Modified silicon carbon negative electrode material, and its preparation method and use

Abstract

This application discloses a modified silicon carbon anode material and its preparation method and use, which includes the steps of (1) mixing the silicon carbon anode material with a lithium alkoxide solution to carry out a solvothermal reaction, and (2) washing the solid powder obtained by the solvothermal reaction in step (1) with alcohol and drying to obtain a modified silicon carbon anode material, in which the lithium alkoxide solution is prepared by mixing metallic lithium with an alcohol solvent.

Description

[Technical Field]

[0001] The present application belongs to the technical field of batteries and relates to anode materials, for example, modified silicon carbon anode materials, and their preparation methods and uses. [Background technology]

[0002] Lithium-ion batteries are widely used in daily life due to their advantages of high energy density, long cycle life, and low cost. However, conventional graphite anodes have low specific capacity, which does not meet the development requirements of the new energy field. Therefore, the development of anode materials with high specific capacity has become crucial.

[0003] Currently, graphite is the most widely used anode material for lithium batteries, but its low theoretical capacity of 372 mAh / g makes it difficult to meet the need for high energy density. Silicon-based anode materials have theoretical capacities more than 10 times higher than commercial graphite anodes, and offer advantages such as low discharge potential and abundant reserves, making them considered one of the most promising anode materials for lithium-ion batteries. However, silicon undergoes severe volume expansion during the lithium ion intercalation process, which causes the active material to pulverize and lose contact with the current collector and conductive material, resulting in reduced battery coulombic efficiency, poor cycling performance, and rapid capacity decay.

[0004] In the case of silicon carbon anode materials (Si / C anode materials), the volume effect during the silicon absorption and desorption process results in low initial Coulombic efficiency and large initial irreversible capacity, leaving room for improvement in high-power charge / discharge performance and cycle life. At the same time, when lithium ions are absorbed and released from the graphite anode, the volume of the graphite unit cell expands and contracts by approximately 10%, which means that graphite, as a matrix, has problems such as low initial charge / discharge efficiency and poor cycle stability.

[0005] CN110890538A discloses a method for improving the initial coulombic efficiency of a silicon-based lithium-ion battery anode material, which includes the steps of (1) measuring the hydroxyl group content on the surface of the silicon anode material, and (2) grafting a silane coupling agent onto the surface of the silicon anode material through organic chemical modification. The method involves measuring the hydroxyl group content on the surface of the silicon anode, and then reacting a specific amount of an inert group-containing silane coupling agent with the hydroxyl groups on the surface of the silicon anode to replace the hydroxyl groups on the surface of the silicon anode, thereby improving the initial coulombic efficiency of the silicon anode. However, the method is complicated to operate and has low commercial viability.

[0006] CN110429265A discloses an MEG / Si / C composite anode material for lithium-ion batteries and its preparation method. The composite anode material contains 2-20 wt% nanosilicon powder, 1-3 wt% surfactant, 10-30 wt% carbon source, and the balance micro-expanded graphite. Expanded graphite is prepared by chemical oxidative intercalation and low-temperature thermal expansion techniques, followed by mechanical milling and high-temperature carbonization to prepare the expanded graphite / silicon / carbon composite anode material for lithium-ion batteries. However, the preparation method suffers from high implementation difficulty, poor controllability, complex operation, high cost, and low commercial viability.

[0007] CN109411717A discloses a prelithiated negative electrode material with high reversible capacity and a method for preparing it. The negative electrode material includes a graphite-based carbon material, a metal oxide or silicon powder uniformly distributed thereon, and lithium carbonate. The preparation method involves stirring and mixing the metal oxide or silicon powder, lithium carbonate powder, graphite-based carbon powder, and a grinding aid, followed by ball milling. The addition of lithium carbonate to the negative electrode material reduces the irreversible capacity and improves the initial coulombic efficiency during the initial charge / discharge process, while the addition of a graphite-based carbon material improves the structural stability of the material and the conductivity of the electrode material during the reaction process. However, this method presents many difficulties in practical implementation due to its high cost, complex process, and certain risks.

[0008] Therefore, there is a need to provide a method for improving the first coulombic efficiency of silicon carbon anode materials that is simple, easy to implement, and efficient. Summary of the Invention [Problem to be solved by the invention]

[0009] The present application aims to provide a modified silicon-carbon anode material, its preparation method, and its use. The preparation method is simple and can achieve surface prelithiation of the silicon-carbon anode material through a simple solvothermal reaction, thereby reducing the irreversible capacity during the initial charge / discharge process and improving the initial coulombic efficiency to above 92%. [Means for solving the problem]

[0010] In order to achieve the object of the present invention, the present application provides the following technical solutions.

[0011] This application is (1) mixing a silicon carbon anode material with a lithium alkoxide solution to carry out a solvothermal reaction; (2) washing the solid powder obtained by the solvothermal reaction in step (1) with alcohol, drying the solid powder, and then obtaining a modified silicon carbon negative electrode material.

[0012] The lithium alkoxide solution is prepared by mixing metallic lithium with an alcohol solvent.

[0013] The silicon carbon anode material according to the present application is a conventional silicon carbon anode material (Si / C anode material) in the art, and any conventional Si / C anode material in the art can be modified by the preparation method according to the present application.

[0014] In this application, metallic lithium is mixed with an alcohol solvent to prepare a lithium alkoxide solution, and then the silicon-carbon material is reacted with the lithium alkoxide through a solvothermal reaction to produce a lithium-silicon compound. This replenishes the irreversible lithium loss during the cycling process of the silicon-carbon material, while the alcohol functional groups form an SEI film on the silicon-carbon surface, improving the stability of the silicon-carbon material and realizing prelithiation of the surface of the silicon-carbon anode material. When the silicon-carbon anode material is used in a lithium-ion battery, it reduces the irreversible capacity during the initial charge / discharge process and improves the initial coulombic efficiency.

[0015] Preferably, the metallic lithium comprises a combination of at least one of lithium powder, lithium block, or lithium strip. Exemplary, but non-limiting, combinations include a combination of lithium powder and lithium block, a combination of lithium block and lithium strip, a combination of lithium powder and lithium strip, or a combination of lithium powder, lithium block, and lithium strip.

[0016] The lithium powder, lithium block, and lithium strip described in this application are named based on the size of metallic lithium. The fact that the metallic lithium according to this application is any one or a combination of at least two selected from lithium powder, lithium block, and lithium strip means that any form of metallic lithium known in the art can be used to prepare a lithium alkoxide solution as long as it is soluble in an alcohol solvent.

[0017] Preferably, the alcohol solvent is a fluorine-containing alcohol.

[0018] The present application describes a method for producing a lithium silicon compound and a fluorine-containing lithium salt compound on the surface of a Si / C anode by mixing a fluorine-containing alcohol with metallic lithium and then subjecting the silicon carbon anode material to a solvothermal reaction with a lithium alkoxide solution. The fluorine-containing lithium salt compound can further improve the lithium ion conductivity of the silicon carbon anode and enhance the electrochemical performance of the silicon carbon material while replenishing the irreversible lithium loss during the cycling process of the silicon carbon material.

[0019] Preferably, the fluorine-containing alcohol includes any one or a combination of at least two of 2-fluoroethanol, 2,2-difluoroethanol, trifluoroacetaldehyde hemiethyl acetal, 2,2,2-trifluoroethanol, 3,3,3-trifluoropropan-1-ol, 2,2,3,3,3-pentafluoro-1-propanol, hexafluoroisopropanol, hexafluorobutanol, perfluorobutanol, hexafluoro-2,3-bis(trifluoromethyl)-2,3-butanediol, 1H,1H,2H,2H-perfluoro-1-octanol, and 1H,1H,7H-dodecafluoro-1-heptanol. Exemplary, but non-limiting, combinations include 2-fluoroethanol and 2,2-difluoroethanol, trifluoroacetaldehyde hemiethyl acetal and 2,2,2-trifluoroethanol, 3,3,3-trifluoropropan-1-ol, 3,3,3-trifluoropropan-1-ol and 2,2,3,3,3-pentafluoro-1-propanol, hexafluoroisopropanol and hexafluorobutanol, perfluorobutanol and hexafluoro-2,3-bis(trifluoromethyl)-2,3-butanediol, 1H,1H,2H,2H-perfluoro-1-octanol and 1H,1H,7H-dodecafluoro-1-heptanol, and 2,2,2-trifluoroethanol and 2,2,3,3,3-pentafluoro-1-propanol. and combinations of 2-fluoroethanol, 2,2-difluoroethanol, trifluoroacetaldehyde hemiethyl acetal, 2,2,2-trifluoroethanol, 3,3,3-trifluoropropan-1-ol, 2,2,3,3,3-pentafluoro-1-propanol, hexafluoroisopropanol, hexafluorobutanol, perfluorobutanol, hexafluoro-2,3-bis(trifluoromethyl)-2,3-butanediol, 1H,1H,2H,2H-perfluoro-1-octanol, and 1H,1H,7H-dodecafluoro-1-heptanol, with 2,2,2-trifluoroethanol and / or 2,2,3,3,3-pentafluoro-1-propanol being preferred.

[0020] Preferably, the solid-liquid ratio of the metallic lithium to the alcohol solvent is (0.1 to 2:1), and may be, for example, 0.1:1, 0.3:1, 0.5:1, 0.8:1, 1:1, 1.2:1, 1.5:1, 1.8:1, or 2:1, but is not limited to the recited values, and other unrecited values within the numerical range also apply. The unit of the solid-liquid ratio is mg / mL.

[0021] Preferably, the particle size D50 of the silicon carbon negative electrode material in step (1) is 5 to 30 μm, and may be, for example, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, or 30 μm, but is not limited to the listed values, and other unlisted values within the numerical range also apply.

[0022] Preferably, the solid-liquid ratio of the silicon carbon anode material to the lithium alkoxide solution in step (1) is (0.01 to 0.5):1, such as 0.01:1, 0.05:1, 0.1:1, 0.15:1, 0.2:1, 0.25:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1, or 0.5:1, but is not limited to the recited values, and other unrecited values within the range also apply. The unit of the solid-liquid ratio is g / mL.

[0023] Preferably, the temperature of the solvothermal reaction in step (1) is 60 to 260°C, and may be, for example, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, or 260°C, but is not limited to the recited values, and other unrecited values within the numerical range also apply.

[0024] Preferably, the solvothermal reaction time in step (1) is 0.5 to 72 hours, and may be, for example, 0.5 hours, 1 hour, 5 hours, 10 hours, 20 hours, 30 hours, 40 hours, 50 hours, 60 hours, 70 hours, or 72 hours, but is not limited to the recited values, and other unrecited values within the numerical range also apply.

[0025] Preferably, the alcohol solvent for the alcohol wash in step (2) comprises any one or a combination of at least two of 2-fluoroethanol, 2,2-difluoroethanol, trifluoroacetaldehyde hemiethyl acetal, 2,2,2-trifluoroethanol, 3,3,3-trifluoropropan-1-ol, 2,2,3,3,3-pentafluoro-1-propanol, hexafluoroisopropanol, hexafluorobutanol, perfluorobutanol, hexafluoro-2,3-bis(trifluoromethyl)-2,3-butanediol, 1H,1H,2H,2H-perfluoro-1-octanol, or 1H,1H,7H-dodecafluoro-1-heptanol. Exemplary, but non-limiting, combinations include 2-fluoroethanol and 2,2-difluoroethanol, trifluoroacetaldehyde hemiethyl acetal and 2,2,2-trifluoroethanol, 3,3,3-trifluoropropan-1-ol, 3,3,3-trifluoropropan-1-ol and 2,2,3,3,3-pentafluoro-1-propanol, hexafluoroisopropanol and hexafluorobutanol, perfluorobutanol and hexafluoro-2,3-bis(trifluoromethyl)-2,3-butanediol, and 1H,1H,2H,2H-perfluoro-1-octanol and 1H,1H,7H-dodecafluoro-1-heptanol. and a combination of 2,2,2-trifluoroethanol and 2,2,3,3,3-pentafluoro-1-propanol, or a combination of 2-fluoroethanol, 2,2-difluoroethanol, trifluoroacetaldehyde hemiethyl acetal, 2,2,2-trifluoroethanol, 3,3,3-trifluoropropan-1-ol, 2,2,3,3,3-pentafluoro-1-propanol, hexafluoroisopropanol, hexafluorobutanol, perfluorobutanol, hexafluoro-2,3-bis(trifluoromethyl)-2,3-butanediol, 1H,1H,2H,2H-perfluoro-1-octanol, and 1H,1H,7H-dodecafluoro-1-heptanol.

[0026] Preferably, the drying in step (2) is vacuum drying.

[0027] Preferably, the temperature for the vacuum drying is 60 to 100°C, and may be, for example, 60°C, 70°C, 80°C, 90°C, or 100°C, but is not limited to the listed values, and other unlisted values within the numerical range also apply.

[0028] Preferably, the vacuum drying time is 10 to 24 hours, and may be, for example, 10 hours, 12 hours, 15 hours, 16 hours, 18 hours, 20 hours, 21 hours, or 24 hours, but is not limited to the listed values, and other unlisted values within the numerical range also apply.

[0029] As a preferred technical solution of the preparation method according to the present application, the preparation method comprises: (1) mixing a silicon carbon anode material and a lithium alkoxide solution in a solid-liquid ratio of (0.01-0.5):1, and carrying out a solvothermal reaction under conditions of 60-260°C for 0.5-72 hours, wherein the solid-liquid ratio is in g / mL, and the particle size D50 of the silicon carbon anode material is 5-30 μm; (2) washing the solid powder obtained by the solvothermal reaction in step (1) with alcohol, and then vacuum drying at 60-100°C for 10-24 hours to obtain a modified silicon carbon anode material; the lithium alkoxide solution is a mixture of metallic lithium and an alcohol solvent, the solid-liquid ratio of the metallic lithium to the alcohol solvent is (0.1 to 2):1, the unit of the solid-liquid ratio is mg / mL, and the alcohol solvent contains any one or a combination of at least two of 2-fluoroethanol, 2,2-difluoroethanol, trifluoroacetaldehyde hemiethyl acetal, 2,2,2-trifluoroethanol, 3,3,3-trifluoropropan-1-ol, 2,2,3,3,3-pentafluoro-1-propanol, hexafluoroisopropanol, hexafluorobutanol, perfluorobutanol, hexafluoro-2,3-bis(trifluoromethyl)-2,3-butanediol, 1H,1H,2H,2H-perfluoro-1-octanol, and 1H,1H,7H-dodecafluoro-1-heptanol; The alcohol solvent for alcohol washing in step (2) is the same as the alcohol solvent for preparing the lithium alkoxide solution.

[0030] In a second aspect, the present application provides a modified silicon carbon anode material obtainable by the preparation method according to the first aspect.

[0031] In a third aspect, the present application provides the use of the modified silicon carbon anode material according to the second aspect in the manufacture of a lithium ion battery. [Effects of the Invention]

[0032] Compared with the prior art, the present application has the following beneficial effects:

[0033] In this invention, lithium metal is reacted with an alcohol-based solvent to produce a lithium alkoxide solution, and then the lithium alkoxide solution is reacted with silicon-carbon powder to perform prelithiation. The silicon-carbon powder is modified in this invention to effectively improve its initial coulombic efficiency. Furthermore, this method has advantages such as simplicity, safety, and low cost, making it favorable for industrial production. [Brief explanation of the drawings]

[0034] [Figure 1] FIG. 1 is a diagram showing charge and discharge curves of the modified silicon carbon negative electrode material in Example 1 and the unmodified silicon carbon negative electrode material in Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0035] The technical solution of the present application will be further described below through specific embodiments. Those skilled in the art should understand that the above examples are only intended to help understand the present application and should not be considered to specifically limit the present application.

[0036] Example 1

[0037] In this embodiment, (1) mixing a silicon carbon anode material and a lithium alkoxide solution in a solid-liquid ratio of 0.2:1, and carrying out a solvothermal reaction at 180°C for 12 hours, wherein the solid-liquid ratio is expressed in g / mL; (2) washing the solid powder obtained by the solvothermal reaction in step (1) with alcohol, and then drying it under vacuum at 60°C for 24 hours to obtain a modified silicon carbon anode material; The lithium alkoxide solution is prepared by mixing metallic lithium with an alcohol solvent, the solid-liquid ratio of the metallic lithium to the alcohol solvent is 1:1, the unit of the solid-liquid ratio is mg / mL, and the alcohol solvent is 2,2,2-trifluoroethanol.

[0038] The alcohol solvent for the alcohol washing in step (2) is the same as the alcohol solvent for preparing the lithium alkoxide solution.

[0039] The silicon carbon anode material in this embodiment has a particle size D50 of 5 μm and is selected from HE-600 manufactured by Yijin New Energy Science and Technology Co., Ltd.

[0040] Example 2

[0041] In this embodiment, (1) mixing a silicon carbon anode material and a lithium alkoxide solution in a solid-liquid ratio of 0.01:1, and carrying out a solvothermal reaction at 120°C for 48 hours, wherein the solid-liquid ratio is expressed in g / mL; (2) washing the solid powder obtained by the solvothermal reaction in step (1) with alcohol, and then drying it under vacuum at 70°C for 20 hours to obtain a modified silicon carbon anode material; The lithium alkoxide solution is prepared by mixing metallic lithium with an alcohol solvent, the solid-liquid ratio of the metallic lithium to the alcohol solvent is 0.1:1, the unit of the solid-liquid ratio is mg / mL, and the alcohol solvent is 2,2,2-trifluoroethanol.

[0042] The alcohol solvent for the alcohol washing in step (2) is the same as the alcohol solvent for preparing the lithium alkoxide solution.

[0043] The silicon carbon anode material in this embodiment has a particle size D50 of 15 μm and is selected from the Si / C composites-600 mAh / g manufactured by Pu-Tailai.

[0044] Example 3

[0045] In this embodiment, (1) mixing a silicon carbon anode material and a lithium alkoxide solution in a solid-liquid ratio of 0.5:1, and carrying out a solvothermal reaction at 260°C for 0.5 hours, wherein the solid-liquid ratio is expressed in g / mL; (2) washing the solid powder obtained by the solvothermal reaction in step (1) with alcohol, and then drying it in vacuum at 100°C for 10 hours to obtain a modified silicon carbon anode material; The lithium alkoxide solution is prepared by mixing metallic lithium with an alcohol solvent, the solid-liquid ratio of the metallic lithium to the alcohol solvent is 2:1, the unit of the solid-liquid ratio is mg / mL, and the alcohol solvent is 2,2,2-trifluoroethanol.

[0046] The alcohol solvent for the alcohol washing in step (2) is the same as the alcohol solvent for preparing the lithium alkoxide solution.

[0047] The silicon carbon anode material in this embodiment has a particle size D50 of 10 μm and is selected from HE-470 manufactured by Yijin New Energy Science and Technology Co., Ltd. Example 4

[0048] In this embodiment, (1) mixing a silicon carbon anode material and a lithium alkoxide solution in a solid-liquid ratio of 0.2:1, and carrying out a solvothermal reaction at 60°C for 72 hours, wherein the solid-liquid ratio is expressed in g / mL; (2) washing the solid powder obtained by the solvothermal reaction in step (1) with alcohol, and then drying it under vacuum at 80°C for 16 hours to obtain a modified silicon carbon anode material; The lithium alkoxide solution is prepared by mixing metallic lithium with an alcohol solvent, the solid-liquid ratio of the metallic lithium to the alcohol solvent is 0.5:1, the unit of the solid-liquid ratio is mg / mL, and the alcohol solvent is 2,2,2-trifluoroethanol.

[0049] The alcohol solvent for the alcohol washing in step (2) is the same as the alcohol solvent for preparing the lithium alkoxide solution.

[0050] The silicon carbon anode material in this embodiment has a particle size D50 of 30 μm and is selected from the Si / C composites-450 mAh / g manufactured by Pu-Tailai.

[0051] Example 5

[0052] This example provides a method for preparing a modified silicon carbon anode material, which is similar to Example 1, except that the alcohol solvent used is 2,2,3,3,3-pentafluoro-1-propanol.

[0053] Example 6

[0054] This example provides a method for preparing a modified silicon carbon negative electrode material, which is similar to Example 1, except that the alcohol solvent used is 2-fluoroethanol.

[0055] Example 7

[0056] This example provides a method for preparing a modified silicon carbon negative electrode material, which is similar to Example 1, except that the alcohol solvent used is 2,2-difluoroethanol.

[0057] Example 8

[0058] This example provides a method for preparing a modified silicon carbon negative electrode material, which is similar to Example 1, except that the alcohol solvent used is hexafluoroisopropanol.

[0059] Example 9

[0060] This example provides a method for preparing a modified silicon carbon anode material, which is similar to Example 1, except that the alcohol solvent used is hexafluorobutanol.

[0061] Example 10

[0062] This example provides a method for preparing a modified silicon carbon anode material, which is similar to Example 1, except that the alcohol solvent used is 1H,1H,2H,2H-perfluoro-1-octanol.

[0063] Example 11

[0064] This example provides a method for preparing a modified silicon carbon anode material, which is similar to Example 1, except that the alcohol solvent used is methanol.

[0065] Example 12

[0066] This example provides a method for preparing a modified silicon carbon negative electrode material, which is similar to Example 1, except that the alcohol solvent used is ethanol.

[0067] Example 13

[0068] This example provides a method for preparing a modified silicon carbon negative electrode material, which is similar to Example 1, except that the alcohol solvent used is n-propanol.

[0069] Example 14

[0070] This example provides a method for preparing a modified silicon carbon negative electrode material, which is similar to Example 1, except that the alcohol solvent used is n-butanol.

[0071] Example 15

[0072] This example provides a method for preparing a modified silicon carbon anode material, which is similar to Example 1, except that the alcohol solvent used is n-heptanol.

[0073] Comparative Example 1

[0074] The carbon silicon negative electrode material according to this comparative example is HE-600 manufactured by Yijin New Energy Science and Technology Co., Ltd., and has a particle size D50 of 5 μm.

[0075] Electrochemical tests were conducted on the modified silicon carbon anode materials obtained in Examples 1 to 15 and the unmodified silicon carbon anode material in Comparative Example 1. The test method was as follows: The obtained modified silicon carbon anode material, acetylene black, SBR, and CMC were mixed in a mass ratio of 85:5:5:5 to form a slurry, with water as the solvent. The slurry was applied to copper foil and used as the working electrode, metallic lithium as the counter electrode, the electrolyte was 1 mol / L LiPF6 / EC+DEC, and the separator model was Celgard 2300, to form a half-cell. The current density during the test was 50 mA / g, and the voltage range was 0.05 to 2 V.

[0076] The charge-discharge curves of the modified silicon carbon anode material obtained in Example 1 and the unmodified silicon carbon anode material in Comparative Example 1 are shown in Figure 1. As can be seen from Figure 1, the first cycle Coulombic efficiency of the half-cell assembled with the modified silicon carbon anode material obtained in Example 1 is as high as 92.5%, while the first cycle Coulombic efficiency of the half-cell assembled with the original silicon carbon anode material is only 72.1%. As can be seen, the method of the present application can effectively improve the first cycle Coulombic efficiency of the silicon carbon anode material.

[0077] The results of the coulombic efficiency in the first cycle obtained in Examples 1 to 15 and Comparative Example 1 are shown in Table 1. [Table 1]

[0078] In summary, the present invention involves reacting metallic lithium with an alcoholic solvent to produce a lithium alkoxide solution, and then reacting the lithium alkoxide solution with silicon-carbon powder to perform prelithiation. The present invention modifies the silicon-carbon powder to effectively improve its initial coulombic efficiency. Furthermore, this method has advantages such as simplicity, safety, and low cost, making it favorable for industrial production.

[0079] The above content is merely a specific embodiment of the present application, and the applicant declares that the scope of protection of the present application is not limited thereto.

Claims

1. (1) mixing a silicon carbon anode material with a lithium alkoxide solution to carry out a solvothermal reaction; (2) washing the solid powder obtained by the solvothermal reaction in step (1) with alcohol and drying it to obtain a modified silicon carbon anode material; A method for preparing a modified silicon carbon negative electrode material, comprising: The lithium alkoxide solution is prepared by mixing metallic lithium with an alcohol solvent, The method for preparing a modified silicon carbon negative electrode material, wherein the alcohol solvent is a fluorine-containing alcohol.

2. 2. The method according to claim 1, wherein the solid-liquid ratio of the metallic lithium to the alcohol solvent is (0.1-2):1, and the unit of the solid-liquid ratio is mg / mL.

3. The fluorine-containing alcohol includes any one or a combination of at least two of 2-fluoroethanol, 2,2-difluoroethanol, trifluoroacetaldehyde hemiethyl acetal, 2,2,2-trifluoroethanol, 3,3,3-trifluoropropan-1-ol, 2,2,3,3,3-pentafluoro-1-propanol, hexafluoroisopropanol, hexafluorobutanol, perfluorobutanol, hexafluoro-2,3-bis(trifluoromethyl)-2,3-butanediol, 1H,1H,2H,2H-perfluoro-1-octanol, and 1H,1H,7H-dodecafluoro-1-heptanol. The preparation method according to claim 1.

4. The preparation method according to any one of claims 1 to 3, wherein the metallic lithium comprises any one or a combination of at least two of lithium powder, lithium block, or lithium strip.

5. The particle size D50 of the silicon carbon negative electrode material in step (1) is 5 to 30 μm; In step (1), the solid-liquid ratio of the silicon carbon negative electrode material to the lithium alkoxide solution is (0.01 to 0.5): 1, and the unit of the solid-liquid ratio is g / mL; The preparation method according to any one of claims 1 to 4.

6. The temperature of the solvothermal reaction in step (1) is 60 to 260°C; The solvothermal reaction time in step (1) is 0.5 to 72 hours. The preparation method according to any one of claims 1 to 5.

7. the alcohol solvent for the alcohol wash in step (2) comprises any one or a combination of at least two of 2-fluoroethanol, 2,2-difluoroethanol, trifluoroacetaldehyde hemiethyl acetal, 2,2,2-trifluoroethanol, 3,3,3-trifluoropropan-1-ol, 2,2,3,3,3-pentafluoro-1-propanol, hexafluoroisopropanol, hexafluorobutanol, perfluorobutanol, hexafluoro-2,3-bis(trifluoromethyl)-2,3-butanediol, 1H,1H,2H,2H-perfluoro-1-octanol, and 1H,1H,7H-dodecafluoro-1-heptanol; The drying in step (2) is vacuum drying; The temperature of the vacuum drying is 60 to 100°C, The vacuum drying time is 10 to 24 hours. The preparation method according to any one of claims 1 to 6.

8. (1) Mixing a silicon carbon anode material and a lithium alkoxide solution in a solid-liquid ratio of (0.01-0.5):1, and carrying out a solvothermal reaction under conditions of 60-260°C for 0.5-72 hours, wherein the solid-liquid ratio is in g / mL, and the particle size D50 of the silicon carbon anode material is 5-30 μm; (2) washing the solid powder obtained by the solvothermal reaction in step (1) with alcohol, and then vacuum drying at 60-100°C for 10-24 hours to obtain a modified silicon carbon anode material; A preparation method comprising: the lithium alkoxide solution is prepared by mixing metallic lithium with an alcohol solvent, the solid-liquid ratio of the metallic lithium to the alcohol solvent is (0.1 to 2):1, and the unit of the solid-liquid ratio is mg / mL; the alcohol solvent includes any one or a combination of at least two of 2-fluoroethanol, 2,2-difluoroethanol, trifluoroacetaldehyde hemiethyl acetal, 2,2,2-trifluoroethanol, 3,3,3-trifluoropropan-1-ol, 2,2,3,3,3-pentafluoro-1-propanol, hexafluoroisopropanol, hexafluorobutanol, perfluorobutanol, hexafluoro-2,3-bis(trifluoromethyl)-2,3-butanediol, 1H,1H,2H,2H-perfluoro-1-octanol, and 1H,1H,7H-dodecafluoro-1-heptanol; The alcohol solvent for alcohol washing in step (2) is the same as the alcohol solvent for preparing the lithium alkoxide solution. The preparation method according to any one of claims 1 to 7.

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