simulated battery is carried out in a glove box containing a high-purity Ar atmosphere, using metallic lithium as the counter electrode, and a solution of 1 mol / L LiPF 6 in ethylene carbonate (EC) / dimethyl carbonate (DMC) (volume ratio 1:1) as the electrolyte to assemble the battery. Use a charge-discharge tester to test in a constant current charge-discharge mode. The discharge cut-off voltage is 0.005 V, the charge cut-off voltage is 1.5 V, and the charge-discharge test is carried out at a current density of C / 10. The measured charge specific capacity and first-cycle efficiency are recorded in Table 1 data.

[0069] Use the electrode sheets prepared from the anode materials obtained in the above Examples 1-3 to assemble a full battery. Use lithium cobaltate cathode material as the cathode active substance, mix it with conductive agent Super P and binder polyvinylidene fluoride (PVDF) in a mass ratio of 90:5:5 to obtain the cathode slurry. Use an automatic coater to coat the cathode slurry on the current collector aluminum foil with a coating thickness of 100 μm, and obtain the cathode sheet after drying. Stack and assemble the cathode shell, cathode sheet, separator, electrolyte, anode, gasket, spring piece, and anode shell in sequence to obtain the battery. Among them, the separator uses a polypropylene (PP) base film, and the electrolyte uses a conventional lithium-ion electrolyte of 1 mol LiPF6 Ethylene carbonate (EC): Dimethyl carbonate (DMC): Ethyl methyl carbonate (EMC) = 1:1:1. After the battery is assembled, it is cycled once at 0.1C in the voltage range of 3.0 - 4.4V, and then cycled 100 times at 1C, 2C, 3C, 4C, and 5C rates respectively to test the C-rate retention. The C-rate retention obtained from the test is recorded in the data of Table 1.

[0070]

[0071] Table 1

[0072] It can be seen that the novel silicon-carbon composite anode material prepared in the embodiments of the present invention has a high specific charge capacity and a first-cycle efficiency. At a rate of 1C, the capacity retention rate can reach more than 98%. At high rates, the capacity retention rate still shows excellent performance. The capacity retention rate at 5C can still reach more than 85%, which fully meets the usage requirements of high-rate charging.

[0073] The material prepared by the present invention combines the dual advantages of porous carbon and niobium oxide as the lining of carbon-based pores, realizes the rapid insertion and extraction of lithium ions, and improves the overall rate performance of the material.

[0074] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of a novel silicon-carbon composite anode material, characterized in that, the preparation method includes: adding a niobium source and potassium citrate into deionized water according to a molar ratio of 1:1 - 1.5:1 to form a mixed solution, and stirring to disperse them evenly; transferring the mixed solution to a sand mill for grinding into a nano-suspension; exporting the nano-suspension from the sand mill, adding a carbon source, stirring evenly and then spray-drying to obtain a precursor powder; heating the precursor powder to 500°C - 650°C under a protective atmosphere, and keeping it warm for 1 - 5 h for sintering the precursor powder. The potassium citrate is thermally decomposed to form potassium carbonate, carbon dioxide and water vapor. The carbon dioxide and water vapor overflow to form a carbon matrix with a pore structure. At the same time, the niobium source is thermally decomposed or hydrolyzed in water vapor to be converted into niobium oxide; wherein the niobium oxide and potassium carbonate exist on the inner wall of the pore structure; washing the sintered material with deionized water and drying it. The potassium carbonate is removed by water washing to obtain a porous carbon substrate material with a pore structure lined with niobium oxide; using the porous carbon substrate material with a pore structure lined with niobium oxide as a substrate, and using a silicon-containing gas as a silicon source for chemical vapor deposition, so as to deposit silicon particles in the pore structure lined with niobium oxide to obtain the novel silicon-carbon composite anode material.

2. The preparation method of the novel silicon-carbon composite anode material according to claim 1, characterized in that, the niobium source includes any one of niobium oxalate, niobium chloride, and niobium nitrate; the ratio of the total mass of the potassium citrate and the niobium source to the mass of the deionized water is 1:5 - 1:20; the stirring speed of the stirring is 400 - 800 r / min, and the stirring and dispersion time is 20 - 60 min.

3. The preparation method of the novel silicon-carbon composite anode material according to claim 1, characterized in that, the particle size range of the solid particles in the nano-suspension obtained after grinding is 50 - 90 nm.

4. The preparation method of the novel silicon-carbon composite anode material according to claim 1, characterized in that, the grinding specifically includes: taking the slurry for particle size testing during the grinding process, and stopping grinding until a nano-suspension is obtained.

5. The preparation method of the novel silicon-carbon composite anode material according to claim 1, characterized in that, the carbon source includes any one of polyethylene glycol, polyvinyl alcohol, polypyrrole, phenolic resin, sucrose, glucose, and citric acid; the ratio of the total mass of the potassium citrate and the niobium source to the mass of the added carbon source is 1:10 - 1:20; the feed temperature of the spray drying is 120°C - 180°C, and the discharge temperature is 80°C - 130°C.

6. The preparation method of the novel silicon-carbon composite anode material according to claim 1, characterized in that, the protective atmosphere is nitrogen or argon, the heating rate is 1 - 5°C / min, the gas flow rate is 1 - 2 L / min, and the drying temperature is 80°C - 100°C.

7. The preparation method of the novel silicon-carbon composite anode material according to claim 1, characterized in that, The gas-phase deposition is carried out in a protective atmosphere of nitrogen and / or argon with a flow rate of 1-4 L / min, the temperature of the gas-phase deposition is 500°C-1200°C, and the time of the gas-phase deposition is 0.5-20 h; the flow rate of the silicon-containing gas is 0.5-10 L / min.

8. A novel silicon-carbon composite anode material prepared by the preparation method according to any one of claims 1-7 above, characterized in that The novel silicon-carbon composite anode material includes a porous carbon matrix, on the inner wall of the pores of the porous carbon matrix there is niobium oxide, and silicon particles are deposited in the pores; wherein the niobium oxide has a ReO 3 two-dimensional shear layer lamellar structure.

9. A lithium battery anode, characterized in that the lithium battery anode comprises the novel silicon-carbon composite anode material according to claim 8 above.

10. A lithium-ion battery, characterized in that the lithium-ion battery comprises the lithium battery anode according to claim 9 above.

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