Boron-doped silicon-carbon negative electrode material and its preparation method and application

Abstract

The present invention provides a boron-doped silicon-carbon anode material and its preparation method and application, relating to the technical field of lithium-ion battery anode materials. The method for preparing a boron-doped silicon-carbon anode material comprises the following steps: S1, subjecting a silicon source to borane deposition to obtain boron-coated silicon particles; S2, mixing the boron-coated silicon particles with a pore-forming agent to obtain a mixture A; S3, granulating the mixture A, a carbon source, carbon nanotubes, and pitch, and crushing and classifying the granulated product to obtain a mixture B; S4, subjecting the mixture B to pores to obtain a porous carbon composite material; S5, subjecting the porous carbon composite material to a vapor-phase co-deposition treatment to obtain a mixture C; and S6, carbon-coating the mixture C to obtain a boron-doped silicon-carbon anode material. The material prepared by the present invention exhibits excellent cycle performance and rate capability.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion battery negative electrode materials, and in particular to a boron-doped silicon-carbon negative electrode material and a preparation method and application thereof. Background Art

[0002] Lithium-ion battery is a secondary battery or rechargeable battery, which mainly relies on the reciprocating movement of lithium ions between the positive and negative electrodes to work. During the charging and discharging process, Li+ is inserted and de-inserted between the two electrodes: + During discharge, the opposite occurs. Lithium-ion batteries, due to their environmental compatibility, long cycle life, and low self-discharge rates, have become the most commonly used energy storage device, widely used in portable devices and electric vehicles.

[0003] Among them, Si-based materials have the highest theoretical specific capacity among the materials studied so far, and the alloys formed by them are Li x For Si, x ranges from 0 to 4.4, and the theoretical specific capacity of pure silicon is 4200 mAh / g. Silicon's voltage plateau is slightly higher than that of graphite, making it less susceptible to surface lithium deposition during charging, offering safety advantages over graphite electrodes. Furthermore, silicon is one of the most abundant elements in the Earth's crust, making it widely available and inexpensive. Furthermore, unlike graphite, silicon alloys exhibit a solvation effect. Their low lithium insertion potential, low atomic weight, high energy density, and high lithium mole fraction in Li-Si alloys have drawn considerable attention for their greater stability compared to other metals and materials. Therefore, silicon is considered the most likely anode material to replace graphite in the near term. Therefore, the development of silicon-based anodes is highly attractive.

[0004] However, silicon negative electrode materials have been slow to achieve large-scale commercial applications. While having many advantages, silicon anode materials also have several disadvantages. First, silicon anode materials will undergo a volume change of up to 300% or more during the charge and discharge process. Such a high volume expansion and contraction can easily cause the electrode material to shatter and lose contact with the current collector and the electrode conductive network. At the same time, the volume change brings about the generation of a new surface, and a new solid-electrolyte interface (SEI) needs to be formed, resulting in a large amount of electrolyte consumption, which in turn leads to a significant reduction in cycle life. On the other hand, the electrical conductivity and lithium ion diffusion rate of silicon are lower than those of graphite, which will limit the performance of silicon under high current and high power conditions. Summary of the Invention

[0005] Based on the technical problems existing in the background technology, the present invention proposes a boron-doped silicon-carbon negative electrode material and its preparation method and application.

[0006] The present invention provides a method for preparing a boron-doped silicon-carbon negative electrode material, comprising the following steps:

[0007] S1, performing borane deposition on the surface of the silicon source to obtain boron-coated silicon particles;

[0008] S2, mixing the boron-coated silicon particles with a pore-forming agent to obtain a mixture A;

[0009] S3, mixing mixture A, carbon source, carbon nanotubes, and asphalt to form granules, and crushing and classifying the granulated product to obtain mixture B;

[0010] S4, forming pores in the mixture B to obtain a porous carbon composite material;

[0011] S5, performing a vapor phase co-deposition treatment on the porous carbon composite material to obtain a mixture C;

[0012] S6. Carbon-coating the mixture C to obtain a boron-doped silicon-carbon negative electrode material.

[0013] The present invention involves in-situ boron coating of silicon particles, then attaching a layer of pore-forming agent to the surface. The resulting composite particles are mixed with a porous carbon source, carbon nanotubes, and pitch, and granulated. The granulated particles are then subjected to high-temperature pore formation to obtain a porous carbon material containing boron-coated nano-silicon particles. Silane and borane are co-deposited on the resulting porous carbon material using a deposition device, and finally a carbon layer is coated on the composite material surface to obtain a boron-doped silicon-carbon negative electrode material. This material can effectively improve the material's electronic and ionic conductivity, significantly enhance the material's rate performance, and effectively address the expansion problem of silicon negative electrode materials.

[0014] Preferably, in the above-mentioned S1, the silicon source is selected from one or more of silicon, silicon oxide, silicon monoxide, and lithium silicate.

[0015] Preferably, in the S1, the average particle size of the silicon source is 50 to 200 nm.

[0016] The average particle size of the silicon source within a certain range helps to alleviate the cycling problems caused by the expansion of the negative electrode material.

[0017] Preferably, in the above-mentioned S1, the mass fraction of boron element in the boron-coated silicon particles is 2wt% to 15w%.

[0018] Preferably, in S1, the deposition includes the following conditions: the borane gas flow rate is 300-600 sccm, the deposition temperature is 550-700° C., and the deposition time is 3-5 hours.

[0019] Preferably, in S2, the pore-forming agent is selected from one or more of zinc chloride, potassium hydroxide, phosphoric acid, and potassium carbonate.

[0020] Selecting the type of pore former helps control the reaction rate with the base carbon and also the size of the pores produced by activation. By adding the pore former to the particles in advance, a more uniform pore structure can be formed inside and outside the particles, which can effectively alleviate the expansion of silicon.

[0021] Preferably, in the S2, the mass ratio of the boron-coated silicon particles to the pore-forming agent is (70-95): (5-30).

[0022] Preferably, in S3, the mass ratio of mixture A, carbon source, carbon nanotubes and asphalt is 2:(5-7):(0.5-2):(0.5-1).

[0023] Controlling the mass ratio of mixture A, carbon source, carbon nanotubes, and asphalt within a certain range helps ensure the material's capacity efficiency and conductivity.

[0024] Preferably, in S3, the carbon source is selected from one or more of petroleum coke, phenolic resin, and coconut shell powder.

[0025] Selecting the type of carbon source helps to improve the strength of the carbon material substrate and can effectively buffer the expansion of the silicon material.

[0026] Preferably, in said S3, the average particle size of the carbon source is 1 μm to 10 μm.

[0027] Preferably, in S3, the carbon nanotubes are selected from one or more of linear carbon nanotubes and helical carbon nanotubes.

[0028] Preferably, in the above S3, the carbon nanotubes have a length of 50 to 500 nm and a diameter of 2 to 10 nm.

[0029] The size of carbon nanotubes within a certain range helps to improve the intrinsic conductivity and ion transport properties of the material, thereby improving the rate performance of the material accordingly.

[0030] Preferably, in said S3, the average particle size D50 of the mixture B after crushing and classification is 5-10 μm, and Dmax ≤ 20 μm.

[0031] Preferably, in said S3, the granulation method is selected from one or more of melt granulation and sintering granulation.

[0032] Preferably, in the step S3, the granulation temperature is 500-800° C., and the granulation time is 5-10 h.

[0033] Controlling the temperature and time of granulation helps to control the particle size and particle strength after granulation.

[0034] Preferably, in said S3, a protective gas needs to be introduced during the granulation process, and the protective gas is selected from one of argon, nitrogen, and argon-hydrogen mixed gas.

[0035] Preferably, in said S4, pore creation includes pore creation by chemical activation method and / or pore creation by physical activation method.

[0036] More preferably, the activator for pore formation by chemical activation is selected from one or more of KOH, NaOH, phosphoric acid, and zinc chloride.

[0037] The selection of the type of activator for chemical activation pore formation helps to control the reaction rate with the base carbon, and also controls the pore size produced by activation.

[0038] More preferably, the mass of the activator used for pore formation by chemical activation accounts for 30 wt% to 60 wt% of the mixture B.

[0039] More preferably, the activation temperature of the chemical activation method for pore formation is 800-1200° C., and the activation time is 3 h to 5 h.

[0040] More preferably, the activator for pore formation by physical activation is selected from one or more of water vapor and carbon dioxide gas.

[0041] More preferably, the gas flow rate of the water vapor and carbon dioxide gas is 100-300 sscm.

[0042] More preferably, the activation temperature of the physical activation method for pore formation is 600-1200° C., and the activation time is 5-15 hours.

[0043] Preferably, in S4, the specific surface area of ​​the porous carbon composite material is 1000 to 2000 m 2 / g, pore size is 2 to 10 nm.

[0044] Preferably, in the above S5, the vapor phase co-deposition treatment includes using silane, borane and hydrogen as reaction gases, the deposition temperature is 400-700° C., and the deposition time is 3-7 hours.

[0045] Controlling the conditions of the vapor phase co-deposition process helps control the amount of silicon and boron deposited in the substrate, thereby controlling the grain size of the silicon and reducing its expansion.

[0046] More preferably, the gas flow ratio of silane, borane and hydrogen is (2-10): (0.2-2): (160-200).

[0047] Preferably, in the above S5, the process further includes evacuating the furnace chamber to a vacuum pressure of 0.1 to 5 kPa before the vapor phase co-deposition process.

[0048] Preferably, in S5, the mass of silane and borane is 40 wt% to 60 wt% of the mixture C.

[0049] Preferably, in said S6, the carbon coating includes liquid phase carbon coating and / or gas phase carbon coating.

[0050] More preferably, the carbon source of the liquid-phase carbon coating is selected from one or more of pitch, glucose, polyaniline, polypyrrole, polythiophene, and polyacrylonitrile.

[0051] More preferably, the carbon source for the gas-phase carbon coating is selected from one or more of acetylene, methane, ethane, propane, ethylene, and propylene.

[0052] Selecting different types of carbon sources can help reduce the specific surface area of ​​the material and further improve the conductive properties of the material.

[0053] The present invention also provides a boron-doped silicon-carbon negative electrode material prepared by the above preparation method.

[0054] A lithium-ion battery comprises the above-mentioned boron-doped silicon-carbon negative electrode material or the boron-doped silicon-carbon negative electrode material prepared by the above-mentioned preparation method.

[0055] The beneficial effects of the present invention are:

[0056] The present invention deposits borane on the surface of the silicon source, i.e., coats the surface with boron, thereby increasing the intrinsic conductivity of the silicon-based negative electrode material, improving the atomic mixing degree in the silicon-based unit cell, and reducing the expansion rate of the material during cyclic charge and discharge. Moreover, the coating with boron can effectively isolate the silicon particles from direct contact with the electrolyte, avoid the generation of side reactions and the consumption of the electrolyte, and improve the cyclic performance of the material. The present invention adopts a method of simultaneous internal and external pore formation to make the internal and external distribution of the pore structure in the material more uniform, which can more effectively alleviate the problem of material expansion. The present invention can better improve the electrical conductivity and ionic conductivity of the material by adding carbon nanotubes, thereby improving the rate performance of the material.

[0057] The boron-doped silicon-carbon negative electrode material prepared by the present invention has good cycle performance and rate performance, and the material structure is more stable, thereby achieving the purpose of improving the material battery performance and having good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is a schematic diagram of the structure of the boron-doped silicon-carbon negative electrode material proposed in the present invention;

[0059] 1-boron-coated silicon particles, 2-CCNTs, 3-CNTs, 4-surface-coated carbon layer.

[0060] Figure 2This is a comparison chart of the charge and discharge curves of lithium-ion batteries assembled with the negative electrode materials of Example 1 and Comparative Example 1 of the present invention.

[0061] Figure 3 This is the XRD pattern of the boron-doped silicon-carbon negative electrode material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0062] The technical solution of the present invention is described in detail through specific embodiments.

[0063] Unless otherwise specified, the materials, reagents, etc. used in the following examples and comparative examples can be obtained from commercial sources.

[0064] Example 1

[0065] A method for preparing a boron-doped silicon-carbon negative electrode material comprises the following steps:

[0066] S1. Borane deposition was performed on nano-silicon particles with an average particle size of 50 nm in a CVD furnace. The borane gas flow rate was 300 sccm, the deposition temperature was 600°C, the deposition time was 3 h, and the mass fraction of the deposited boron element was 5 w%, to obtain boron-coated silicon particles.

[0067] S2. Mixing the boron-coated silicon particles with a pore-forming agent, potassium hydroxide / potassium carbonate, in a mass ratio of 3:1 to obtain a mixture A, wherein the mass ratio of potassium hydroxide to potassium carbonate is 3:1;

[0068] S3. Mixture A, petroleum coke, CCNTs / CNTs, and asphalt are mixed and granulated in a mass ratio of 2:5:1:0.5 at a granulation temperature of 800°C. The granulated product is crushed and classified to obtain a mixture B having an average particle size of D50-7 μm and Dmax-18 μm; wherein the mass ratio of CCNTs to CNTs is 3:2;

[0069] S4. The mixture B was chemically activated to form pores by adding 40 wt% of a KOH / NaOH mixture (KOH / NaOH = 3:1) and activated at 900 ° C for 3 h. The excess activator was removed by using a 0.5 mol / L hydrochloric acid solution, and then washed with water to remove the excess acid solution. The mixture was centrifuged and dried to obtain a specific surface area of ​​1800 m 2 / g, porous carbon composite material with a pore size of 2 nm;

[0070] S5. The porous carbon composite material was transferred to a PECVD furnace, and the furnace chamber was evacuated to 0.1 kPa. During the deposition process, the gas flow rate of silane was controlled to 6 sccm, the gas flow rate of borane was controlled to 1 sccm, the gas flow rate of hydrogen was controlled to 180 sccm, the deposition temperature was controlled to 550° C., and the deposition time was controlled to 5.5 h to obtain a mixture C.

[0071] S6. Performing vapor-phase carbon coating on the mixture C to obtain a boron-doped silicon-carbon negative electrode material.

[0072] Example 2

[0073] A method for preparing a boron-doped silicon-carbon negative electrode material comprises the following steps:

[0074] S1. Borane deposition was performed on nano-silicon particles with an average particle size of 50 nm in a CVD furnace. The borane gas flow rate was 300 sccm, the deposition temperature was 500°C, the deposition time was 2 h, and the mass fraction of the deposited boron element was 5 w%, to obtain boron-coated silicon particles.

[0075] S2. mixing the boron-coated silicon particles with a pore-forming agent, potassium hydroxide / potassium carbonate, in a mass ratio of 3:1 to obtain a mixture A, wherein the mass ratio of potassium hydroxide to potassium carbonate is 3:1;

[0076] S3. Mixture A, petroleum coke, CCNTs / CNTs, and asphalt are mixed and granulated in a mass ratio of 2:5:1:0.5 at a granulation temperature of 800°C. The granulated product is crushed and classified to obtain a mixture B having an average particle size of D50-7 μm and Dmax-18 μm, wherein the mass ratio of CCNTs to CNTs is 3:1;

[0077] S4. The mixture B was chemically activated to form pores by adding 40 wt% of a KOH / NaOH mixture (KOH / NaOH = 3:1) and activated at 900 ° C for 3 h. The excess activator was removed by using a 0.5 mol / L hydrochloric acid solution, and then washed with water to remove the excess acid solution. The mixture was centrifuged and dried to obtain a specific surface area of ​​1800 m 2 / g, porous carbon composite material with a pore size of 2 nm;

[0078] S5. The porous carbon composite material was transferred to a PECVD furnace, and the furnace chamber was evacuated to 0.1 kPa. During the deposition process, the gas flow rate of silane was controlled to 6 sccm, the gas flow rate of borane was controlled to 1 sccm, the gas flow rate of hydrogen was controlled to 180 sccm, the deposition temperature was controlled to 550° C., and the deposition time was controlled to 5.5 h to obtain a mixture C.

[0079] S6. Performing vapor-phase carbon coating on the mixture C to obtain a boron-doped silicon-carbon negative electrode material.

[0080] Example 3

[0081] A method for preparing a boron-doped silicon-carbon negative electrode material comprises the following steps:

[0082] S1. Borane deposition was performed on nano-silicon particles with an average particle size of 50 nm in a CVD furnace. The borane gas flow rate was 300 sccm, the deposition temperature was 500°C, the deposition time was 2 h, and the mass fraction of the deposited boron element was 5 w%, to obtain boron-coated silicon particles.

[0083] S2. Mixing the boron-coated silicon particles with a pore-forming agent, potassium hydroxide / potassium carbonate, in a mass ratio of 3:1 to obtain a mixture A, wherein the mass ratio of potassium hydroxide to potassium carbonate is 3:1;

[0084] S3. Mixture A, petroleum coke, CCNTs / CNTs, and asphalt are mixed and granulated in a mass ratio of 2:5:1:0.5 at a granulation temperature of 800°C. The granulated product is crushed and classified to obtain a mixture B having an average particle size of D50-5 μm and Dmax-12 μm, wherein the mass ratio of CCNTs to CNTs is 3:2;

[0085] S4. The mixture B was chemically activated to form pores by adding 40 wt% of a KOH / NaOH mixture (KOH / NaOH = 3:1) and activated at 900 ° C for 3 h. The excess activator was removed by using a 0.5 mol / L hydrochloric acid solution, and then washed with water to remove the excess acid solution. The mixture was centrifuged and dried to obtain a specific surface area of ​​1800 m 2 / g, porous carbon composite material with a pore size of 1.5 nm;

[0086] S5. The porous carbon composite material was transferred to a PECVD furnace, and the furnace chamber was evacuated to 0.1 kPa. During the deposition process, the gas flow rate of silane was controlled to 6 sccm, the gas flow rate of borane was controlled to 1 sccm, the gas flow rate of hydrogen was controlled to 180 sccm, the deposition temperature was controlled to 550° C., and the deposition time was controlled to 5.5 h to obtain a mixture C.

[0087] S6. Performing vapor-phase carbon coating on the mixture C to obtain a boron-doped silicon-carbon negative electrode material.

[0088] Comparative Example 1

[0089] The GROUP14 silicon-carbon negative electrode material sold on the market is used as the negative electrode material.

[0090] Comparative Example 2

[0091] A method for preparing a silicon-carbon negative electrode material comprises the following steps:

[0092] S1. Borane deposition was performed on nano-silicon particles with an average particle size of 50 nm in a CVD furnace. The borane gas flow rate was 500 sccm, the deposition temperature was 600°C, the deposition time was 5 h, and the mass fraction of the deposited boron element was 10 w%, to obtain boron-coated silicon particles.

[0093] S2. Mixing the boron-coated silicon particles with a pore-forming agent, potassium hydroxide / potassium carbonate, in a mass ratio of 3:1 to obtain a mixture A, wherein the mass ratio of potassium hydroxide to potassium carbonate is 3:5;

[0094] S3. Mixture A, petroleum coke, and asphalt are mixed and granulated in a mass ratio of 2:5:1 at a granulation temperature of 800° C. The granulated product is crushed and classified to obtain mixture B with a D50-7 μm and a Dmax-18 μm;

[0095] S4. The mixture B was chemically activated to form pores by adding 40 wt% of a KOH / NaOH mixture (KOH / NaOH = 3:1) and activated at 900 ° C for 3 h. The excess activator was removed by using a 0.5 mol / L hydrochloric acid solution, and then washed with water to remove the excess acid solution. The mixture was centrifuged and dried to obtain a specific surface area of ​​1800 m 2 / g, porous carbon composite material with a pore size of 1.5 nm;

[0096] S5. The porous carbon composite material was transferred to a PECVD furnace, and the furnace chamber was evacuated to 0.1 kPa. During the deposition process, the gas flow rate of silane was controlled to 6 sccm, the gas flow rate of borane was controlled to 1 sccm, the gas flow rate of hydrogen was controlled to 180 sccm, the deposition temperature was controlled to 550° C., and the deposition time was controlled to 5.5 h to obtain a mixture C.

[0097] S6. Performing vapor-phase carbon coating on the mixture C to obtain a silicon-carbon negative electrode material.

[0098] Comparative Example 3

[0099] A method for preparing a silicon-carbon negative electrode material comprises the following steps:

[0100] S1. Mixing nano-silicon particles with an average particle size of 50 nm with pore-forming agents potassium hydroxide / potassium carbonate in a mass ratio of 3:1 to obtain a mixture A, wherein the mass ratio of potassium hydroxide to potassium carbonate is 3:5;

[0101] S3. Mixture A, petroleum coke, CCNTs / CNTs, and asphalt are mixed and granulated in a mass ratio of 2:5:1:0.5 at a granulation temperature of 800°C. The granulated product is crushed and classified to obtain a mixture B having an average particle size of D50-7 μm and Dmax-18 μm; wherein the mass ratio of CCNTs to CNTs is 3:1;

[0102] S4. The mixture B was chemically activated to form pores by adding 40 wt% of a KOH / NaOH mixture (KOH / NaOH = 3:1) and activated at 900 ° C for 3 h. The excess activator was removed by using a 0.5 mol / L hydrochloric acid solution, and then washed with water to remove the excess acid solution. The mixture was centrifuged and dried to obtain a specific surface area of ​​1500 m 2 / g, porous carbon composite material with a pore size of 2 nm;

[0103] S5. The porous carbon composite material was transferred to a PECVD furnace, and the furnace chamber was evacuated to 0.1 kPa. During the deposition process, the gas flow rate of silane was controlled to 6 sccm, the gas flow rate of hydrogen was controlled to 180 sccm, the deposition temperature was 550° C., and the deposition time was 5.5 h to obtain a mixture C.

[0104] S6. Performing vapor-phase carbon coating on the mixture C to obtain a silicon-carbon negative electrode material.

[0105] The above silicon-carbon negative electrode material is mixed with graphite with a gram capacity of 600mAh / g, and then slurried with sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), and conductive carbon black (SP) in a mass ratio of 94:3:2:1. Then, after coating, rolling, and slitting, the negative electrode sheet is prepared and assembled with the positive electrode sheet, electrolyte, and separator to form a lithium-ion battery.

[0106] The lithium ion batteries using silicon-carbon negative electrode materials of Examples 1 to 3 and Comparative Examples 1 to 3 were tested for their expansion rate and rate performance during cyclic charge and discharge. The test results are shown in Table 1.

[0107] Table 1

[0108] serial number Full electrode expansion rate Double charge capacity retention rate (3C) Discharge capacity retention rate (3C) Example 1 40％ 88％ 92％ Comparative Example 1 55％ 80％ 85％ Comparative Example 2 45％ 82％ 88％ Comparative Example 3 45％ 85％ 90％

[0109] The data in Table 1 demonstrate that the boron-doped silicon-carbon anode material prepared by the present invention exhibits a low expansion coefficient and superior rate performance. Comparative Example 1 and Example 1 demonstrate that the commercially available silicon-carbon anode material exhibits a higher full-charge expansion coefficient than that of Example 1, and that the anode material of the present invention exhibits superior rate performance. The data from Comparative Examples 2 and 3, along with those of Example 1, demonstrate that the anode material without CCNTs / CNTs or boron coating exhibits inferior overall rate performance compared to the anode material of the present invention.

[0110] like Figure 1 As shown, Figure 1 This is a schematic diagram of the structure of the boron-doped silicon-carbon negative electrode material proposed in the present invention. Figure 2 Comparison of the charge and discharge curves of lithium-ion batteries assembled with the negative electrode materials of Example 1 and Comparative Example 1. Figure 2It can be seen that since the base carbon material used in the present invention adopts a process of simultaneous internal and external pore formation, the silicon deposition amount is greater and more uniform, so the capacity and first effect of the material are higher than those of comparative example 1. Figure 3 This is the XRD pattern of the boron-doped silicon-carbon negative electrode material prepared in Example 1 of the present invention. Figure 3 It can be seen that due to the large amount of silicon deposition in the embodiment, the silicon peak of the material is relatively high. At the same time, due to the existence of the internal porous structure, an internal buffer space is provided for the material, so the cycle performance of the material will be improved.

[0111] In summary, the boron-doped silicon-carbon negative electrode material provided by the present invention has good cycle performance and rate performance.

[0112] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a boron-doped silicon-carbon negative electrode material, characterized in that: The following steps are involved: S1, performing borane deposition on the surface of the silicon source to obtain boron-coated silicon particles; S2, mixing the boron-coated silicon particles with a pore-forming agent to obtain a mixture A; S3, mixing and granulating the mixture A, the carbon source, the carbon nanotubes, and the pitch in a mass ratio of 2:(5-7):(0.5-2):(0.5-1), and crushing and classifying the granulated product to obtain a mixture B; S4, forming pores in the mixture B to obtain a porous carbon composite material; S5, performing a vapor co-deposition treatment on the porous carbon composite material using silane, borane and hydrogen as reaction gases at a deposition temperature of 400 to 700° C. for 3 to 7 hours to obtain a mixture C; S6. Carbon-coating the mixture C to obtain a boron-doped silicon-carbon negative electrode material.

2. The preparation method according to claim 1, characterized in that In the S1, the average particle size of the silicon source is 50 to 200 nm.

3. The preparation method according to claim 1, characterized in that In the above-mentioned S2, the pore-forming agent is selected from one or more of zinc chloride, potassium hydroxide, phosphoric acid, and potassium carbonate.

4. The preparation method according to claim 1, characterized in that In said S3, the carbon source is selected from one or more of petroleum coke, phenolic resin, and coconut shell powder.

5. The preparation method according to claim 1, characterized in that In the step S3, the granulation temperature is 500-800° C., and the granulation time is 5-10 hours.

6. The preparation method according to claim 1, characterized in that In the above-mentioned S4, pore formation includes chemical activation pore formation and / or physical activation pore formation; the activator of the chemical activation pore formation is selected from one or more of KOH, NaOH, phosphoric acid, and zinc chloride.

7. The preparation method according to claim 1, characterized in that In the above-mentioned S6, the carbon coating includes liquid phase carbon coating and / or gas phase carbon coating.

8. A boron-doped silicon-carbon negative electrode material, characterized in that: The compound is prepared by the preparation method according to any one of claims 1 to 7.

9. A lithium-ion battery, characterized in that: The invention comprises the boron-doped silicon-carbon negative electrode material according to claim 8 or the boron-doped silicon-carbon negative electrode material prepared by the preparation method according to any one of claims 1 to 7.

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