Plasma modification preparation method for silicon-carbon composite material, silicon-carbon composite material, and use

Abstract

A plasma modification preparation method for a silicon-carbon composite material, a silicon-carbon composite material, and a use. The method at least comprises operation steps of: S10) placing aminated porous carbon in a deposition cavity, introducing silane gas into the deposition cavity, and depositing nanosilicon in the aminated porous carbon to obtain a silicon-carbon precursor material; S20), transferring the silicon-carbon precursor material into a plasma method modification cavity, introducing halogen gas by means of a plasma method, and depositing generated halide ions on the surface of the silicon-carbon precursor material to obtain a halocarbon-coated silicon-carbon precursor material; and S30) stopping introducing the halogen gas, and introducing carbon source gas by means of the plasma method. The prepared silicon-carbon composite material has a stable core-shell structure, and can significantly mitigate the problem of silicon expansion and significantly improve the cycle performance of batteries using the silicon-carbon composite material. In addition, the process is simple, a silicon-carbon material is modified by using a plasma method, and large-batch preparation and large-scale industrialization are easy to achieve.

Description

Plasma modification preparation method of silicon-carbon composite material, silicon-carbon composite material and application thereof

[0001] This application claims priority to a Chinese patent application filed with the Patent Office of the State Intellectual Property Office of China on June 27, 2023, with application number 2023107730517 and invention name “Plasma modification preparation method of silicon-carbon composite materials, silicon-carbon composite materials and applications”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present invention belongs to the field of lithium ion battery material preparation, and specifically relates to a plasma modification preparation method of a silicon-carbon composite material. The present invention also relates to the silicon-carbon composite material obtained by the preparation method and its application. Background Art

[0003] Silicon-carbon composites are widely used in high-energy-density lithium-ion batteries due to their high energy density and abundant material resources. Conventional preparation methods involve depositing nanosilicon within porous carbon via silane cracking and then coating it with amorphous carbon via vapor deposition at temperatures between 700°C and 1000°C. However, the resulting silicon-carbon composites suffer from structural instability in the outer carbon coating and significant silicon expansion due to silicon grain growth at temperatures between 700°C and 1000°C, significantly negatively impacting battery cycling performance.

[0004] Therefore, the applicant hopes to seek technical solutions to improve the above technical problems.

[0005] Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a plasma modification preparation method of a silicon-carbon composite material, a silicon-carbon composite material and its application. The prepared silicon-carbon composite material forms a structurally stable core-shell structure, which can significantly reduce the silicon expansion problem and significantly improve the cycle performance of the battery used therein; in addition, the preparation method provided in this application has a simple process, and the silicon-carbon material is modified by a plasma method, which is easy to achieve large-scale preparation and easy to industrialize on a large scale.

[0007] The technical solution adopted in the present invention is as follows:

[0008] A plasma modification preparation method for a silicon-carbon composite material comprises at least the following steps:

[0009] S10), placing the amino-treated porous carbon in a deposition chamber, introducing silane gas at a flow rate of 100-1000 ml / min into the deposition chamber, and introducing the silane gas at a temperature of 400-600° C. for at least 30 minutes to deposit nano-silicon in the amino-treated porous carbon to obtain a silicon-carbon precursor material;

[0010] S20), transferring the silicon-carbon precursor material obtained in step S10) into a plasma modification chamber, introducing a halogen gas into the plasma modification chamber by plasma, and generating halogen ions to deposit on the surface of the silicon-carbon precursor material to obtain a halocarbon-coated silicon-carbon precursor material;

[0011] S30), stopping the introduction of the halogen gas, and introducing a carbon source gas into the plasma modification chamber by plasma to obtain the silicon-carbon composite material.

[0012] Preferably, in step S20), the parameters of the plasma modification chamber are set as follows: vacuum degree is 1-10 Pa, temperature is 300-600 ° C, output power of the plasma method is 500-1000 W; and / or the flow rate of the halogen gas is 100-500 sccm, and the introduction time is at least 10 minutes.

[0013] Preferably, in step S30), the parameters of the plasma modification chamber are set as follows: vacuum degree is 1-10 Pa, temperature is 300-600 ° C, output power of the plasma method is 500-1000 W; and / or the flow rate of the carbon source gas is 100-500 sccm, and the introduction time is at least 10 minutes.

[0014] Preferably, in step S10), the method for preparing the amino-modified porous carbon comprises the following steps:

[0015] S11), pre-acidifying the porous carbon with concentrated nitric acid to obtain acid-treated porous carbon;

[0016] S12), mixing the porous carbon treated by acidification in step S11) with thionyl chloride and N,N-dimethylformamide, and reacting them at a temperature of 30-100° C. for at least 1 hour to obtain chlorinated porous carbon;

[0017] S13), reacting the chlorinated porous carbon obtained in step S12) with aniline to obtain amidated porous carbon, which is used as the amination porous carbon.

[0018] Preferably, the preparation method of the amino-modified porous carbon comprises the following steps:

[0019] S11), adding the porous carbon to concentrated nitric acid, wherein the mass ratio of the porous carbon to the concentrated nitric acid is 1:200-500, and heating under reflux at a temperature of 30-100° C. for at least 1 hour to obtain an acidified porous carbon;

[0020] S12), mixing the porous carbon treated by acidification in step S11) with thionyl chloride and N,N-dimethylformamide, wherein the mass ratio of the acidified porous carbon, thionyl chloride and N,N-dimethylformamide is 1:20-80:5-15, and reacting at a temperature of 30-100° C. for at least 1 hour to obtain chlorinated porous carbon;

[0021] S13), reacting the chlorinated porous carbon obtained in step S12) with aniline at a temperature of 0-40°C for at least 1 hour to obtain amidated porous carbon, which is used as the amination porous carbon; wherein the mass ratio of the chlorinated porous carbon to aniline is 1:10-30.

[0022] 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 acyl chloride 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.

[0023] Preferably, in step S20), the halogen gas is one of fluorine gas, chlorine gas, and bromine gas, or a mixture of any of them.

[0024] Preferably, in step S30), the carbon source gas is one of methane, ethylene, acetylene, and ethylene, or a mixture of any of them.

[0025] Preferably, a silicon-carbon composite material is provided, wherein the silicon-carbon composite material is prepared by the plasma modification preparation method of the silicon-carbon composite material as described above, wherein the silicon-carbon composite material includes a core-shell structure consisting of a core and an outer shell, the core includes a nitrogen-doped silicon-carbon composite material, and the outer shell includes a halogenated carbon and amorphous carbon.

[0026] Preferably, an 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 preparing battery pole pieces, preferably as an active material raw material for lithium-ion battery negative pole pieces.

[0027] The present invention utilizes the amino groups on the surface of the amidated porous carbon to form chemical bonds with the silicon free radicals generated by the decomposition of silane gas, thereby improving the stability of the core structure of the material and improving the cycle performance of the battery to which it is applied. The present invention further adopts a plasma method to introduce halogen gas into the silicon-carbon precursor material (as the core structure) to form a halogenated carbon coated on the surface of the silicon-carbon precursor material. Compared with the conventional vapor deposition method, the diffusion of halogen ions in the material can be promoted, and the halogenation time and the halogenation temperature can be significantly shortened, thereby further reducing the impact on the growth of silicon grains. At the same time, after the formation of the halogenated carbon, the present application further forms amorphous carbon on the surface of the halogenated carbon by a plasma method, forming an outer shell structure composed of halogenated carbon and amorphous carbon, forming a structurally stable core-shell structure with the core structure of the material, which can significantly reduce the silicon expansion problem and significantly improve the cycle performance of the battery to which it is applied. In addition, the preparation method provided by the present application is simple in process, and the silicon-carbon material is modified by a plasma method, which is easy to achieve large-scale preparation and easy to scale industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG1 is a block diagram of the steps for preparing a silicon-carbon composite material according to a specific embodiment of the present invention;

[0029] FIG2 is a SEM image of the silicon-carbon composite material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0030] Referring to FIG1 , this embodiment provides a plasma modification preparation method for a silicon-carbon composite material, which includes at least the following steps:

[0031] S10), placing the amino-treated porous carbon into a deposition chamber, introducing silane gas at a flow rate of 100-1000 ml / min into the deposition chamber (the silane gas is preferably a mixed gas of silane and an inert gas, wherein the volume ratio of silane to the inert gas is 1:5-15, more preferably 1:8-12), and introducing the silane gas at a temperature of 400-600° C. for at least 30 minutes (preferably 30-300 minutes) to deposit nano-silicon in the amino-treated porous carbon to obtain a silicon-carbon precursor material;

[0032] S20), transferring the silicon-carbon precursor material obtained in step S10) into a plasma modification chamber, introducing a halogen gas into the plasma modification chamber by plasma, and the generated halogen ions are deposited on the surface of the silicon-carbon precursor material to obtain a halocarbon-coated silicon-carbon precursor material; preferably, in order to further facilitate the halocarbon coating deposition effect, in this step S20), the parameters of the plasma modification chamber are set to: a vacuum degree of 1-10 Pa, a temperature of 300-600 ° C, an output power of the plasma method of 500-1000 W; and / or a flow rate of the halogen gas of 100-500 sccm, a passage time of at least 10 minutes, and more preferably a passage time of 10-60 minutes; preferably, in this step S20), the halogen gas is one of fluorine, chlorine, and bromine, or a mixture of any of them;

[0033] S30), stop introducing halogen gas, and introduce carbon source gas into the plasma modification chamber through plasma to obtain a silicon-carbon composite material; preferably, in order to further facilitate the coating deposition effect of amorphous carbon, in this step S30), the parameters of the plasma modification chamber are set to: vacuum degree of 1-10pa, temperature of 300-600°C, output power of the plasma method of 500-1000W; and / or the flow rate of the carbon source gas is 100-500sccm, the introduction time is at least 10 minutes, and the introduction time is more preferably 10-60 minutes; preferably, in this step S30), the carbon source gas is one of methane, ethylene, acetylene, ethylene or a mixture of any of them.

[0034] Preferably, in step S10) of this embodiment, the method for preparing the amination-modified porous carbon includes the following steps:

[0035] S11), pre-acidifying the porous carbon with concentrated nitric acid to obtain acid-treated porous carbon;

[0036] S12), mixing the porous carbon treated by acidification in step S11) with thionyl chloride and N,N-dimethylformamide, and reacting them at a temperature of 30-100° C. for at least 1 hour to obtain chlorinated porous carbon;

[0037] S13), reacting the chlorinated porous carbon obtained in step S12) with aniline to obtain amidated porous carbon, which is used as amination porous carbon.

[0038] Further preferably, in step S10) of this embodiment, the method for preparing the amination-modified porous carbon comprises the following steps:

[0039] S11), adding porous carbon to concentrated nitric acid, with a mass ratio of porous carbon to concentrated nitric acid of 1:200-500, and heating and refluxing at a temperature of 30-100° C. for at least 1 hour, preferably a heating and refluxing time of 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 the next step S12);

[0040] S12), mixing the porous carbon treated by acidification in step S11) with thionyl chloride and N,N-dimethylformamide, wherein the mass ratio of the acidified porous carbon, thionyl chloride and N,N-dimethylformamide is 1:20-80:5-15, and reacting 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);

[0041] S13), reacting the chlorinated porous carbon obtained in step S12) with aniline at a temperature of 0-40°C for at least 1 hour to obtain amidated porous carbon, which is used as the amidated porous carbon; wherein the mass ratio of the chlorinated porous carbon to the aniline is 1:10-30; preferably, in this step S13), the amidated porous carbon prepared by the reaction is washed with acetone until it is colorless, and then used as the amidated porous carbon in step S10) of this embodiment.

[0042] Preferably, a silicon-carbon composite material is prepared by the plasma modification preparation method of the silicon-carbon composite material as described above, wherein the silicon-carbon composite material includes a core-shell structure consisting of a core and an outer shell, the core includes a nitrogen-doped silicon-carbon composite material, and the outer shell includes halogenated carbon and amorphous carbon.

[0043] Preferably, an 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 preparing battery pole pieces, preferably as an active material raw material for lithium-ion battery negative pole pieces. Of course, it can also be used as required.

[0044] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0045] Based on the above-described embodiments, the present application further proposes the following specific examples 1-3:

[0046] It should be noted that the amino-modified porous carbons in Examples 1-3 were prepared using the following steps:

[0047] S11), adding 10 g of porous carbon to 300 g of concentrated nitric acid, heating and refluxing at 80° C. for 3 hours, standing and washing with deionized water, filtering, and then vacuum drying at 80° C. for 24 hours to obtain acidified porous carbon;

[0048] S12), taking 1 g of the acidified porous carbon obtained in step S11) and adding it to 60 g of thionyl chloride, and simultaneously adding 10 g of N,N-dimethylformamide, reacting at a temperature of 80° C. for 3 hours, then washing with tetrahydrofuran (abbreviated as “THF”) and drying to obtain chlorinated porous carbon;

[0049] S13), taking 1g of the chlorinated porous carbon obtained in step S12) and reacting it with 20g of aniline at a temperature of 20°C for 3 hours, and then washing it with acetone until it is colorless to obtain amidated porous carbon, which is used as the amination porous carbon.

[0050] Example 1: A silicon-carbon composite material was prepared according to the following steps:

[0051] Step S10), placing 100 g of amino-treated porous carbon into a deposition chamber, first introducing a silane mixed gas (silane gas: argon gas volume ratio = 1:10) into the deposition chamber, setting the temperature of the deposition chamber at 500° C., the flow rate of the silane mixed gas at 50 ml / min, and the introduction time for 90 minutes, depositing nano-silicon in the amino-treated porous carbon to obtain a silicon-carbon precursor material;

[0052] Step S20), transferring 100 g of the silicon-carbon precursor material obtained in step S10) into a plasma modification chamber, and introducing chlorine gas into the plasma modification chamber by plasma, wherein the parameters of the plasma modification chamber are set as follows: vacuum degree of 5 Pa, temperature of 400 ° C, output power of the plasma method of 800 W, flow rate of chlorine gas of 300 sccm, and introduction time of 30 minutes; the generated chloride ions are deposited on the surface of the silicon-carbon precursor material to obtain a chlorinated carbon-coated silicon-carbon precursor material;

[0053] S30), stop introducing chlorine gas, and introduce methane gas into the plasma modification chamber through plasma to obtain a silicon-carbon composite material; wherein the parameters of the plasma modification chamber are set as: vacuum degree is 5 Pa, temperature is 400 ° C, output power of the plasma method is 800 W; flow rate of methane gas is 300 sccm, and introduction time is 30 minutes.

[0054] The silicon-carbon composite material obtained in Example 1 comprises a core-shell structure consisting of a core and an outer shell, wherein the core comprises the nitrogen-doped silicon-carbon composite material, and the outer shell comprises chlorinated carbon and amorphous carbon coated on the surface of the chlorinated carbon.

[0055] The present application conducted an SEM test on the silicon-carbon composite material prepared in Example 1. The test results are shown in Figure 2. As can be seen from Figure 2, the silicon-carbon composite material provided in this Example 1 has a spherical structure, a uniform size distribution, and slight adhesion, and the material particle size distribution is reasonable, and the particle size is between 1-5 μm.

[0056] Example 2: A silicon-carbon composite material was prepared according to the following steps:

[0057] Step S10), placing 100 g of amino-treated porous carbon into a deposition chamber, first introducing a silane mixed gas (silane gas: argon gas volume ratio = 1:10) into the deposition chamber, setting the temperature of the deposition chamber at 400 ° C, the flow rate of the silane mixed gas at 10 ml / min, and the introduction time for 300 minutes, depositing nano-silicon in the amino-treated porous carbon to obtain a silicon-carbon precursor material;

[0058] Step S20), transferring 100 g of the silicon-carbon precursor material obtained in step S10) into a plasma modification chamber, and introducing fluorine gas into the plasma modification chamber by plasma, wherein the parameters of the plasma modification chamber are set as follows: vacuum degree of 1 Pa, temperature of 300 ° C, output power of the plasma method of 500 W, flow rate of fluorine gas of 100 sccm, and introduction time of 60 minutes; the generated fluorine ions are deposited on the surface of the silicon-carbon precursor material to obtain a fluorinated carbon-coated silicon-carbon precursor material;

[0059] S30), stop introducing fluorine gas, and introduce ethylene gas into the plasma modification chamber through plasma to obtain a silicon-carbon composite material; wherein the parameters of the plasma modification chamber are set as: vacuum degree is 1 Pa, temperature is 300 ° C, output power of the plasma method is 500 W; flow rate of ethylene gas is 100 sccm, and introduction time is 60 minutes.

[0060] The silicon-carbon composite material obtained in this Example 2 includes a core-shell structure consisting of a core and an outer shell, wherein the core includes the nitrogen-doped silicon-carbon composite material, and the outer shell includes carbon fluoride and amorphous carbon coated on the surface of the carbon fluoride.

[0061] Example 3: A silicon-carbon composite material was prepared according to the following steps:

[0062] Step S10), placing 100 g of amino-treated porous carbon into a deposition chamber, first introducing a silane mixed gas (silane gas: argon gas volume ratio = 1:10) into the deposition chamber, setting the temperature of the deposition chamber at 600 ° C, the flow rate of the silane mixed gas at 100 ml / min, and the introduction time for 30 minutes, depositing nano-silicon in the amino-treated porous carbon to obtain a silicon-carbon precursor material;

[0063] Step S20), transferring 100 g of the silicon-carbon precursor material obtained in step S10) into a plasma modification chamber, introducing bromine gas into the plasma modification chamber by plasma, wherein the parameters of the plasma modification chamber are set as follows: vacuum degree of 10 Pa, temperature of 600 ° C, output power of the plasma method of 1000 W, flow rate of bromine gas of 500 sccm, and introduction time of 10 minutes; the generated bromide ions are deposited on the surface of the silicon-carbon precursor material to obtain a brominated carbon-coated silicon-carbon precursor material;

[0064] S30), stop introducing bromine gas, and introduce acetylene gas into the plasma modification chamber through plasma to obtain a silicon-carbon composite material; wherein the parameters of the plasma modification chamber are set as: vacuum degree is 10 Pa, temperature is 500 ° C, output power of the plasma method is 1000 W; flow rate of acetylene gas is 500 sccm, and introduction time is 10 minutes.

[0065] The silicon-carbon composite material obtained in this Example 3 includes a core-shell structure consisting of a core and an outer shell, wherein the core includes the nitrogen-doped silicon-carbon composite material, and the outer shell includes carbon bromide and amorphous carbon coated on the surface of the carbon bromide.

[0066] Comparative Example 1: The remaining 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) is used to replace the amino-treated porous carbon in Example 1.

[0067] Comparative Example 2: The remaining 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 canceled, and step S30) of Example 1 is replaced as follows:

[0068] S30), transfer 100g of the silicon-carbon precursor material obtained in step S10) to a plasma modification chamber, and introduce ethylene gas into the plasma modification chamber by plasma to obtain a silicon-carbon composite material; wherein the parameters of the plasma modification chamber are set as: vacuum degree is 1pa, temperature is 300°C, output power of the plasma method is 500W; flow rate of ethylene gas is 100sccm, and introduction time is 60 minutes.

[0069] Comparative Example 3: Using the halogen-doped carbon-silicon nanomaterial disclosed in Example 1 of CN105047894A, the preparation method was as follows: 10g of silicon nanoparticles and 10g of a carbon source were evenly dispersed in 200mL of an ethanol solution containing polyvinylidene fluoride, polyvinylidene chloride, and polytetrafluoroethylene in a molar ratio of 1:2:1. After stirring, the mixture was ball-milled for 3 hours and dried in a 100°C oven for 12 hours. Finally, the mixture was carbonized in a nitrogen atmosphere at a heating rate of 5°C / min to 800°C, held for 2 hours, and cooled to obtain the halogen-doped carbon-silicon nanomaterial.

[0070] In order to compare and verify the effects of the above examples and comparative examples, the present application conducted the following physical and chemical tests on the composite materials obtained in the above examples 1-3 and comparative examples 1-3:

[0071] (1) The specific surface area and tap density of each silicon-carbon composite material were tested with reference to the national standard GB / T 38823-2020 "Silicon Carbon", the electrical conductivity of each silicon-carbon composite material was tested using a four-probe tester, and the silicon grains of each silicon-carbon composite material were tested by XRD; the test results are shown in Table 1 below.

[0072] (2) Button battery test:

[0073] The silicon-carbon composite materials corresponding to Examples 1-3 and Comparative Examples 1-3 were used as negative electrode materials for lithium-ion batteries to prepare button batteries according to the following method:

[0074] A binder, a conductive agent and a solvent were added to each corresponding silicon-carbon composite material, stirred to form a slurry, coated on a copper foil, and 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 usage ratio of the silicon-carbon composite material, SP, LA132, and NMP was 95g:1g:4g:220mL; the electrolyte was a solution with LiPF6 as the electrolyte with a concentration of 1 mol / L, wherein the solvent was a mixture of EC and DEC with a volume ratio of 1:1; the metal lithium sheet was the counter electrode, and the diaphragm was a polypropylene (PP) film.

[0075] Each button cell was assembled in an argon-filled glove box, and then the electrochemical performance was tested. Specifically, the electrochemical performance was tested on a Wuhan Blue Power CT2001A battery tester. The charge and discharge voltage range was 0.005V to 2.0V, and the charge and discharge rate was 0.1C. The test results are shown in Table 1 below.

[0076] The negative electrode sheets of the above button batteries were also tested for expansion when fully charged. The specific test process was as follows: the thickness D1 of the negative electrode sheet of the rolled button battery sheet was tested, and then the full-charge thickness D2 of the negative electrode sheet was dissected when the button battery was fully charged to 100% SOC, and then the expansion rate was calculated (expansion rate = (D2-D1) / D1*100%); the test results are shown in Table 1 below.

[0077] Table 1

[0078] It can be seen from the data in Table 1 above that the silicon-carbon composite materials prepared in Examples 1-3 of the present application are significantly better than those in Comparative Examples 1-3 in terms of initial efficiency and full-charge expansion.

[0079] (3) Soft pack performance test:

[0080] The silicon-carbon composite materials corresponding to Examples 1-3 and Comparative Examples 1-3 were doped with 90% artificial graphite as negative electrode materials (i.e., negative electrode sheets), and the positive electrode ternary materials (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2), electrolyte and diaphragm are assembled into a 5Ah soft-pack battery; wherein, the diaphragm is celegard 2400, the electrolyte is LiPF6 solution (the solvent is a mixed solution of EC and DEC with a volume ratio of 1:1, and the concentration of LiPF6 is 1.3 mol / L) to prepare the soft-pack battery.

[0081] The following performance tests are performed on each soft pack battery:

[0082] a. Liquid Absorption Capacity Test: Use a 1mL burette and draw VmL of electrolyte. Add one drop of electrolyte to the surface of each negative electrode. Measure the time until the electrolyte is completely absorbed. Record the time t and calculate the liquid absorption rate S = V / t for each negative electrode. The test results are shown in Table 2 below.

[0083] b. Liquid retention rate test: Calculate the theoretical liquid absorption m1 of the corresponding negative electrode according to the parameters of each negative electrode, and weigh the weight of the negative electrode as m2. Then, place the negative electrode in the electrolyte and soak it for 24 hours. Weigh the weight of the negative electrode as m3. Calculate the liquid absorption of the negative electrode as m3-m2 according to the following formula:

[0084] Liquid retention rate = (m3-m2)*100% / m1; the test results are shown in Table 2 below.

[0085] Table 2

[0086] It can be seen from Table 2 above that the liquid absorption and retention capabilities of the silicon-carbon composite materials provided by Examples 1-3 are higher than those of Comparative Examples 1-3.

[0087] c. Cycle Performance Test: The prepared soft-pack batteries were subjected to a cycle performance test. The test conditions for the cycle performance test were: a charge and discharge voltage range of 2.5 to 4.2 V, a temperature of 25 ± 3.0°C, a charge and discharge rate of 1.0 C / 1.0 C, and 500 cycles. The test results are shown in Table 3 below.

[0088] Table 3

[0089] As can be seen from Table 3 above, the cycle performance of the soft-pack lithium-ion batteries prepared using the silicon-carbon composite materials provided in Examples 1-3 is significantly better than that of Comparative Examples 1-3.

[0090] d. Rate performance test: The prepared soft-pack batteries were subjected to rate performance tests. The test conditions for the rate performance test were as follows: a charge and discharge voltage range of 2.5 to 4.2 V, a temperature of 25 ± 3.0°C, charging at 1.0 C, 3.0 C, 5.0 C, and 10.0 C, and discharging at 1.0 C. The test results are shown in Table 4 below.

[0091] Table 4

[0092] It can be seen from Table 4 above that the rate performance of the soft-pack lithium-ion batteries prepared using the silicon-carbon composite materials provided in Examples 1-3 is significantly better than that of Comparative Examples 1-3, that is, the soft-pack batteries prepared using the silicon-carbon composite materials provided in Examples 1-3 have a shorter charging time.

[0093] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0094] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A plasma modification preparation method for a silicon-carbon composite material, characterized in that: At least the following steps are included: S10), placing the aminated porous carbon in a deposition chamber, introducing silane gas at a flow rate of 100-1000 ml / min into the deposition chamber, introducing the silane gas at a temperature of 400-600° C. for at least 30 minutes, depositing nano-silicon in the aminated porous carbon, and obtaining a silicon-carbon precursor material; S20), transferring the silicon-carbon precursor material obtained in step S10) to a plasma modification chamber, introducing a halogen gas into the plasma modification chamber by plasma, and depositing the generated halogen ions on the surface of the silicon-carbon precursor material to obtain a halogenated carbon-coated silicon-carbon precursor material; S30), stopping the introduction of halogen gas, and introducing carbon source gas into the plasma modification chamber by plasma to obtain the silicon-carbon composite material.

2. The plasma modification preparation method of the silicon-carbon composite material according to claim 1, characterized in that: In the step S20), the parameters of the plasma modification chamber are set as follows: vacuum degree is 1-10pa, temperature is 300-600°C, output power of the plasma method is 500-1000W; and / or the flow rate of the halogen gas is 100-500sccm, and the introduction time is at least 10 minutes.

3. The plasma modification preparation method of the silicon-carbon composite material according to claim 1, characterized in that: In the step S30), the parameters of the plasma modification chamber are set as follows: vacuum degree is 1-10pa, temperature is 300-600°C, output power of the plasma method is 500-1000W; and / or the flow rate of the carbon source gas is 100-500sccm, and the introduction time is at least 10 minutes.

4. The plasma modification preparation method of the silicon-carbon composite material according to claim 1, characterized in that: In the step S10), the method for preparing the aminated porous carbon comprises the following steps: S11), pre-acidifying the porous carbon with concentrated nitric acid to obtain acid-treated porous carbon; S12), mixing the porous carbon treated by acidification in step S11) with thionyl chloride and N,N-dimethylformamide, and reacting them at a temperature of 30-100° C. for at least 1 hour to obtain chlorinated porous carbon; S13), reacting the chlorinated porous carbon obtained in step S12) with aniline to obtain an amidated The porous carbon is amidated porous carbon as the amination porous carbon.

5. The plasma modification preparation method of the silicon-carbon composite material according to claim 1, characterized in that: The preparation method of the amination porous carbon comprises the following steps: S11), adding porous carbon to concentrated nitric acid, wherein the mass ratio of the porous carbon to the concentrated nitric acid is 1:200-500, and heating under reflux at a temperature of 30-100° C. for at least 1 hour to obtain acid-treated porous carbon; S12), mixing the porous carbon treated by acidification in step S11) with thionyl chloride and N,N-dimethylformamide, wherein the mass ratio of the acidified porous carbon, thionyl chloride and N,N-dimethylformamide is 1:20-80:5-15, and reacting at a temperature of 30-100° C. for at least 1 hour to obtain chlorinated porous carbon; S13), reacting the chlorinated porous carbon obtained in step S12) with aniline at a temperature of 0-40°C for at least 1 hour to obtain amidated porous carbon, which is used as the amination porous carbon; wherein the mass ratio of the chlorinated porous carbon to aniline is 1:10-30.

6. The plasma modification preparation method of the silicon-carbon composite material according to claim 4 or 5, characterized in that: 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 acyl chloride 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.

7. The plasma modification preparation method of the silicon-carbon composite material according to claim 1, characterized in that: In the step S20), the halogen gas is one of fluorine gas, chlorine gas, and bromine gas, or a mixture of any of them.

8. The plasma modification preparation method of the silicon-carbon composite material according to claim 1, characterized in that: In the step S30), the carbon source gas is one of methane, ethylene, acetylene, ethylene, or a mixture of any of them.

9. A silicon-carbon composite material, characterized in that: The silicon-carbon composite material is prepared by the plasma modification preparation method of the silicon-carbon composite material according to one of claims 1-8, wherein the silicon-carbon composite material includes a core-shell structure consisting of a core and an outer shell, the core includes a nitrogen-doped silicon-carbon composite material, and the outer shell includes halogenated carbon and amorphous carbon.

10. An application of the silicon-carbon composite material according to claim 9, characterized in that: The silicon-carbon composite material is used as an active material raw material for preparing battery pole pieces, preferably as an active material raw material for lithium-ion battery negative pole pieces.

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