Boron-doped porous carbon, silicon-carbon negative electrode prepared from boron-doped porous carbon, and preparation method and application of silicon-carbon negative electrode

Abstract

The invention discloses boron-doped porous carbon, a silicon-carbon negative electrode material prepared from the boron-doped porous carbon, a preparation method and application, and belongs to the technical field of energy storage materials, and the preparation method comprises the following steps: dissolving a carbon source and a boron source in deionized water, uniformly stirring, then carrying out a hydrothermal synthesis reaction, adding an activator and deionized water into the obtained precursor, stirring, carrying out vacuum filtration, and drying to obtain boron-doped porous carbon; the preparation method comprises the following steps: carrying out vacuum drying, introducing inert gas into an obtained powder substance, sequentially carrying out an activation reaction and carbonization at a high temperature, washing obtained black powder with hydrochloric acid until the powder is neutral, washing with deionized water, carrying out spray drying, introducing nitrogen and silane gas into obtained boron-doped porous carbon, and carrying out silane deposition, so as to obtain the boron-doped porous carbon. And introducing acetylene gas to carry out carbon coating reaction, and naturally cooling to room temperature to obtain the silicon-carbon negative electrode material. The porous carbon prepared by the method has the advantages of large specific surface area, high pore volume and high micropore proportion, the pore structure is in a gradient regulation state, the conductivity of the porous carbon is improved, and the electrochemical performance of the silicon-carbon negative electrode is obviously improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of energy storage materials, and relates to boron-doped porous carbon and a silicon-carbon negative electrode prepared from the same, and a preparation method and application thereof. BACKGROUND

[0002] With the maturity of chemical vapor deposition (CVD) technology and the cost reduction of the industrial chain, a new generation of CVD silicon-carbon negative electrode materials are expected to become the mainstream choice in the field of power batteries after 2025, and to promote the energy density of lithium batteries to break through the 500 Wh / kg threshold. In the new silicon-carbon negative electrode system, the core of the porous carbon is to solve the problems of volume expansion and electrical conductivity of silicon, and to achieve a balance between high performance and low cost through structural design and process innovation. The porous carbon skeleton is suitable for CVD deposition method to realize uniform loading of nano-silicon. For example, the initial efficiency of the CVD method silicon-carbon negative electrode can reach 90%, and the cycle life can break through 1500 times. The high specific surface area (1100-2200 m 2 / g) and hierarchical pore (micropore, mesopore, macropore) design of the porous carbon can provide physical buffer space for the volume expansion of silicon and inhibit structural rupture. The doping of elements such as boron and nitrogen can enhance the electrical conductivity and electrolyte wettability of the porous carbon.

[0003] The interface between silicon particles and porous carbon is prone to detachment due to volume change, and the bonding force needs to be enhanced through element doping (such as nitrogen and boron) or pre-lithiation, but the doping process is complex and the cost is increased. The silicon-carbon negative electrode is prone to lithium precipitation due to limited ion transport under high rate (such as 20 minutes to 80%) and needs to be combined with conductive network optimization (such as single-walled carbon nanotubes) to improve the fast charging capacity.

[0004] The current mainstream porous carbon is mainly divided into biomass, petroleum coke and porous carbon according to the carbon source substrate. The biomass-based material has wide sources, low cost, environmental benefits and mature physical activation method technology, and can realize continuous production, but the stability of the raw material is poor; the petroleum coke-based material has low cost, high carbonization efficiency and good electrical conductivity, but has high impurity content and difficulty in physical activation; the raw material has high purity, stable quality, high pore-forming stability and good micropore consistency, but the current raw material cost is high.

[0005] Therefore, how to develop a boron-doped porous carbon with low cost, stable and adjustable pore structure and good electrical conductivity, and a silicon-carbon negative electrode prepared from the same, and a preparation method and application thereof is a problem to be solved by those skilled in the art. SUMMARY

[0006] Therefore, the application provides a boron-doped porous carbon and a silicon-carbon negative electrode prepared from the same, and a preparation method and application thereof.

[0007] In order to achieve the above-mentioned purpose, the application adopts the following technical solutions:

[0008] A preparation method of boron-doped porous carbon, comprising the following steps:

[0009] (1) Dissolve a carbon source and a boron source in deionized water, uniformly stir, and then place in a hydrothermal synthesis tank, and then place the hydrothermal synthesis tank in an oven to perform a hydrothermal synthesis reaction, to obtain a boron-doped modified polymer precursor solution;

[0010] (2) Add the boron-doped modified polymer precursor solution obtained in step (1) into an activator and deionized water to stir, and then perform vacuum filtration to obtain a solid substance, and then perform vacuum drying to obtain a powder substance;

[0011] (3) Place the powder substance obtained in step (2) in a rotary furnace, introduce inert gas, and sequentially perform activation reaction and carbonization at high temperature to obtain black powder, then wash the black powder with hydrochloric acid until neutral, then wash with deionized water, and finally perform spray drying to obtain the boron-doped porous carbon.

[0012] Further, in step (1), the carbon source is any one of sucrose, glucose, starch, phenolic resin or polyvinyl chloride resin, the boron source is boric acid or sodium borohydride, and the mass ratio of the carbon source, the boron source and the deionized water is (1-2):1:5.

[0013] Further, in step (1), the temperature of the hydrothermal synthesis reaction is 150-200℃, and the reaction time is 15h.

[0014] The beneficial effects of the above further technical solutions are: through the hydrothermal synthesis reaction, the boron source compound can be grafted with the carbon source molecular chain in the form of a chemical bond, so that the boron doping modification is more uniform, the chemical bond is more firm, and the boron is not easy to fall off in the subsequent carbonization process.

[0015] Further, in step (2), the activator is one or more of potassium hydroxide, sodium hydroxide, potassium bicarbonate or sodium bicarbonate, and the mass ratio of the total mass of the activator, the carbon source and the boron source added in step (1) and the deionized water in step (2) is (1-3):1:2.

[0016] Further, in step (2), the stirring time of the boron-doped modified polymer precursor solution obtained in step (1) added into the activator is 5h, the stirring speed is 300r / min; the filter membrane pore size of the vacuum filtration is 0.5-2μm; the vacuum degree of the vacuum drying is 50-100Pa, the vacuum drying time is 5h, and the vacuum drying temperature is 105℃.

[0017] Further, in step (3), the inert gas is nitrogen or argon, the flow rate of the inert gas is 1-3 L / min; the activation reaction temperature is 300-700 DEG C, the activation reaction time is 0.5-3 h; the carbonization temperature is 500-900 DEG C, the carbonization time is 1-5 h; the inlet air temperature of the spray drying is 150 DEG C, the feeding rate is 0.5-1 L / h, the inlet air volume is 40-50 m 3 / h, and the outlet air temperature is 60 DEG C.

[0018] The application further provides a boron-doped porous carbon prepared by the method, which has a specific surface area of 1800-2300 m 2 / g, a pore volume of 0.7-1.2 cm 3 / g, contains micropores with a pore size of <2 nm, mesopores with a pore size of 2-50 nm and macropores with a pore size of 50 nm, the micropores account for >70%, and the average pore size D50 is in the range of 5-10 mu m.

[0019] The application further provides a method for preparing a silicon-carbon negative electrode material by using the boron-doped porous carbon, which comprises the following steps:

[0020] The boron-doped porous carbon is placed in a fluidized bed reactor, nitrogen and silane gas are introduced for silane deposition, the introduction of silane is stopped, the temperature of the fluidized bed is increased, acetylene gas is introduced for carbon coating reaction, the introduction of acetylene is stopped, and the silicon-carbon negative electrode material is obtained after natural cooling to room temperature.

[0021] Further, the silane deposition temperature is 550 DEG C, the silane deposition time is 300-400 min; the carbon coating reaction temperature is 700 DEG C, and the carbon coating reaction time is 100-200 min.

[0022] Further, the flow rate of the introduced nitrogen is 10 L / min, the flow rate of the introduced silane gas is 1.5 L / min, and the flow rate of the introduced acetylene gas is 1.2 L / min.

[0023] The application further provides a silicon-carbon negative electrode material prepared by the method.

[0024] The application further provides an application of the silicon-carbon negative electrode material in assembling lithium batteries.

[0025] The application has the following advantages: the application adopts a hydrothermal method to synthesize a precursor, and simultaneously introduces element-doped groups; the element doping is uniform due to solution dispersion; the chemical bonds formed make the groups more firmly combined; the process has the advantages of simple operation process, wide source of carbon source, no need of strong acid or strong base, and the ability to be performed at a lower temperature; the prepared activated carbon has the advantages of low cost, stable and adjustable pore structure, and good conductivity, which can effectively improve the conductivity of the porous carbon, increase the stability and uniformity of silicon deposition, and improve the cycle life and rate performance of the silicon-carbon negative electrode material.

[0026] The porous carbon prepared by the method has a large specific surface area, a high pore volume, a high micropore ratio, and a gradient-adjusted pore structure, and is suitable for CVD deposition to prepare a silicon-carbon negative electrode material. The porous carbon with the structure can effectively relieve the volume expansion of nano-silicon and improve the conductivity of the porous carbon, and the electrochemical performance of the silicon-carbon negative electrode is obviously improved.

[0027] Improved electron transport efficiency: Boron atoms, as electron-deficient centers, can induce the Fermi level shift of the carbon matrix by doping, reduce the band gap, and thus improve the conductivity of the material.

[0028] Improved surface wettability: The polar functional groups (such as B-O and B-C) introduced by boron doping can reduce the contact angle of the porous carbon and the electrolyte, enhance the electrolyte wettability, and promote ion diffusion. Experiments show that the contact angle of the boron-doped carbon ball with water is reduced, and the wettability is significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 BJH adsorption integral pore volume of the boron-doped modified porous carbon of Example 1.

[0030] Figure 2 BJH adsorption integral pore volume of the boron-doped modified porous carbon of Example 2.

[0031] Figure 3 BJH adsorption integral pore volume of the boron-doped modified porous carbon of Example 3.

[0032] Figure 4 Particle size distribution of the boron-doped modified porous carbon of Example 3.

[0033] Figure 5 BJH adsorption integral pore volume of the boron-doped modified porous carbon of Example 4.

[0034] Figure 6 BJH adsorption integral pore volume of the boron-doped modified porous carbon of Example 5. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0036] Example 1

[0037] The method for preparing a silicon-carbon negative electrode material by using boron-doped porous carbon comprises the following steps:

[0038] (1) 100 g sucrose and 50 g boric acid were dissolved in 500 mL deionized water, and after electromagnetic stirring at a speed of 1000 rpm for 30 min, they were placed in a hydrothermal synthesis tank and then placed in an oven for heating to perform a hydrothermal synthesis reaction. The oven temperature was set to 150°C, and the hydrothermal synthesis reaction time was 15 h to obtain a boron-doped modified polymer precursor solution;

[0039] (2) The boron-doped modified polymer precursor solution obtained in step (1) was added to 300 g potassium hydroxide and 200 g deionized water and stirred at a speed of 50 rpm for 5 h. Then, vacuum filtration was performed with a filter membrane having a pore size of 1 μm. Vacuum drying was performed at a vacuum degree of 100 Pa for 5 h at a temperature of 105°C to obtain a solid material, which was then vacuum dried to obtain a powder material;

[0040] (3) The powder material obtained in step (2) was placed in a rotary furnace, nitrogen gas was introduced at a flow rate of 1 L / min, and activation and carbonization were sequentially performed at high temperatures. The activation temperature was 300°C, and the activation time was 3 h. The carbonization temperature was 500°C, and the carbonization time was 3 h to obtain black powder. The black powder was then washed with hydrochloric acid until it was neutral, washed with deionized water, and finally spray dried. The spray drying was performed at an inlet air temperature of 150°C, an inlet material flow rate of 1 L / h, an inlet air flow of 45 m 3 / h, and an outlet air temperature of 60°C to obtain boron-doped porous carbon;

[0041] (4) The boron-doped porous carbon obtained in step (3) was placed in a fluidized bed reactor, nitrogen gas was introduced at a flow rate of 10 L / min, and silane gas was introduced at a flow rate of 1.5 L / min to perform silane deposition. The silane deposition temperature was 550°C, and the silane deposition time was 300 min. After stopping the introduction of silane, the fluidized bed temperature was increased, and acetylene gas was introduced at a flow rate of 1.2 L / min to perform carbon coating. The carbon coating temperature was 700°C, and the carbon coating time was 100 min. After stopping the introduction of acetylene and naturally cooling to room temperature, a silicon-carbon negative electrode material was obtained.

[0042] Example 2

[0043] A method for preparing a silicon-carbon negative electrode material using boron-doped porous carbon includes the following steps:

[0044] (1) 100 g sucrose and 75 g boric acid were dissolved in 500 mL deionized water, and after electromagnetic stirring at a speed of 1000 rpm for 30 min, they were placed in a hydrothermal synthesis tank and then placed in an oven for heating to perform a hydrothermal synthesis reaction. The oven temperature was set to 150°C, and the hydrothermal synthesis reaction time was 15 h to obtain a boron-doped modified polymer precursor solution;

[0045] (2) The boron-doped modified polymer precursor solution obtained in step (1) is added to 300 g of potassium hydroxide and 200 g of deionized water and stirred for 5 h at a stirring speed of 50 r / min, and then vacuum filtration is performed, the filter membrane pore size of the vacuum filtration is 1 μm; the vacuum degree of the vacuum drying is 100 Pa, the vacuum drying time is 5 h, and the vacuum drying temperature is 105 °C, to obtain a solid substance, which is vacuum dried again to obtain a powder substance;

[0046] (3) The powder substance obtained in step (2) is placed in a rotary furnace, nitrogen gas is introduced at a flow rate of 1.5 L / min, and activation reaction and carbonization are sequentially performed at high temperature, the activation reaction temperature is 300 °C, the activation reaction time is 3 h; the carbonization temperature is 500 °C, and the carbonization time is 3 h, to obtain black powder, which is then washed with hydrochloric acid until neutral, washed with deionized water, and finally spray dried, the inlet air temperature of the spray drying is 150 °C, the feeding rate is 1 L / h, the inlet air volume is 45 m 3 / h, and the outlet air temperature is 60 °C, to obtain boron-doped porous carbon;

[0047] (4) The boron-doped porous carbon obtained in step (3) is placed in a fluidized bed reactor, nitrogen gas is introduced at a flow rate of 10 L / min, and silane gas is introduced at a flow rate of 1.5 L / min to perform silane deposition, the silane deposition temperature is 550 °C, and the silane deposition time is 300 min, the introduction of silane is stopped, the temperature of the fluidized bed is increased, acetylene gas is introduced at a flow rate of 1.2 L / min to perform carbon coating reaction, the carbon coating reaction temperature is 700 °C, and the carbon coating reaction time is 100 min, the introduction of acetylene is stopped, and the temperature is naturally lowered to room temperature, to obtain a silicon-carbon negative electrode material.

[0048] Example 3

[0049] The method for preparing a silicon-carbon negative electrode material by using boron-doped porous carbon comprises the following steps:

[0050] (1) 100 g of sucrose and 100 g of boric acid are dissolved in 500 mL of deionized water, and then placed in a hydrothermal synthesis tank after electromagnetic stirring at a speed of 1000 r / min for 30 min, and then placed in an oven for heating to perform a hydrothermal synthesis reaction, the oven temperature is set to 150 °C, and the hydrothermal synthesis reaction time is 15 h, to obtain a boron-doped modified polymer precursor solution;

[0051] (2) The boron-doped modified polymer precursor solution obtained in step (1) is added to 300 g of potassium hydroxide and 200 g of deionized water and stirred for 5 h at a stirring speed of 50 r / min, and then vacuum filtration is performed, the filter membrane pore size of the vacuum filtration is 1 μm; the vacuum degree of the vacuum drying is 100 Pa, the vacuum drying time is 5 h, and the vacuum drying temperature is 105 °C, to obtain a solid substance, which is vacuum dried again to obtain a powder substance;

[0052] (3) The powder material obtained in step (2) is placed in a rotary furnace, nitrogen gas is introduced at a flow rate of 2 L / min, and activation reaction and carbonization are sequentially performed at high temperature, the activation reaction temperature is 300°C, the activation reaction time is 3 h; the carbonization temperature is 500°C, the carbonization time is 3 h, a black powder is obtained, then the black powder is washed to neutral with hydrochloric acid, and then washed with deionized water, and finally spray dried, the inlet air temperature of the spray drying is 150°C, the feeding rate is 1 L / h, the inlet air volume is 45 m 3 / h, and the outlet air temperature is 60°C, to obtain boron-doped porous carbon;

[0053] (4) The boron-doped porous carbon obtained in step (3) is placed in a fluidized bed reactor, nitrogen gas is introduced at a flow rate of 10 L / min and silane gas is introduced at a flow rate of 1.5 L / min to perform silane deposition, the silane deposition temperature is 550°C, the silane deposition time is 300 min, the silane is stopped, the fluidized bed temperature is increased, acetylene gas is introduced at a flow rate of 1.2 L / min to perform carbon coating reaction, the carbon coating reaction temperature is 700°C, the carbon coating reaction time is 100 min, the acetylene is stopped, and the temperature is naturally cooled to room temperature to obtain a silicon-carbon negative electrode material.

[0054] Example 4

[0055] The method for preparing a silicon-carbon negative electrode material by using boron-doped porous carbon comprises the following steps:

[0056] (1) 100 g of sucrose and 50 g of boric acid are dissolved in 500 mL of deionized water, stirred at a speed of 1000 rpm for 30 min, then placed in a hydrothermal synthesis tank, and then placed in an oven for heating to perform a hydrothermal synthesis reaction, the oven temperature is set to 200°C, and the hydrothermal synthesis reaction time is 15 h to obtain a boron-doped modified high molecular precursor solution;

[0057] (2) The boron-doped modified high molecular precursor solution obtained in step (1) is added to 300 g of potassium hydroxide and 200 g of deionized water and stirred for 5 h at a stirring speed of 50 rpm, then vacuum filtered, the filter membrane pore size of the vacuum filtration is 1 μm; the vacuum degree of the vacuum drying is 100 Pa, the vacuum drying time is 5 h, and the vacuum drying temperature is 105°C, to obtain a solid material, which is then vacuum dried to obtain a powder material;

[0058] (3) The powder material obtained in step (2) is placed in a rotary furnace, nitrogen gas is introduced at a flow rate of 1 L / min, and activation reaction and carbonization are sequentially performed at high temperature, the activation reaction temperature is 300°C, the activation reaction time is 3 h; the carbonization temperature is 500°C, the carbonization time is 3 h, a black powder is obtained, then the black powder is washed to neutral with hydrochloric acid, and then washed with deionized water, and finally spray dried, the inlet air temperature of the spray drying is 150°C, the feeding rate is 1 L / h, the inlet air volume is 45 m 3 / h, the outlet air temperature is 60°C, and a boron-doped porous carbon is obtained;

[0059] (4) The boron-doped porous carbon obtained in step (3) is placed in a fluidized bed reactor, nitrogen gas is introduced at a flow rate of 10 L / min and silane gas is introduced at a flow rate of 1.5 L / min to perform silane deposition, the silane deposition temperature is 550°C, the silane deposition time is 300 min, the silane is stopped, the fluidized bed temperature is increased, acetylene gas is introduced at a flow rate of 1.2 L / min to perform carbon coating reaction, the carbon coating reaction temperature is 700°C, the carbon coating reaction time is 100 min, the acetylene is stopped, and the temperature is naturally cooled to room temperature, and a silicon-carbon negative electrode material is obtained.

[0060] Example 5

[0061] The method for preparing a silicon-carbon negative electrode material by using boron-doped porous carbon comprises the following steps:

[0062] (1) 100 g of sucrose and 75 g of boric acid are dissolved in 500 mL of deionized water, stirred at a speed of 1000 rpm for 30 min, then placed in a hydrothermal synthesis tank, and then placed in an oven for heating to perform a hydrothermal synthesis reaction, the oven temperature is set to 150°C, and the hydrothermal synthesis reaction time is 15 h, to obtain a boron-doped modified high molecular precursor solution;

[0063] (2) The boron-doped modified high molecular precursor solution obtained in step (1) is added to 450 g of potassium hydroxide and 200 g of deionized water and stirred for 5 h at a stirring speed of 50 rpm, then vacuum filtered, the filter membrane pore size of the vacuum filtration is 1 μm; the vacuum drying degree is 100 Pa, the vacuum drying time is 5 h, and the vacuum drying temperature is 105°C, to obtain a solid material, which is then vacuum dried to obtain a powder material;

[0064] (3) the powder material obtained in step (2) is placed in a rotary furnace, nitrogen is introduced at a flow rate of 1 L / min, and activation reaction and carbonization are sequentially carried out at high temperature, the activation reaction temperature is 300 DEG C, the activation reaction time is 3 h; the carbonization temperature is 500 DEG C, the carbonization time is 3 h, a black powder is obtained, then the black powder is washed to neutral with hydrochloric acid, and then washed with deionized water, and finally spray dried, the inlet air temperature of the spray drying is 150 DEG C, the feeding rate is 1 L / h, the inlet air volume is 45 m 3 / h, and the outlet air temperature is 60 DEG C, to obtain boron-doped porous carbon;

[0065] (4) the boron-doped porous carbon obtained in step (3) is placed in a fluidized bed reactor, nitrogen is introduced at a flow rate of 10 L / min, and silane gas is introduced at a flow rate of 1.5 L / min to carry out silane deposition, the silane deposition temperature is 550 DEG C, the silane deposition time is 300 min, the introduction of silane is stopped, the fluidized bed temperature is increased, acetylene gas is introduced at a flow rate of 1.2 L / min to carry out carbon coating reaction, the carbon coating reaction temperature is 700 DEG C, the carbon coating reaction time is 100 min, the introduction of acetylene is stopped, and the temperature is naturally lowered to room temperature, to obtain a silicon-carbon negative electrode material.

[0066] The boron-doped porous carbon prepared in examples 1-5 has a specific surface area of 1800-2300 m 2 / g, a pore volume of 0.7-1.2 cm 3 / g, contains micropores with a pore size of <2 nm, mesopores with a pore size of 2-50 nm, and macropores with a pore size of 50 nm, the micropore content is >70%, and the average pore size D50 is in the range of 5-10 mu m.

[0067] Comparative example 1

[0068] Comparative example 1 has the same process conditions as example 5, and the only difference is that no boric acid is added, the amount of sucrose is changed to 175 g, and the others are the same.

[0069] The conductivity of the porous carbon prepared in the above examples and comparative examples is tested by using a four-probe flat resistance tester. The silicon-carbon negative electrode material prepared in the above examples and comparative examples is prepared into a negative electrode sheet according to an active material loading of 1 mg / cm 2 , then a CR2032 type button half-cell is prepared by using a lithium metal sheet as a counter electrode, and a battery tester is used to sequentially test the electrochemical rate performance of each button cell at current densities of 100 mA / g, 200 mA / g, 500 mA / g, 1000 mA / g, and 100 mA / g.

[0070]

[0071] The foregoing description of the embodiments will enable one skilled in the art to implement or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for producing boron-doped porous carbon, characterized by, The method comprises the following steps: (1) dissolving a carbon source and a boron source in deionized water, stirring uniformly, and then placing in a hydrothermal synthesis tank, and then placing the hydrothermal synthesis tank in an oven to perform a hydrothermal synthesis reaction, to obtain a boron-doped modified polymer precursor solution; (2) adding the boron-doped modified polymer precursor solution obtained in step (1) into an activator and deionized water to stir, and then vacuum filtering to obtain a solid substance, and then vacuum drying to obtain a powder substance; (3) placing the powder substance obtained in step (2) in a rotary furnace, introducing an inert gas, and sequentially performing an activation reaction and carbonization at a high temperature to obtain a black powder, and then washing the black powder with hydrochloric acid until neutral, and then washing with deionized water, and finally spray drying to obtain the boron-doped porous carbon.

2. The method for preparing boron-doped porous carbon according to claim 1, characterized in that, In step (1), the carbon source is any one of sucrose, glucose, starch, phenolic resin or polyvinyl chloride resin, the boron source is boric acid or sodium borohydride, and the mass ratio of the carbon source, the boron source and the deionized water is (1-2):1:

5.

3. The method for preparing boron-doped porous carbon according to claim 1, characterized in that, In step (1), the temperature of the hydrothermal synthesis reaction is 150-200℃, and the reaction time is 15h.

4. The method for preparing boron-doped porous carbon according to claim 1, characterized in that, In step (2), the activator is one or more of potassium hydroxide, sodium hydroxide, potassium bicarbonate or sodium bicarbonate, and the mass ratio of the total mass of the activator, the carbon source and the boron source added in step (1) to the deionized water in step (2) is (1-3):1:

2.

5. The method for preparing boron-doped porous carbon according to claim 1, characterized in that, In step (2), the stirring time for adding the boron-doped modified polymer precursor solution obtained in step (1) into the activator is 5h, the stirring speed is 300r / min, the filter membrane pore size for vacuum filtration is 0.5-2μm, the vacuum degree for vacuum drying is 50-100Pa, the vacuum drying time is 5h, and the vacuum drying temperature is 105℃.

6. The method for preparing boron-doped porous carbon according to claim 1, characterized in that, In step (3), the inert gas is nitrogen or argon, the flow rate of the inert gas is 1-3 L / min; the activation reaction temperature is 300-700℃, the activation reaction time is 0.5-3h; the carbonization temperature is 500-900℃, the carbonization time is 1-5h; the inlet air temperature of the spray drying is 150℃, the feeding rate is 0.5-1 L / h, the inlet air volume is 40-50 m 3 / h, and the outlet air temperature is 60℃.

7. The boron-doped porous carbon prepared by the method of any one of claims 1-6, characterized in that, a specific surface area of 1800-2300 m 2 / g, and a pore volume of 0.7-1.2 cm 3 / g, comprising micropores with a pore size < 2 nm, mesopores with a pore size of 2-50 nm, and macropores with a pore size of 50 nm, the micropores accounting for > 70%, and the average pore size D50 being in the range of 5-10 pm.

8. A method for preparing a silicon-carbon negative electrode material using the boron-doped porous carbon of claim 7, characterized in that, The method comprises the following steps: placing the boron-doped porous carbon in a fluidized bed reactor, introducing nitrogen and silane gas to perform silane deposition, stopping the introduction of silane, increasing the temperature of the fluidized bed, introducing acetylene gas to perform carbon coating reaction, stopping the introduction of acetylene, naturally cooling to room temperature, and obtaining a silicon-carbon negative electrode material.

9. A silicon-carbon negative electrode material prepared by the method of claim 8.

10. Use of the silicon-carbon negative electrode material of claim 9 in assembling a lithium battery.

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