Silicon-carbon composite material, preparation method thereof, negative electrode and battery

Abstract

The application relates to the technical field of negative electrode material preparation, and discloses a carbon composite material, a preparation method thereof, a negative electrode and a battery. The preparation method of the disclosed silicon-carbon composite material comprises the following steps: depositing silicon in the pores of porous carbon in stages in a cracking mode under different pressures and temperatures through a silicon source gas. The disclosed silicon-carbon composite material is prepared by using the above preparation method. The disclosed negative electrode is prepared by using the above silicon-carbon composite material. The disclosed battery comprises the above negative electrode. The preparation method provided by the application can guarantee high preparation efficiency and can prepare a silicon-carbon negative electrode material with good electrochemical performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of negative electrode material preparation, in particular to a silicon-carbon composite material, a preparation method thereof, a negative electrode and a battery. BACKGROUND

[0002] Graphite is the most widely used negative electrode material for lithium ion batteries, but commercial graphite negative electrode material has reached its theoretical specific capacity of 372 mAh / g. In order to meet the development of new energy vehicles, high specific capacity negative electrode materials need to be sought. Silicon negative electrode material has attracted the attention of researchers due to its high specific capacity and abundant resources. However, the high expansion rate and poor conductivity of silicon negative electrode material have become factors restricting its wide application. Most of the existing technologies use in-situ coating of organic carbon source or direct mixing and doping of inorganic graphite materials. Such process is not conducive to the expansion and contraction effect of silicon material, which further causes the negative electrode to crack and powder after a period of cycle, resulting in material degradation. At present, the preparation method of silicon-carbon composite material with better performance usually uses silicon to deposit into the pores of porous carbon when silane is cracked. Although the silicon-carbon composite material prepared by this method has better performance, there are still some problems, such as the problem of incomplete filling of the carbon pore bottom of the prepared silicon-carbon negative electrode material, and the problem of nanosilicon deposited on the surface of porous carbon.

[0003] In view of this, the present application is proposed. SUMMARY

[0004] The present application aims to provide a silicon-carbon composite material, a preparation method thereof, a negative electrode and a battery, and aims to improve at least one problem mentioned in the background art.

[0005] The present application is implemented as follows:

[0006] In a first aspect, the present application provides a preparation method of a silicon-carbon composite material, which comprises depositing silicon in stages in the pores of porous carbon by cracking of silicon source gas at different pressures and temperatures.

[0007] In an optional embodiment, the pressure is 10 Pa to 0.15 MPa, and the temperature is 400 to 1000℃.

[0008] In an optional embodiment, the mass concentration of the silicon source gas is 1% to 100%, and the gas flow rate is 0.1 to 10 L / min.

[0009] In an optional embodiment, the entire deposition process comprises:

[0010] In the first stage, the deposition is carried out according to the following parameters: pressure 0.01 to 0.15 MPa, temperature 400 to 600℃;

[0011] The second stage is performed according to the following parameters: pressure 10 Pa-0.01 MPa, temperature 500-1000 °C.

[0012] In an alternative embodiment, the first stage refers to the period from the beginning of deposition to the time when the mass percentage of silicon in the deposited composite material reaches 1%-5%.

[0013] The second stage refers to the period from the first stage to the time when the mass percentage of silicon in the deposited composite material reaches 40%-55%.

[0014] In an alternative embodiment, in the first stage, the mass concentration of silicon source gas is 1%-10%, and the gas flow rate is 0.1-1 L / min; in the second stage, the mass concentration of silicon source gas is 10%-100%, and the gas flow rate is 1-10 L / min.

[0015] In an alternative embodiment, the entire deposition process further includes a third stage, and the third stage is performed according to the following parameters: mass concentration of silicon source gas 1%-10%, pressure 0.01-0.15 MPa, gas flow rate 0.1-1 L / min, temperature 400-600 °C.

[0016] The third stage refers to the period from the second stage to the time when the mass percentage of silicon in the deposited composite material is 1%-5% more than that in the second stage.

[0017] In an alternative embodiment, in the first stage, the deposition is performed according to the following parameters: mass concentration of silicon source gas 1%-10%, pressure 0.01-0.15 MPa, gas flow rate 0.4-1 L / min, temperature 400-600 °C.

[0018] In the second stage, the deposition is performed according to the following parameters: mass concentration of silicon source gas 15%-100%, pressure 100 Pa-0.01 MPa, gas flow rate 1-8 L / min, temperature 500-1000 °C.

[0019] In the third stage, the deposition is performed according to the following parameters: mass concentration of silicon source gas 1%-10%, pressure 0.01-0.15 MPa, gas flow rate 0.4-1 L / min, temperature 400-600 °C.

[0020] In an alternative embodiment, before depositing silicon in the pores of the porous carbon, the porous carbon is further subjected to heat treatment at a temperature of 100-1600 °C for 2-8 h.

[0021] In an alternative embodiment, the tap density of the porous carbon is 0.1-1.2 g / cm 3 .

[0022] In an alternative embodiment, the specific surface area of the porous carbon is 100-3000 m2 / g, preferably 500-1600 m 2 / g.

[0023] In an optional embodiment, the porous carbon has a pore volume of 0.1-2 cm 3 / g, preferably 0.4-1.2 cm 3 / g.

[0024] In an optional embodiment, the porous carbon has a mesopore ratio of 10%-90%, preferably 30%-70%.

[0025] In an optional embodiment, the porous carbon is selected from at least one of wood-based carbon, coal-based carbon, resin-based carbon, and biomass-based carbon.

[0026] In an optional embodiment, in the process of depositing silicon in the pores of the porous carbon, the carrier gas used is a combination of one or more of inert gas and hydrogen.

[0027] In an optional embodiment, the inert gas includes at least one of nitrogen and argon.

[0028] In an optional embodiment, the silicon source gas is a combination of one or more of monosilane, disilane, trichlorosilane, dichlorosilane, and chlorosilane.

[0029] In an optional embodiment, after the process of depositing silicon in the pores of the porous carbon, a carbon coating layer is further included, and the method for forming the carbon coating layer is:

[0030] After the process of depositing silicon in the pores of the porous carbon, the initial product of the composite material is obtained, the silicon source gas is replaced with a carbon source gas, and in a manner of cracking the carbon source gas, a constant temperature reaction is performed at 500-1000°C for 1-100 h, and a nanoscale carbon coating layer is deposited on the surface of the particles of the initial product of the composite material.

[0031] In an optional embodiment, in the process of forming the carbon coating layer, the carrier gas used is a combination of one or more of inert gas and hydrogen.

[0032] In an optional embodiment, the inert gas includes at least one of nitrogen and argon.

[0033] In an optional embodiment, the carbon source gas is a hydrocarbon; preferably, it is a combination of one or more of acetylene, methane, or propane.

[0034] In an optional embodiment, in the process of depositing silicon in the pores of the porous carbon, and / or, in the process of forming the carbon coating layer, the equipment used is a chemical vapor deposition furnace.

[0035] In an optional embodiment, the chemical vapor deposition furnace is a horizontal furnace or a vertical furnace.

[0036] In a second aspect, the present application provides a silicon-carbon composite material prepared by the method of any one of the preceding embodiments.

[0037] In a third aspect, the present application provides a negative electrode prepared by the silicon-carbon composite material of the preceding embodiments.

[0038] In a fourth aspect, the present application provides a battery comprising the negative electrode of the preceding embodiments.

[0039] The present application has the following advantages:

[0040] The method for preparing a silicon-carbon composite material provided by the present application uses different deposition parameters for silicon deposition at different deposition stages; the use of a multi-stage process to deposit silane can ensure efficiency while taking into account performance, precisely control the silane deposition process, and the prepared silicon-carbon negative electrode material has the advantages of high specific capacity, long cycle life, and low specific surface area. DETAILED DESCRIPTION

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below. If specific conditions are not specified in the embodiments, conventional conditions or manufacturer-recommended conditions are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0042] The silicon-carbon composite material, the method for preparing the same, the negative electrode, and the battery provided by the embodiments of the present application will be described in detail below.

[0043] The method for preparing a silicon-carbon composite material provided by the embodiments of the present application includes depositing silicon in the pores of a porous carbon in stages by cracking the silicon source gas at different pressures and temperatures.

[0044] The method for preparing provided by the present application uses a multi-stage process to deposit silane, which can ensure efficiency while taking into account performance, precisely control the silane deposition process, and the prepared silicon-carbon negative electrode material has the advantages of high specific capacity, long cycle life, and low specific surface area.

[0045] Specifically, the method for preparing is as follows:

[0046] S1, selecting raw materials and equipment

[0047] The porous carbon used as the substrate for silane deposition is selected from at least one of wood-based carbon, coal-based carbon, and biomass carbon. The porous carbon can be obtained by direct purchase or self-preparation, and the self-preparation method can be, for example, an activation method or a template method.

[0048] To make the prepared silicon-carbon composite material have better performance, the tap density of the selected porous carbon is 0.1-1.2 g / cm 3The specific surface area of the porous carbon is 100-3000 m 2 / g, preferably 500-1600 m 2 / g; the pore volume of the porous carbon is 0.1-2 cm 3 / g, preferably 0.4-1.2 cm 3 / g; the mesopore ratio of the porous carbon is 10%-90%, preferably 30%-70%.

[0049] The silicon source gas can be one or more of a combination of silane SiH4, disilane Si2H6, trichlorosilane SiH3Cl, dichlorosilane SiH2Cl2, and monochlorosilane SiHCl3.

[0050] The carrier gas used in the deposition process is selected as a combination of one or more of inert gas and hydrogen;

[0051] Optionally, the inert gas includes at least one of nitrogen and argon.

[0052] The chemical vapor deposition furnace is selected as the deposition device, for example, a horizontal furnace or a vertical furnace.

[0053] In an optional embodiment, the porous carbon can be heat treated at a temperature of 100-1600°C (for example, 100°C, 200°C, 500°C, 800°C, 1000°C, 1300°C, 1500°C, or 1600°C) for 2-8 hours (for example, 2 hours, 4 hours, 6 hours, or 8 hours) before depositing silicon in the pores of the porous carbon. The purpose is to close the micropores of the porous carbon after high-temperature treatment.

[0054] S2, depositing silicon in the pores of the porous carbon

[0055] The porous carbon is placed in the chemical vapor deposition furnace, and a mixed gas of the carrier gas and the silicon source gas is introduced into the furnace.

[0056] Taking the deposition of silicon by silane cracking as an example, the reaction formula is:

[0057] SiH4→Si+2H2;

[0058] The nanosilicon generated by silane cracking is deposited on the pores and surface of the porous carbon. The reaction is affected by temperature, concentration, and pressure, and the temperature directly affects the grain size of the nanosilicon, which in turn affects the electrochemical performance of the entire silicon-carbon composite material. Therefore, precise control is needed during the silane deposition process.

[0059] The specific deposition method is as follows:

[0060] The first stage is characterized by a silicon source gas concentration of 1% to 10% (e.g., 1%, 2%, 5%, 8%, or 10%), a pressure of 0.01 to 0.15 MPa (e.g., 0.01 MPa, 0.02 MPa, 0.05 MPa, 0.08 MPa, 0.1 MPa, or 0.15 MPa), a gas flow rate of 0.1 to 1 L / min (e.g., 0.1 L / min, 0.3 L / min, 0.5 L / min, 0.8 L / min, or 1 L / min), and a temperature of 400 to 600°C (e.g., 400°C, 450°C, 500°C, 550°C, or 600°C).

[0061] The second stage is characterized by a silicon source gas concentration of 10% to 100% (e.g., 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%), a pressure of 10 Pa to 0.01 MPa (e.g., 10 Pa, 20 Pa, 100 Pa, 500 Pa, 1000 Pa, 5000 Pa, 0.01 MPa, 0.05 MPa, or 0.1 MPa), a gas flow rate of 1 to 10 L / min (1 L / min, 2 L / min, 5 L / min, 8 L / min, or 10 L / min), and a temperature of 500 to 1000°C (500°C, 600°C, 700°C, 800°C, 900°C, or 1000°C).

[0062] The third stage is characterized by a silicon source gas concentration of 1% to 10% (e.g., 1%, 2%, 5%, 8%, or 10%), a pressure of 0.01 to 0.15 MPa (e.g., 0.01 MPa, 0.02 MPa, 0.05 MPa, 0.08 MPa, 0.1 MPa, or 0.15 MPa), a gas flow rate of 0.1 to 1 L / min (e.g., 0.1 L / min, 0.3 L / min, 0.5 L / min, 0.8 L / min, or 1 L / min), and a temperature of 400 to 600°C (e.g., 400°C, 450°C, 500°C, 550°C, or 600°C).

[0063] The first stage refers to a period from the start of deposition to the time when the mass percentage of silicon in the composite material obtained by deposition reaches 1% to 5% (e.g., 1%, 3%, or 5%).

[0064] The second stage refers to a period from the first stage to the time when the mass percentage of silicon in the composite material obtained by deposition reaches 40% to 55% (e.g., 40%, 45%, 50%, or 55%).

[0065] The third stage refers to a period from the second stage to the time when the mass percentage of silicon in the composite material obtained by deposition is 1% to 5% (e.g., 1%, 3%, or 5%) more than that in the second stage.

[0066] The above-mentioned silicon source gas concentration refers to the mass concentration of the silicon source gas in the mixed gas of the silicon source gas and the carrier gas.

[0067] The specific deposition method, using lower concentration of silicon source gas, higher pressure, lower flow rate and lower temperature to deposit silicon in the first stage of silane deposition, makes the nano-silicon particles more closely combined with the porous carbon, with less stress, and effectively prevents the silane deposition rate from being too fast, causing the porous carbon pores to be not filled with nano-silicon; using higher concentration of silicon source gas, lower pressure, higher flow rate and higher temperature to deposit silicon in the second stage of silane deposition, this stage accelerates the silane deposition rate and improves production efficiency; using lower concentration of silicon source gas, higher pressure, lower flow rate and lower temperature to deposit silicon again in the third stage of silane deposition, this stage generates nano-silicon with smaller grain size and slowly deposits into the remaining pores, avoiding a large amount of nano-silicon from being deposited on the surface of the porous carbon.

[0068] Therefore, the specific deposition method has high preparation efficiency, and the prepared silicon-carbon negative electrode material has the characteristics of low specific surface, high specific capacity, high first cycle efficiency and low expansion rate.

[0069] Further, to ensure high deposition efficiency and obtain high-quality composite material, in the first stage, the deposition is carried out according to the following parameters: silicon source gas mass concentration 1% to 10%, pressure 0.01 to 0.15 MPa, gas flow rate 0.4 to 1 L / min, and temperature 400 to 600°C.

[0070] In the second stage, the deposition is carried out according to the following parameters: silicon source gas mass concentration 15% to 100%, pressure 100 Pa to 0.01 MPa, gas flow rate 1 to 8 L / min, and temperature 500 to 1000°C.

[0071] In the third stage, the deposition is carried out according to the following parameters: silicon source gas mass concentration 1% to 10%, pressure 0.01 to 0.15 MPa, gas flow rate 0.4 to 1 L / min, and temperature 400 to 600°C.

[0072] Further, if porous carbon doped with certain special elements is to be prepared, for example, the silicon deposition can be temporarily interrupted at any period of the first stage, the second stage or the third stage, the silicon source gas is replaced with the gas corresponding to the element to be deposited, and the parameters are adjusted to be suitable for depositing the doped element; after the deposition of the doped element is completed, the silicon deposition is continued according to the deposition parameters corresponding to the period.

[0073] S3, carbon layer coating

[0074] After the initial product of the composite material is obtained by depositing silicon in the pores of the porous carbon, the silicon source gas is replaced by carbon source gas, and the carbon source gas is cracked at 500-1000°C (500°C, 800°C or 1000°C) for 1-100h (for example, 1h, 5h, 10h, 50h, 80h or 100h) to deposit a nanoscale carbon coating on the surface of the particles of the initial product of the composite material to prevent the nanosilicon deposited in the pores of the composite material from being oxidized by air.

[0075] Optionally, in the process of coating the carbon layer, the carrier gas used is a combination of one or more of inert gas and hydrogen; further, the inert gas includes at least one of nitrogen and argon.

[0076] Optionally, the carbon source gas is a hydrocarbon, preferably acetylene.

[0077] Optionally, in this step, the carbon source gas has a concentration of 5%-100% (for example, 5%, 10%, 20%, 50%, 80% or 100%), a pressure of 10Pa-0.01MPa (for example, 10Pa, 20Pa, 100Pa, 500Pa, 1000Pa, 5000Pa, 0.01MPa, 0.05MPa or 0.1MPa), and a gas flow rate of 1-10L / min (1L / min, 2L / min, 5L / min, 8L / min or 10L / min).

[0078] The silicon-carbon composite material provided by the embodiments of the present application is prepared by the preparation method provided by the embodiments of the present application. The carbon-silicon composite material has better electrochemical performance.

[0079] The negative electrode provided by the embodiments of the present application is prepared by the silicon-carbon composite material provided by the embodiments of the present application.

[0080] The battery provided by the embodiments of the present application includes the negative electrode provided by the embodiments of the present application.

[0081] The features and performance of the present application are further described in detail below in combination with the embodiments.

[0082] The specific parameters of the preparation method of the silicon-carbon composite material provided by embodiments 1-4 are shown in the following table:

[0083] Table 1 shows the specific parameter settings of embodiments 1-4

[0084]

[0085]

[0086] The silicon source gas concentration in the above table refers to the mass concentration of the silicon source gas in the mixed gas composed of the carrier gas; the carbon source gas concentration refers to the mass concentration of the carbon source gas in the mixed gas composed of the carrier gas; and the silicon deposition amount refers to the mass percentage of the deposited silicon in the silicon-carbon composite material obtained at the corresponding time.

[0087] The biomass carbon used in the above table has a tap density of 0.4 g / cm 3 , a specific surface area of 1500 m 2 / g, a pore volume of 0.8 cm 3 / g, and a mesopore ratio of 50%.

[0088] The resin carbon used in the above table has a tap density of 0.3 g / cm 3 , a specific surface area of 1500 m 2 / g, a pore volume of 0.7 cm 3 / g, and a mesopore ratio of 60%.

[0089] Comparative Example 1

[0090] This comparative example is a conventional silane deposition method for preparing a silicon-carbon composite material. Except for the specific operation mode of depositing silicon in the pores of the porous carbon, the other operation parameters are the same as those of Example 1.

[0091] In this comparative example, the process of depositing silicon in the pores of the porous carbon is a one-stage deposition, and the deposition parameters throughout the process are as follows:

[0092] The mass concentration of silane is 40%, the furnace pressure is 0.01 MPa, the gas flow rate is 5 L / min, the temperature is 550°C, and the reaction time is 24 h, thereby obtaining a primary silicon-carbon composite material with a silicon deposition amount of 50%.

[0093] The same carbon layer coating method as that of Example 1 is used to coat a nano-carbon coating layer on the surface of the primary silicon-carbon composite material.

[0094] Comparative Example 2

[0095] This comparative example is basically the same as Example 1, except that:

[0096] The deposition parameters of the second stage are used to replace the operation parameters of the first stage.

[0097] Comparative Example 3

[0098] This comparative example is basically the same as Example 1, except that:

[0099] The deposition parameters of the second stage are used to replace the operation parameters of the third stage.

[0100] Experimental Example

[0101] The specific surface area of the silicon-carbon composite materials prepared in Examples 1-4 and Comparative Examples 1-3 was tested, and the results were recorded in Table 2.

[0102] Lithium ion battery related parameter testing:

[0103] Specific capacity and first cycle efficiency testing: After mixing, coating, and drying, the silicon-carbon composite material was prepared into a negative electrode sheet, a lithium sheet was used as a counter electrode, and a button cell was assembled for testing. The button cell was discharged at 0.1C to 1.0mV, and discharged at 0.01C to 1.0mV, and the discharge capacity D was recorded. The button cell was charged at 0.05C to 1.5V, and the capacity of the button cell at this time was recorded as the specific capacity C, and the first cycle efficiency was calculated as C / D x 100%.

[0104] Lithium ion battery full charge expansion rate testing: The thickness of the lithium ion battery was measured three times using a flat plate PPG (gauge: micrometer, pressure: 600g) to obtain the average thickness of the lithium ion battery. The thickness of the fresh lithium ion battery at full charge was tested as the initial thickness. After the charge and discharge cycle to a specific number of cycles, the lithium ion battery was in a full charge state, and the thickness of the battery was tested again using the flat plate PPG.

[0105] After 100 cycles, the full charge expansion rate = (the thickness of the lithium ion battery at the 100th cycle / the thickness of the lithium ion battery at the first cycle) x 100%.

[0106] The measured results were recorded in Table 2.

[0107] Table 2: Electrochemical performance test results of the batteries prepared from the composite materials of each example and comparative example

[0108]

[0109] As can be seen from the above table, the silicon-carbon composite material prepared in each example of the present application has a significantly lower specific surface area than each comparative example, and the prepared battery has better electrochemical performance. Comparing Example 1 with Comparative Example 1, the specific capacity and first cycle efficiency of Example 1 are higher. Comparing Example 1 with Comparative Examples 1 and 2, the first cycle efficiency of Example 1 is higher, and the full charge expansion rate after 100 cycles is lower. As can be seen from the above, the silicon-carbon negative electrode material prepared by the stepwise deposition method provided in the examples of the present application has the characteristics of low specific surface area, high specific capacity, high first cycle efficiency, and low expansion rate.

[0110] In summary, the preparation method of the silicon-carbon composite material provided in the examples of the present application has the following characteristics:

[0111] (1) Low concentration, low flow rate, high pressure, low temperature conditions, the rate of silane cracking deposition is slow, but the generated nano silicon grain size is smaller and the stress between the porous carbon is smaller, the combination is more closely, the first stage can fill the bottom of the porous carbon pore, in the third stage, silicon is deposited in the remaining pores of the porous carbon, which can avoid a large amount of nano silicon deposited on the surface of the porous carbon;

[0112] (2) High concentration, high flow rate, low pressure, high temperature conditions, the speed of silane cracking deposition is fast, in the second stage, nano silicon is deposited in the pores of the porous carbon by fast cracking deposition, since the bottom has been filled in the initial stage of deposition, the situation that the bottom has no nano silicon while the neck is filled due to the fast deposition rate in the pores of the porous carbon will not occur;

[0113] (3) The deposition of silane by using a multi-stage process can ensure efficiency while taking into account performance, precisely control the silane deposition process, and the prepared silicon-carbon negative electrode material has the advantages of high specific capacity, long cycle life and low specific surface.

[0114] The above is only the preferred embodiment of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for producing a silicon-carbon composite material, characterized by, The method comprises depositing silicon in the pores of the porous carbon in stages by cracking a silicon source gas at different pressures and temperatures; The whole deposition process comprises: A first stage, wherein the deposition is carried out according to the following parameters: a silicon source gas mass concentration of 1% to 10%, a pressure of 0.01 to 0.15 MPa, a gas flow rate of 0.4 to 1 L / min, and a temperature of 400 to 600 ℃; A second stage, wherein the deposition is carried out according to the following parameters: a silicon source gas mass concentration of 15% to 100%, a pressure of 100 Pa to 0.01 MPa, a gas flow rate of 1 to 8 L / min, and a temperature of 500 to 1000 ℃; A third stage, wherein the deposition is carried out according to the following parameters: a silicon source gas mass concentration of 1% to 10%, a pressure of 0.01 to 0.15 MPa, a gas flow rate of 0.4 to 1 L / min, and a temperature of 400 to 600 ℃.

2. The production method according to claim 1, characterized by, The first stage refers to a period from the start of the deposition to the time when the mass percentage of silicon in the obtained composite material reaches 1% to 5%; The second stage refers to a period from the first stage to the time when the mass percentage of silicon in the obtained composite material reaches 40% to 55%; The third stage refers to a period from the second stage to the time when the mass percentage of silicon in the obtained composite material is 1% to 5% more than that in the second stage.

3. The preparation method according to claim 1, characterized in that, Further comprising at least one of the following features (1) to (4): (1) Before depositing silicon in the pores of the porous carbon, the porous carbon is further heat-treated at a temperature of 100 to 1600 ℃ for 2 to 8 h; (2) the tap density of the porous carbon is 0.1-1.2 g / cm 3 ; (3) During the process of depositing silicon in the pores of the porous carbon, the carrier gas used is a combination of one or more of inert gas and hydrogen; (4) The silicon source gas is a combination of one or more of monosilane, disilane, monochlorotrisilane, dichlorodisilane, and trichloromonosilane.

4. The preparation method according to claim 1, characterized in that, The specific surface area of the porous carbon is 100-3000 m 2 / g.

5. The preparation method according to claim 4, characterized in that, The specific surface area of the porous carbon is 500-1600 m 2 / g.

6. The preparation method according to claim 1, characterized in that, The porous carbon has a pore volume of 0.1 to 2 cm 3 / g.

7. The preparation method according to claim 6, characterized in that, The porous carbon has a pore volume of 0.4 to 1.2 cm 3 / g.

8. The method of claim 1, wherein, The mesoporous proportion of the porous carbon is 10% to 90%.

9. The production method according to claim 8, characterized by, The mesoporous proportion of the porous carbon is 30% to 70%.

10. The method of claim 1, wherein, The porous carbon is selected from at least one of wood-based carbon, coal-based carbon, and resin-based carbon.

11. The method of claim 1, wherein, After depositing silicon in the pores of the porous carbon, a carbon coating layer is further formed, and the method for forming the carbon coating layer is as follows: After obtaining the preliminary product of the composite material by depositing silicon in the pores of the porous carbon, the silicon source gas is replaced with a carbon source gas, and a nano-scale carbon coating layer is deposited on the surface of the particles of the preliminary product of the composite material by cracking the carbon source gas at a constant temperature of 500 to 1000 ℃ for 1 to 100 h.

12. The method of claim 11, wherein, During the process of forming the carbon coating layer, the carrier gas used is a combination of one or more of inert gas and hydrogen.

13. The preparation method according to claim 11, characterized in that, The carbon source gas is a hydrocarbon.

14. The method of claim 11, wherein, The carbon source gas is a combination of one or more of acetylene, methane, and propane.

15. A silicon-carbon composite material, characterized by, The silicon-carbon composite material is prepared by using the preparation method according to any one of claims 1 to 14.

16. A negative electrode characterized by comprising: The silicon-carbon composite material is prepared by using the preparation method according to claim 15.

17. A battery, characterized by The negative electrode comprises the silicon-carbon composite material according to claim 16.

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