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

Abstract

The invention provides a silicon-carbon negative electrode material, a preparation method thereof and a lithium ion battery. The preparation method comprises the following steps: S1, carrying out heat treatment on a green coke material to obtain a modified coke material; s2, activating and pore-forming the modified coke material to obtain a porous carbon carrier; and S3, contacting the porous carbon material with gas-phase silane, and carrying out vapor deposition to obtain the silicon-carbon negative electrode material. According to the preparation method disclosed by the invention, the modified coke material subjected to specific heat treatment is used as a preparation raw material of the porous carbon carrier, and the porous carbon carrier which is more beneficial to silicon deposition is obtained, so that after the porous carbon carrier is subsequently compounded with a silicon material, the volume expansion of silicon is inhibited, and the capacity and cycle performance of the silicon-carbon negative electrode material are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion batteries, and relates to a silicon-carbon negative electrode material, a preparation method thereof and a lithium ion battery. BACKGROUND

[0002] With the increasing demand for endurance of new energy vehicles, the negative electrode material of lithium batteries is also developing towards high specific capacity. The theoretical specific capacity of silicon is 4200mAh / g, which is much higher than that of graphite-based negative electrode materials. Therefore, lithium batteries using silicon-based negative electrode materials have significant comparative advantages in energy density, endurance and the like.

[0003] However, the silicon material will swell and shrink during the charging and discharging process of the battery. Multiple cycles will not only cause the electrical contact performance of the silicon material to fail, but also continuously destroy the SEI film that has been formed and continuously generate new SEI films. Multiple cycles will produce a large amount of by-products that are densely packed in the SEI film, accelerate the peeling of the carbon layer, and cause the electrochemical performance of the silicon negative electrode material to deteriorate sharply.

[0004] Therefore, how to improve the electrochemical performance of the silicon negative electrode has become a technical problem to be solved by those skilled in the art. SUMMARY

[0005] In view of the deficiencies in the prior art, the purpose of the present application is to provide a silicon-carbon negative electrode material, a preparation method thereof and a lithium ion battery. The porous carbon carrier prepared by using the modified coke after heat treatment as a preparation raw material can not only provide a confined space to bind the volume expansion of the nano-silicon, but also has high conductivity, which is beneficial to the improvement of the electrochemical performance of the silicon-carbon negative electrode material.

[0006] To achieve the purpose of the present application, the following technical solutions are adopted:

[0007] In a first aspect, the present application provides a preparation method of a silicon-carbon negative electrode material, which comprises the following steps:

[0008] S1: heat treating green coke material to obtain modified coke material;

[0009] S2: activating and pore-making the modified coke material to obtain a porous carbon carrier;

[0010] S3: contacting the porous carbon carrier with a gaseous silicon source to obtain a silicon-carbon negative electrode material by vapor deposition.

[0011] The following is a preferred technical solution of the present application, but is not a limitation on the technical solutions provided by the present application. Through the following preferred technical solution, the technical purpose and beneficial effects of the present application can be better achieved and realized.

[0012] Preferably, the method for activating pores in step S2 comprises chemical activation and / or physical activation, preferably chemical activation and physical activation.

[0013] Preferably, the method for activating pores in step S2 comprises:

[0014] The chemical activation agent is mixed with the modified coke material, and a physical activation agent is introduced, and then the temperature is raised to the activation temperature for activation treatment to complete the activation of pores.

[0015] Preferably, the mass ratio of the chemical activation agent to the modified coke material is (1-3): 1.

[0016] Preferably, the flow rate of the physical activation agent introduced is 4 L / min to 12 L / min.

[0017] Preferably, the temperature of the activation treatment is 700°C to 900°C.

[0018] Preferably, the time of the activation treatment is 3h to 5h.

[0019] Preferably, step S2 further comprises crushing the porous carbon carrier, and the median particle size Dv50 of the porous carbon carrier after crushing is 6 μm to 15 μm.

[0020] Preferably, the introduction of the gas-phase silicon source in step S3 further comprises a carrier gas.

[0021] Preferably, the flow rate of the gas-phase silicon source introduced in step S3 is 5 L / min to 10 L / min.

[0022] Preferably, the flow rate of the carrier gas is 50 L / min to 80 L / min.

[0023] Preferably, the deposition temperature of the gas-phase deposition in step S3 is 500°C to 600°C.

[0024] Preferably, the deposition time of the gas-phase deposition in step S3 is 6h to 10h.

[0025] Preferably, after the deposition of the gas-phase silicon source in step S3 is completed, the product after deposition is subjected to carbon coating treatment to obtain the silicon-carbon negative electrode material.

[0026] Preferably, the median particle size Dv50 of the green coke material in step S1 is 0.1 mm to 5 mm.

[0027] Preferably, the temperature of the heat treatment in step S1 is 600°C to 800°C.

[0028] Preferably, the time of the heat treatment in step S1 is 2h to 6h.

[0029] In a second aspect, the present application provides a silicon-carbon negative electrode material, which is prepared by the preparation method according to the first aspect.

[0030] The silicon-carbon negative electrode material comprises a porous carbon carrier and a silicon material in the internal pores of the porous carbon carrier.

[0031] Preferably, the silicon-carbon negative electrode material further comprises a carbon coating layer coated on the surface of the porous carbon carrier.

[0032] In a third aspect, the present application further provides a lithium ion battery comprising the silicon-carbon negative electrode material according to the second aspect.

[0033] Compared with the prior art, the present application has the following beneficial effects:

[0034] In the technical scheme of the present application, the green coke material is subjected to heat treatment, and the volatile components in the green coke raw material are effectively removed after the heat treatment, which facilitates the activation of the coke, and the fibers in the green coke raw material are developed after the heat treatment, the size of the anisotropic structure is increased, and the orientation is improved, and the proportion of streamline structure is increased, which facilitates the improvement of the graphitization degree when the modified coke material is used to prepare the porous carbon material, so that the porous carbon carrier with large specific surface area, rich pores and excellent electrical conductivity is prepared, and then the porous carbon carrier is contacted with the gas-phase silicon source to deposit silicon, which is beneficial to the improvement of the electrochemical performance of the silicon-carbon negative electrode material. DETAILED DESCRIPTION

[0035] The technical scheme of the present application will be further described by specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application, and should not be regarded as specific limitation to the present application.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application; the terms "comprising" and "having," and any variations thereof, are intended to cover not exclusively including.

[0037] In the description of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0038] In one embodiment, the first aspect of the present application provides a preparation method of a silicon-carbon negative electrode material, which comprises the following steps:

[0039] S1: heat treating the green coke material to obtain a modified coke material;

[0040] S2: activating and forming pores in the modified coke material to obtain a porous carbon carrier;

[0041] S3: contacting the porous carbon carrier with a gas-phase silicon source to obtain a silicon-carbon negative electrode material through vapor deposition.

[0042] In the technical solution of the present application, the green coke material is heat treated, and the volatile components in the green coke material are effectively removed after heat treatment, which facilitates the activation of the coke and the growth of fibers in the green coke material after heat treatment. The size of the anisotropic structure is increased, the orientation is improved, and the proportion of streamline structure is increased. The graphitization degree of the porous carbon material prepared from the modified coke material is improved, thereby preparing a porous carbon carrier with a large specific surface area, rich pores, and excellent electrical conductivity. The prepared porous carbon carrier can provide a confined space and bind the volume expansion of nano-silicon after the subsequent silicon compounding, and has high electrical conductivity, which is beneficial to the improvement of the electrochemical performance of the silicon-carbon negative electrode material.

[0043] The following is a preferred technical solution of the present application, but is not a limitation on the technical solution provided by the present application. Through the following preferred technical solution, the technical purpose and beneficial effects of the present application can be better achieved and realized.

[0044] In some embodiments, the method of activating and forming pores in step S2 includes chemical activation and / or physical activation, preferably chemical activation and physical activation.

[0045] Through the synergistic effect of chemical activation and physical activation, the activation and pore forming effect is obviously improved, which is more conducive to the regulation of the pores of the porous carbon carrier.

[0046] In some embodiments, the activation and pore forming in step S2 includes:

[0047] The chemical activator is mixed with the modified coke material, and the physical activator is introduced at the same time, and then the temperature is raised to the activation temperature for activation treatment to complete the activation and pore forming.

[0048] In some embodiments, the mass ratio of the chemical activator to the modified coke material is (1-3):1, for example, 1:1, 1.3:1, 1.5:1, 1.8:1, 2:1, 2.3:1, 2.5:1, 2.8:1, or 3:1, etc., but is not limited to the listed values. Other values not listed in this range are also applicable.

[0049] In some embodiments, the physical activator is introduced at a flow rate of 4 L / min to 12 L / min, such as 4 L / min, 5 L / min, 6 L / min, 7 L / min, 8 L / min, 9 L / min, 10 L / min, 11 L / min, or 12 L / min, or the like, but not limited to the listed values, and other values not listed within the range are also applicable.

[0050] It should be noted that the specific types of chemical activators and physical activators in the present application are not limited, and any known substance that can be used to activate the pore-forming is applicable in principle without deviating from the inventive concept of the present application.

[0051] For example, the chemical activator includes, but is not limited to, sodium hydroxide (NaOH) and / or potassium hydroxide (KOH), and the like, and the physical activator includes, but is not limited to, carbon dioxide gas and / or water vapor, and the like.

[0052] In some embodiments, the activation treatment is performed at a temperature of 700°C to 900°C, such as 700°C, 725°C, 750°C, 775°C, 800°C, 825°C, 850°C, 875°C, or 900°C, or the like, but not limited to the listed values, and other values not listed within the range are also applicable.

[0053] After the activation treatment, the carbonization of the modified coke material is completed while the pore-forming is achieved, so that the porous carbon carrier with rich pore structure is obtained in one step.

[0054] In some embodiments, the activation treatment is performed for a time of 3 h to 5 h, such as 3 h, 4 h, or 5 h, or the like, but not limited to the listed values, and other values not listed within the range are also applicable.

[0055] In some embodiments, the substance after the activation treatment is sequentially washed and dried to obtain the porous carbon carrier.

[0056] It can be understood that after the activation treatment, the product can be treated to obtain the porous carbon carrier with less impurities and higher purity, and the present application does not make further detailed limitations on the specific washing and drying process, and the conventional washing and drying process is applicable in principle without deviating from the inventive concept of the present application.

[0057] For example, the washing and drying include: adding the product after the activation treatment into sufficient deionized water for stirring and water washing for 3 h to 5 h (such as 3 h, 4 h, or 5 h, or the like), then suction filtering, adding the material obtained by suction filtering into a beaker, and performing acid washing and neutralization by configuring hydrochloric acid aqueous solution, and finally suction filtering and drying at 90°C to obtain the porous carbon carrier.

[0058] In some embodiments, the median particle size Dv50 of the porous carbon carrier in step S2 is 6-15 μm, for example 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm, etc., but not only limited to the listed values, other values not listed in the range are also applicable.

[0059] In some embodiments, the gas phase silicon source in step S3 also includes a carrier gas.

[0060] In some embodiments, the flow rate of the gas phase silicon source in step S3 is 5-10 L / min, for example 5 L / min, 6 L / min, 7 L / min, 8 L / min, 9 L / min or 10 L / min, etc., but not only limited to the listed values, other values not listed in the range are also applicable.

[0061] In some embodiments, the flow rate of the carrier gas is 50-80 L / min, for example 50 L / min, 55 L / min, 60 L / min, 65 L / min, 70 L / min, 75 L / min or 80 L / min, etc., but not only limited to the listed values, other values not listed in the range are also applicable.

[0062] In some embodiments, the gas phase silicon source in the present application includes at least one of monosilane, disilane, trisilane, dimethylsilane, dichlorodisilane, trichlorosilane or silicon tetrachloride, but not limited thereto.

[0063] In some embodiments, the carrier gas in the present application is selected from at least one of gases that do not participate in the reaction, for example nitrogen, argon or helium, etc.

[0064] In some embodiments, the deposition temperature of the vapor deposition in step S3 is 500-600 °C, for example 500 °C, 510 °C, 520 °C, 530 °C, 540 °C, 550 °C, 560 °C, 570 °C, 580 °C, 590 °C or 600 °C, etc., but not only limited to the listed values, other values not listed in the range are also applicable.

[0065] In some embodiments, the deposition time of the vapor deposition in step S3 is 6-10 h, for example 6 h, 7 h, 8 h, 9 h or 10 h, etc., but not only limited to the listed values, other values not listed in the range are also applicable.

[0066] In some embodiments, after the deposition of the gas phase silicon source in step S3, the product after deposition is subjected to carbon coating treatment to obtain the silicon-carbon negative electrode material.

[0067] The carbon-coated material after silicon deposition is subjected to carbon coating on the outer surface of the porous carbon carrier again, which can better inhibit the volume expansion of silicon and further increase the conductivity of the material; and the specific carbon coating method is a conventional technical solution, and the person skilled in the art can make adaptive selection and adjustment according to the actual needs.

[0068] Further, in some embodiments, the carbon coating method includes solid-phase carbon coating, liquid-phase carbon coating or gas-phase carbon coating, and preferably gas-phase carbon coating, which can better achieve uniform carbon coating.

[0069] Specifically, the gas-phase carbon coating includes introducing a carbon source gas into the product after gas-phase deposition to perform carbon coating.

[0070] The carbon source gas is selected from at least one of methane, ethane, propane, ethylene or propylene, the carbon coating temperature is 500-600°C, for example 500°C, 550°C or 600°C, and the carbon coating time is 6-12h, for example 6h, 7h, 8h, 9h, 10h, 11h or 12h.

[0071] In some embodiments, the median particle size Dv50 of the green coke material in step S1 is 0.1-5mm, for example 0.1mm, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm or 5mm, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0072] In some embodiments, the heat treatment temperature in step S1 is 500-900°C, for example 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C or 900°C, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0073] In some embodiments, the heat treatment time in step S1 is 2-6h, for example 2h, 3h, 4h, 5h or 6h, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0074] In one embodiment, the second aspect of the present application provides a silicon-carbon negative electrode material prepared by the preparation method of the first aspect.

[0075] The silicon-carbon negative electrode material includes a porous carbon carrier and a silicon material in the internal pores of the porous carbon carrier.

[0076] In some embodiments, the silicon-carbon negative electrode material further includes a carbon coating layer coated on the surface of the porous carbon carrier.

[0077] In one embodiment, the third aspect of the present application further provides a lithium ion battery comprising the silicon-carbon negative electrode material according to the second aspect.

[0078] Specifically, the lithium ion battery in the present application includes any one of liquid lithium ion battery, solid-state lithium ion battery or semi-solid lithium ion battery or a combination of at least two of them, and does not exclude the possibility of its use in other lithium ion electrochemical devices, which can be adapted and adjusted by the skilled person in the art according to the actual needs.

[0079] In some embodiments, the lithium ion battery comprises a positive electrode, a negative electrode containing the silicon-carbon negative electrode material in the present application, and an electrolyte, and can further contain a separator structure, and the electrolyte includes a solid-state electrolyte or a non-aqueous electrolyte, etc.

[0080] It can be understood that, in addition to the silicon-carbon negative electrode material in the present application, other materials and structures in the lithium ion battery are conventional technical solutions, and any known type of lithium ion battery can be applied in principle without deviating from the inventive concept of the present application.

[0081] Example 1

[0082] The present embodiment provides a preparation method of a silicon-carbon negative electrode material, which is as follows:

[0083] S1: Petroleum coke green coke particles with a Dv50 of 5 mm are subjected to low-temperature heat treatment at a temperature of 600°C for 6 h to obtain modified coke.

[0084] S2: The modified coke is physically mixed with KOH (mass ratio of 1:1), and the mixture is put into an anticorrosion liner and loaded into a rotary furnace, and nitrogen gas is blown at a flow rate of 2 L / min to replace the air in the furnace. Then the rotation is opened, and water vapor is introduced at a flow rate of 4 L / min, and the temperature is slowly raised to the rated temperature of 700°C for activation treatment for 3 h. After the temperature is lowered to room temperature, the material is taken out, washed with water to neutral, and dried to obtain a porous carbon carrier;

[0085] S3: The porous carbon is crushed to a porous carbon with a median particle size Dv50 of 7 μm, and chemical vapor deposition is performed with silane as the gas-phase silicon source, the flow rate of silane is 5 L / min, nitrogen gas is used as the carrier gas, the flow rate of the carrier gas is 60 L / min, the temperature for silane reaction and deposition is 500°C, and the time is 8 h;

[0086] S4: stop passing silane, replace silane with acetylene for carbon coating treatment, the flow rate of acetylene is 5 L / min, the temperature of carbon coating treatment is 500℃, and the time is 3h, to obtain the silicon-carbon negative electrode material, the silicon-carbon negative electrode material comprises a porous carbon carrier and a silicon material in the internal pores of the porous carbon carrier, and the surface of the porous carbon carrier is further coated with a carbon coating layer.

[0087] Example 2-15

[0088] Example 2-15 is different from Example 1, as shown in Tables 1, 2 and 3.

[0089] The remaining preparation methods and parameters are consistent with Example 1.

[0090] Table 1

[0091]

[0092]

[0093] Table 2

[0094]

[0095]

[0096] Table 3

[0097]

[0098]

[0099] Comparative Example 1

[0100] The difference between this comparative example and Example 1 is that in this comparative example, the green coke material is directly subjected to step S2, i.e., without the heat treatment process of step S1.

[0101] The remaining preparation methods and parameters are consistent with Example 1.

[0102] [Performance Test]

[0103] I Silicon content test:

[0104] The silicon content of the silicon-carbon negative electrode materials provided by the examples and comparative examples was tested, and the content was defined by the following formula: silicon content = 100% * (mass of silicon contained in the silicon-carbon material) / (mass of the silicon-carbon material), in mass%, the sample was filled in a sample cup, and the silicon content (content of Si element) was calculated in mass% by using the fundamental parameter method (FP method) by the following method. Fluorescent X-ray device: NEX CG manufactured by Rigaku; tube voltage: 50 kV; tube current: 1.00 mA; sample cup: Φ3212 mL CH1530; sample weight: 2-3 g; sample height: 5-18 mm; the sample was filled into the sample cup, and the silicon content in the composite particles was calculated in mass% by using the fundamental parameter (FP method) by the above method.

[0105] II Powder resistivity:

[0106] The powder resistivity of the silicon-carbon negative electrode materials provided by the examples and comparative examples was tested, and the silicon-carbon negative electrode material was placed in the jig cavity of the powder resistometer, and the four-probe method was used for testing, the test pressure was 30 MPa, and the pressure holding time was 20 s.

[0107] III Electrochemical performance:

[0108] a) Preparation of button-type half cells: the silicon-carbon negative electrode materials, conductive additives carbon black, and adhesives (sodium carboxymethyl cellulose and butadiene rubber with a mass ratio of 1:1) obtained from each of the examples and comparative examples were weighed according to a mass ratio of 94:2:4, slurry preparation was performed by using a beater, and negative electrode slurry was obtained; then the above negative electrode slurry was coated on the surface of the negative electrode current collector (specifically, a copper foil), and then drying, cutting, and assembling into button-type batteries with lithium metal sheets in a glove box were sequentially performed.

[0109] Performance of button-type half cells: at a constant temperature of 25±2℃, constant current charge and discharge mode testing was performed using a charge and discharge instrument, the discharge cutoff voltage was 0.005 V, the charge cutoff voltage was 2 V, the first week of charge and discharge testing was performed at a current density of 1C / 10, and the reversible capacity and the first coulombic efficiency were obtained. First coulombic efficiency = first charge capacity / first discharge capacity x 100%.

[0110] b) Full battery preparation: the negative electrode active material prepared in each example and the comparative example is configured into a composite with a specific capacity of 450 mAg / h with graphite, and then an electrically conductive additive and a binder are prepared into a negative electrode slurry at a mass ratio of 94:2:4, the negative electrode slurry is coated on a current collector (specifically a copper foil) to obtain a negative electrode sheet; the positive electrode active material LiCoO2, conductive carbon black and the binder polyvinylidene fluoride (PVDF) are mixed uniformly in a N-methylpyrrolidone solvent system at a weight ratio of 96.7:1.7:1.6, and then coated on an Al foil, dried and cold-pressed to obtain a positive electrode sheet; a porous polymeric polypropylene film is used as a separator film; the above positive electrode sheet, the separator film and the negative electrode sheet are stacked in order, with the separator film between the positive electrode sheet and the negative electrode sheet to play a separating role, and are wound to obtain a bare battery cell. The bare battery cell is placed in an outer package, injected with prepared electrolyte (1.0 mol / L LiPF6 in a volume ratio of 1:1 of ethyl carbonate / dimethyl carbonate solution as electrolyte) and packaged, and then subjected to processes such as formation, degassing and edge cutting to obtain a full battery cell.

[0111] Full battery cycle performance: at a constant temperature of 25±2℃, the above full battery cells are subjected to constant current charge and discharge tests using a blue electric charge and discharge instrument, the discharge cutoff voltage is 2.75V, the charge cutoff voltage is 4.2V, and the charge and discharge tests are carried out at a current density of 1C. After 300 cycles, the capacity retention rate after 300 cycles is recorded, and the capacity retention rate = the discharge capacity of the 300th cycle / the discharge capacity of the 1st cycle x 100%.

[0112] The test results of the above tests are shown in Table 4.

[0113] Table 4

[0114]

[0115]

[0116] In summary, in the technical scheme of the present application, the green coke material is subjected to heat treatment, and the volatile matter in the green coke raw material is effectively removed after heat treatment, which facilitates the activation of the coke, and the fibers in the green coke raw material develop after heat treatment, the size of the anisotropic structure increases, and the orientation becomes better, and the proportion of streamline structure increases, which facilitates the improvement of the graphitization degree when the modified coke material is used to prepare a porous carbon material, so that a porous carbon carrier with large specific surface area, rich pores and excellent electrical conductivity is prepared, and then the porous carbon carrier is contacted with a gas-phase silicon source to deposit silicon, which is beneficial to the improvement of the electrochemical performance of the silicon-carbon negative electrode material.

[0117] The applicant states that the above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and it should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought out by those skilled in the art, and all of them fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for preparing a silicon-carbon negative electrode material, characterized by, The preparation method comprises the following steps: S1: heat treating green coke material to obtain modified coke material; S2: activating and forming pores of the modified coke material to obtain a porous carbon carrier; S3: contacting the porous carbon carrier with a gas-phase silicon source to perform gas-phase deposition to obtain a silicon-carbon negative electrode material.

2. The production method according to claim 1, characterized by, The method for activating and forming pores in step S2 comprises chemical activation and / or physical activation, preferably chemical activation and physical activation.

3. The production method according to claim 2, characterized by, The activation and pore forming in step S2 comprises: mixing a chemical activator with the modified coke material, while introducing a physical activator, and then heating to an activation temperature to perform activation treatment to complete the activation and pore forming; Preferably, the mass ratio of the chemical activator to the modified coke material is (1-3): 1; Preferably, the flow rate of the physical activator introduced is 4 L / min to 12 L / min; Preferably, the temperature of the activation treatment is 700°C to 900°C, and the time of the activation treatment is 3 h to 5 h.

4. The method of claim 1, wherein, Step S2 further comprises crushing the porous carbon carrier, and the median particle size Dv50 of the porous carbon carrier after crushing is 6 μm to 15 μm.

5. The preparation method according to claim 1, characterized in that, The introduction process of the gas-phase silicon source in step S3 further comprises a carrier gas; Preferably, the flow rate of the gas-phase silicon source introduced in step S3 is 5 L / min to 10 L / min; Preferably, the flow rate of the carrier gas introduced is 50 L / min to 80 L / min; Preferably, the deposition temperature of the gas-phase deposition in step S3 is 500°C to 600°C, and the deposition time of the gas-phase deposition is 6 h to 10 h.

6. The method of claim 1, wherein, After the deposition of the gas-phase silicon source in step S3 is completed, the product after deposition is subjected to carbon coating treatment to obtain the silicon-carbon negative electrode material.

7. The preparation method according to claim 1, characterized in that, The median particle size Dv50 of the green coke material in step S1 is 0.1 mm to 5 mm; Preferably, the temperature of the heat treatment in step S1 is 500°C to 900°C, and the time of the heat treatment is 2 h to 6 h.

8. A silicon-carbon negative electrode material, characterized by, The silicon-carbon negative electrode material is prepared by the preparation method in any one of claims 1-7. The silicon-carbon negative electrode material comprises a porous carbon carrier and a silicon material in the internal pores of the porous carbon carrier.

9. The silicon-carbon negative electrode material of claim 8, wherein, The silicon-carbon negative electrode material further comprises a carbon coating layer coated on the surface of the porous carbon carrier.

10. A lithium-ion battery, characterized by, The lithium ion battery comprises the silicon-carbon negative electrode material in claim 8 or 9.

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