A core-shell structured powdered carbon material and its preparation and application

Abstract

This invention relates to the field of lithium-ion batteries, and more particularly to a negative electrode material for lithium-ion batteries and its preparation method. The invention provides a powdered carbon material with a core-shell structure. The core of this microporous carbon material is coated with a carbon material shell. The core has a particle size of 3-8 μm and contains a large number of micropores with a pore size of 0.001-0.5 nm, accounting for 60-90% of the total pore volume of the core. The remainder consists of micropores with a pore size greater than 0.5 nm-50 nm. The interlayer spacing of the 002 crystal planes constituting the core is 0.39-0.41 nm. The shell has a thickness of 10-1000 nm, preferably 10-200 nm, with a pore size of 0.001-10 nm. The interlayer spacing of the 002 crystal planes constituting the shell is 0.34-0.36 nm. The negative electrode material provided by this invention has a hard carbon structure with a large interlayer spacing, which facilitates the diffusion of lithium ions within it, enabling rapid charging and discharging within the electrode and achieving high-rate performance of the negative electrode material.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion batteries, and more particularly to a negative electrode material for lithium-ion batteries and its preparation method. Background Technology

[0002] Lithium-ion batteries, as the mainstream rechargeable battery technology, are widely used in consumer electronics, electric vehicles, and large-scale energy storage, greatly improving people's lives. With changing application environments, there is an increasing demand for lithium-ion batteries with rapid charge and discharge capabilities, such as in start-stop batteries for automobiles, high-speed trains, subways, and batteries for drones and model aircraft.

[0003] Rapid charge-discharge performance requires lithium-ion batteries to complete electrochemical reactions in an extremely short time. Therefore, high requirements are placed on electron and ion transport, especially the transport speed of lithium ions in and around the negative electrode, which is a key factor limiting the high specific power of lithium-ion batteries. Currently commercially available negative electrode materials include graphite, amorphous carbon materials, and lithium titanate. Graphite can achieve a specific capacity of over 300 mA·h / g and a first-cycle coulombic efficiency of over 90%. However, graphite materials suffer from poor structural stability and poor compatibility with electrolytes. During charge and discharge, it is prone to co-intercalation reactions with propylene carbonate organic solvents in the electrolyte, leading to structural damage and affecting the battery's cycle stability and charge-discharge efficiency. Furthermore, the anisotropic structure of graphite restricts the free diffusion of lithium ions within the graphite structure, and the small interlayer spacing affects the rate performance of graphite negative electrode materials. Amorphous carbon materials mainly include hard carbon and soft carbon. Compared with graphite, they have lower crystallinity, micropores, and less regular and ordered layered structures. Repeating graphite layers are generally less than 2-3 layers. This interlaced layered structure allows Li+ to intercalate and deintercalate from various angles of the material, and the larger interlayer spacing facilitates rapid lithium-ion diffusion, enabling rapid charge and discharge. Because they do not exhibit solvent co-intercalation and significant lattice expansion and contraction, which are common in graphite materials, hard and soft carbon materials have the advantage of good cycle performance. Furthermore, since the processing does not require graphitization, their cost is significantly lower than that of graphite-based anode materials. However, these materials have low initial cycle efficiency (40-60%) and low specific capacity (around 300 mAh / g), limiting their commercial application. Summary of the Invention

[0004] The technical problem to be solved by this invention (the purpose of the invention)

[0005] To address the problem of low first-cycle coulombic efficiency in existing hard carbon materials made from biomass, this invention provides a lithium-ion battery anode material that reduces the specific surface area and surface oxygen content through heat treatment and asphalt coating.

[0006] The complete technical solution provided by this invention is as follows:

[0007] This invention provides a powdered carbon material with a core-shell structure. The core of the microporous carbon material is covered with a carbon material shell. The core has a particle size of 3-8 μm and contains a large number of micropores with a pore size of 0.001-0.5 nm, accounting for 60-90% of the total pore volume of the core. The remainder consists of micropores with a pore size greater than 0.5 nm-50 nm. The interlayer spacing of the 002 crystal planes of the carbon material constituting the core is 0.39-0.41 nm. The shell has a thickness of 10-1000 nm, preferably 10-200 nm, a pore size of 0.001-10 nm, and an interlayer spacing of 002 crystal planes of the carbon material constituting the shell of 0.34-0.36 nm.

[0008] The specific surface area of ​​core-shell structured powdered carbon materials is 0.5-3 m². 2 / g, in the surface layer from the outer surface of the core-shell structured powdered carbon material to 20nm below the outer surface, the molar content of oxygen atoms is 1-3% of the sum of the molar contents of carbon atoms and oxygen atoms in the surface layer.

[0009] The present invention also provides a method for preparing the above-mentioned negative electrode material, comprising the following steps: 1) after drying and pulverizing the biomass raw material, pre-carbonizing it in an inert atmosphere at 400-600℃ (preferably 400-550℃, more preferably 450-550℃) for 1-3 hours to obtain product A;

[0010] 2) Product A was successively immersed and stirred in NaOH solution and acid solution for washing, then filtered, washed with water until neutral, dried, and then pulverized by air jet mill to obtain carbon powder B with a particle size of 3-8 μm;

[0011] 3) Immerse and stir carbon powder B in NaCl and / or Na2CO3 solution, then filter and dry to obtain carbon powder C. The molar ratio of carbon to NaCl and / or Na2CO3 is 10 / 1 to 100 / 1 (preferably 20 / 1 to 100 / 1, more preferably 50 / 1 to 100 / 1).

[0012] 4) Put carbon powder C and asphalt into an asphalt coating machine, heat it to 250-350℃ in an inert atmosphere, stir and mix for 20-60 minutes to obtain carbon powder C coated with asphalt.

[0013] 5) The carbon powder C coated with asphalt is heated to 1100-1300℃ (preferably 1100-1200℃) in an inert atmosphere and heat-treated at a constant temperature for 1-3 hours. Then it is cooled to room temperature in a mixed atmosphere of hydrogen and inert gas to obtain the negative electrode material.

[0014] in,

[0015] The biomass raw material mentioned in step 1) is one or more of coconut shells, peach shells, apricot shells, and walnut shells; it is crushed to a particle size of less than or equal to 20 micrometers.

[0016] The inert atmospheres mentioned in steps 1), 4), and 5) are nitrogen atmosphere and / or argon atmosphere, respectively.

[0017] The concentration of the NaOH solution in step 2) is 1-5 mol / L (preferably 2-5 mol / L, more preferably 3-5 mol / L), and the acid solution is one or more of hydrochloric acid solution, sulfuric acid solution or nitric acid solution, with a concentration of 1-5 mol / L (preferably 2-5 mol / L, more preferably 3-5 mol / L); the purpose of cleaning is to remove impurities other than carbon from the raw materials (the impurities include one or more of silicon, metal elements, etc.).

[0018] The soaking and stirring time described in step 2) is 1-100h, preferably 25-50h; the temperature range during stirring is 25-70℃, preferably 50-70℃.

[0019] In step 3), the concentration of NaCl and / or Na2CO3 solution is 1-5 mol / L; the impregnation and stirring time is 1-100 h, preferably 25-50 h; and the temperature range during stirring is 25-50℃.

[0020] The asphalt mentioned in step 4) is petroleum asphalt with a softening point of 200-250℃;

[0021] The mass ratio of carbon powder C to asphalt in step 4) is 7 / 3 to 9 / 1 (preferably 8 / 2 to 9 / 1).

[0022] In step 5), the volume ratio of hydrogen to inert gas in the mixed atmosphere is 1 / 9 to 3 / 7 (preferably 1 / 9 to 2 / 8).

[0023] Beneficial effects of the technical solution of this invention

[0024] (1) The negative electrode material provided by the present invention has a hard carbon structure inside with a large interlayer spacing, which is conducive to the diffusion of lithium ions in it, and can meet the requirements of rapid charging and discharging inside the electrode, thus realizing the high rate performance of the negative electrode material.

[0025] (2) The negative electrode material provided by the present invention has a lower specific surface area than hard carbon material, which can reduce the irreversible capacity loss caused by the formation of too much solid electrolyte interface film and has a higher first-cycle coulombic efficiency.

[0026] (3) The negative electrode material provided by the present invention has a lower surface oxygen content, which can reduce the irreversible capacity in the first cycle and facilitate obtaining a higher coulombic efficiency in the first cycle. Detailed Implementation

[0027] The present invention will now be described in detail through specific embodiments.

[0028] This invention uses the prepared negative electrode material in a coin cell for testing. The battery testing methods in the examples and comparative examples are the same, specifically as follows: The prepared negative electrode material, conductive agent (Super-P), and polyvinylidene fluoride are mixed and uniformly dispersed in N-methylpyrrolidone at a mass ratio of 90:2:8. This mixture is then coated onto the surface of a copper foil to form an electrode sheet containing 3 ± 0.3 mg of negative electrode material per square centimeter of copper foil. After the electrode sheet is formed into a disc, it forms a sandwich structure battery structure with a separator (Celgard) and lithium metal. An electrolyte (lithium hexafluorophosphate concentration of 1 mol / L, solvent of ethylene carbonate, dimethyl carbonate, and diethyl carbonate (volume ratio of 1:1:1), and also containing 2% by mass of vinylene carbonate) is added. Battery performance testing used the CCCV charge-discharge method, which involves charging to 0V at 0.1C, then charging at a constant voltage to 0.02C, and finally discharging to 1.5V at 0.1C as one cycle. The first-cycle coulombic efficiency of the negative electrode material was obtained by using the ratio of discharge capacity to charge capacity and recorded in Table 1. Subsequently, charge-discharge was performed at 1C, 2C, and 5C currents, with a cutoff voltage of 0V to 1.5V. Five cycles were run at each current, and the average value was recorded in Table 1.

[0029] Example 1

[0030] 10 kg of coconut shells were dried in a vacuum drying oven at 110°C for 8 hours, then pulverized to a particle size of ≤20 μm. Pre-carbonization was performed under an argon atmosphere at 500°C for 2 hours. The shells were then ultrasonically cleaned in a 1M NaOH solution for 2 hours, followed by ultrasonic cleaning in a 2M hydrochloric acid solution for 2 hours. After filtration, the shells were rinsed with deionized water until the pH reached 7. After drying at 110°C, the shells were pulverized using an air jet mill to obtain carbon powder with a particle size of 3-8 μm. 3 kg of this carbon powder was then added to a 2M... The carbon powder was impregnated in NaCl solution at room temperature for 25 hours. The molar ratio of carbon powder to NaCl was 10 / 1. After filtration and drying, it was added to petroleum asphalt with a softening point of 200℃ at a ratio of 8 / 2 in an asphalt coating machine. The temperature was raised to 250℃ and stirred for 30 minutes. After uniform mixing, it was removed and placed in a high-temperature carbonization furnace. Under nitrogen atmosphere protection, the temperature was raised to 1100℃ and kept constant for 2 hours. Then, it was subjected to a mixed atmosphere of hydrogen and nitrogen (N2 / N2). The material is cooled to room temperature under H2 (8 / 2), then pulverized and sieved to obtain the core-shell structured anode material. The core has a particle size of 3-8 μm and contains a large number of micropores with a diameter of 0.001-0.5 nm, accounting for 75% of the total core pore volume. The remainder consists of micropores with a diameter of 0.5-50 nm. The interlayer spacing of the 002 crystal planes is 0.39 nm. The shell thickness is 50-200 nm, the interlayer spacing of the 002 crystal planes is 0.35 nm, and the specific surface area is 1.8 m².2 / g, with a surface oxygen atom content of 2.32%.

[0031] The negative electrode material was made into a button cell, and the battery performance was tested. The reversible charge-discharge specific capacity of the battery was 433 mAh / g, the first cycle coulombic efficiency was 86.2%, and the reversible capacity at 5C and at 0.1C was 72.3%.

[0032] Example 2

[0033] 10 kg of coconut shells were dried in a vacuum drying oven at 110°C for 8 hours, then pulverized to a particle size of ≤20 μm. Pre-carbonization was performed under an argon atmosphere at 600°C for 2 hours. The shells were then ultrasonically cleaned in a 1M NaOH solution for 2 hours, followed by ultrasonic cleaning in a 2M hydrochloric acid solution for 2 hours. After filtration, the shells were rinsed with deionized water until the pH reached 7. After drying at 110°C, the shells were pulverized using an air jet mill to obtain carbon powder with a particle size of 3-8 μm. 3 kg of this carbon powder was then added to a 2M... The carbon powder was impregnated in NaCl solution at room temperature for 25 hours. The molar ratio of carbon powder to NaCl was 20 / 1. After filtration and drying, it was added to petroleum asphalt with a softening point of 200℃ at a ratio of 8 / 2 in an asphalt coating machine. The temperature was raised to 250℃ and stirred for 30 minutes. After uniform mixing, it was removed and placed in a high-temperature carbonization furnace. Under nitrogen atmosphere protection, the temperature was raised to 1100℃ and kept constant for 2 hours. Then, it was subjected to a mixed atmosphere of hydrogen and nitrogen (N2 / H2O). The material is cooled to room temperature at a temperature of 2 = 9 / 1), then pulverized and sieved to obtain the core-shell structured anode material. The core has a particle size of 3-8 μm and contains a large number of micropores with a diameter of 0.001-0.5 nm, accounting for 72% of the total core pore volume. The remainder consists of micropores with a diameter of 0.5 nm-50 nm. The interlayer spacing of the 002 crystal planes is 0.4 nm. The shell thickness is 100-500 nm, the interlayer spacing of the 002 crystal planes is 0.35 nm, and the specific surface area is 1.7 m². 2 The surface oxygen atom content is 2.21% / g. This negative electrode material was used to make a coin cell, and its performance is shown in Table 2.

[0034] Example 3

[0035] 10 kg of coconut shells were dried in a vacuum drying oven at 110°C for 8 hours, then pulverized to a particle size of ≤20 μm. Pre-carbonization was performed under an argon atmosphere at 500°C for 2 hours. The shells were then ultrasonically cleaned in a 1M NaOH solution for 2 hours, followed by ultrasonic cleaning in a 2M hydrochloric acid solution for 2 hours. After filtration, the shells were rinsed with deionized water until the pH reached 7. After drying at 110°C, the shells were pulverized using an air jet mill to obtain carbon powder with a particle size of 3-8 μm. 3 kg of this carbon powder was then added to a 2M... The carbon powder was impregnated in NaCl solution at room temperature for 25 hours. The molar ratio of carbon powder to NaCl was 50 / 1. After filtration and drying, it was added to petroleum asphalt with a softening point of 250℃ at a ratio of 8 / 2 in an asphalt coating machine. The temperature was raised to 300℃ and stirred for 30 minutes. After uniform mixing, it was removed and placed in a high-temperature carbonization furnace. Under nitrogen atmosphere protection, the temperature was raised to 1200℃ and kept constant for 2 hours. Then, it was subjected to a mixed atmosphere of hydrogen and nitrogen (N2 / H2). =8 / 2) cooled to room temperature, then pulverized and sieved to obtain the core-shell structured anode material, wherein the core particle size is 3-8 μm, containing a large number of micropores with a pore size of 0.001-0.5 nm, accounting for 70% of the total core pore volume, and the remainder consists of micropores with a pore size of 0.5 nm-50 nm. The 002 crystal interlayer spacing is 0.39 nm, the shell thickness is 100-500 nm, the 002 crystal interlayer spacing is 0.35 nm, and the specific surface area is 1.4 m². 2 The surface oxygen atom content is 1.74% (g). This negative electrode material was used to make a coin cell, and its performance is shown in Table 2.

[0036] Examples 4-8

[0037] The preparation conditions of the negative electrode material in each embodiment are shown in Table 1, and the performance is shown in Table 2.

[0038] Comparative Example 1

[0039] 10 kg of coconut shells were dried in a vacuum drying oven at 110°C for 8 hours, then pulverized to a particle size of ≤20 μm. Pre-carbonization was performed under an argon atmosphere at 500°C for 2 hours. The shells were then ultrasonically cleaned in a 1M NaOH solution for 2 hours, followed by ultrasonic cleaning in a 2M hydrochloric acid solution for 2 hours. After filtration, the shells were rinsed with deionized water until the pH reached 7. After drying at 110°C, the shells were pulverized using an air jet mill to obtain carbon powder with a particle size of 3-8 μm. 3 kg of this carbon powder was then added to a 2M... The carbon powder was impregnated in NaCl solution at room temperature for 25 hours. The molar ratio of carbon powder to NaCl was 10 / 1. After filtration and drying, it was mixed with petroleum asphalt with a softening point of 200℃ at a ratio of 8 / 2 in a mixer. The mixer temperature was 220℃ and the mixing time was 25 minutes. After uniform mixing, the mixture was removed and carbonized at 1100℃ for 1 hour in an argon atmosphere. After cooling to room temperature, it was pulverized and sieved to obtain the core-shell structured anode material. The core particle size was 3-8 μm, containing a large number of micropores with a pore size of 0.001-0.5 nm, accounting for 75% of the total core pore volume. The remainder consisted of micropores with a pore size of 0.5 nm-50 nm. The interlayer spacing of the 002 crystal planes was 0.39 nm. The shell thickness was 50-200 nm, the interlayer spacing of the 002 crystal planes was 0.35 nm, and the specific surface area was 3.5 m². 2 The surface oxygen atom content is 10.7% (g). This negative electrode material was used to make a coin cell, and its performance is shown in Table 2.

[0040] Comparative Example 2

[0041] 10 kg of coconut shells were dried in a vacuum drying oven at 110°C for 8 hours, then pulverized to a particle size of ≤20 μm. Pre-carbonization was performed under an argon atmosphere at 500°C for 2 hours. The shells were then ultrasonically cleaned in a 1M NaOH solution for 2 hours, followed by ultrasonic cleaning in a 2M hydrochloric acid solution for 2 hours. After filtration, the shells were rinsed with deionized water until the pH reached 7. After drying at 110°C, the shells were pulverized using an air jet mill to obtain carbon powder with a particle size of 3-8 μm. 3 kg of this carbon powder was then added to a 2M... The carbon powder was impregnated in NaCl solution at room temperature for 25 hours. The molar ratio of carbon powder to NaCl was 50 / 1. After filtration and drying, it was mixed with petroleum asphalt with a softening point of 200℃ at a ratio of 8 / 2 in a mixer. The mixer temperature was 220℃ and the mixing time was 25 minutes. After uniform mixing, the mixture was removed and carbonized at 1200℃ for 1 hour in an argon atmosphere. After cooling to room temperature, it was pulverized and sieved to obtain the core-shell structured anode material. The core particle size was 3-8 μm, containing a large number of micropores with a pore size of 0.001-0.5 nm, accounting for 70% of the total core pore volume. The remainder consisted of micropores with a pore size of 0.5 nm-50 nm. The interlayer spacing of the 002 crystal planes was 0.39 nm. The shell thickness was 100-500 nm, the interlayer spacing of the 002 crystal planes was 0.35 nm, and the specific surface area was 2.3 m². 2 The surface oxygen atom content is 10.1% (g). This negative electrode material was used to make a coin cell, and its performance is shown in Table 2.

[0042] Comparative Example 3

[0043] 10 kg of coconut shells were dried in a vacuum drying oven at 110°C for 8 hours, then pulverized to a particle size of ≤20 μm. Pre-carbonization was performed under an argon atmosphere at 500°C for 2 hours. The shells were then ultrasonically cleaned in 1M NaOH solution for 2 hours, followed by ultrasonic cleaning in 2M hydrochloric acid solution for 2 hours. After filtration, the shells were rinsed with deionized water until the pH reached 7. After drying at 110°C, the shells were pulverized using an air jet mill to obtain carbon powder with a particle size of 3-8 μm. This carbon powder was then mixed with petroleum asphalt (softening point 200°C) and xylene according to… The carbon powder was added to the reactor at a mass ratio of 80:20:50 for coating treatment at 220℃ for 2 hours. The coated carbon powder was then carbonized under an argon atmosphere at 1100℃ for 2 hours. After cooling to room temperature, it was pulverized and sieved to obtain a core-shell structured anode material. The core particle size was 3-8 μm, with micropores of 0.001-0.5 nm accounting for 60% of the total core pore volume. The 002 crystal interlayer spacing was 0.38 nm. The shell thickness was 100-500 nm, the 002 crystal interlayer spacing was 0.35 nm, and the specific surface area was 4.5 m². 2 / g, with a surface oxygen atom content of 10.1%. When made into a coin cell, its performance is shown in Table 1.

[0044] Comparative Example 4-11

[0045] The preparation conditions of the negative electrode materials in each comparative example are shown in Table 1, and the performance is shown in Table 2.

[0046] Table 1 Key parameters for the preparation of negative electrode materials in each embodiment and comparative example.

[0047]

[0048] Table 2 Battery performance of the negative electrode materials prepared in each embodiment and comparative example.

[0049]

[0050]

[0051] Results show that compared with Comparative Examples 1 and 2, the first-cycle coulombic efficiency of the battery prepared using the negative electrode material of this invention is improved by about 4%. This is due to the better asphalt coating effect, which further reduces the specific surface area, and the reduction of surface oxygen atom content caused by heat treatment in a hydrogen atmosphere. Compared with Comparative Example 3, the introduction of Na salt in the preparation steps of this invention creates more micropores inside the particles during the subsequent high-temperature carbonization process, utilizing the activation and pore-forming ability of Na ions. This provides space for lithium ion storage, thereby improving the reversible charge-discharge specific capacity. Moreover, the reduction of surface oxygen atom content caused by thermal reduction treatment in a hydrogen atmosphere also leads to a high first-cycle coulombic efficiency. Compared with Comparative Examples 4 and 5, a high C / Na salt molar ratio increases the reversible specific capacity but decreases the first-cycle coulombic efficiency; a low C / Na salt molar ratio results in a relatively high first-cycle coulombic efficiency but a low reversible specific capacity. Compared with Comparative Examples 6 and 7, a higher asphalt mass fraction results in a relatively high first-cycle coulombic efficiency but a low reversible specific capacity; a low asphalt mass fraction results in an insufficiently high first-cycle coulombic efficiency. Compared to Comparative Examples 8 and 9, the high-temperature carbonization temperature was too low, resulting in a higher reversible specific capacity but a lower first-cycle coulombic efficiency; the high-temperature carbonization temperature was too high, which, while improving the first-cycle coulombic efficiency, significantly reduced the capacity. Compared to Comparative Examples 10 and 11, the N2 / H2 volume ratio was too low, resulting in a sufficiently high first-cycle coulombic efficiency but a lower reversible specific capacity; while the volume ratio was too high, leading to a significant decrease in first-cycle coulombic efficiency. Based on extensive experiments, this invention proposes the parameter range for the preparation process of this invention. In summary, using the anode material of this invention, both high reversible capacity and high first-cycle coulombic efficiency can be obtained.

Claims

1. The application of a core-shell structured powdered carbon material as a negative electrode active material in the negative electrode of a lithium-ion battery, characterized in that: The carbon material core is covered with a carbon material shell. The core has a particle size of 3-8 μm and contains a large number of micropores with a pore size of 0.001-0.5 nm, accounting for 60%-90% of the total pore volume of the core. The rest are pores with a pore size greater than 0.5 nm and less than or equal to 50 nm. The interlayer spacing of the carbon material (002) constituting the core is 0.39-0.41 nm. The shell has a thickness of 10-1000 nm, a pore size of 0.001-10 nm, and the interlayer spacing of the carbon material (002) constituting the shell is 0.34-0.36 nm. The specific surface area of the core-shell structured powdered carbon material is 0.5-3 m 2 The molar content of oxygen atoms in the surface layer of the outer surface of the core-shell structured powdered carbon material to 20 nm below the outer surface is 1-3% of the sum of the molar content of carbon atoms and the molar content of oxygen atoms in the surface layer. The method for preparing the powdered carbon material includes the following steps: 1) After drying and pulverizing the biomass raw material, pre-carbonize it at 400-600℃ for 1-3 hours in an inert atmosphere to obtain product A; 2) Product A was successively immersed and stirred in NaOH solution and acid solution for washing, then filtered, washed with water until neutral, dried, and then pulverized by air jet mill to obtain carbon powder B with a particle size of 3-8 μm; 3) Immerse and stir carbon powder B in NaCl and / or Na2CO3 solution, then filter and dry to obtain carbon powder C. The molar ratio of carbon powder B to NaCl and / or Na2CO3 is 10 / 1 to 100 / 1. 4) Put carbon powder C and asphalt into an asphalt coating machine, heat it to 250-350℃ in an inert atmosphere, stir and mix for 20-60 minutes to obtain carbon powder C coated with asphalt. 5) The carbon powder C coated with asphalt is heated to 1100-1300℃ in an inert atmosphere and heat-treated at a constant temperature for 1-3 hours. Then it is cooled to room temperature in a mixed atmosphere of hydrogen and inert gas to obtain the negative electrode material. The volume ratio of hydrogen to inert gas in the mixed atmosphere described in step 5) is 1 / 9 to 3 / 7.

2. The application of the powdered carbon material according to claim 1, characterized in that: The biomass raw material is one or more of coconut shells, peach shells, apricot shells, and walnut shells; in step 1), it is crushed to a particle size of less than or equal to 20 micrometers; The inert atmosphere described in steps 1), 4) and 5) is a nitrogen atmosphere and / or an argon atmosphere.

3. The application of the powdered carbon material according to claim 1, characterized in that: In step 1), the material is pre-carbonized at 400-550°C in an inert atmosphere.

4. The application of the powdered carbon material according to claim 1, characterized in that: In step 1), the material is pre-carbonized at 450-550°C in an inert atmosphere.

5. The application of the powdered carbon material according to claim 2, characterized in that: In step 2), the concentration of the NaOH solution is 1-5 mol / L, and the acid solution is one or more of hydrochloric acid, sulfuric acid, or nitric acid, with a concentration of 1-5 mol / L.

6. The application of the powdered carbon material according to claim 1 or 5, characterized in that: The impregnation and stirring time described in step 2) is 1-100h; the temperature range during stirring is 25-70℃.

7. The application of the powdered carbon material according to claim 1, characterized in that: In step 3), the concentration of NaCl and / or Na2CO3 solution is 1-5 mol / L; the impregnation and stirring time is 1-100 h; and the temperature range during stirring is 25-50℃.

8. The application of the powdered carbon material according to claim 1, characterized in that: In step 3), the molar ratio of carbon powder B to NaCl and / or Na2CO3 is 20 / 1 to 100 / 1.

9. The application of the powdered carbon material according to claim 1, characterized in that: In step 3), the molar ratio of carbon powder B to NaCl and / or Na2CO3 is 50 / 1-100 / 1.

10. The application of the powdered carbon material according to claim 1, characterized in that: The asphalt mentioned in step 4) is petroleum asphalt with a softening point of 200-250℃; The mass ratio of carbon powder C to asphalt in step 4) is 7 / 3 to 9 / 1.

11. The application of the powdered carbon material according to claim 1, characterized in that: The volume ratio of hydrogen to inert gas in the mixed atmosphere described in step 5) is 1 / 9 to 2 / 8.

12. The application of the powdered carbon material according to claim 1, characterized in that: In step 5), the carbon powder C coated with asphalt is heated to 1100-1200℃ in an inert atmosphere.

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