Silicon-carbon negative electrode material, preparation method and application thereof

Abstract

This invention relates to a silicon-carbon anode material, its preparation method, and its applications. The silicon-carbon anode material comprises an outer shell and a core. The core includes porous carbon and nano-silicon particles. The nano-silicon particles are deposited within the pore structure of the porous carbon. The outer shell covers the outer surface of the core and includes a carbon coating layer and a tar carbonization layer. The tar carbonization layer covers the outer side of the core, and the carbon coating layer is located outside the tar carbonization layer. In this invention, the tar carbonization layer in the outer shell ensures sufficient internal space to buffer the volume changes that occur during the expansion of the nano-silicon particles, thus improving the mechanical strength of the silicon-carbon anode material. The carbon coating layer further buffers the volume expansion and contraction of the nano-silicon particles during charging and discharging, improving the structural stability of the material.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and in particular to a silicon-carbon anode material, its preparation method, and its application. Background Technology

[0002] Silicon-based anode materials possess extremely high theoretical specific capacity, far exceeding that of currently widely used graphite anode materials. Graphite's specific capacity is approximately 372 mAh / g, while silicon's can reach 4200 mAh / g. This means that using silicon-based anodes can significantly improve battery energy density, thereby extending the driving range of electric vehicles or reducing battery size and weight. Silicon is the second most abundant element in the Earth's crust, making it relatively plentiful and helping to reduce costs and dependence on rare resources. However, silicon-based anode materials undergo significant volume expansion (up to 300% or more) during charge and discharge, which can lead to electrode structure damage and shorten battery cycle life, greatly limiting their large-scale commercialization. Therefore, effectively suppressing the volume expansion of silicon-based anode materials is crucial. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies by providing a silicon-carbon anode material, its preparation method, and its applications.

[0004] To achieve the above objectives, in a first aspect, the present invention provides a silicon-carbon anode material, the structure of which includes an outer shell and a core;

[0005] The core comprises porous carbon and nano-silicon particles; the nano-silicon particles are deposited in the porous structure of the porous carbon.

[0006] The outer shell covers the outer surface of the core, and the outer shell includes a carbon coating layer and a tar carbonization layer; the tar carbonization layer covers the outside of the core; the carbon coating layer is located outside the tar carbonization layer.

[0007] Preferably, the porous carbon has a pore size of 2nm-30nm and a specific surface area of ​​100m². 2 / g-3000m 2 / g.

[0008] Preferably, the thickness of the carbon coating layer is 1nm-50nm.

[0009] In a second aspect, the present invention provides a method for preparing the silicon-carbon anode material according to any one of the first aspects, the method comprising:

[0010] Silicon source gas is introduced into a reactor carrying a porous carbon matrix for vapor phase deposition to obtain a porous silicon-carbon composite.

[0011] After the porous silicon-carbon composite is mixed with tar, it is subjected to carbonization treatment to obtain a silicon-carbon composite coated with a tar carbonization layer.

[0012] A carbon source gas is introduced to carbonize the silicon-carbon composite material coated with the tar carbonization layer, thereby obtaining the silicon-carbon anode material.

[0013] Preferably, the porous carbon matrix includes one or more of biomass-based porous carbon, resin-based porous carbon, graphite-based porous carbon, and tar-based porous carbon; the silicon source gas includes one or more of silicon vapor, silane, propane, dichlorosilane, trichlorosilane, and tetrachlorosilane.

[0014] Preferably, the step of mixing the porous silicon-carbon composite with tar specifically includes:

[0015] The porous silicon-carbon composite and tar are mixed in a mixer at a speed of 100 rpm to 500 rpm for 1 to 8 hours.

[0016] Preferably, the carbonization treatment is carried out at a temperature of 300℃-800℃ for 1 hour to 6 hours.

[0017] Preferably, the carbon coating is carried out in a rotary kiln at a rotation speed of 6Hz-20Hz, a temperature of 400℃-900℃, a time of 1 hour-15 hours, and a carbon source gas flow rate of 1L / min-15L / min.

[0018] Thirdly, the present invention provides a negative electrode sheet, the negative electrode sheet comprising any of the silicon-carbon negative electrode materials described in the first aspect or silicon-carbon negative electrode materials prepared by any of the preparation methods described in the second aspect.

[0019] Fourthly, the present invention provides a lithium-ion battery, the lithium-ion battery comprising the negative electrode sheet described in the third aspect.

[0020] The silicon-carbon anode material provided in this invention comprises a core and a shell. The tar-carbonized layer in the shell firstly ensures sufficient internal space to buffer the volume changes that occur during the expansion of the silicon nanoparticles, thus improving the mechanical strength of the silicon-carbon anode material. Secondly, it protects the core, preventing it from contacting oxygen in the air, reducing oxidation, and maintaining the stability of the material. Thirdly, it forms a conductive network with the porous carbon, improving the conductivity of the silicon-carbon anode material. Finally, it reduces the amount of carbon coating, increases the silicon content in the silicon-carbon anode material, and improves the specific capacity of the entire material. The carbon coating can further form a conductive network with the carbon in the tar-carbonized layer, further improving the conductivity of the silicon-carbon anode material. It can also further buffer the volume expansion and contraction of the silicon nanoparticles during charging and discharging, improving the structural stability of the material. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the silicon-carbon anode material provided in an embodiment of the present invention;

[0022] Figure 2 A flowchart illustrating the preparation method of silicon-carbon anode material provided in an embodiment of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0024] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0025] This invention provides a silicon-carbon anode material, the structure of which is as follows: Figure 1 As shown, it specifically includes the outer shell and the core.

[0026] The core specifically comprises porous carbon and nano-silicon particles. Porous carbon serves as the framework of the core. The pore size of the porous carbon is 2nm-30nm, and its specific surface area is 100m². 2 / g-3000m 2 / g, Dv50 is 1μm-120μm. Nano-silicon particles are deposited in the porous structure of porous carbon.

[0027] Porous carbon has good electronic conductivity, and when combined with nano-silicon particles, it can improve the conductivity of silicon-carbon anode materials.

[0028] The outer shell consists of a carbon coating layer and a tar-carbonized layer. The tar-carbonized layer coats the outer surface of the core. The function of the tar-carbonized layer is as follows:

[0029] First, it ensures sufficient internal space to buffer the volume changes that occur during the expansion of silicon nanoparticles, thus improving the mechanical strength of the silicon-carbon anode material. Second, it protects the core, preventing it from contacting oxygen in the air, reducing oxidation, and maintaining the material's stability. Third, it forms a conductive network with the porous carbon, improving the conductivity of the silicon-carbon anode material. Finally, it reduces the amount of carbon coating, increases the silicon content in the silicon-carbon anode material, and improves the overall specific capacity.

[0030] The carbon coating layer is located on the outside of the tar carbonization layer. The thickness of the carbon coating layer is specifically 1nm-50nm.

[0031] The carbon coating layer serves several key functions: First, it can form a conductive network with the carbon in the tar carbonization layer, further enhancing the conductivity of the silicon-carbon anode material. Second, it prevents the aggregation of nanoparticles, maintaining the nanoscale of the material and its high specific surface area. Third, it further buffers the volume expansion and contraction of the silicon nanoparticles during charging and discharging, improving the structural stability of the material.

[0032] This invention also provides a method for preparing the silicon-carbon anode material described above, the process of which is as follows: Figure 2 As shown, it includes the following steps:

[0033] Step 110: The silicon source gas is introduced into a reactor carrying a porous carbon matrix for vapor phase deposition to obtain a porous silicon-carbon composite.

[0034] Specifically, the porous carbon matrix may include one or more of the following: biomass-based porous carbon, resin-based porous carbon, graphite-based porous carbon, and tar-based porous carbon; the silicon source gas may include one or more of the following: silicon vapor, silane, propane, dichlorosilane, trichlorosilane, and tetrachlorosilane. The flow rate of the silicon source gas may be 10 L / min to 100 L / min, and the reaction time may be 30 min to 400 min. The reactor may be a tube furnace. The pore size of the porous carbon matrix is ​​2 nm to 30 nm, and the specific surface area is 100 m². 2 / g-3000m 2 / g, Dv50 is 1μm-120μm. The porous silicon-carbon composite is the core of the silicon-carbon anode material. The vapor deposition atmosphere is one or both of nitrogen and argon atmospheres.

[0035] Step 120: After mixing the porous silicon-carbon composite with tar, carbonization treatment is performed to obtain a silicon-carbon composite coated with a tar carbonization layer.

[0036] Specifically, the porous silicon-carbon composite and tar are mixed in a mixer at a speed of 100-500 rpm for 1-8 hours. After homogenization, the mixture is transferred to a rotary kiln for carbonization. The tar accounts for 2%-30% of the mass of the final mixture. The carbonization temperature can be 300℃-800℃, and the time can be 1-6 hours. The carbonization atmosphere is one or both of nitrogen and argon atmospheres.

[0037] Encapsulating porous carbon-silicon-carbon composites with tar before carbonization offers several advantages:

[0038] First, due to its inherent properties, tar can act as a binder during the carbonization process, enhancing the internal bonding force of carbon materials, thereby improving the mechanical strength and wear resistance of the materials.

[0039] Second, after carbonization, the tar forms a conductive carbon network with the porous carbon matrix, which can improve the overall conductivity of the material.

[0040] Third, some tar enters the porous structure of the porous carbon, sealing the pores. Subsequent carbonization inhibits the expansion of silicon particles. Some tar on the surface of the porous carbon buffers the stress caused by changes in silicon particle volume, improving the material's mechanical strength. Due to the sealing effect of the tar carbonization layer, the specific surface area reduction / carbon coating amount increases, meaning a larger reduction in specific surface area per unit carbon coating. This reduces the amount of carbon used in the subsequent carbon coating layer, thus increasing the silicon content to some extent compared to silicon-carbon anode materials with only a carbon coating, thereby improving the material's specific capacity.

[0041] Fourth, carbonization of tar can also form a porous structure, which helps to increase the specific surface area of ​​the material.

[0042] Step 130: Introduce carbon source gas to carbonize the silicon-carbon composite coated with tar carbonization layer to obtain silicon-carbon anode material.

[0043] Specifically, carbon coating can be carried out in a rotary kiln at a rotation speed of 6Hz-20Hz, a temperature of 400℃-900℃, and a time of 1 hour-15 hours. The flow rate of the carbon source gas can be 1L / min-15L / min. The carbon source gas can be one or more of methane, ethylene, and propane.

[0044] The carbon coating process allows the carbon in the tar-carbonized layer to form a conductive network, further improving the conductivity of the silicon-carbon anode material. It also further buffers the volume expansion and contraction of the nano-silicon particles during charging and discharging, enhancing the material's structural stability. The carbon coating atmosphere is one or both of nitrogen and argon. The thickness of the carbon coating layer is specifically 1 nm to 50 nm.

[0045] In summary, the method for preparing a silicon-carbon anode material provided by this invention involves encapsulating a porous silicon-carbon composite core with tar to seal the pores of the porous carbon matrix. Subsequent carbonization treatment creates a conductive network between the carbon in the porous carbon matrix and the carbon in the tar-carbonized layer. The tar-carbonized layer also ensures sufficient internal space to buffer the volume changes of the silicon nanoparticles during expansion, improving the material's mechanical properties. Simultaneously, it reduces the amount of carbon used in the carbon coating, thus increasing the silicon content to some extent and improving the material's specific capacity. A subsequent carbon coating treatment further enhances the conductivity of the silicon-carbon anode material by forming a conductive network.

[0046] The silicon-carbon anode material provided by this invention can be used as an electrode material in energy storage devices such as supercapacitors, lithium-ion batteries, sodium-ion batteries, and dye-sensitized batteries.

[0047] To better understand the technical solution provided by the present invention, the following uses several specific examples to illustrate the specific process of preparing silicon-carbon anode materials using the method provided in the above embodiments of the present invention, as well as the electrochemical characteristics of the prepared silicon-carbon anode materials.

[0048] Example 1

[0049] In the first step, under a nitrogen atmosphere, trichlorosilane was introduced into a reactor containing 2 kg of biomass-based porous carbon matrix at a gas flow rate of 10 L / min for vapor deposition for 400 min to obtain a porous silicon-carbon composite. The specific surface area of ​​the biomass-based porous carbon matrix was 1800 m² / s. 2 / g, pore size is 4nm, Dv50 is 10μm.

[0050] The second step involves placing the porous silicon-carbon composite and tar in a mixer and mixing at 500 rpm for 4 hours. The mixture is then transferred to a rotary kiln for carbonization in a nitrogen atmosphere at 10 Hz and 500°C for 3 hours, resulting in a silicon-carbon composite coated with a tar carbonization layer. The tar accounts for 2% of the mass of the mixed material.

[0051] The third step involves introducing methane into a rotary kiln under a nitrogen atmosphere at a gas flow rate of 8 L / min to perform carbon coating, thereby obtaining silicon-carbon anode material. The rotary kiln operates at a speed of 6 Hz, a temperature of 660 °C, and a time of 2 hours.

[0052] Subsequently, the prepared silicon-carbon anode material was used as the anode active material to prepare an electrode sheet, and this electrode sheet was used to assemble a full-electric battery for testing, as detailed below:

[0053] First, the prepared silicon-carbon anode material was mixed with a specific capacity of 350 mAh g. -1 The composite anode material is composed of graphite, and its theoretical capacity is 480 mAh g. -1 .

[0054] Next, the composite negative electrode material, conductive agent (Super P), binder carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) are mixed in a mass ratio of 94.5:2:2:1.5, ground into a slurry, and then coated onto copper foil to prepare the negative electrode sheet. The positive electrode uses a high-nickel ternary (811 type) material. The positive electrode active material (811 type high-nickel ternary material), conductive agent 1 (Super P), conductive agent 2 (single-walled CNT), and binder (PVDF) are mixed in a mass ratio of 95.2:1.8:1:2, ground into a slurry, and then coated onto aluminum foil to prepare the positive electrode sheet. Eleven negative electrode sheets and ten positive electrode sheets are assembled into a 5085 type small soft-pack battery. The electrolyte is 1 mol / L LiPF6 (the solvent is ethylene carbonate, dimethyl carbonate, and diethyl carbonate in a volume ratio of 1:1:1).

[0055] Then, the initial thickness h1 of the negative electrode sheet was measured;

[0056] Subsequently, under the conditions of a charging cutoff voltage of 4.25V and a discharging cutoff voltage of 2.75V, the battery was fully charged at a rate of 0.5C, and its lithium intercalation capacity and first-cycle coulombic efficiency were tested. The battery was then disassembled, and the thickness h2 of the electrode was measured again to calculate the expansion rate. The expansion rate was calculated using the formula (h2-h1) / h1.

[0057] Example 2

[0058] In the first step, under a nitrogen atmosphere, trichlorosilane was introduced into a reactor containing 2 kg of biomass-based porous carbon matrix at a gas flow rate of 100 L / min for vapor phase deposition for 30 min to obtain a porous silicon-carbon composite. The specific surface area of ​​the biomass-based porous carbon matrix was 1600 m² / s. 2 / g, pore size is 3.8nm, Dv50 is 6μm.

[0059] The second step involves placing the porous silicon-carbon composite and tar in a mixer and mixing them at 200 rpm for 8 hours. The mixture is then transferred to a rotary kiln for carbonization in a nitrogen atmosphere. The rotary kiln operates at a speed of 6 Hz, a temperature of 600°C, and a time of 5 hours, resulting in a silicon-carbon composite coated with a tar carbonization layer. The tar constitutes 5% of the mass of the mixed material.

[0060] The third step involves introducing ethylene into a rotary kiln under a nitrogen atmosphere at a gas flow rate of 10 L / min for carbon coating to obtain silicon-carbon anode material. The rotary kiln operates at a speed of 15 Hz, a temperature of 550 °C, and a time of 4 hours.

[0061] The testing process is the same as in Example 1.

[0062] Example 3

[0063] In the first step, under a nitrogen atmosphere, trichlorosilane was introduced into a reactor containing 2 kg of biomass-based porous carbon matrix at a gas flow rate of 50 L / min for vapor phase deposition for 300 min to obtain a porous silicon-carbon composite. The specific surface area of ​​the biomass-based porous carbon matrix was 500 m² / s. 2 / g, pore size is 8.1nm, Dv50 is 9 micrometers.

[0064] The second step involves placing the porous silicon-carbon composite and tar in a mixer and mixing them at 400 rpm for 1 hour. The mixture is then transferred to a rotary kiln for carbonization in a nitrogen atmosphere. The rotary kiln operates at 6 Hz, a temperature of 500°C, and a time of 4 hours, resulting in a silicon-carbon composite coated with a tar carbonization layer. The tar constitutes 15% of the mass of the mixed material.

[0065] The third step involves introducing propane into a rotary kiln under a nitrogen atmosphere at a gas flow rate of 6 L / min to perform carbon coating, thereby obtaining silicon-carbon anode material. The rotary kiln operates at a speed of 10 Hz, a temperature of 480 °C, and a time of 15 hours.

[0066] The testing process is the same as in Example 1.

[0067] Example 4

[0068] In the first step, under an argon atmosphere, propane silane was introduced into a reactor containing 4 kg of resin-based porous carbon matrix at a gas flow rate of 30 L / min for vapor deposition for 300 min to obtain a porous silicon-carbon composite. The resin-based porous carbon matrix had a specific surface area of ​​3000 m². 2 / g, pore size is 2nm, Dv50 is 50μm.

[0069] The second step involves placing the porous silicon-carbon composite and tar in a mixer and mixing them at 100 rpm for 7 hours. The mixture is then transferred to a rotary kiln under an argon atmosphere for carbonization. The rotary kiln operates at 6 Hz, a temperature of 300°C, and a time of 6 hours, resulting in a silicon-carbon composite coated with a tar carbonization layer. The tar constitutes 30% of the mass of the mixed material.

[0070] The third step involves introducing propane into a rotary kiln under an argon atmosphere at a gas flow rate of 1 L / min to perform carbon coating, thereby obtaining silicon-carbon anode material. The rotary kiln operates at a speed of 20 Hz, a temperature of 440 °C, and a time of 15 hours.

[0071] The testing process is the same as in Example 1.

[0072] Example 5

[0073] In the first step, silicon vapor was introduced into a reactor containing 8 kg of tar-based porous carbon matrix at a flow rate of 60 L / min under a nitrogen atmosphere for vapor deposition for 300 min, resulting in a porous silicon-carbon composite. The tar-based porous carbon matrix had a specific surface area of ​​100 m². 2 / g, pore size is 30nm, Dv50 is 120μm.

[0074] The second step involves placing the porous silicon-carbon composite and tar in a mixer and mixing them at 300 rpm for 4 hours. The mixture is then transferred to a rotary kiln under an argon atmosphere for carbonization. The rotary kiln operates at 6 Hz, a temperature of 800°C, and a time of 1 hour, resulting in a silicon-carbon composite coated with a tar carbonization layer. The tar constitutes 18% of the mass of the mixed material.

[0075] The third step involves introducing propane into a rotary kiln under an argon atmosphere at a gas flow rate of 15 L / min to perform carbon coating, thereby obtaining silicon-carbon anode material. The rotary kiln operates at a speed of 16 Hz, a temperature of 900 °C, and a time of 1 hour.

[0076] The testing process is the same as in Example 1.

[0077] Comparative Example 1

[0078] In the first step, under a nitrogen atmosphere, trichlorosilane was introduced into a reactor containing 2 kg of biomass-based porous carbon matrix at a gas flow rate of 10 L / min for vapor deposition for 400 min to obtain a porous silicon-carbon composite. The specific surface area of ​​the biomass-based porous carbon matrix was 1800 m² / s. 2 / g, pore size is 4nm, Dv50 is 10μm.

[0079] The second step involves introducing methane into a rotary kiln under a nitrogen atmosphere at a gas flow rate of 8 L / min to perform carbon coating, thereby obtaining silicon-carbon anode material. The rotary kiln operates at a speed of 6 Hz, a temperature of 660 °C, and a time of 2 hours.

[0080] The testing process is the same as in Example 1.

[0081] Comparative Example 2

[0082] In the first step, under a nitrogen atmosphere, trichlorosilane was introduced into a reactor containing 2 kg of biomass-based porous carbon matrix at a gas flow rate of 10 L / min for vapor deposition for 400 min to obtain a porous silicon-carbon composite. The specific surface area of ​​the biomass-based porous carbon matrix was 1800 m² / s. 2 / g, pore size is 4nm, Dv50 is 10μm.

[0083] The second step involves placing the porous silicon-carbon composite and tar in a mixer and mixing them at 500 rpm for 4 hours to obtain a tar-coated silicon-carbon composite. The tar accounts for 2% of the mass of the tar-coated silicon-carbon composite.

[0084] The third step involves introducing propane into a rotary kiln under a nitrogen atmosphere at a gas flow rate of 8 L / min to perform carbon coating, thereby obtaining silicon-carbon anode material. The rotary kiln operates at a speed of 6 Hz, a temperature of 660 °C, and a time of 2 hours.

[0085] The testing process is the same as in Example 1.

[0086] Table 1 summarizes the electrochemical data tests of the silicon-carbon anode materials prepared in Examples 1-5 and Comparative Examples 1-2 of this invention.

[0087]

[0088]

[0089] Table 1

[0090] As shown in Table 1, compared to Comparative Examples 1 and 2, the silicon-carbon anode materials prepared in Examples 1-5 of this invention have lower expansion rates. This is because the tar carbonization layer provides a buffer space for the volume expansion of silicon, reducing the expansion rate. Comparative Example 1 directly carbon-coated the silicon-carbon composite without undergoing the tar-coating and carbonization process, resulting in a higher expansion rate. Although Comparative Example 2 involved tar coating, which to some extent suppressed silicon expansion, the lack of tar carbonization meant that the carbon generated from the tar and the carbon generated from propane would interact during the subsequent carbon coating process, reducing carbon density and failing to effectively suppress silicon expansion, thus resulting in a higher expansion rate.

[0091] The high lithium intercalation capacity of Examples 1-5 of this invention is due to the fact that carbonization of the tar reduces the specific surface area of ​​the silicon-carbon anode material and increases the carbon coating amount, thereby reducing the amount of carbon used in the carbon coating layer. This results in a higher silicon content in the final silicon-carbon anode material, leading to a correspondingly higher lithium intercalation capacity. In contrast, Comparative Example 1 involves direct vapor-phase coating, and Comparative Document 2 does not involve carbonization of the tar, so the amount of carbon used in the carbon coating layer does not decrease.

[0092] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A silicon-carbon negative electrode material, characterized by, The structure of the silicon-carbon anode material includes an outer shell and a core; The core comprises porous carbon and nano-silicon particles; the nano-silicon particles are deposited in the porous structure of the porous carbon. The outer shell covers the outer surface of the core, and the outer shell includes a carbon coating layer and a tar carbonization layer; the tar carbonization layer covers the outside of the core; the carbon coating layer is located outside the tar carbonization layer.

2. The silicon-carbon negative electrode material of claim 1, wherein, The porous carbon has a pore size of 2 nm to 30 nm, a specific surface area of 100 m 2 / g to 3000 m 2 / g.

3. The silicon-carbon negative electrode material of claim 1, wherein, The thickness of the carbon coating layer is 1nm-50nm.

4. A method for preparing the silicon-carbon negative electrode material according to any one of claims 1 to 3, characterized in that The preparation method includes: Silicon source gas is introduced into a reactor carrying a porous carbon matrix for vapor phase deposition to obtain a porous silicon-carbon composite. After the porous silicon-carbon composite is mixed with tar, it is subjected to carbonization treatment to obtain a silicon-carbon composite coated with a tar carbonization layer. A carbon source gas is introduced to carbonize the silicon-carbon composite material coated with the tar carbonization layer, thereby obtaining the silicon-carbon anode material.

5. The preparation method according to claim 4, characterized in that, The porous carbon matrix includes one or more of biomass-based porous carbon, resin-based porous carbon, graphite-based porous carbon, and tar-based porous carbon; the silicon source gas includes one or more of silicon vapor, silane, propane, dichlorosilane, trichlorosilane, and tetrachlorosilane.

6. The preparation method according to claim 4, characterized in that, The process of mixing the porous silicon-carbon composite with tar specifically includes: The porous silicon-carbon composite and tar are mixed in a mixer at a speed of 100 rpm to 500 rpm for 1 to 8 hours.

7. The preparation method according to claim 4, characterized in that, The carbonization process is carried out at a temperature of 300℃-800℃ for 1 hour to 6 hours.

8. The preparation method according to claim 4, characterized in that, The carbon coating is carried out in a rotary kiln at a rotation speed of 6Hz-20Hz, a temperature of 400℃-900℃, a time of 1 hour-15 hours, and a carbon source gas flow rate of 1L / min-15L / min.

9. A negative electrode sheet, characterized in that, The negative electrode sheet comprises the silicon-carbon negative electrode material according to any one of claims 1-3 or the silicon-carbon negative electrode material prepared by any one of claims 4-8.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the negative electrode sheet as described in claim 9.

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