Oxide-coated fibrous silicon-carbon composite material and method for preparing the same

Abstract

The application relates to the technical field of material preparation, and discloses an oxide-coated fibrous silicon-carbon composite material and a preparation method thereof. The oxide-coated fibrous silicon-carbon composite material is of a core-shell structure, and sequentially comprises an inner core, a first shell and a second shell from inside to outside. The inner core is a metal-doped silicon-carbon material, the first shell is a metal oxide, and the second shell is amorphous carbon. The mass ratio of the inner core, the first shell and the second shell is 80-90:5-10:5-10. The above technical scheme solves the problems of low rate performance and high expansion performance of the silicon-carbon composite material in the related art.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of material preparation, in particular to an oxide-coated fibrous silicon-carbon composite material and a preparation method thereof. BACKGROUND

[0002] Silicon-carbon composite material is a very promising anode material for lithium ion batteries. Due to its high specific capacity and good cycle stability, it can effectively improve the energy density of the battery and prolong the service life of the battery. It has wide application prospects in high-performance electric vehicle batteries, portable electronic device batteries and the like. The silicon-carbon composite material on the market at present is mainly prepared by depositing nano-silicon in porous carbon through silane cracking and passivating the surface thereof. The morphology of the material is granular structure, which causes high swelling at full charge. Moreover, the porous structure of the inner core causes many defects in the material and poor ion conductivity. This not only reduces the charge and discharge efficiency of the battery and affects the rate performance of the battery, but also limits the cycle life of the battery. Therefore, it is necessary to develop a silicon-carbon composite material with high rate performance and low swelling. SUMMARY

[0003] The present application provides an oxide-coated fibrous silicon-carbon composite material and a preparation method thereof, which solves the problem of low rate performance and high swelling performance of the silicon-carbon composite material in the related art.

[0004] The technical scheme of the present application is as follows: The present application provides an oxide-coated fibrous silicon-carbon composite material, which has a core-shell structure and sequentially comprises an inner core, a first outer shell and a second outer shell from inside to outside. The inner core is a metal-doped silicon-carbon material, the first outer shell is a metal oxide, and the second outer shell is amorphous carbon. The mass ratio of the inner core, the first outer shell and the second outer shell is 80-90:5-10:5-10.

[0005] As a further technical scheme, the inner core comprises the following components by weight: 100 parts of a polymer, 40-50 parts of a metal wire, 1-5 parts of a dispersing agent, 100-500 parts of a carbon-based compound and 1-5 parts of a lithium compound.

[0006] As a further technical scheme, the carbon-based compound comprises one or more of glucose, sucrose and maltose.

[0007] As a further technical scheme, the preparation method of the inner core comprises the following steps:

[0008] S1, disperse the polymer in water, and sequentially add the dispersing agent and the metal wire to obtain a metal wire solution;

[0009] S2, dispersing the carbon-based compound in water, sequentially adding a metal wire solution and a lithium compound, and obtaining fibrous metal-doped porous carbon after reaction, filtration, carbonization and activation;

[0010] S3, obtaining the core after depositing nano-silicon on the fibrous metal-doped porous carbon.

[0011] As a further technical solution, the metal wire is a metal nanowire.

[0012] In the present application, by coating the surface of the metal nanowire with amorphous carbon, carbonization, using the fibrous structure of the metal nanowire as a matrix to coat porous carbon on its surface, the electronic conductivity of the material is improved, and the fibrous structure has lower expansion than the granular structure. At the same time, lithium salt is chemically deposited in the porous carbon, activated to obtain lithium-doped fibrous metal-doped porous carbon, which reduces defects, improves the initial efficiency and reduces expansion.

[0013] As a further technical solution, the mass ratio of the polymer to water is 1-5:100.

[0014] As a further technical solution, the mass ratio of the polymer, dispersant and metal wire is 100:1:40-100:5:50.

[0015] As a further technical solution, the mass ratio of the porous carbon to the water is 1-10:100.

[0016] As a further technical solution, the mass ratio of the porous carbon to the metal wire solution is 100:100-500.

[0017] As a further technical solution, the temperature of the reaction is 50-100 DEG C, and the reaction time is 1-6h.

[0018] As a further technical solution, the gas passed during carbonization is carbon dioxide, the flow rate is 10 SCCM, and the passing time is 60 minutes.

[0019] As a further technical solution, the carbonization temperature is 700-1000 DEG C, and the carbonization time is 1-6h.

[0020] As a further technical solution, the activation temperature is 1200-1500 DEG C.

[0021] As a further technical solution, the deposition method used is chemical deposition.

[0022] As a further technical solution, the deposition temperature is 450-550 DEG C, the gas used for deposition is a silane mixed gas, and the silane mixed gas is composed of silane gas and nitrogen in a volume ratio of 1-5:10.

[0023] As a further technical solution, the flow rate of the silane mixed gas is 10-50 SCCM, and the time is 30-300 min.

[0024] As a further technical solution, after the fibrous metal-doped porous carbon deposits nanosilicon, the method further comprises the following steps: cooling to room temperature, and introducing oxygen mixed gas to obtain the core.

[0025] As a further technical solution, the oxygen mixed gas is composed of oxygen and nitrogen in a volume ratio of 1-5:10.

[0026] As a further technical solution, the oxygen mixed gas is introduced for 10-60 min.

[0027] As a further technical solution, the polymer includes one or more of polyacrylic acid, polyvinylpyrrolidone, and polyacrylamide.

[0028] As a further technical solution, the metal wire includes one or more of nanosilver wire, nanocopper wire, nanonickel wire, and nanomagnesium wire.

[0029] As a further technical solution, the length of the metal wire is 0.5-2 μm, and the diameter is 10-500 nm.

[0030] As a further technical solution, the lithium compound includes one or more of lithium difluoro(oxalato)borate, lithium difluorophosphate, lithium tetrafluoroborate, lithium difluoroborate, and lithium triflate.

[0031] As a further technical solution, the dispersant includes one or more of polypropylene glycol, polyvinyl acetate, and polyacrylate.

[0032] As a further technical solution, when the dispersant is polyacrylate, the polyacrylate is composed of poly(methyl acrylate) and poly(2,2,2-trifluoroethyl acrylate) in a mass ratio of 1:2-3.

[0033] In the present application, poly(methyl acrylate) and poly(2,2,2-trifluoroethyl acrylate) are used as dispersants at the same time, and the synergistic effect of both is exerted, further improving the rate performance of the composite material and reducing the expansion performance of the silicon-carbon composite material.

[0034] The present application also proposes a preparation method of an oxide-coated fibrous silicon-carbon composite material, which comprises the following steps: after sequentially depositing metal oxide and amorphous carbon on the surface of the core, a composite material is obtained.

[0035] As a further technical solution, the depositing metal oxide comprises the following steps: placing the core in a vacuum reaction device, introducing metal oxide gas in a reducing gas atmosphere to perform atomic vapor deposition, thereby obtaining the metal oxide coated core.

[0036] As a further technical solution, the vacuum degree is ≤1 Torr.

[0037] As a further technical solution, the reducing gas atmosphere comprises one or both of hydrogen and carbon monoxide.

[0038] As a further technical solution, the deposition temperature is 500-1100℃, and the deposition time is 10-60 min.

[0039] As a further technical solution, the flow rate of the introduced metal oxide gas is 10-100 SCCM.

[0040] As a further technical solution, the depositing amorphous carbon comprises the following steps: transferring the metal oxide coated core to a tube furnace, introducing carbon-containing gas to perform atomic vapor deposition, thereby obtaining the composite material.

[0041] As a further technical solution, the deposition temperature is 700-900℃, and the deposition time is 30-300 min.

[0042] As a further technical solution, the carbon-containing gas is acetylene carbon source gas.

[0043] As a further technical solution, the flow rate of the carbon-containing gas is 10-50 SCCM.

[0044] As a further technical solution, the metal oxide comprises one or more of lithium oxide, magnesium oxide, and nickel oxide.

[0045] The working principle and beneficial effects of the present application are as follows:

[0046] In the present application, the metal-doped silicon-carbon material is used as the core, metal oxide is deposited on the surface of the core to form a continuous conductive network, thereby providing a rapid transmission channel for electrons, and amorphous carbon is further deposited on the outer surface of the core to reduce direct contact with the electrolyte, reduce side reactions, improve the initial efficiency, and further improve the rate performance and expansion performance of the silicon-carbon composite material. BRIEF DESCRIPTION OF DRAWINGS

[0047] The present application will be further described in detail below in combination with the drawings and specific embodiments.

[0048] Figure 1 SEM image of the oxide coated fibrous silicon-carbon composite material prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0049] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work, are within the protection scope of the present application.

[0050] The following examples and comparative examples are:

[0051] Polyacrylic acid: effective content of 50wt%, manufacturer is Zibo Dongrun Chemical Technology Co., Ltd.;

[0052] Methyl polyacrylate: weight average molecular weight of 40000, purchased from Shanghai Jizisheng Chemical Technology Co., Ltd.;

[0053] Nano silver wire: length of 1μm, diameter of 120nm;

[0054] Nano magnesium wire: length of 1μm, diameter of 120nm;

[0055] Nano copper wire: length of 1μm, diameter of 120nm;

[0056] Silver particles: average particle size of 40nm;

[0057] Polyvinylpyrrolidone: average molecular weight of 8000, purchased from Macklin Reagent;

[0058] Polyacrylamide: non-ionic, molecular weight of 12 million, purchased from Macklin Reagent;

[0059] Polyvinyl alcohol: number average molecular weight of 3000, purchased from Macklin Reagent;

[0060] Polyvinyl acetate: weight average molecular weight of 10000, purchased from Macklin Reagent.

[0061] Example 1

[0062] The preparation method of the core comprises the following steps:

[0063] S1, disperse 100 parts of polyacrylic acid in 5000 parts of water, add 1 part of methyl polyacrylate and 40 parts of nano silver wire in sequence, disperse uniformly, and obtain a metal wire solution;

[0064] S2, 100 parts of glucose was dispersed in 1000 parts of water, 100 parts of metal wire solution was added and mixed uniformly, then 1 part of lithium difluorooxalate was added, and the mixture was reacted by chemical deposition method at a temperature of 50℃ for 6h, then the obtained material was carbonized at 700℃ for 6h, then the temperature was increased to 1200℃, and carbon dioxide gas was introduced at a flow rate of 50 SCCM for 60min, to obtain the fibrous metal-doped porous carbon;

[0065] S3, the fibrous metal-doped porous carbon was transferred into a fluidized bed, and nitrogen gas was introduced to replace the air in the pipe, then the temperature was increased to 450℃, and silane mixed gas (volume ratio of disilane gas:nitrogen = 1:10) was introduced at a flow rate of 10 SCCM for 300min, then the temperature was decreased to room temperature, and oxygen mixed gas (volume ratio of oxygen:nitrogen = 1:10) was introduced for 60min to obtain the core;

[0066] S4, the core was transferred into a vacuum furnace, then the silicon-carbon precursor material was placed in a vacuum reaction device, the vacuum degree was 0.1 Torr, the temperature was increased to 500℃ in a hydrogen atmosphere, lithium oxide gas was introduced, the hydrogen flow rate was maintained at 10 SCCM, and the deposition was performed for 60min to obtain the first shell, then the obtained material was transferred into a tube furnace, nitrogen was introduced to replace the air in the pipe, then the temperature was increased to 700℃, and acetylene carbon source gas was introduced at a flow rate of 10 SCCM for 300min to obtain the second shell, thereby obtaining the composite material, wherein the mass ratio of the core, the first shell and the second shell is 80:5:5.

[0067] The SEM image of the oxide-coated fibrous silicon-carbon composite material prepared in Example 1 is shown in Figure 1 .

[0068] Example 2

[0069] The preparation method of the core comprises the following steps:

[0070] S1, 100 parts of polyvinylpyrrolidone was dispersed in 7500 parts of water, 3 parts of polyvinyl acetate and 45 parts of nano-magnesium wire were added in sequence and uniformly dispersed to obtain a metal wire solution;

[0071] S2, 100 parts of glucose was dispersed in 5000 parts of water, 300 parts of metal wire solution was added and mixed uniformly, then 3 parts of lithium difluorophosphate was added, and the mixture was reacted by chemical deposition method at a temperature of 80℃ for 3h, then the obtained material was carbonized at 900℃ for 3h, then the temperature was increased to 1350℃, and carbon dioxide gas was introduced at a flow rate of 50 SCCM for 60min to obtain the fibrous metal-doped porous carbon;

[0072] S3, transfer the fibrous metal-doped porous carbon to a fluidized bed, discharge the air in the tube with nitrogen gas, then heat to 500°C, pass in silane mixed gas (volume ratio of disilane gas: nitrogen = 3: 10) according to the flow rate of 20 SCCM for 200 min, then cool to room temperature, and change to pass in oxygen mixed gas (volume ratio of oxygen: nitrogen = 3: 10) for 30 min, to obtain a core;

[0073] S4, transfer the core to a vacuum furnace, then by atomic vapor deposition method, place the silicon-carbon precursor material in a vacuum reaction device, vacuum degree is 0.1 Torr, in hydrogen atmosphere, heat to 850°C, then pass in magnesium oxide gas, while keeping the hydrogen flow rate of 50 SCCM, deposit for 30 min, to obtain a first shell, then transfer the obtained material to a tube furnace, first pass in nitrogen to discharge the air in the tube, then heat to 800°C, and pass in acetylene carbon source gas, according to the flow rate of 30 SCCM for 200 min, to obtain a second shell, that is, the composite material, wherein the mass ratio of the core, the first shell and the second shell is 90:8:8.

[0074] Example 3

[0075] The preparation method of the core comprises the following steps:

[0076] S1, disperse 100 parts of polyacrylamide in 10000 parts of water, add 5 parts of polyvinyl alcohol and 50 parts of nano copper wire in sequence, disperse uniformly, to obtain a metal wire solution;

[0077] S2, disperse 100 parts of glucose in 10000 parts of water, add 500 parts of the metal wire solution and mix uniformly, then add 5 parts of lithium tetrafluoroborate, react at a temperature of 100°C for 1 h by chemical deposition method, filter, carbonize the obtained material at 1000°C for 1 h, then heat to 1500°C, pass in carbon dioxide gas according to the flow rate of 50 SCCM for 60 min, to obtain fibrous metal-doped porous carbon;

[0078] S3, transfer the fibrous metal-doped porous carbon to a fluidized bed, discharge the air in the tube with nitrogen gas, then heat to 500°C, pass in silane mixed gas (volume ratio of disilane gas: nitrogen = 3: 10) according to the flow rate of 20 SCCM for 200 min, then cool to room temperature, and change to pass in oxygen mixed gas (volume ratio of oxygen: nitrogen = 3: 10) for 30 min, to obtain a core;

[0079] S4, transfer the core into a vacuum furnace, then place the silicon-carbon precursor material into a vacuum reaction device by atomic vapor deposition method, vacuum degree is 0.1 Torr, in hydrogen atmosphere, heat to 1100℃, then pass nickel oxide gas, while keeping hydrogen flow 100 SCCM, deposit 10 min, get the first shell, then transfer the obtained material into a tube furnace, first pass nitrogen to discharge the air in the tube, then heat to 900℃, and pass acetylene carbon source gas, according to flow 50 SCCM, pass for 30 min, get the second shell, then get the composite material, wherein the mass ratio of the core, the first shell and the second shell is 100:10:10.

[0080] Example 4

[0081] Compared with Example 1, the difference of Example 4 is that in the preparation of the core, the lithium difluorooxalate in S2 is added into the aqueous solution of polyacrylic acid together with the polymethyl acrylate in S1, to obtain the metal wire solution.

[0082] Example 5

[0083] Compared with Example 1, the difference of Example 5 is that no lithium difluorooxalate is added.

[0084] Example 6

[0085] Compared with Example 1, the difference of Example 6 is that the nano-silver wire is replaced by an equal amount of silver particles.

[0086] Example 7

[0087] Compared with Example 1, the difference of Example 7 is that the polymethyl acrylate is replaced by polymethyl acrylate and poly(2,2,2-trifluoroethyl acrylate) with a mass ratio of 1:2.

[0088] Example 8

[0089] Compared with Example 1, the difference of Example 8 is that the polymethyl acrylate is replaced by polymethyl acrylate and poly(2,2,2-trifluoroethyl acrylate) with a mass ratio of 1:3.

[0090] Comparative Example 1

[0091] Compared with Example 1, the difference of Comparative Example 1 is that in this example, step S4 is:

[0092] S4, the inner core is transferred to a vacuum furnace, and then to a tube furnace. Nitrogen is first introduced to remove air in the tube, and then the temperature is raised to 700℃, and acetylene carbon source gas is introduced at a flow rate of 10 SCCM for 300 min to obtain a first shell. Then the inner core is transferred to a vacuum furnace, and then a silicon-carbon precursor material is placed in a vacuum reaction device by atomic vapor deposition method. The vacuum degree is ≤1 Torr, the temperature is raised to 500℃ in a hydrogen atmosphere, and lithium oxide gas is introduced while maintaining a hydrogen flow rate of 10 SCCM for 60 min to obtain a second shell, i.e. a composite material, wherein the mass ratio of the inner core, the first shell and the second shell is 80:5:5.

[0093] Comparative Example 2

[0094] Comparative Example 2 differs from Example 1 in that in this example, step S4 is:

[0095] S4, the inner core is transferred to a vacuum furnace, and then to a tube furnace. Nitrogen is first introduced to remove air in the tube, and then the temperature is raised to 700℃, and acetylene carbon source gas is introduced at a flow rate of 10 SCCM for 300 min to obtain a first shell. Then the inner core is transferred to a vacuum furnace, and then a silicon-carbon precursor material is placed in a vacuum reaction device by atomic vapor deposition method. The vacuum degree is ≤1 Torr, the temperature is raised to 500℃ in a hydrogen atmosphere, and lithium oxide gas is introduced while maintaining a hydrogen flow rate of 10 SCCM for 60 min to obtain a second shell, i.e. a composite material, wherein the mass ratio of the inner core, the first shell and the second shell is 80:5:5.

[0096] Comparative Example 3

[0097] Comparative Example 3 differs from Example 1 in that in this example, step S4 is:

[0098] S4, the inner core is transferred to a vacuum furnace, and then to a tube furnace. Nitrogen is first introduced to remove air in the tube, and then the temperature is raised to 700℃, and acetylene carbon source gas is introduced at a flow rate of 10 SCCM for 300 min to obtain a first shell. Then the inner core is transferred to a vacuum furnace, and then a silicon-carbon precursor material is placed in a vacuum reaction device by atomic vapor deposition method. The vacuum degree is ≤1 Torr, the temperature is raised to 500℃ in a hydrogen atmosphere, and lithium oxide gas is introduced while maintaining a hydrogen flow rate of 10 SCCM for 60 min to obtain a second shell, i.e. a composite material, wherein the mass ratio of the inner core, the first shell and the second shell is 80:5:5.

[0099] Comparative Example 4

[0100] Comparative Example 4 differs from Example 1 in that in this example, step S1 is: 100 parts of polyacrylic acid are dispersed in 5000 parts of water, 1 part of polyacrylate and 40 parts of nano silver wire are added in turn, and uniformly dispersed to obtain a metal wire solution.

[0101] Comparative Example 5

[0102] Comparative Example 5 differs from Example 1 in that in this example, the composite material is the inner core prepared in Example 1.

[0103] The silicon-carbon composite materials prepared in Examples 1-8 and Comparative Examples 1-5 are tested according to the following method:

[0104] 1. SEM test: The oxide-coated fibrous silicon-carbon composite material prepared in Example 1 was subjected to SEM test, and the results are shown in FIG. 1. Figure 1 As can be seen from FIG. 1, the material presents a fibrous structure, with a length of 1-10 μm and a diameter of 10-100 nm. Figure 1

[0105] 2. Physicochemical test: The tap density and specific surface area of the composite materials in Examples 1-8 and Comparative Examples 1-5 were tested according to the test method specified in GB / T 38823-2020 “Silicon-carbon”, the powder resistivity of the powder material was tested by a four-probe tester, and the test results are shown in Table 1 below.

[0106] 3. Button cell test: The silicon-carbon composite materials prepared in Examples 1-8 and Comparative Examples 1-5 were assembled into button cells according to the following method: the silicon-carbon composite material was used as the negative electrode, and lithium sheet, electrolyte and separator were assembled into button cells in an argon glove box with water content less than 0.1 ppm. The separator was celegard 2400; the electrolyte was a solution of LiPF6, and the concentration of LiPF6 in the electrolyte was 1 mol / L, and the solvent was a mixed solution of ethylene carbonate and diethyl carbonate obtained by mixing them in a weight ratio of 1:1.

[0107] The prepared button cells were marked as A-1, B-1, C-1, D-1, E-1, F-1, G-1, H-1, I-1, G-1, K-1, L-1, and M-1, respectively, and the performance of the button cells was tested by a blue power tester, with the test conditions being: 0.1C rate charge and discharge, voltage range of 0.005-2V, stop after 3 cycles, then test the discharge capacity under 1C condition, calculate the rate performance of 1C / 0.1C, cycle performance (25±3℃, 0.1C / 0.1C, 100 cycles), and at the same time, the button cells were fully charged to 100% SOC, and the full charge expansion of the negative electrode sheet was tested, and the test results are shown in Table 2 below.

[0108] 4. Soft package battery performance test: The silicon-carbon composite materials prepared in Examples 1-8 and Comparative Examples 1-5 were doped with 95% artificial graphite as the negative active material, and the positive active material was ternary material (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 ​O2), electrolyte and separator to assemble a 5 Ah soft package battery, wherein the separator is celegard 2400, the electrolyte is a LiPF6 solution (the solvent is a mixed solution of EC, DEC and EMC in a volume ratio of 1:1:1, and the concentration of LiPF6 is 1.1 mol / L), and the prepared soft package battery is respectively marked as A-2, B-2, C-2, D-2, E-2, F-2, G-2, H-2, I-2, G-2, K-2, L-2 and M-2, and the cycle and rate performance of the battery is tested. The cycle performance is tested at a charge / discharge rate of 1C / 1C, a cycle number of 500 times, a voltage range of 2.5V-4.2V and a temperature of 25±3℃; the rate performance is tested at 0.33C, 0.5C, 1C and 2C, respectively, and then the rate performance at different rates is calculated. The test results are shown in Table 3.

[0109] The test results are shown in the following table:

[0110] Table 1 Performance test results of silicon-carbon composite materials prepared in Examples 1-8 and Comparative Examples 1-5

[0111]

[0112] Table 2 Performance test results of silicon-carbon composite materials prepared in Examples 1-8 and Comparative Examples 1-5

[0113]

[0114] Table 3 Performance test results of silicon-carbon composite materials prepared in Examples 1-8 and Comparative Examples 1-5

[0115]

[0116] Compared with Comparative Examples 1-3 and 5, Example 1 has a metal-doped silicon-carbon material as the core, and a first shell and a second shell are sequentially coated outside. The results show that the physicochemical properties, button cell performance and soft package battery performance of Example 1 are all better than those of Comparative Examples 1-3 and 5, indicating that when the metal-doped silicon-carbon material is used as the core, the metal oxide is used as the first shell, and the amorphous carbon is used as the second shell, the electrochemical performance of the composite material can be improved.

[0117] Compared with Example 1, Example 4 adds lithium difluoro(oxalato)phosphate to the aqueous solution of poly(methyl acrylate) in S1, and Example 5 does not add lithium difluoro(oxalato)phosphate. The results show that the physicochemical properties, button cell performance and soft package battery performance of Example 1 are all better than those of Examples 4 and 5, indicating that when the polymer is mixed first and then lithium difluoro(oxalato)phosphate is added, the electrochemical performance of the composite material can be further improved.

[0118] Compared with example 6 and comparative example 4, example 1 adds nanometer metal wire, and the physicochemical properties, button cell performance and soft package cell performance of example 1 are all better than those of example 6 and comparative example 4, indicating that when the added metal is nanometer metal wire, the electrochemical performance of the obtained composite material is better.

[0119] Compared with example 1, examples 7 and 8 simultaneously add poly(methyl acrylate) and poly(2,2,2-trifluoroethyl acrylate) as dispersants, and the physicochemical properties, button cell performance and soft package cell performance of examples 7 and 8 are all better than those of example 1, indicating that poly(methyl acrylate) and poly(2,2,2-trifluoroethyl acrylate) play a synergistic role, and can further improve the electrochemical performance of the composite material.

[0120] The above only is the preferred embodiment of the present application, and does not limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. An oxide-coated fibrous silicon-carbon composite material, characterized in that, The composite material has a core-shell structure, consisting of a core, a first outer shell, and a second outer shell from the inside out. The core is a metal-doped silicon-carbon material, the first outer shell is a metal oxide, and the second outer shell is amorphous carbon. The mass ratio of the core, the first outer shell, and the second outer shell is 80~90:5~10:5~10. The core comprises the following raw materials in parts by weight: 100 parts polymer, 40-50 parts nano-metal wires, 1-5 parts dispersant, 100-500 parts carbon-based compound, and 1-5 parts lithium compound; The method for preparing the kernel includes the following steps: S1. The polymer is dispersed in water, and a dispersant and nanowires are added sequentially to obtain a metal wire solution; S2. Disperse the carbon-based compound in water, add metal wire solution and lithium compound in sequence, and after reaction, filter, carbonize and activate to obtain fibrous metal-doped porous carbon. S3. After depositing nano-silicon with fibrous metal-doped porous carbon, a core is obtained; The polymer includes one or more of polyacrylic acid, polyvinylpyrrolidone, and polyacrylamide; The lithium compound includes one or more of lithium difluorooxalate, lithium difluorophosphate, lithium tetrafluoroborate, lithium difluoroborate, and lithium trifluoromethanesulfonate. The dispersant includes one or both of polyacryl alcohol and polyvinyl acetate.

2. The oxide-coated fibrous silicon-carbon composite material according to claim 1, characterized in that, The nanowires include one or more of the following: silver nanowires, copper nanowires, nickel nanowires, and magnesium nanowires.

3. A method for preparing an oxide-coated fibrous silicon-carbon composite material according to any one of claims 1 to 2, characterized in that, Includes the following steps: A composite material is obtained by sequentially depositing metal oxides and amorphous carbon on the core surface.

4. The method for preparing an oxide-coated fibrous silicon-carbon composite material according to claim 3, characterized in that, The metal oxide includes one or more of lithium oxide, magnesium oxide, and nickel oxide.

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