A silicon-carbon composite material, its preparation method, electrode, and application.

Abstract

This invention discloses a silicon-carbon composite material, its preparation method, electrode, and applications. The preparation method of the silicon-carbon composite material includes the following steps: S1, sequentially subjecting mixture A to carbonization and reduction reactions to obtain porous carbon; mixture A comprises a carbon matrix and a composite template agent; the composite template agent comprises a mixture of a first template agent and a manganese source; the specific surface area of ​​the porous carbon is 1600-2200 m². 2 / g; S2, porous carbon is sequentially subjected to silane deposition and gas-phase carbon coating. This invention, by introducing a manganese source during the preparation of the silicon-carbon composite material, can effectively control silane deposition and carbon layer coating. Batteries made from the obtained silicon-carbon composite material exhibit superior cycle performance.

Description

Technical Field

[0001] This invention relates to a silicon-carbon composite material, its preparation method, electrode, and application. Background Technology

[0002] To address range anxiety in new energy vehicles, the demand for high-energy-density lithium-ion batteries has increased significantly. Compared to traditional graphite anodes (372 mAh / g), silicon has a higher theoretical specific capacity (4200 mAh / g). Therefore, the application of silicon-based anodes can significantly improve the energy density of lithium-ion batteries. However, silicon-based anodes often experience significant volume expansion during charge and discharge. This substantial volume expansion often leads to particle breakage, and the regeneration of the SEI film on the surface of the broken particles results in a significant reduction in the cycle life of the battery cell.

[0003] Therefore, silane is often deposited in the porous carbon channels via vapor deposition. The confinement effect of the porous carbon suppresses the volume expansion of the silicon-based anode, thereby improving the cycle life of the battery cell. During vapor deposition and carbon coating, the controllable deposition of silane and the uniform coating of the carbon layer largely determine the electrochemical performance, especially the cycle performance, of the battery made from silicon-carbon materials. However, in current technologies, the poor control over the deposition of silane and the degree of carbon layer coating results in unsatisfactory cycle performance of batteries made from silicon-carbon composite materials, which requires further improvement. Summary of the Invention

[0004] The technical problem this invention aims to solve is to overcome the shortcomings of existing silicon-carbon composite material preparation processes, which suffer from poor control over silane deposition and carbon layer coating, resulting in poor cycle performance of the resulting batteries. This invention provides a silicon-carbon composite material, its preparation method, electrodes, and applications. By introducing a manganese source during the preparation of the silicon-carbon composite material, this invention can effectively control silane deposition and carbon layer coating. Batteries made from the obtained silicon-carbon composite material exhibit superior cycle performance.

[0005] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0006] This invention provides a method for preparing a silicon-carbon composite material, comprising the following steps:

[0007] S1. Mixture A is subjected to carbonization and reduction reactions sequentially to obtain porous carbon; mixture A comprises a carbon matrix and a composite template agent; the composite template agent comprises a mixture of a first template agent and a manganese source; the specific surface area of ​​the porous carbon is 1600-2200 m². 2 / g;

[0008] S2. The porous carbon is sequentially subjected to silane deposition and gas-phase carbon coating.

[0009] In S1 of this invention, the type of carbon matrix can be conventional in the art, preferably including phenolic resin and / or bitumen, such as phenolic resin.

[0010] When the carbon matrix is ​​phenolic resin, the preparation method of the phenolic resin can be obtained by conventional methods in the art, preferably including the following steps: mixing resorcinol, formaldehyde, ammonia, ethanol and water, and performing a polymerization reaction.

[0011] The preferred mass-to-volume ratio of resorcinol to formaldehyde is 80g:(100-140)mL, for example, 80g:120mL. The preferred mass ratio of resorcinol to ammonia is (1-3):1, for example, 2:1. The preferred mass ratio of resorcinol to ethanol is (70-90):990, for example, 80:990. The preferred mass ratio of resorcinol to water is 80:(6500-7500), for example, 80:6930. The preferred temperature for the polymerization reaction is 90-110℃, for example, 100℃. The preferred reaction time is 20-30h, for example, 24h.

[0012] In this process, when mixing resorcinol, formaldehyde, ammonia, ethanol, and water, it is preferable to first mix and stir the water, ethanol, and ammonia, then mix and stir the resorcinol, and finally mix and stir the formaldehyde. The temperature for the first mixing can be 30°C. The stirring speed for the first stirring is preferably 700-900 r / min, for example, 800 r / min. The stirring time for the first stirring is preferably 20-40 min, for example, 30 min. The temperature for the second mixing can be 30°C. The stirring speed for the second stirring is preferably 700-900 r / min, for example, 800 r / min. The stirring time for the second stirring is preferably 5-15 min, for example, 10 min. The temperature for the third mixing can be 30°C. The stirring speed for the third stirring is preferably 700-900 r / min, for example, 800 r / min. The stirring time for the third stirring is preferably 20-30 h, for example, 24 h.

[0013] In S1 of the present invention, the first template agent can be of a type conventional in the art, preferably including one or more of Pluronic F-127, Synperonic F-108, Pluronic F-68, hexadecyltrimethylammonium bromide and sodium dodecyl sulfate, such as hexadecyltrimethylammonium bromide.

[0014] In S1 of this invention, the manganese source is preferably manganese oleate and / or manganese chloride, such as manganese oleate or manganese chloride.

[0015] In S1 of the present invention, the preparation method of the composite template agent preferably involves the following steps: under nitrogen atmosphere, the aqueous solution of the first template agent and the manganese source are mixed and stirred.

[0016] The stirring temperature can be 50-70℃, for example 60℃. The stirring time can be 5-7 hours, for example 6 hours.

[0017] In S1 of this invention, the mass concentration of the first template agent in the composite template agent can be 6%-15%, preferably 6.66%-14%, for example 9%, 10%, 11% or 13.3%. The mass concentration of the manganese source can be 5%-20%, preferably 8%-12%, for example 9%, 10% or 11%.

[0018] In S1 of the present invention, the mass ratio of the first template agent to the manganese source in the composite template agent can be (0.5-2):1, preferably (0.66-1.5):1, for example 1:1 or 1.33:1.

[0019] In S1 of this invention, the mass ratio of the carbon matrix to the composite template agent can be (300-700):1, for example 400:1, 500:1 or 600:1.

[0020] In S1 of this invention, the carbonization temperature can be 600-1000℃, for example 700, 800 or 900℃.

[0021] In S1 of this invention, the carbonization treatment time can be 1-5 hours, for example, 3 hours.

[0022] In S1 of this invention, the first template agent is decomposed and removed during the carbonization process.

[0023] In S1 of the present invention, after the carbonization treatment and before the reduction reaction, a carbon dioxide activation step is preferably included.

[0024] The preferred temperature for carbon dioxide activation is 800-1000℃, for example, 900℃.

[0025] During carbon dioxide activation, the carbon dioxide flow rate can be 20-40 L / min, for example, 30 L / min.

[0026] The activation time of the carbon dioxide is preferably 6-10 hours, for example 8 hours.

[0027] The preferred mass-to-volume ratio of the carbon matrix to the carbon dioxide is 1 g:(1-2) L, for example, 1 g:1.44 L.

[0028] In S1 of this invention, a reducing agent is generally added during the reduction reaction. The type of reducing agent can be conventional in the art, such as a hydrogen-nitrogen mixture. In the hydrogen-nitrogen mixture, the volume concentration of hydrogen is preferably 1%-5%, for example, 3%. The mass-to-volume ratio of the carbon matrix to the reducing agent can be 10 kg:(20-30) L, for example, 10 kg:27 L.

[0029] In S1 of this invention, the reduction reaction time can be 3-7 hours, for example, 5 hours.

[0030] In S1 of this invention, the specific surface area of ​​the porous carbon is preferably 1650-2100 m². 2 / g, for example 1811, 1824, 1807, 1795, 1487, 2015, 2088, 1701, 1664 or 1703m 2 / g.

[0031] In S2 of this invention, the silane deposition operation can be conventional in the art, for example, carried out in a rotary kiln.

[0032] In S2 of the present invention, the temperature of silane deposition can be 400-600°C, for example 500°C.

[0033] In S2 of the present invention, the silane deposition time can be 10-14 hours, for example, 12 hours.

[0034] In S2 of this invention, the type of silicon source gas used during silane deposition can be conventional in the art, such as methanesilane.

[0035] In S2 of this invention, the rate of heating from room temperature to the temperature at which silane is deposited can be 3-7°C / min, for example 5°C / min.

[0036] In S2 of this invention, a carrier gas is preferably introduced during silane deposition. The carrier gas is preferably nitrogen. The volume ratio of the carrier gas to the silicon source gas used in silane deposition can be 1:(1-3), for example, 1:2.

[0037] In S2 of the present invention, the mass-to-volume ratio of the porous carbon and the silicon source gas deposited by the silane can be 1g:(1-2)L, for example 1g:1.44L.

[0038] In S2 of the present invention, the operation of gas phase carbon coating can be conventional in the art, and is preferably carried out in a rotary kiln.

[0039] In S2 of the present invention, the temperature of the gas phase carbon coating can be 400-600℃, for example 550℃.

[0040] In S2 of this invention, the time for gaseous carbon coating can be 2-6 hours, for example, 4 hours.

[0041] In S2 of the present invention, the carbon source gas used in the gas phase carbon coating can be one or more of methane, acetylene, ethylene and propylene, for example, acetylene.

[0042] In S2 of this invention, a carrier gas is preferably introduced during the gaseous carbon coating process. The carrier gas is preferably nitrogen. The volume ratio of the carrier gas to the carbon source gas used for gaseous carbon coating can be 1:(1-3), for example, 1:2.

[0043] In S2 of the present invention, the mass-to-volume ratio of the porous carbon and the carbon source gas coated with the gas phase carbon can be 1g:(0.1-1)L, for example 1g:0.24L.

[0044] In this invention, the applicant discovered during the research and development process that when a manganese source is added to the composite template agent, manganese atoms are directionally introduced into the pores as the template agent creates pores, thereby improving the deposition efficiency of silane deposition and vapor-phase carbon coating.

[0045] The present invention also provides a silicon-carbon composite material, which is prepared by the silicon-carbon composite material preparation method described above.

[0046] The present invention also provides a silicon-carbon composite material having a core-shell structure, comprising a core and an outer shell, the outer shell covering the core; the core comprises porous carbon, silicon, and manganese; the specific surface area of ​​the porous carbon is 1600-2200 m². 2 / g; the silicon and manganese are both distributed in the pores of the porous carbon; the outer shell includes a carbon coating layer.

[0047] In this invention, the specific surface area of ​​the porous carbon is preferably 1650-2100 m². 2 / g, for example 1811, 1824, 1807, 1795, 1487, 2015, 2088, 1701, 1664 or 1703m 2 / g.

[0048] In this invention, the manganese content in the silicon-carbon composite material can be 0.3%-1.5% by mass, for example 0.74%, 0.31%, 0.94%, 1.21%, 0.69%, 0.65%, 0.77%, 0.79%, 0.68%, or 0.71%.

[0049] In this invention, the specific surface area of ​​the silicon-carbon composite material can be 1-36 m². 2 / g, for example 2.4, 2.2, 2.7, 3.1, 1.8, 18.6, 21.4, 1.9, 1.8 or 9.6m 2 / g.

[0050] The present invention also provides an electrode comprising the silicon-carbon composite material as described above.

[0051] The present invention also provides an application of the electrode as described above in an electrochemical device.

[0052] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0053] The reagents and raw materials used in this invention are all commercially available.

[0054] The positive and progressive effects of this invention are as follows:

[0055] (1) The present invention combines the first template agent and the manganese source to form a composite template agent, which creates pores in the carbon matrix to obtain porous carbon. This allows manganese atoms to be oriented within the pores of the porous carbon, which is beneficial to improving the deposition efficiency of silane and gas phase carbon coating.

[0056] (2) The battery made from the silicon-carbon composite material obtained by the present invention has better cycle performance. Detailed Implementation

[0057] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0058] Example 1

[0059] S1, (1) Under nitrogen conditions, manganese oleate was added to a 10% (w / w) aqueous solution of hexadecyltrimethylammonium bromide (CTAB), heated to 60°C, and stirred for 6 hours to make the manganese oleate concentration in the solution 10% to obtain a composite template agent; the mass ratio of CTAB to manganese oleate was 1:1.

[0060] (2) 6930g water, 990g ethanol and 40g ammonia were stirred at 800r / min at 30℃ for 30min. Then 80g resorcinol was added and stirred at 800r / min at 30℃ for 10min. Then 120ml formaldehyde solution and 20g of the composite template agent prepared in step (1) were added and stirred at 800r / min at 30℃ for 24h. Then the above mixed solution was transferred to a high pressure vessel and polymerized at 100℃ for 24h. After centrifugation and drying at 120℃ for 48h, a carbon matrix was obtained.

[0061] (2) The 10 kg carbon matrix obtained above was heated to 800°C in a rotary kiln for carbonization treatment for 3 h to remove CTAB. Then the temperature was raised to 900°C and CO2 was introduced at 30 L / min for 8 h. Then nitrogen was introduced for 30 min to remove CO2 from the furnace. A hydrogen-nitrogen mixture with a gas flow rate of 3 L / min (the volume concentration of hydrogen in the hydrogen-nitrogen mixture was 3%) was introduced. After the reduction reaction was carried out for 5 h, the material was discharged to obtain porous carbon.

[0062] S2. Add 1 kg of the prepared porous carbon to a rotary kiln. The nitrogen flow rate is 1 L / min. The temperature is raised to 500°C at 5°C / min. Then, silane is introduced at 2 L / min for silane deposition. The temperature is kept constant for 12 h. Then, the silicon source gas is turned off. The temperature is then raised to 550°C. Acetylene gas is introduced at 1 L / min for gas phase carbon coating. The process is continued for 4 h. Then, the temperature is lowered and the material is discharged.

[0063] Example 2

[0064] The only difference from Example 1 is that step S1(1) is to add manganese oleate to a 10% CTAB aqueous solution under nitrogen conditions, heat to 60°C, and stir for 6 hours to make the mass concentration of manganese oleate in the solution 5% to obtain a composite template agent, with the mass ratio of CTAB to manganese oleate being 2:1.

[0065] Example 3

[0066] The only difference from Example 1 is that step S1(1) is to add manganese oleate to a 10% CTAB aqueous solution under nitrogen conditions, heat to 60°C, and stir for 6 hours to make the mass concentration of manganese oleate in the solution 15% to obtain a composite template agent, with the mass ratio of CTAB to manganese oleate being 0.66:1.

[0067] Example 4

[0068] The only difference from Example 1 is that step S1(1) is to add manganese oleate to a 10% CTAB aqueous solution under nitrogen conditions, heat to 60°C, and stir for 6 hours to make the mass concentration of manganese oleate in the solution 20% to obtain a composite template agent, with the mass ratio of CTAB to manganese oleate being 0.5:1.

[0069] Example 5

[0070] The only difference from Example 1 is that step S1(1) is to add manganese oleate to a CTAB aqueous solution with a mass concentration of 6.66% under nitrogen conditions, heat to 60°C, and stir for 6 hours to make the mass concentration of manganese oleate in the solution 10% to obtain a composite template agent, with the mass ratio of CTAB to manganese oleate being 0.66:1.

[0071] Example 6

[0072] The only difference from Example 1 is that step S1(1) is to add manganese oleate to a CTAB aqueous solution with a mass concentration of 13.3% under nitrogen conditions, heat to 60°C, and stir for 6 hours to make the mass concentration of manganese oleate in the solution 10% to obtain a composite template agent, with the mass ratio of CTAB to manganese oleate being 1.33:1.

[0073] Example 7

[0074] The only difference from Example 1 is that step S1(1) is to add manganese oleate to a 15% CTAB aqueous solution under nitrogen conditions, heat to 60°C, and stir for 6 hours to make the mass concentration of manganese oleate in the solution 10% to obtain a composite template agent, with the mass ratio of CTAB to manganese oleate being 1.5:1.

[0075] Example 8

[0076] The only difference from Example 1 is that in step S1(2), the CO2 introduction time is 6 hours.

[0077] Example 9

[0078] The only difference from Example 1 is that in step S1(2), the CO2 introduction time is 12h.

[0079] Example 10

[0080] The only difference from Example 1 is that manganese oleate is replaced with MnCl2.

[0081] Comparative Example 1

[0082] The only difference from Example 1 is that the composite template agent contains only a 10% (w / w) aqueous solution of manganese oleate.

[0083] Comparative Example 2

[0084] The only difference from Example 1 is that the composite template agent contains only a 10% (w / w) aqueous solution of CTAB.

[0085] Comparative Example 3

[0086] The only difference from Example 1 is that no composite template agent is added.

[0087] Example 1

[0088] The specific surface area of ​​the porous carbon and silicon-carbon composite materials prepared in the above embodiments or comparative examples was tested using a Bestar nitrogen adsorption-desorption device.

[0089] The silicon-carbon composite materials prepared in the above examples or comparative examples were tested for Mn content using an inductively coupled plasma (ICP) analyzer. The test method was as follows: (1) Microwave digestion pretreatment: 0.5g of the silicon-carbon composite materials prepared in the examples or comparative examples were placed in a digestion vessel, and 3mL of concentrated nitric acid and 9mL of concentrated sulfuric acid were added sequentially using a liquid adder. The mixture was shaken and agitated. The mixture was then kept at 160℃ for 3min, 180℃ for 3min, 200℃ for 10min, and 220℃ for 10min sequentially. After cooling to room temperature, the mixture was filtered using quantitative filter paper, and the filtrate was placed in a 50mL volumetric flask as the test solution. (2) The test solution was tested using a PerkinElmer ICP spectrometer Avio. TM The test was conducted in 200 equipment; the test conditions were an air pressure of 2.5 MPa.

[0090] The results are shown in Table 1.

[0091] Table 1

[0092] Specific surface area of ​​porous carbon (m² / g) Specific surface area of ​​silicon-carbon composite material (m² / g) Mn content % Example 1 1811 2.4 0.74 Example 2 1824 2.2 0.31 Example 3 1807 2.7 0.94 Example 4 1795 3.1 1.21 Example 5 1487 1.8 0.69 Example 6 2015 18.6 0.65 Example 7 2088 21.4 0.77 Example 8 1701 1.9 0.79 Example 9 1664 1.8 0.68 Example 10 1703 9.6 0.71 Comparative Example 1 1473 1.7 0.11 Comparative Example 2 1789 11.2 0 Comparative Example 3 1484 1.4 0

[0093] Note: Mn content % indicates the percentage of Mn mass in the silicon-carbon composite material.

[0094] Example 2

[0095] A mixture of silicon-carbon composite material, binder (sodium carboxymethyl cellulose, CMC; styrene-butadiene rubber, SBR), and conductive agent (conductive carbon black, SP; single-walled carbon nanotubes, SWCNT) prepared in the above examples or comparative examples (wherein the mass ratio of silicon-carbon composite material: SP: SWCNT: CMC: SBR = 90: 4.5: 0.5: 2.5: 2.5) was homogenized and coated onto copper foil. The resulting negative electrode was obtained by vacuum drying, rolling, and slitting. A lithium metal sheet was used as the counter electrode. The electrolyte consisted of 1M LiPF6, 89% ethylene carbonate (EC) and diethyl carbonate (DEC) by volume (volume ratio 1:1), 10% fluoroethylene carbonate (FEC) by volume, and 1% vinylene carbonate (VC) by volume. A polypropylene microporous membrane was used as the separator. The mixture was assembled into a coin cell using an argon-filled inert gas glove box system.

[0096] At 25℃, the assembled half-cell was subjected to charge-discharge cycle tests using a Blue Electric testing instrument to obtain data such as reversible specific capacity, initial coulombic efficiency, and cycle life. The test procedure was as follows: discharge to 5mV at 0.1C, discharge to 5mV at 0.05C, charge to 2V at 0.1C; cycle format: discharge to 5mV at 0.5C, discharge to 5mV at 0.05C, charge to 1V at 0.5C.

[0097] The results are shown in Table 2.

[0098] Table 2

[0099] Reversible specific capacity mAh / g First Coulomb efficiency % 500-cycle retention rate % Example 1 1788 93.0 92.2 Example 2 1812 88.7 90.7 Example 3 1694 92.7 90.5 Example 4 1676 89.4 87.9 Example 5 1913 92.3 84.1 Example 6 1654 88.5 85.2 Example 7 1546 86.5 87.0 Example 8 1768 93.1 88.2 Example 9 1657 91.3 84.4 Example 10 1713 86.2 87.1 Comparative Example 1 1870 82.4 82.1 Comparative Example 2 1694 84.7 82.2 Comparative Example 3 1703 85.1 76.7

[0100] As shown in Table 2, compared with Comparative Examples 1-3, Examples 1-10 obtained porous carbon by creating pores in the carbon matrix under the composite template agent (first template agent and manganese source), which allows manganese atoms to be oriented and distributed in the pores of the porous carbon. This is beneficial to improving the deposition efficiency of silane and gas phase carbon coating, thereby enabling the silicon-carbon composite material batteries assembled in Examples 1-10 to have better cycle performance and first coulombic efficiency.

Claims

1. A method for preparing a silicon-carbon composite material, characterized in that, It includes the following steps: S1. Mixture A is subjected to carbonization and reduction reactions sequentially to obtain porous carbon; mixture A comprises a carbon matrix and a composite template agent; the composite template agent comprises a mixture of a first template agent and a manganese source; the first template agent is hexadecyltrimethylammonium bromide; the manganese source is manganese oleate; the specific surface area of ​​the porous carbon is 1701-1824 m². 2 / g; S2. The porous carbon is sequentially subjected to silane deposition and gas-phase carbon coating.

2. The method for preparing the silicon-carbon composite material as described in claim 1, characterized in that, The preparation method of the silicon-carbon composite material satisfies one or more of the following conditions: In A and S1, the mass concentration of the first template agent in the composite template agent is 6%-15%; In B and S1, the mass concentration of the manganese source in the composite template agent is 5%-20%; In C and S1, the mass ratio of the first template agent to the manganese source in the composite template agent is (0.5-2):

1.

3. The method for preparing the silicon-carbon composite material as described in claim 2, characterized in that, The preparation method of the silicon-carbon composite material satisfies one or more of the following conditions: In A and S1, the mass concentration of the first template agent in the composite template agent is 6.66%-14%; In B and S1, the mass concentration of the manganese source in the composite template agent is 8%-12%; In C and S1, the mass ratio of the first template agent to the manganese source in the composite template agent is (0.66-1.5):

1.

4. The method for preparing the silicon-carbon composite material as described in claim 3, characterized in that, The preparation method of the silicon-carbon composite material satisfies one or more of the following conditions: In A and S1, the mass concentration of the first template agent in the composite template agent is 9%, 10%, 11%, or 13.3%. In B and S1, the mass concentration of the manganese source in the composite template agent is 9%, 10%, or 11%. In C and S1, the mass ratio of the first template agent to the manganese source in the composite template agent is 1:1 or 1.33:

1.

5. The method for preparing the silicon-carbon composite material as described in claim 1, characterized in that, The preparation method of the silicon-carbon composite material satisfies one or more of the following conditions: In A and S1, the types of carbon matrix include phenolic resin and / or asphalt; In B and S1, the mass ratio of the carbon matrix to the composite template agent is (300-700):1; In C and S1, the carbonization temperature is 600-1000℃; In D and S1, the carbonization treatment time is 1-5 hours; In E and S1, after the carbonization treatment and before the reduction reaction, a carbon dioxide activation step is also included; In F and S1, a reducing agent is added during the reduction reaction; In G and S1, the mass-to-volume ratio of the carbon matrix to the reducing agent is 10 kg: (20-30) L; In H and S1, the reduction reaction takes 3-7 hours; In I and S1, the specific surface area of ​​the porous carbon is 1811, 1824, 1807, 1795, or 1703 m². 2 / g.

6. The method for preparing the silicon-carbon composite material as described in claim 5, characterized in that, The preparation method of the silicon-carbon composite material satisfies one or more of the following conditions: In A and S1, the carbon matrix includes phenolic resin; In B and S1, the mass ratio of the carbon matrix to the composite template agent is 400:1, 500:1, or 600:1; In C and S1, the carbonization temperature is 700, 800 or 900°C. In D and S1, the carbonization treatment time is 3 hours; In E and S1, the reducing agent is a hydrogen-nitrogen mixture; In F and S1, the mass-to-volume ratio of the carbon matrix to the reducing agent is 10 kg: 27 L; In G and S1, the reduction reaction takes 5 hours.

7. The method for preparing the silicon-carbon composite material as described in claim 6, characterized in that, In the hydrogen-nitrogen mixture, the volume concentration of hydrogen is 1%-5%.

8. The method for preparing the silicon-carbon composite material as described in claim 7, characterized in that, The hydrogen-nitrogen mixture has a hydrogen volume concentration of 3%.

9. The method for preparing the silicon-carbon composite material as described in claim 5, characterized in that, The preparation method of the silicon-carbon composite material satisfies one or more of the following conditions: In A and S1, when the carbon matrix is ​​phenolic resin, the preparation method of the phenolic resin includes the following steps: mixing resorcinol, formaldehyde, ammonia, ethanol and water, and performing a polymerization reaction; In B and S1, the activation temperature of the carbon dioxide is 800-1000℃; In C and S1, the carbon dioxide flow rate during activation is 20-40 L / min; In D and S1, the carbon dioxide activation time is 6-10 hours; In E and S1, the mass-to-volume ratio of the carbon matrix to the carbon dioxide is 1 g: (1-2) L.

10. The method for preparing the silicon-carbon composite material as described in claim 9, characterized in that, The preparation method of the silicon-carbon composite material satisfies one or more of the following conditions: In A and S1, the mass-to-volume ratio of resorcinol to formaldehyde is 80 g: (100-140) mL; In B and S1, the mass ratio of resorcinol to ammonia is (1-3):1; In C and S1, the mass ratio of resorcinol to ethanol is (70-90):990; In D and S1, the mass ratio of resorcinol to water is 80:(6500-7500). In E and S1, the polymerization reaction temperature is 90-110℃; In F and S1, the polymerization reaction takes 20-30 hours. In G and S1, the activation temperature of the carbon dioxide is 900℃; In H and S1, the carbon dioxide flow rate during activation is 30 L / min; In I and S1, the carbon dioxide activation time is 8 hours; In J and S1, the mass-to-volume ratio of the carbon matrix to the carbon dioxide is 1 g: 1.44 L.

11. The method for preparing the silicon-carbon composite material as described in claim 10, characterized in that, The preparation method of the silicon-carbon composite material satisfies one or more of the following conditions: In A and S1, the mass-to-volume ratio of resorcinol and formaldehyde is 80g:120mL; In B and S1, the mass ratio of resorcinol to ammonia is 2:1; In C and S1, the mass ratio of resorcinol to ethanol is 80:990; In D and S1, the mass ratio of resorcinol to water is 80:6930; In E and S1, the polymerization reaction temperature is 100°C; In F and S1, the polymerization reaction takes 24 hours.

12. The method for preparing the silicon-carbon composite material as described in claim 1, characterized in that, The preparation method of the silicon-carbon composite material satisfies one or more of the following conditions: In A and S2, the temperature for silane deposition is 400-600℃; In B and S2, the silane deposition time is 10-14 hours; In C and S2, the rate of heating from room temperature to the temperature at which silane is deposited is 3-7 °C / min; In D and S2, the mass-to-volume ratio of the porous carbon to the silane gas deposited by the silane is 1 g: (1-2) L; In E and S2, the temperature of the gaseous carbon coating is 400-600℃; In F and S2, the time for gaseous carbon coating is 2-6 hours; In G and S2, the mass-to-volume ratio of the porous carbon and the carbon source gas coated with gaseous carbon is 1 g : (0.1-1) L.

13. The method for preparing the silicon-carbon composite material as described in claim 12, characterized in that, The preparation method of the silicon-carbon composite material satisfies one or more of the following conditions: In A and S2, the temperature for silane deposition is 500°C; In B and S2, the silane deposition time is 12 hours; In C and S2, the rate of heating from room temperature to the temperature at which silane is deposited is 5 °C / min; In D and S2, the mass-to-volume ratio of the porous carbon and the silane gas deposited by the silane is 1 g: 1.44 L; In E and S2, the temperature of the gas phase carbon coating is 550°C; In F and S2, the time for gaseous carbon coating is 4 hours; In G and S2, the mass-to-volume ratio of the porous carbon and the carbon source gas coated with gaseous carbon is 1g:0.24L.

14. A silicon-carbon composite material, characterized in that, It is prepared by the method of any one of claims 1-13 for the preparation of silicon-carbon composite materials.

15. A silicon-carbon composite material, characterized in that, It has a core-shell structure, comprising a core and an outer shell, with the outer shell covering the core; the core comprises porous carbon, silicon, and manganese; the specific surface area of ​​the porous carbon is 1701-1824 m². 2 / g; the silicon and manganese are both distributed in the pores of the porous carbon; the outer shell includes a carbon coating layer; The raw materials of the silicon-carbon composite material include a carbon matrix and a composite template agent; the composite template agent includes a mixture of a first template agent and a manganese source; the first template agent is hexadecyltrimethylammonium bromide; and the manganese source is manganese oleate.

16. The silicon-carbon composite material as described in claim 15, characterized in that, The silicon-carbon composite material satisfies one or more of the following conditions: A. The specific surface area of ​​the porous carbon is 1703-1824 m². 2 / g; B. In the silicon-carbon composite material, the manganese content is 0.3%-1.5% by mass; C. The specific surface area of ​​the silicon-carbon composite material is 1-36 m². 2 / g.

17. The silicon-carbon composite material as described in claim 16, characterized in that, The silicon-carbon composite material satisfies one or more of the following conditions: A. The specific surface area of ​​the porous carbon is 1811, 1824, 1807, 1795 or 1703 m². 2 / g; B. In the silicon-carbon composite material, the mass content of manganese is 0.74%, 0.31%, 0.94%, 1.21%, 0.69%, 0.65%, 0.77%, 0.79%, 0.68%, or 0.71%. C. The specific surface area of ​​the silicon-carbon composite material is 2.4, 2.2, 2.7, 3.1, 1.8, 18.6, 21.4, 1.9, 1.8, or 9.6 m². 2 / g.

18. An electrode sheet, characterized in that, It includes silicon-carbon composite materials as described in any one of claims 14-17.

19. The application of the electrode as described in claim 18 in an electrochemical device.