Silicon-carbon negative electrode material and preparation method thereof

Abstract

The invention discloses a silicon-carbon negative electrode material and a preparation method thereof. The preparation method of the silicon-carbon negative electrode material comprises the following steps: (1) mixing a silicon-containing compound with an organic solvent to obtain a silicon-containing material flow; (2) uniformly mixing the porous carbon material with a modifier, separating and drying to obtain a modified porous carbon material; and (3) fully contacting a silicon-containing material flow with the modified porous carbon material, then separating, and carbonizing a solid-phase-containing material flow obtained after separation to obtain the carbon-silicon negative electrode material. The invention also provides the silicon-carbon negative electrode material obtained by adopting the preparation method and application of the silicon-carbon negative electrode material in a lithium ion battery. The silicon-carbon negative electrode material prepared by the method has relatively high specific capacity and first coulombic efficiency.

Description

Technical Field

[0001] The present invention relates to the field of electrochemistry, and in particular to a silicon-carbon negative electrode material with high specific capacity and a preparation method thereof. Background Art

[0002] At present, the technology of lithium-ion batteries is relatively mature, but key technologies such as high energy density, rate performance and safety continue to attract the attention of the industry. High-energy-density materials belong to the category of underlying technologies, which fundamentally determine the application performance of the system and have always been the focus of academia and industry. The current commercial graphite anode has a specific capacity of more than 360mAh / g, which is close to the theoretical specific capacity of 372mAh / g. The potential for improvement is limited, and the development of new high-capacity anode materials is an inevitable choice. The maximum theoretical capacity of silicon-based anode lithium storage reaches 4200mAh / g, which is the main direction of future development of lithium battery anodes.

[0003] CN116169248A discloses a silicon-carbon negative electrode and a preparation method and application for improving the cyclic expansion of a silicon-carbon negative electrode battery. The present invention combines a graphene-coated silicon-carbon negative electrode material with a graphene-coated copper foil to form a synergistic effect, and exerts the unique properties of graphene to improve the cyclic expansion of the silicon-carbon negative electrode. Due to the van der Waals force between the graphene coating and the graphene coated on the outside of the silicon-carbon negative electrode and the organic functional groups, the bonding force between the silicon-carbon negative electrode and the current collector is greatly enhanced, and the silicon-carbon negative electrode active material can be reduced from falling off the current collector to form gaps during the cycle process, thereby effectively improving the overall expansion of the battery. At the same time, due to the excellent conductivity of graphene, the cycle of the battery can also be improved. The results show that the cyclic expansion of the silicon-carbon negative electrode battery is significantly improved in the battery with graphene-coated copper foil and the battery without coating.

[0004] CN107565115A discloses a method for preparing a silicon-carbon negative electrode material, a silicon-carbon negative electrode material and a lithium-ion battery. The method for preparing a silicon-carbon negative electrode material provided by the present invention comprises the following steps: (a) using silicon monoxide as a matrix material, heating silicon monoxide to cause silicon monoxide to undergo a disproportionation reaction to generate c-SiO; (b) placing c-SiO in a chemical vapor deposition furnace, heating it under a protective atmosphere, introducing a carbon source after heating it to the reaction temperature, and performing a vapor deposition reaction to obtain c-SiO / C, wherein the carbon source is a liquid or solid compound; (c) corroding c-SiO / C with an etching solution to obtain a silicon-carbon negative electrode material c-SiO / Si / C. The process of the present invention is simple and easy to operate, and the obtained silicon-carbon negative electrode material has both the high lithium storage characteristics of silicon materials and the high cycle stability of carbon materials, and has high specific capacity, good conductivity and good cycle performance.

[0005] Combined with the above content, the preparation of existing silicon-carbon negative electrode materials mainly includes two technical routes: the first is to prepare nano-silicon first, and then compound it with carbon after silicon nano-sizing, and use carbon buffering to solve the volume change. Nano-silicon generally needs to be ground to the nanoscale. Generally, the industry can only grind nano-silicon powder to 50nm. After silicon nano-sizing, the surface energy increases and it is easy to agglomerate, so there is an upper limit on the particle size, and the cost is relatively high. The maximum amount of silicon added can only reach about 5-10%. The second is silicon monoxide, which is obtained by reacting silicon with silicon dioxide and then carbon-coated. It has small volume expansion and improved cycle stability compared to elemental silicon, but the initial efficiency is low, and pre-lithiation or pre-magnesiation is required. The process is complicated and the cost is high. Summary of the invention

[0006] In view of the problems and difficulties in the existing technical route for preparing silicon-carbon negative electrode materials in engineering and product performance, the present invention provides a silicon-carbon negative electrode material and a preparation method thereof. The prepared silicon-carbon negative electrode material has high specific capacity and first coulombic efficiency.

[0007] The present invention provides a method for preparing a silicon-carbon negative electrode material, the preparation method comprising the following steps:

[0008] (1) mixing a silicon-containing compound with an organic solvent to obtain a silicon-containing stream;

[0009] (2) mixing the porous carbon material and the modifier evenly, and obtaining the modified porous carbon material after separation and drying;

[0010] (3) under mixing conditions, fully contacting the silicon-containing stream obtained in step (1) with the modified porous carbon material obtained in step (2), and then separating them;

[0011] (4) The solid phase-containing material stream obtained after separation in step (3) is carbonized to obtain a carbon-silicon negative electrode material.

[0012] Preferably, in the method for preparing the above-mentioned silicon-carbon negative electrode material, the silicon-containing compound in step (1) can be one or both of trichlorosilane and silicon chloride.

[0013] Preferably, in the method for preparing the silicon-carbon negative electrode material, the organic solvent in step (1) can be one or more of benzene, petroleum ether, and diethyl ether, preferably diethyl ether.

[0014] Preferably, in the method for preparing the above silicon-carbon negative electrode material, the silicon content in the silicon-containing stream in step (1) is 5wt% to 60wt%, preferably 30wt% to 50wt%, calculated as the element.

[0015] Preferably, in the preparation method of the above-mentioned silicon-carbon negative electrode material, the porous carbon material in step (2) can be derived from one or more of coal-based, petroleum-based, biomass-based, and resin-based porous carbon materials, preferably a coal-based porous carbon material.

[0016] Preferably, in the method for preparing the silicon-carbon negative electrode material, the specific surface area of ​​the porous carbon material in step (2) is 500 to 3500 m 2 / g, pore volume is 0.3~2.0cm 3 / g, the most probable pore diameter is 0.4-5nm, and the pores with a pore diameter of 1-2nm account for 10%-70%, preferably 35%-60%.

[0017] Preferably, in the preparation method of the above-mentioned silicon-carbon negative electrode material, the modifier in step (2) is at least one of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, preferably including 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, wherein the mass ratio of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt to 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt is 0.05 to 3:1, preferably 0.1 to 1:1.

[0018] Preferably, in the method for preparing the above silicon-carbon negative electrode material, the mass ratio of the modifier to the porous carbon material in step (2) is 0.1 to 5:1, preferably 0.5 to 2:1.

[0019] Preferably, in the method for preparing the above silicon-carbon negative electrode material, the weight ratio of the modified porous carbon material to the silicon-containing stream in step (3) is 0.05 to 1:1.

[0020] Preferably, in the preparation method of the above-mentioned silicon-carbon negative electrode material, the mixing conditions in step (3) are as follows: the mixing temperature of the silicon-containing material flow obtained in step (1) and the modified porous carbon material obtained in step (2) is -30 to 20°C, preferably -10 to 10°C; the mixing time of the silicon-containing material flow obtained in step (1) and the modified porous carbon material obtained in step (2) is generally controlled to be 4 to 72 hours, preferably 12 to 48 hours.

[0021] Preferably, in the method for preparing the silicon-carbon negative electrode material, the separation in step (3) is solid-liquid two-phase separation, and the liquid content in the solid-phase stream obtained after separation is controlled to be 1% to 25%, preferably 5% to 15%. Any of the existing means for achieving solid-liquid two-phase separation in the art can be used.

[0022] Preferably, in the method for preparing the above silicon-carbon negative electrode material, the carbonization treatment temperature in step (4) is 500-1200°C, preferably 700-1100°C.

[0023] Preferably, in the method for preparing the above silicon-carbon negative electrode material, the carbonization treatment time in step (4) is 4 to 48 hours, preferably 8 to 24 hours.

[0024] Preferably, in the method for preparing the above-mentioned silicon-carbon negative electrode material, the carbonization treatment in step (4) is carried out under inert atmosphere conditions.

[0025] A second aspect of the present invention provides a silicon-carbon negative electrode material obtained by the above-mentioned preparation method.

[0026] A third aspect of the present invention provides an application of the silicon-carbon negative electrode material obtained by the above preparation method in a lithium ion battery.

[0027] Compared with the prior art, the method for preparing the silicon-carbon negative electrode material provided by the present invention has the following advantages:

[0028] 1. Compared with the existing technical route, the method for preparing the silicon-carbon negative electrode material provided by the present invention has significantly improved specific capacity and first coulombic efficiency of the product produced, and the method for preparing the silicon-carbon negative electrode material provided by the present invention has low production cost and better economy.

[0029] 2. In the preparation method of the silicon-carbon negative electrode material provided by the present invention, the loaded impregnation method is used to load and impregnate organic silicon on the porous carbon, thereby avoiding the safety problems caused by the deposition of silane by the CVI method, and is an intrinsically safe technology.

[0030] 3. In the preparation method of the silicon-carbon negative electrode material provided by the present invention, benzene, petroleum ether, and ether are used as solvents. During carbonization, the liquid phase solvent is directly carbonized to form a coating, which reduces the CVD process once and reduces the cost.

[0031] 4. In the preparation method of the silicon-carbon negative electrode material provided by the present invention, an ionic liquid with high selectivity for silane is loaded and impregnated in the pores of the porous carbon material, thereby increasing the silicon holding capacity of the porous carbon material, and introducing S and N heteroatoms into the pores of the porous carbon material to form doping, which can improve the electrochemical performance of the negative electrode material. DETAILED DESCRIPTION

[0032] The technical scheme and the effects of the implementation of the present invention are further described below in conjunction with specific embodiments and comparative examples, but are not limited to the following embodiments.

[0033] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0034] In this document, unless otherwise expressly stated, all percentages and contents are based on mass.

[0035] In this article, the obtained samples were tested according to the method of "GB / T 24533-2019-Graphite Negative Electrode Materials for Lithium-ion Batteries". The active material (silicon-carbon material): conductive agent (acetylene black): binder (PVDF) were mixed in a ratio of 92:3:5. NMP was used as a solvent and a mixed slurry was obtained by high-energy ball milling. The mixed slurry was then evenly coated on a copper foil. After drying for 12 hours under vacuum at 100°C, the electrode required for battery assembly was obtained by slicing and weighing. The prepared electrode was moved into an argon-filled glove box (H 2 O and O 2 <0.1ppm) to prepare button cells. The entire half-cell is mainly composed of a pole piece, a lithium sheet, a diaphragm, an electrolyte and a fixing device. The prepared half-cell is evaluated in the form of constant current charge and discharge to obtain the specific capacity and first coulomb efficiency parameters of the material. The instrument used is the Xinwei CT-4000 battery tester.

[0036] Example 1

[0037] (1) The specific surface area of ​​porous carbon material is 1737 m 2 / g, pore volume is 0.65cm 3 / g, the most probable pore diameter is 1.1nm, and pores with a diameter of 1-2nm account for 50.6%.

[0038] (2) The porous carbon is immersed in a modifier, wherein the mass ratio of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt in the modifier is 0.1:1, the mass ratio of the modifier to the porous carbon is 1:1, and the immersion time is 8 hours. The separated solid phase material is then dried at 120°C for 4 hours to obtain a modified porous carbon material.

[0039] (3) The concentration of silicon in the silicon-containing stream prepared by mixing silicon chloride and diethyl ether is 40 wt%.

[0040] (4) The modified porous carbon material obtained in step (2) was mixed with the silicon-containing stream in step (3) in a ratio of 0.3:1, the mixing temperature was 0°C, the mixing time was 24 hours, and then solid-liquid separation was performed. The liquid content in the solid-containing stream obtained after separation was controlled to be 10%. The product was further carbonized under nitrogen atmosphere at a carbide temperature of 1000°C and a carbonization time of 12 hours. The obtained product was A-1. The performance test results are shown in Table 1.

[0041] Example 2

[0042] (1) The specific surface area of ​​porous carbon material is 612 m 2 / g, pore volume is 0.25cm 3 / g, the most probable pore diameter is 1.2nm, and pores with a diameter of 1-2nm account for 52.9%.

[0043] (2) The porous carbon is immersed in a modifier, wherein the mass ratio of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt in the modifier is 0.5:1, the mass ratio of the modifier to the porous carbon is 0.5:1, and the immersion time is 8 hours. The separated solid phase material is then dried at 120°C for 4 hours to obtain a modified porous carbon material.

[0044] (3) The concentration of silicon in the silicon-containing stream prepared by mixing silicon chloride and diethyl ether is 30%.

[0045] (4) The modified porous carbon material obtained in step (2) was mixed with the silicon-containing stream in step (3) in a ratio of 0.8:1, the mixing temperature was 0°C, and the mixing time was 24 hours; then solid-liquid separation was performed, and the liquid content in the solid-containing stream obtained after separation was controlled to be 8%, and further carbonization was performed under nitrogen atmosphere conditions, the carbide temperature was 1100°C, the carbonization time was 12 hours, and the obtained product was A-2. The performance test results are shown in Table 1.

[0046] Example 3

[0047] (1) The specific surface area of ​​porous carbon material is 3139 m 2 / g, pore volume is 1.65cm 3 / g, the most probable pore diameter is 1.4nm, and pores with a diameter of 1-2nm account for 59.3%.

[0048] (2) The porous carbon is immersed in a modifier, wherein the mass ratio of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt in the modifier is 0.1:1, the mass ratio of the modifier to the porous carbon is 1:1, and the immersion time is 8 hours. The separated solid phase material is then dried at 120°C for 4 hours to obtain a modified porous carbon material.

[0049] (3) The concentration of silicon in the silicon-containing stream prepared by mixing silicon chloride and diethyl ether is 50%.

[0050] (4) The modified porous carbon material obtained in step (2) was mixed with the silicon-containing stream in step (3) in a ratio of 0.2:1, the mixing temperature was 0°C, and the mixing time was 12 h; then solid-liquid separation was performed, and the liquid content in the solid-containing stream obtained after separation was controlled to be 7%, and further carbonization was performed under nitrogen atmosphere conditions, the carbide temperature was 900°C, the carbonization time was 12 h, and the obtained product was A-3. The performance test results are shown in Table 1.

[0051] Example 4

[0052] (1) The specific surface area of ​​porous carbon material is 2153 m 2 / g, pore volume is 1.04cm 3 / g, the most probable pore diameter is 1.1nm, and pores with a diameter of 1-2nm account for 43.7%.

[0053] (2) The porous carbon was immersed in a modifier, the mass ratio of 1-ethyl-3-methylimidazolium bis-trifluoromethanesulfonyl imide salt and 1-butyl-3-methylimidazolium bis-trifluoromethanesulfonyl imide salt in the modifier was 0.3:1, the mass ratio of the modifier to the porous carbon was 2:1, the immersion time was 8 hours, and a modified sample was obtained after taking it out. The modified sample was dried at 120° C. for 4 hours.

[0054] (3) The concentration of silicon in the silicon-containing stream prepared by mixing silicon chloride and diethyl ether is 31%.

[0055] (4) The modified porous carbon material obtained in step (2) was mixed with the silicon-containing stream in step (3) in a ratio of 0.05:1, the mixing temperature was 0°C, and the mixing time was 48 hours; then solid-liquid separation was performed, and the liquid content in the solid-containing stream obtained after separation was controlled to be 15%, and further carbonization was performed under nitrogen atmosphere conditions, the carbide temperature was 1000°C, the carbonization time was 24 hours, and the obtained product was A-4. The performance test results are shown in Table 1.

[0056] Example 5

[0057] (1) The specific surface area of ​​porous carbon material is 1737 m 2 / g, pore volume is 0.65cm 3 / g, the most probable pore diameter is 1.1nm, and pores with a diameter of 1-2nm account for 50.6%.

[0058] (2) The porous carbon is immersed in a modifier, wherein the mass ratio of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt in the modifier is 0.8:1, the mass ratio of the modifier to the porous carbon is 1:1, and the immersion time is 8 hours. The separated solid phase material is then dried at 120°C for 4 hours to obtain a modified porous carbon material.

[0059] (3) The concentration of silicon in the silicon-containing stream prepared by mixing silicon chloride and diethyl ether is 30%.

[0060] (4) The modified porous carbon material obtained in step (2) was mixed with the silicon-containing stream in step (3) in a ratio of 1:1, the mixing temperature was 0°C, and the mixing time was 24 hours; then solid-liquid separation was performed, and the liquid content in the solid-containing stream obtained after separation was controlled to be 5%, and further carbonization was performed under nitrogen atmosphere conditions, the carbide temperature was 700°C, the carbonization time was 8 hours, and the obtained product was A-5. The performance test results are shown in Table 1.

[0061] Example 6

[0062] (1) The specific surface area of ​​porous carbon material is 1597 m 2 / g, pore volume is 0.59cm 3 / g, the most probable pore diameter is 1.0nm, and pores with a diameter of 1-2nm account for 60.1%.

[0063] (2) The porous carbon is immersed in a modifier, wherein the mass ratio of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt in the modifier is 0.1:1, the mass ratio of the modifier to the porous carbon is 1:1, and the immersion time is 8 hours. The separated solid phase material is then dried at 120°C for 4 hours to obtain a modified porous carbon material.

[0064] (3) The concentration of silicon in the silicon-containing stream prepared by mixing silicon chloride and ether is 35%;

[0065] (4) The modified porous carbon material obtained in step (2) was mixed with the silicon-containing stream in step (3) in a ratio of 0.1:1, the mixing temperature was -10°C, and the mixing time was 48 hours; then solid-liquid separation was performed, and the liquid content in the solid-containing stream obtained after separation was controlled to be 15%, and further carbonization was performed under nitrogen atmosphere conditions, the carbide temperature was 1000°C, the carbonization time was 8 hours, and the obtained product was A-6. The performance test results are shown in Table 1.

[0066] Comparative Example 1

[0067] (1) The specific surface area of ​​porous carbon material is 1737 m 2 / g, pore volume is 0.65cm 3 / g, the most probable pore diameter is 1.1nm, and pores with a diameter of 1-2nm account for 50.6%.

[0068] (2) The porous carbon is immersed in a modifier, wherein the mass ratio of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt in the modifier is 0.1:1, the mass ratio of the modifier to the porous carbon is 1:1, and the immersion time is 8 hours. The separated solid phase material is then dried at 120°C for 4 hours to obtain a modified porous carbon material.

[0069] (3) Silica powder was mixed with modified porous carbon material, and the mixing ratio of porous carbon to silica powder was 1:1; then carbonization was carried out under nitrogen atmosphere, the carbide temperature was 1000°C, the carbonization time was 12h, and the obtained product was D-1. The performance test results are shown in Table 1.

[0070] Comparative Example 2

[0071] (1) The specific surface area of ​​porous carbon material is 1737 m 2 / g, pore volume is 0.65cm 3 / g, the most probable pore diameter is 1.1nm, and pores with a diameter of 1-2nm account for 50.6%.

[0072] (2) The concentration of silicon in the silicon-containing stream prepared by mixing silicon chloride and diethyl ether is 40 wt%.

[0073] (3) The porous carbon material of step (1) and the silicon-containing material flow of step (2) were mixed in a ratio of 0.3:1, the mixing temperature was 0°C, the mixing time was 24 hours, and then solid-liquid separation was performed. The liquid content in the solid-containing material flow obtained after separation was controlled to be 10%. The material was further carbonized under nitrogen atmosphere at a carbide temperature of 1000°C and a carbonization time of 12 hours. The obtained product was D-2. The performance test results are shown in Table 1.

[0074] Comparative Example 3

[0075] (1) The specific surface area of ​​porous carbon material is 3139 m 2 / g, pore volume is 1.65cm 3 / g, the most probable pore diameter is 1.4nm, and pores with a diameter of 1-2nm account for 59.3%.

[0076] (2) The porous carbon is immersed in a modifier, wherein the mass ratio of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt in the modifier is 0.1:1, the mass ratio of the modifier to the porous carbon is 1:1, and the immersion time is 8 hours. The separated solid phase material is then dried at 120°C for 4 hours to obtain a modified porous carbon material.

[0077] (3) The concentration of silicon in the silicon-containing stream prepared by mixing silicon chloride and diethyl ether is 50%.

[0078] (4) The modified porous carbon material obtained in step (2) was mixed with the silicon-containing stream in step (3) in a ratio of 0.2:1, the mixing temperature was 0°C, and the mixing time was 12 h; then solid-liquid separation was performed, and the mixture was dried at 120°C for 12 h. The obtained product was D-3. The performance test results are shown in Table 1.

[0079] Table 1 Electrochemical test results

[0080] Serial number Specific capacity, mAh / g First coulombic efficiency, % A-1 819.59 91.3 A-2 351.81 92.4 A-3 1765.34 90.7 A-4 1579.81 91.9 A-5 647.91 90.3 A-6 1713.97 91.2 D-1 213.41 37.4 D-2 240.75 41.6 D-3 241.92 25.9

[0081] The embodiments of the present invention are only detailed descriptions of the technical solutions of the present invention, but the present invention is not limited to the above embodiments, that is, the present invention can be implemented without relying on the steps described in the above embodiments. In summary, any improvements made to the present invention by those skilled in the art, as long as they do not deviate from the content of the technical solutions of the present invention, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention, shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a silicon-carbon negative electrode material, the preparation method comprising the following steps: (1) mixing a silicon-containing compound with an organic solvent to obtain a silicon-containing stream; (2) The porous carbon material and the modifier are uniformly mixed, and the modified porous carbon material is obtained after separation and drying; the modifier is at least one of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt; (3) under mixing conditions, fully contacting the silicon-containing stream obtained in step (1) with the modified porous carbon material obtained in step (2), and then separating them; (4) The solid phase-containing material stream obtained after separation in step (3) is carbonized to obtain a carbon-silicon negative electrode material.

2. The method for preparing the silicon-carbon negative electrode material according to claim 1, Features: The silicon-containing compound in step (1) is one or both of trichlorosilane and silicon chloride.

3. The method for preparing the silicon-carbon negative electrode material according to claim 1, Features: The organic solvent in step (1) is one or more of benzene, petroleum ether and diethyl ether, preferably diethyl ether.

4. Preferably, in the method for preparing the silicon-carbon negative electrode material, the silicon content in the silicon-containing stream in step (1) is 5wt% to 60wt%, preferably 30wt% to 50wt%, calculated as the element.

5. The method for preparing the silicon-carbon negative electrode material according to claim 1, Features: The specific surface area of ​​the porous carbon material in step (2) is 500 to 3500 m 2 / g, pore volume is 0.3~2.0 cm 3 / g, the most probable pore size is 0.4-5nm, and the pores with a pore size of 1-2 nm account for 10%-70% of the pore structure, preferably 35%-60%.

6. The method for preparing the silicon-carbon negative electrode material according to claim 1, Features: The modifier in step (2) is 1-ethyl-3-methylimidazolium bis-trifluoromethanesulfonyl imide salt and 1-butyl-3-methylimidazolium bis-trifluoromethanesulfonyl imide salt, wherein the mass ratio of 1-ethyl-3-methylimidazolium bis-trifluoromethanesulfonyl imide salt to 1-butyl-3-methylimidazolium bis-trifluoromethanesulfonyl imide salt is 0.05 to 3:1, preferably 0.1 to 1:

1.

7. The method for preparing the silicon-carbon negative electrode material according to claim 1, Features: The mass ratio of the modifier to the porous carbon material in step (2) is 0.1 to 5:1, preferably 0.5 to 2:

1.

8. The method for preparing the silicon-carbon negative electrode material according to claim 1, Features: The weight ratio of the modified porous carbon material to the silicon-containing stream in step (3) is 0.05 to 1:

1.

9. The method for preparing the silicon-carbon negative electrode material according to claim 1, Features: The mixing conditions in step (3) are as follows: the mixing temperature of the silicon-containing stream obtained in step (1) and the modified porous carbon material obtained in step (2) is -30 to 20°C, preferably -10 to 10°C.

10. The method for preparing the silicon-carbon negative electrode material according to claim 1, Features: The separation in step (3) is solid-liquid two-phase separation, and the liquid content in the solid-phase-containing stream obtained after separation is controlled to be 1% to 25%, preferably 5% to 15%.

11. The method for preparing the silicon-carbon negative electrode material according to claim 1, Features: The carbonization treatment temperature in step (4) is 500-1200°C, preferably 700-1100°C.

12. The method for preparing the silicon-carbon negative electrode material according to claim 1, Features: The carbonization treatment in step (4) is carried out under inert atmosphere conditions.

13. A silicon-carbon negative electrode material obtained by the preparation method described in any one of claims 1 to 12.

14. Use of a silicon-carbon negative electrode material obtained by the preparation method according to any one of claims 1 to 12 in a lithium-ion battery.