Method for preparing silicon carbon composite materials by plasma modification, silicon carbon composite materials and applications

Abstract

The present invention discloses a method for preparing a silicon-carbon composite material by plasma modification, the silicon-carbon composite material and its applications. It includes at least the following steps: Step S10) putting aminated porous carbon into a deposition chamber, passing silane gas through the deposition chamber to deposit nanosilicon on the aminated porous carbon to obtain a silicon-carbon precursor material; Step S20) transferring the silicon-carbon precursor material to a chamber for plasma modification, passing a halogen gas in the form of plasma, and depositing the generated halogen ions on the surface of the silicon-carbon precursor material to obtain a silicon-carbon precursor material coated with halogenated carbon; Step S30) stopping the passage of the halogen gas and passing a carbon source gas in the form of plasma. The prepared silicon-carbon composite material forms a structurally stable core-shell structure, greatly reduces the expansion problem of silicon, and can significantly improve the cycle performance of a battery applied therewith. In addition, the process of this application is simple, and by using the plasma method to modify the silicon-carbon material, it is easy to achieve mass preparation and large-scale industrialization.

Description

[Technical Field]

[0001] This application claims priority from Chinese Patent Application No. 2023107730517, filed with the Patent Office of the State Intellectual Property Administration of the People's Republic of China on June 27, 2023, entitled "Method for preparing silicon carbon composite material by plasma modification, silicon carbon composite material and application," the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to the field of lithium ion battery material preparation, specifically to a method for preparing silicon carbon composite materials by plasma modification, and further to the silicon carbon composite materials obtained by the preparation method and their applications. [Background technology]

[0003] Silicon-carbon composites are widely used in high-energy-density lithium-ion batteries due to their advantages, such as high energy density and abundant natural resources. Their typical preparation method involves depositing nanosilicon on porous carbon by silane pyrolysis, followed by deposition of amorphous carbon by vapor deposition at temperatures between 700 and 1000°C. Silicon-carbon composites prepared by this method suffer from unstable carbon structures in the outer layer, and significant expansion of the silicon due to the growth of silicon crystal grains at temperatures between 700 and 1000°C, which significantly adversely affects the cycle performance of the battery.

[0004] Therefore, the applicant would like to seek a technical solution to improve the above technical problems. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a method for preparing a silicon carbon composite material by plasma modification, a silicon carbon composite material, and applications thereof. The prepared silicon carbon composite material forms a structurally stable core-shell structure, significantly reduces the problem of silicon expansion, and can significantly improve the cycle performance of batteries using the same. Furthermore, the preparation method provided in this application is simple, and by using a plasma method to modify the silicon carbon material, it is easy to achieve mass preparation and large-scale industrialization.

[0006] The technical solutions used in the present invention are as follows:

[0007] 1. A method for preparing a silicon carbon composite material by plasma modification, comprising: Step S10) placing the aminated porous carbon into a deposition chamber, passing silane gas at a flow rate of 100 to 1000 ml / min into the deposition chamber, and passing the silane gas at a temperature of 400 to 600°C for at least 30 minutes to deposit nanosilicon on the aminated porous carbon, thereby obtaining a silicon-carbon precursor material; Step S20) of transferring the silicon carbon precursor material obtained in step S10) to a plasma process modification chamber, passing a halogen gas in the form of plasma through the plasma process modification chamber, and depositing the generated halogen ions on the surface of the silicon carbon precursor material to obtain a silicon carbon precursor material coated with halocarbon; and (S30) stopping the flow of the halogen gas and passing a carbon source gas in the form of plasma through the plasma modification chamber to obtain the silicon carbon composite material.

[0008] Preferably, in step S20, the parameter of the plasma method modification chamber is set to a vacuum degree of 1 to 10. Pa The temperature is set to 300 to 600° C., the power of the plasma method is set to 500 to 1000 W, and / or the flow rate of the halogen gas is set to 100 to 500 sccm, and the time for passing the gas is set to at least 10 minutes.

[0009] Preferably, in step S30, the parameter of the plasma method modification chamber is set to a vacuum degree of 1 to 10. Pa The temperature is set to 300 to 600° C., the power of the plasma method is set to 500 to 1000 W, and / or the flow rate of the carbon source gas is set to 100 to 500 sccm, and the time for passing the gas is set to at least 10 minutes.

[0010] Preferably, in step S10), the method for preparing the aminated porous carbon includes: Step S11) of pre-acidifying the porous carbon with concentrated nitric acid to obtain acidified porous carbon; Step S12) of mixing the acidified porous carbon from step S11 with thionyl chloride and N,N-dimethylformamide and reacting at a temperature of 30 to 100°C for at least 1 hour to obtain chlorinated porous carbon; and step S13) of reacting the chlorinated porous carbon obtained in step S12) with aniline to obtain amidated porous carbon as the aminated porous carbon.

[0011] Preferably, the method for preparing aminated porous carbon comprises the steps of: Step S11) of adding porous carbon to concentrated nitric acid in a mass ratio of the porous carbon to concentrated nitric acid of 1:200-500, and heating under reflux at a temperature of 30-100°C for at least 1 hour to obtain acidified porous carbon; Step S12) of mixing the acidified porous carbon in step S11) with thionyl chloride and N,N-dimethylformamide to set the mass ratio of the acidified porous carbon, thionyl chloride, and N,N-dimethylformamide to 1:20 to 80:5 to 15, and reacting at a temperature of 30 to 100°C for at least 1 hour to obtain chlorinated porous carbon; and step S13) of reacting the chlorinated porous carbon obtained in step S12) with aniline at a temperature of 0 to 40°C for at least 1 hour to obtain amidated porous carbon as the aminated porous carbon, in which the mass ratio of the chlorinated porous carbon to aniline is 1:10 to 30.

[0012] Preferably, in step S11), the acidified porous carbon is washed with deionized water and dried before proceeding to step S12), and / or in step S12), the chlorinated porous carbon is washed with tetrahydrofuran and dried before proceeding to step S13), and / or in step S13), the amidated porous carbon is washed with acetone until it becomes colorless.

[0013] Preferably, in step S20, the halogen gas is any one of fluorine, chlorine, and bromine, or a mixture of any two or more thereof.

[0014] Preferably, in step S30, the carbon source gas is methane, ethylene, acetylene, N It may be any one of these or a mixture of any two or more of these.

[0015] Preferably, the silicon carbon composite is prepared by the method for preparing a silicon carbon composite by plasma modification as described above, wherein the silicon carbon composite comprises a core-shell structure consisting of a core and a shell, the core comprises a nitrogen-doped silicon carbon composite, and the shell comprises a halogenated carbon and amorphous carbon.

[0016] A preferred application of the silicon carbon composite material as described above is to use the silicon carbon composite material as an active material raw material for manufacturing an electrode sheet of a battery, preferably as an active material raw material for manufacturing an anode sheet of a lithium ion battery.

[0017] In the present invention, a chemical bond is formed between the amino groups on the surface of the amidated porous carbon and silicon radicals generated by pyrolysis of silane gas, thereby enhancing the stability of the core structure of the material and improving the cycle performance of batteries using the material. Furthermore, halogen gas is passed through a silicon-carbon precursor material (as the core structure) in the form of plasma to form a halocarbon coating on the surface of the silicon-carbon precursor material. This facilitates the diffusion of halogen ions within the material compared to conventional vapor deposition methods, significantly shortens the halogenation time and temperature, and reduces the impact on the growth of silicon crystal grains. In the present application, after the halocarbon is formed, amorphous carbon is further formed on the surface of the halocarbon in the form of plasma, forming a shell structure composed of the halocarbon and amorphous carbon. This forms a core-shell structure that is structurally stable with the core structure of the material, significantly reducing the problem of silicon expansion and significantly improving the cycle performance of batteries using the material. The preparation method provided in the present application is simple, and the use of a plasma method to modify the silicon-carbon material makes it easy to mass-produce and industrialize. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a block diagram of the steps for preparing a silicon carbon composite material according to a specific embodiment of the present invention. [Figure 2] FIG. 1 is an SEM image of the silicon carbon composite material prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] Referring to FIG. 1, this embodiment provides a method for preparing silicon carbon composite materials by plasma modification, which includes at least the following operation steps S10) to S30).

[0020] In step S10, the aminated porous carbon is placed in a deposition chamber, and silane gas (preferably a mixture of silane and inert gas, where the volume ratio of silane to inert gas is 1:5-15, more preferably 1:8-12) is passed through the deposition chamber at a flow rate of 100-1000 ml / min. The silane gas is passed through the deposition chamber at a temperature of 400-600°C for at least 30 minutes (preferably 30-300 minutes), depositing nanosilicon on the aminated porous carbon to obtain a silicon-carbon precursor material.

[0021] In step S20), the silicon carbon precursor material obtained in step S10) is transferred to a plasma process modification chamber, and halogen gas is passed through the plasma process modification chamber in the form of plasma to deposit the generated halogen ions on the surface of the silicon carbon precursor material, thereby obtaining a silicon carbon precursor material coated with halocarbon. Preferably, in step S20), the parameters of the plasma process modification chamber are set to a vacuum degree of 1 to 10°C, in order to further promote the coating and deposition effect of halocarbon. Pa The temperature is set to 300 to 600°C, the power of the plasma method is set to 500 to 1000 W, and / or the flow rate of the halogen gas is set to 100 to 500 sccm, and the time for passing the halogen gas is set to at least 10 minutes, more preferably 10 to 60 minutes, and preferably in this step S20), the halogen gas is any one of fluorine, chlorine, and bromine, or a mixture of any two or more thereof.

[0022] In step S30), the flow of the halogen gas is stopped, and the carbon source gas is passed through the plasma-processing chamber in the form of plasma to obtain a silicon carbon composite material. Preferably, in order to further promote the coating deposition effect of amorphous carbon, the parameters of the plasma-processing chamber in step S30) are set to a vacuum degree of 1 to 10. Pa The temperature is set to 300 to 600°C, the power of the plasma method is set to 500 to 1000 W, and / or the flow rate of the carbon source gas is set to 100 to 500 sccm, and the time for passing the carbon source gas is set to at least 10 minutes, more preferably 10 to 60 minutes. Preferably, in this step S30), the carbon source gas is methane, ethylene, acetylene, or the like. NIt may be any one of these or a mixture of any two or more of them.

[0023] Preferably, in step S10) of this embodiment, the method for preparing aminated porous carbon includes: Step S11) of pre-acidifying the porous carbon with concentrated nitric acid to obtain acidified porous carbon; Step S12) of mixing the acidified porous carbon from step S11 with thionyl chloride and N,N-dimethylformamide and reacting at a temperature of 30 to 100°C for at least 1 hour to obtain chlorinated porous carbon; and step S13) of reacting the chlorinated porous carbon obtained in step S12) with aniline to obtain amidated porous carbon as aminated porous carbon.

[0024] More preferably, in step S10) of this embodiment, the method for preparing aminated porous carbon includes the following operation steps S11) to S13).

[0025] In S11), the porous carbon is added to concentrated nitric acid, and the mass ratio of the porous carbon to the concentrated nitric acid is 1:200-500. The mixture is heated under reflux at a temperature of 30-100°C for at least 1 hour, preferably 1-6 hours, to obtain acidified porous carbon. Preferably, in this step S11), the acidified porous carbon is washed with deionized water, filtered, and vacuum dried before proceeding to step S12).

[0026] In S12), the porous carbon acidified in step S11) is mixed with thionyl chloride and N,N-dimethylformamide in a mass ratio of acidified porous carbon, thionyl chloride, and N,N-dimethylformamide of 1:20-80:5-15, and reacted at a temperature of 30-100°C for at least 1 hour to obtain chlorinated porous carbon. Preferably, in this step S12), the chlorinated porous carbon is washed with tetrahydrofuran and dried before proceeding to step S13).

[0027] In S13), the chlorinated porous carbon obtained in step S12) is reacted with aniline at a temperature of 0 to 40°C for at least 1 hour to obtain amidated porous carbon as aminated porous carbon, in which the mass ratio of chlorinated porous carbon to aniline is 1:10 to 30. Preferably, in this step S13), the amidated porous carbon prepared by the reaction is washed with acetone until it becomes colorless, and then used as the aminated porous carbon in step S10) of this embodiment.

[0028] Preferably, the silicon carbon composite is prepared by the method for preparing a silicon carbon composite by plasma modification as described above, wherein the silicon carbon composite has a core-shell structure consisting of a core and a shell, the core comprises a nitrogen-doped silicon carbon composite, and the shell comprises a halogenated carbon and amorphous carbon.

[0029] Preferably, the silicon carbon composite material is used as an active material raw material for the manufacture of an electrode sheet for a battery, preferably as an active material raw material for the manufacture of an anode sheet for a lithium ion battery, but this can be applied as needed.

[0030] In order to allow those skilled in the art to easily understand the technical solutions of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention, and of course, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without any creative efforts shall fall within the protection scope of the present invention.

[0031] Based on the above-mentioned embodiments, the present application further provides the following specific Examples 1 to 3.

[0032] It should be noted that in all of the specific Examples 1 to 3, aminated porous carbon was prepared by the following steps S11) to S13).

[0033] In S11), 10 g of porous carbon was added to 300 g of concentrated nitric acid, heated under reflux at 80°C for 3 hours, allowed to stand, washed with deionized water, filtered, and dried in vacuum at 80°C for 24 hours to obtain acidified porous carbon.

[0034] In S12), 1 g of the acidified porous carbon obtained in the previous step S11) was taken and added to 60 g of thionyl chloride, and at the same time, 10 g of N,N-dimethylformamide was added, and the mixture was reacted at a temperature of 80°C for 3 hours, after which it was washed with tetrahydrofuran (abbreviated as "THF") and dried to obtain chlorinated porous carbon.

[0035] In S13), 1 g of chlorinated porous carbon obtained in the previous step S12) was reacted with 20 g of aniline at a temperature of 20°C for 3 hours, and then washed with acetone until it became colorless, thereby obtaining amidated porous carbon as aminated porous carbon.

[0036] Example 1: A silicon carbon composite material was prepared by the following steps S10) to S30).

[0037] In step S10, 100 g of aminated porous carbon was placed in a deposition chamber, and a silane mixed gas (volume ratio of silane gas to argon gas = 1:10) was first passed through the deposition chamber. The temperature of the deposition chamber was set to 500°C, the flow rate of the silane mixed gas was set to 50 ml / min, and the passage time was set to 90 minutes. Nanosilicon was then deposited on the aminated porous carbon, and a silicon-carbon precursor material was obtained.

[0038] In step S20), 100 g of the silicon carbon precursor material obtained in step S10) is transferred to a plasma-processing chamber, and chlorine gas in the form of plasma is passed through the plasma-processing chamber, where the parameters of the plasma-processing chamber are a vacuum degree of 5 Pa The temperature was set to 400°C, the plasma power was set to 800 W, the chlorine gas flow rate was set to 300 sccm, and the time for passing the gas was set to 30 minutes. The generated chlorine ions were deposited on the surface of the silicon carbon precursor material, and a silicon carbon precursor material coated with carbon chloride was obtained.

[0039] In step S30, the flow of chlorine gas is stopped, and methane gas in the form of plasma is passed through the plasma reforming chamber to obtain a silicon carbon composite material. Here, the parameters of the plasma reforming chamber are a vacuum degree of 5°C, a pressure of 1000kJ / cm2, a temperature of 1000kJ / cm2, a pressure ... Pa The temperature was set to 400° C., the power of the plasma method was set to 800 W, the flow rate of methane gas was set to 300 sccm, and the time for passing the gas was set to 30 minutes.

[0040] The silicon carbon composite material obtained in this Example 1 has a core-shell structure consisting of a core and a shell, where the core contains the nitrogen-doped silicon carbon composite material, and the shell contains carbon chloride and amorphous carbon coated on the surface of the carbon chloride.

[0041] The present application conducted SEM testing on the silicon carbon composite material prepared in Example 1, and the test results are shown in Figure 2. As can be seen from Figure 2, the silicon carbon composite material provided in Example 1 exhibits a spherical structure with uniform particle size distribution and slight bonding, and the material particle size distribution is reasonable, with the particle size ranging from 1 to 5 μm.

[0042] Example 2: A silicon carbon composite material was prepared by the following steps S10) to S30).

[0043] In step S10, 100 g of aminated porous carbon was placed in a deposition chamber, and a silane mixed gas (volume ratio of silane gas to argon gas = 1:10) was first passed through the deposition chamber. The temperature of the deposition chamber was set to 400°C, the flow rate of the silane mixed gas was set to 10 ml / min, and the passage time was set to 300 minutes. Nanosilicon was then deposited on the aminated porous carbon, and a silicon-carbon precursor material was obtained.

[0044] In step S20), 100 g of the silicon carbon precursor material obtained in step S10) is transferred to a plasma-processing chamber, and fluorine gas in the form of plasma is passed through the plasma-processing chamber, where the parameters of the plasma-processing chamber are a vacuum degree of 1. PaThe temperature was set to 300°C, the plasma power to 500 W, the fluorine gas flow rate to 100 sccm, and the time to pass the gas through the chamber was set to 60 minutes. The generated fluorine ions were deposited on the surface of the silicon carbon precursor material, yielding a silicon carbon precursor material coated with fluorocarbon.

[0045] In step S30, the flow of fluorine gas is stopped, and ethylene gas in the form of plasma is passed through the plasma process reforming chamber to obtain a silicon carbon composite material. Here, the parameters of the plasma process reforming chamber are a degree of vacuum of 1. Pa The temperature was set to 300° C., the power of the plasma method was set to 500 W, the flow rate of ethylene gas was set to 100 sccm, and the time for passing the gas was set to 60 minutes.

[0046] The silicon carbon composite material obtained in this example has a core-shell structure consisting of a core and a shell, where the core contains the nitrogen-doped silicon carbon composite material, and the shell contains fluorocarbon and amorphous carbon coated on the surface of the fluorocarbon.

[0047] Example 3: A silicon carbon composite material was prepared by the following steps S10) to S30).

[0048] In step S10, 100 g of aminated porous carbon was placed in a deposition chamber, and a silane mixed gas (volume ratio of silane gas to argon gas = 1:10) was first passed through the deposition chamber. The temperature of the deposition chamber was set to 600°C, the flow rate of the silane mixed gas was set to 100 ml / min, and the passage time was set to 30 minutes. Nanosilicon was then deposited on the aminated porous carbon, and a silicon-carbon precursor material was obtained.

[0049] In step S20), 100 g of the silicon carbon precursor material obtained in step S10) is transferred to a plasma-processing chamber, and bromine gas is passed through the plasma-processing chamber in the form of plasma. The parameters of the plasma-processing chamber include a vacuum level of 10 PaThe temperature was set to 600°C, the plasma power to 1000 W, the bromine gas flow rate to 500 sccm, and the time for passing the gas to 10 minutes. The generated bromine ions were deposited on the surface of the silicon carbon precursor material, and a silicon carbon precursor material coated with carbon bromide was obtained.

[0050] In step S30, the flow of bromine gas is stopped, and acetylene gas is passed through the plasma reforming chamber in the form of plasma to obtain a silicon carbon composite material. Here, the parameters of the plasma reforming chamber are a vacuum degree of 10 Pa The temperature was set to 500°C, the power of the plasma method was set to 1000 W, the flow rate of acetylene gas was set to 500 sccm, and the time for passing the gas was set to 10 minutes.

[0051] The silicon carbon composite material obtained in this Example 3 has a core-shell structure consisting of a core and a shell, where the core contains the nitrogen-doped silicon carbon composite material, and the shell contains carbon bromide and amorphous carbon coated on the surface of the carbon bromide.

[0052] Comparative Example 1: The other technical solutions of this Comparative Example 1 are the same as those of Example 1, except that in this Comparative Example 1, porous carbon (purchased directly) was used instead of the aminated porous carbon of Example 1.

[0053] Comparative Example 2: The other technical solutions of this Comparative Example 2 are the same as those of Example 1, except that in this Comparative Example 2, step S20) is omitted and step S30) of Example 1 is replaced as follows:

[0054] In step S30), 100 g of the silicon-carbon precursor material obtained in step S10) is transferred to a plasma-processing chamber, and ethylene gas is passed through the plasma-processing chamber to obtain a silicon-carbon composite material, where the parameters of the plasma-processing chamber are a vacuum degree of 1. Pa The temperature was set to 300° C., the power of the plasma method was set to 500 W, the flow rate of ethylene gas was set to 100 sccm, and the time for passing the gas was set to 60 minutes.

[0055] Comparative Example 3: Using the halogen-doped silicon carbon nanomaterial disclosed in Example 1 of CN105047894A, this was prepared as follows: 10 g of silicon nanoparticles and 10 g of carbon source were uniformly dispersed in 200 mL of ethanol solution (polyvinylidene fluoride, polyvinylidene chloride, and polytetrafluoroethylene in a molar ratio of 1:2:1). After uniform stirring, the mixture was ball milled for 3 hours and then dried in an oven at 100°C for 12 hours. Finally, the mixture was carbonized in a nitrogen atmosphere at a heating rate of 5°C / min up to 800°C, maintained at this temperature for 2 hours, and then cooled to obtain the halogen-doped silicon carbon nanomaterial.

[0056] In order to compare and verify the effects of the above Examples and Comparative Examples, the present application carried out the following physicochemical tests on the composite materials obtained in Examples 1 to 3 and Comparative Examples 1 to 3.

[0057] (1) In accordance with the Chinese national standard GB / T 38823-2020 "Silicon Carbon," the specific surface area and tap density of each silicon carbon composite were tested. The electrical conductivity of each silicon carbon composite was tested using a four-point probe tester. The silicon grains of each silicon carbon composite were tested using XRD. The test results are shown in Table 1 below.

[0058] (2) Button battery testing:

[0059] The corresponding silicon carbon composite materials in Examples 1 to 3 and Comparative Examples 1 to 3 were used as negative electrode materials for lithium ion batteries, and button batteries were prepared according to the following method.

[0060] A binder, conductive agent, and solvent were added to each corresponding silicon carbon composite material, and the mixture was stirred to form a paste. This paste was then applied to copper foil, dried, and rolled to obtain a negative electrode sheet. The binder used was LA132, the conductive agent was SP (conductive carbon black), and the solvent was NMP. The ratio of the silicon carbon composite material, SP, LA132, and NMP used was 95g:1g:4g:220mL. The electrolyte was a solution containing LiPF6 as an electrolyte, with a concentration of 1mol / L. The solvent was a mixture of EC and DEC in a volume ratio of 1:1. A metallic lithium sheet was used as the counter electrode, and a polypropylene (PP) membrane was used as the diaphragm.

[0061] Each button battery was assembled in an argon-filled glove box and then tested for electrochemical performance. Specifically, the electrochemical performance was tested using a Wuhan Land CT2001A battery tester with a charge / discharge voltage range of 0.005V to 2.0V and a charge / discharge rate of 0.1C. The test results are shown in Table 1 below.

[0062] The negative electrode sheet of the above button battery was also fully charged and expanded. The specific testing process was as follows: The thickness D1 of the negative electrode sheet of the button battery after rolling was tested, and then the button battery was fully charged to 100% SOC to measure the fully charged thickness D2 of the negative electrode sheet. The expansion rate (expansion rate = (D2 - D1) / D1 * 100%) was calculated, and the test results are shown in Table 1 below.

[0063] As can be seen from the data in Table 1 above, the silicon carbon composite materials prepared in Examples 1 to 3 of the present application are significantly superior to Comparative Examples 1 to 3 in terms of initial efficiency and expansion at full charge.

[0064] (3) Pouch performance test:

[0065] The corresponding silicon carbon composite materials in Examples 1 to 3 and Comparative Examples 1 to 3 were doped with 90% artificial graphite as the negative electrode material (i.e., negative electrode sheet) to form the positive electrode ternary material (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3O2), electrolyte and diaphragm were assembled to produce a 5 Ah pouch battery. Here, the diaphragm was made of Celegard 2400, and the electrolyte was prepared as LiPF6 solution (the solvent was a mixed solution of EC and DEC in a volume ratio of 1:1, and the LiPF6 concentration was 1.3 mol / L), and a pouch battery was produced.

[0066] The following performance tests were carried out on each pouch battery.

[0067] a. Liquid absorption test: Using a 1 mL burette, V mL of electrolyte was drawn up and one drop was placed on the surface of each negative electrode sheet. The time until the electrolyte was completely absorbed was measured as time t, and the liquid absorption rate S of the negative electrode sheet was calculated as V / t. The test results are shown in Table 2 below.

[0068] b. Liquid retention rate test: The theoretical liquid absorption amount m1 of the corresponding sheet is calculated from the parameters of each negative electrode sheet, the weight of the negative electrode sheet is measured as m2, and then the negative electrode sheet is immersed in the electrolyte for 24 hours, the weight of the negative electrode sheet is measured as m3, and the liquid absorption amount m3-m2 of the negative electrode sheet is calculated; and The calculation was performed according to the formula: Liquid retention rate = (m3-m2)*100% / m1, and the test results are shown in Table 2 below.

[0069] As can be seen from Table 2 above, the liquid absorption and retention rates of the silicon carbon composite materials provided in Examples 1 to 3 are superior to those of Comparative Examples 1 to 3.

[0070] c. Cycle performance test: A cycle performance test was conducted on each of the produced pouch batteries. The test conditions for the cycle performance test were a charge / discharge voltage range of 2.5 to 4.2 V, a temperature of 25±3.0°C, a charge / discharge rate of 1.0 C / 1.0 C, and 500 cycles. The test results are shown in Table 3 below.

[0071] As can be seen from Table 3 above, the cycle performance of the pouch lithium ion batteries fabricated using the silicon carbon composite materials provided in Examples 1-3 is significantly better than that of Comparative Examples 1-3.

[0072] d. Rate performance test: A rate performance test was conducted on each of the produced pouch batteries. The test conditions for the rate performance test were as follows: charge / discharge voltage range of 2.5 to 4.2 V, temperature of 25±3.0°C, charging at 1.0 C, 3.0 C, 5.0 C, 10.0 C, and discharging at 1.0 C, and the test results are shown in Table 4 below.

[0073] As can be seen from Table 4 above, the rate performance of the pouch lithium-ion batteries fabricated using the silicon carbon composites provided in Examples 1-3 is significantly better than that of Comparative Examples 1-3, i.e., the pouch batteries fabricated using the silicon carbon composites provided in Examples 1-3 have shorter charging times.

[0074] The present invention is not limited to the details of the illustrative examples set forth above, and it will be apparent to those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the present invention. Accordingly, the examples are to be considered in all respects as illustrative and not limiting, and the scope of the present invention is limited not by the above description but by the appended claims, and all modifications that come within the meaning and range of equivalent elements of the claims are intended to be embraced by the present invention. Any reference numerals appearing in the claims should not be construed as limiting the scope of those claims.

[0075] Furthermore, it should be understood that although the present specification is described according to embodiments, each embodiment does not include only one separate technical solution, and such description manner in the present specification is merely for the purpose of clarifying the description, and those skilled in the art should take the present specification as a whole, and the technical solutions of each example can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. Step S10) placing the aminated porous carbon into a deposition chamber, passing silane gas at a flow rate of 100-1000 ml / min into the deposition chamber, and passing the silane gas at a temperature of 400-600° C. for at least 30 minutes to deposit nanosilicon on the aminated porous carbon, thereby obtaining a silicon-carbon precursor material; Step S20) of transferring the silicon carbon precursor material obtained in step S10) to a plasma process modification chamber, passing a halogen gas in the form of plasma through the plasma process modification chamber, and depositing the generated halogen ions on the surface of the silicon carbon precursor material to obtain a silicon carbon precursor material coated with halocarbon; and (S30) stopping the flow of halogen gas and passing a carbon source gas in the form of plasma through the plasma modification chamber to obtain a silicon carbon composite material.

2. 2. The method for preparing a silicon carbon composite material by plasma modification according to claim 1, wherein in step S20, the parameters of the plasma modification chamber are set as follows: a degree of vacuum of 1 to 10 Pa, a temperature of 300 to 600°C, and a plasma power of 500 to 1000 W; and / or a flow rate of the halogen gas of 100 to 500 sccm and a time for passing the halogen gas for at least 10 minutes.

3. 2. The method for preparing a silicon carbon composite material by plasma modification according to claim 1, wherein in step S30, the parameters of the plasma modification chamber are set as follows: a degree of vacuum of 1 to 10 Pa, a temperature of 300 to 600°C, and a plasma power of 500 to 1000 W; and / or a flow rate of the carbon source gas of 100 to 500 sccm and a time for passing the carbon source gas of at least 10 minutes.

4. In the step S10), the method for preparing the aminated porous carbon comprises the steps of: Step S11) pre-acidifying the porous carbon with concentrated nitric acid to obtain acidified porous carbon; Step S12) of mixing the acidified porous carbon from step S11) with thionyl chloride and N,N-dimethylformamide and reacting at a temperature of 30 to 100° C. for at least 1 hour to obtain chlorinated porous carbon; and step S13) reacting the chlorinated porous carbon obtained in step S12) with aniline to obtain amidated porous carbon as the aminated porous carbon.

5. The method for preparing the aminated porous carbon includes the steps of: Step S11) adding the porous carbon to concentrated nitric acid in a mass ratio of the porous carbon to concentrated nitric acid of 1:200-500, and heating under reflux at a temperature of 30-100°C for at least 1 hour to obtain acidified porous carbon; Step S12) of mixing the acidified porous carbon in step S11) with thionyl chloride and N,N-dimethylformamide in a mass ratio of the acidified porous carbon, thionyl chloride, and N,N-dimethylformamide of 1:20 to 80:5 to 15, and reacting at a temperature of 30 to 100°C for at least 1 hour to obtain chlorinated porous carbon; and step S13) of reacting the chlorinated porous carbon obtained in step S12) with aniline at a temperature of 0 to 40°C for at least 1 hour to obtain amidated porous carbon as the aminated porous carbon, in which the mass ratio of the chlorinated porous carbon to the aniline is 1:10 to 30.

6. 2. The method for preparing a silicon carbon composite material by plasma modification according to claim 1, wherein in step S20, the halogen gas is any one of fluorine, chlorine, and bromine, or a mixture of any two or more thereof.

7. 2. The method for preparing a silicon carbon composite material by plasma modification according to claim 1, wherein in step S30, the carbon source gas is any one of methane, ethylene, and acetylene, or a mixture of any two or more thereof.

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