Preparation method of a bio-based carbon black and battery thereof

Abstract

The application discloses a preparation method of a bio-based carbon black and a battery thereof. The preparation method comprises the following steps: a mixing step, in which a carbon source and a matrix modifier are mixed to obtain a mixture; and a heating step, in which the mixture is carbonized under a heating condition to obtain the bio-based carbon black. The bio-based carbon black is prepared by mixing peanut shell powder and sodium chloride powder, and then high-temperature carbonization and matrix modification, and when the bio-based carbon black is used as a conductive agent of a lithium ion battery, the bio-based carbon black has higher specific capacity and cycle stability.

Description

Technical Field

[0001] This invention relates to the field of batteries, specifically to a method for preparing bio-based carbon black and its battery. Background Technology

[0002] Carbon black is an indispensable chemical raw material in the modern national economy, playing a vital role in many basic industrial sectors. For example, in the rubber industry, it is an important reinforcing agent and filler for rubber products; in the ink and coating industry, it is one of the most important additives affecting the blackness of products. In the plastics industry, carbon black not only colors and tones products but also prevents UV aging, provides antistatic properties, or promotes conductivity; in the synthetic leather industry, as a black colorant for coating polyurethane solutions, carbon black is an indispensable raw material for preparing black synthetic leather. In addition, carbon black is widely used in dry batteries, electrical and electronic components, high-purity artificial graphite materials, printing and dyeing, photographic film, gunpowder, cement, and casting.

[0003] In the 1920s, gas furnace carbon black production technology using natural gas as a raw material emerged. Due to rising natural gas prices, from the 1970s onwards, the oil furnace carbon black production process successfully replaced the original process, gaining widespread application worldwide and producing many new carbon black varieties with applications in new fields. With advancements in materials technology, particularly the development of the rubber industry, higher requirements have been placed on some basic performance indicators of carbon black, such as particle size, dispersion, and conductivity. Simultaneously, the economic model of sustainable development and the urgency of environmental protection also require reasonable innovations to existing production processes and raw material routes. Introducing new technologies into traditional processes is an important means of innovation; however, carbon black suitable for use as a high-end conductive agent in lithium-ion batteries remains lacking. Summary of the Invention

[0004] According to the first aspect, one embodiment provides a method for preparing bio-based carbon black, comprising: The mixing step includes mixing a carbon source with a matrix modifier to obtain a mixture; The heating step includes carbonizing the mixture under heating conditions to obtain the bio-based carbon black.

[0005] In one embodiment, the matrix modifier includes sodium chloride.

[0006] In one embodiment, the carbon source includes peanut shells.

[0007] In one embodiment, a washing step is also included, comprising washing and drying the bio-based carbon black to obtain dried bio-based carbon black.

[0008] In one embodiment, a method for preparing bio-based carbon black is provided, comprising the following steps: (1) Crush the peanut shells and then pass them through a 200-mesh sieve to obtain peanut shell powder; (2) Crush sodium chloride and then pass it through a 200-mesh sieve to obtain sodium chloride powder; (3) Mix peanut shell powder and sodium chloride powder; (4) The mixture is heated to 800-1200 °C in a nitrogen atmosphere to obtain a crude product; (5) Wash the crude product with deionized water and then dry it to obtain bio-based carbon black.

[0009] In one embodiment, this invention provides for the first time a method for preparing bio-based carbon black using peanut shells as a carbon source. The inventors made a significant discovery through extensive experimentation: mixing peanut shell powder and sodium chloride powder, followed by high-temperature carbonization and matrix modification to obtain a crude product, and then washing and drying to obtain bio-based carbon black; when used as a conductive agent in lithium-ion batteries, the bio-based carbon black exhibits high specific capacity and cycle stability; specific experimental studies show that when used as a conductive agent in lithium-ion batteries, bio-based carbon black has a high specific capacity; after 1000 cycles, no significant decrease in specific capacity was observed, demonstrating excellent cycle performance.

[0010] Furthermore, the inventors emphasize that each reaction step in this invention is crucial and indispensable. Without any step, the bio-based carbon black prepared will not exhibit excellent cycle performance when used as a conductive agent in lithium-ion batteries. In one embodiment, using peanut shell powder as the carbon source, the bio-based carbon black prepared through two steps—mixing peanut shell powder and sodium chloride powder, followed by high-temperature carbonization and matrix modification—exhibits excellent cycle performance when used as a conductive agent in lithium-ion batteries.

[0011] In one embodiment, the inventors discovered that the choice of matrix modifier plays a crucial role in determining the excellent cycle performance of the prepared bio-based carbon black when used as a conductive agent in lithium-ion batteries, during the preparation of bio-based carbon black using the method described in this invention. The inventors were surprised to find that when sodium chloride was used as the matrix modifier, the prepared bio-based carbon black exhibited excellent cycle performance when used as a conductive agent in lithium-ion batteries; its cycle performance was far superior to that of bio-based carbon black prepared without sodium chloride.

[0012] In one embodiment, the heating step is performed in an inert gas atmosphere.

[0013] In one embodiment, the inert gas in the heating step includes, but is not limited to, at least one of nitrogen, helium, neon, and argon.

[0014] In one embodiment, the mixture in the mixing step is in powder form. The method for preparing the powder is not limited; for example, the carbon source and matrix modifier can be mixed and then pulverized using mechanical equipment to obtain a powdered mixture, or the carbon source and matrix modifier can be pulverized separately beforehand and then mixed to obtain a powdered mixture.

[0015] In one embodiment, the pulverization method includes, but is not limited to, air jet milling and mechanical milling.

[0016] In one embodiment, the method of mixing the carbon source with the matrix modifier includes, but is not limited to, ball milling, stirring, and oscillation mixing.

[0017] In one embodiment, during the mixing step, the particle size of the mixture is 200-300 mesh. The desired particle size can be obtained by sieving with a screen.

[0018] In one embodiment, the carbon source is in powder form during the mixing step.

[0019] In one embodiment, the matrix modifier in the mixing step is in powder form.

[0020] In one embodiment, the particle size of the carbon source in the mixing step is 200-300 mesh.

[0021] In one embodiment, during the mixing step, the particle size of the matrix modifier is 200-300 mesh.

[0022] In one embodiment, during the mixing step, the matrix modifier: carbon source ratio is (12-25): (5-7) by mass.

[0023] In one embodiment, during the heating step, the mixture is heated to 800-1200 °C.

[0024] In one embodiment, during the heating step, the heating rate of the mixture is 2-8 °C / min.

[0025] According to the second aspect, one embodiment provides a bio-based carbon black prepared by the preparation method described in the first aspect.

[0026] According to a third aspect, one embodiment provides a conductive agent containing the bio-based carbon black described in the second aspect.

[0027] According to the fourth aspect, one embodiment provides a battery containing the bio-based carbon black described in the second aspect or the conductive agent described in the third aspect.

[0028] In one embodiment, the battery includes, but is not limited to, lithium-ion batteries and sodium-ion batteries.

[0029] In one embodiment, the present invention provides a novel method for preparing bio-based carbon black using peanut shells as a carbon source. The present invention prepares bio-based carbon black through two steps: mixing peanut shell powder and sodium chloride powder, followed by high-temperature carbonization and matrix modification. When used as a conductive agent in lithium-ion batteries, this bio-based carbon black exhibits high specific capacity and cycle stability.

[0030] In one embodiment, the method provided by the present invention is safe and environmentally friendly, easy to operate, low in preparation cost, and easy to industrialize. Attached Figure Description

[0031] Figure 1 This is an appearance diagram of the bio-based carbon black powder prepared in Example 1 of the present invention.

[0032] Figure 2 Transmission electron microscope image of the bio-based carbon black powder prepared in Example 1 of this invention. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings. In the following embodiments, many details are described to facilitate a better understanding of the present application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other materials or methods. In some cases, certain operations related to the present application are not shown or described in the specification. This is to avoid obscuring the core parts of the present application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0034] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can be rearranged or adjusted in a manner obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.

[0035] The serial numbers assigned to components in this article, such as "first" and "second", are used only to distinguish the objects being described and have no sequential or technical meaning.

[0036] In one embodiment, the present invention aims to provide a method for efficiently preparing a high-end bio-based carbon black using peanut shells as a carbon source and sodium chloride as a structural modifier.

[0037] Example 1 First, peanut shells and sodium chloride were pulverized using a pulverizer, and then passed through a 200-mesh sieve to obtain peanut shell powder and sodium chloride powder. 18 g of sodium chloride powder and 6 g of peanut shell powder were added to a ball mill jar and ball-milled for 1 hour. The milled material was then added to a corundum crucible and heated to 1100 °C at a heating rate of 6 °C / min under a nitrogen atmosphere for high-temperature carbonization and matrix modification to obtain a crude product. The crude product was washed with deionized water and finally dried at 80 °C to obtain bio-based carbon black.

[0038] Figure 1 This is an appearance diagram of the bio-based carbon black powder prepared in this embodiment.

[0039] Figure 2 Transmission electron microscope image of the bio-based carbon black powder prepared in this embodiment.

[0040] Example 2 First, peanut shells and sodium chloride were pulverized using a pulverizer, and then passed through a 200-mesh sieve to obtain peanut shell powder and sodium chloride powder. 18 g of sodium chloride powder and 6 g of peanut shell powder were added to a ball mill jar and ball-milled for 1 hour. The milled material was then added to an alumina crucible and heated to 800 °C at a heating rate of 6 °C / min under a nitrogen atmosphere for high-temperature carbonization and matrix modification to obtain a crude product. The crude product was washed with deionized water and finally dried at 80 °C to obtain bio-based carbon black.

[0041] The difference between Example 2 and Example 1 is that the high-temperature carbonization and matrix modification temperature of Example 2 is 800 ℃, while the high-temperature carbonization and matrix modification temperature of Example 1 is 1100 ℃.

[0042] Example 3 First, peanut shells and sodium chloride were pulverized using a pulverizer, and then passed through a 200-mesh sieve to obtain peanut shell powder and sodium chloride powder. 18 g of sodium chloride powder and 6 g of peanut shell powder were added to a ball mill jar and ball-milled for 1 hour. The milled material was then added to an alumina crucible and heated to 900 °C at a heating rate of 6 °C / min under a nitrogen atmosphere for high-temperature carbonization and matrix modification to obtain a crude product. The crude product was washed with deionized water and finally dried at 80 °C to obtain bio-based carbon black.

[0043] The difference between Example 3 and Example 1 is that the high-temperature carbonization and matrix modification temperature of Example 3 is 900 ℃, while the high-temperature carbonization and matrix modification temperature of Example 1 is 1100 ℃.

[0044] Example 4 First, peanut shells and sodium chloride were pulverized using a pulverizer, and then passed through a 200-mesh sieve to obtain peanut shell powder and sodium chloride powder. 18 g of sodium chloride powder and 6 g of peanut shell powder were added to a ball mill jar and ball-milled for 1 hour. The milled material was then added to an alumina crucible and heated to 1000 °C at a heating rate of 6 °C / min under a nitrogen atmosphere for high-temperature carbonization and matrix modification to obtain a crude product. The crude product was washed with deionized water and finally dried at 80 °C to obtain bio-based carbon black.

[0045] The difference between Example 4 and Example 1 is that the high-temperature carbonization and matrix modification temperature of Example 4 is 1000 ℃, while the high-temperature carbonization and matrix modification temperature of Example 1 is 1100 ℃.

[0046] Example 5 First, peanut shells and sodium chloride were pulverized using a pulverizer, and then passed through a 200-mesh sieve to obtain peanut shell powder and sodium chloride powder. 18 g of sodium chloride powder and 6 g of peanut shell powder were added to a ball mill jar and ball-milled for 1 hour. The milled material was then added to a corundum crucible and heated to 1200 °C at a heating rate of 6 °C / min under a nitrogen atmosphere for high-temperature carbonization and matrix modification to obtain a crude product. The crude product was washed with deionized water and finally dried at 80 °C to obtain bio-based carbon black.

[0047] The difference between Example 5 and Example 1 is that the high-temperature carbonization and matrix modification temperature of Example 5 is 1200 ℃, while the high-temperature carbonization and matrix modification temperature of Example 1 is 1100 ℃.

[0048] Example 6 First, peanut shells and sodium chloride were pulverized using a pulverizer, and then passed through a 200-mesh sieve to obtain peanut shell powder and sodium chloride powder. 18 g of sodium chloride powder and 6 g of peanut shell powder were added to a ball mill jar and ball-milled for 1 hour. The milled material was then added to an alumina crucible and heated to 1100 °C at a heating rate of 2 °C / min under a nitrogen atmosphere for high-temperature carbonization and matrix modification to obtain a crude product. The crude product was washed with deionized water and finally dried at 80 °C to obtain bio-based carbon black.

[0049] The difference between Example 6 and Example 1 is that the heating rate in Example 6 is 2 °C / min, while the heating rate in Example 1 is 6 °C / min.

[0050] Example 7 First, peanut shells and sodium chloride were pulverized using a pulverizer, and then passed through a 200-mesh sieve to obtain peanut shell powder and sodium chloride powder. 18 g of sodium chloride powder and 6 g of peanut shell powder were added to a ball mill jar and ball-milled for 1 hour. The milled material was then added to an alumina crucible and heated to 1100 °C at a heating rate of 4 °C / min under a nitrogen atmosphere for high-temperature carbonization and matrix modification to obtain a crude product. The crude product was washed with deionized water and finally dried at 80 °C to obtain bio-based carbon black.

[0051] The difference between Example 7 and Example 1 is that the heating rate in Example 7 is 4 °C / min, while the heating rate in Example 1 is 6 °C / min.

[0052] Example 8 First, peanut shells and sodium chloride were pulverized using a pulverizer, and then passed through a 200-mesh sieve to obtain peanut shell powder and sodium chloride powder. 18 g of sodium chloride powder and 6 g of peanut shell powder were added to a ball mill jar and ball-milled for 1 hour. The milled material was then added to an alumina crucible and heated to 1100 °C at a heating rate of 8 °C / min under a nitrogen atmosphere for high-temperature carbonization and matrix modification to obtain a crude product. The crude product was washed with deionized water and finally dried at 80 °C to obtain bio-based carbon black.

[0053] The difference between Example 8 and Example 1 is that the heating rate in Example 8 is 8 °C / min, while the heating rate in Example 1 is 6 °C / min.

[0054] Comparative Example 1 First, peanut shells and sodium chloride were pulverized using a pulverizer, and then passed through a 200-mesh sieve to obtain peanut shell powder and sodium chloride powder. 6 g of peanut shell powder was added to a ball mill jar and ball-milled for 1 hour. The milled material was then added to an alumina crucible and heated to 1100 °C at a heating rate of 6 °C / min under a nitrogen atmosphere for high-temperature carbonization and matrix modification to obtain a crude product. The crude product was washed with deionized water and finally dried at 80 °C to obtain bio-based carbon black.

[0055] The difference between Comparative Example 1 and Example 1 is that sodium chloride powder was not used as a matrix modifier in Comparative Example 1, while sodium chloride powder was used as a matrix modifier in Example 1.

[0056] Comparative Example 2 First, peanut shells and lithium chloride were pulverized using a pulverizer, and then passed through a 200-mesh sieve to obtain peanut shell powder and sodium chloride powder. 18 g of lithium chloride powder and 6 g of peanut shell powder were added to a ball mill jar and ball-milled for 1 hour. The milled material was then added to an alumina crucible and heated to 1100 °C at a heating rate of 6 °C / min under a nitrogen atmosphere for high-temperature carbonization and matrix modification to obtain a crude product. The crude product was washed with deionized water and finally dried at 80 °C to obtain bio-based carbon black.

[0057] The difference between Comparative Example 2 and Example 1 is that lithium chloride powder was used as the matrix modifier in Comparative Example 2, while sodium chloride powder was used as the matrix modifier in Example 1.

[0058] Comparative Example 3 First, peanut shells and potassium chloride were pulverized using a pulverizer, and then passed through a 200-mesh sieve to obtain peanut shell powder and sodium chloride powder. 18 g of potassium chloride powder and 6 g of peanut shell powder were added to a ball mill jar and ball-milled for 1 hour. The milled material was then added to a corundum crucible and heated to 1100 °C at a heating rate of 6 °C / min under a nitrogen atmosphere for high-temperature carbonization and matrix modification to obtain a crude product. The crude product was washed with deionized water and finally dried at 80 °C to obtain bio-based carbon black.

[0059] The difference between Comparative Example 3 and Example 1 is that potassium chloride powder was used as the matrix modifier in Comparative Example 3, while sodium chloride powder was used as the matrix modifier in Example 1.

[0060] Comparative Example 4 First, bamboo and sodium chloride were pulverized using a pulverizer, and then passed through a 200-mesh sieve to obtain bamboo powder and sodium chloride powder. 18 g of sodium chloride powder and 6 g of bamboo powder were added to a ball mill jar and ball-milled for 1 hour. The milled material was then added to a corundum crucible and heated to 1100 °C at a heating rate of 6 °C / min under a nitrogen atmosphere for high-temperature carbonization and matrix modification to obtain a crude product. The crude product was washed with deionized water and finally dried at 80 °C to obtain bio-based carbon black.

[0061] The difference between Comparative Example 4 and Example 1 is that Comparative Example 4 uses bamboo as the carbon source, while Example 1 uses peanut shells as the carbon source.

[0062] Comparative Example 5 First, coconut shells and sodium chloride were pulverized using a pulverizer, and then passed through a 200-mesh sieve to obtain coconut shell powder and sodium chloride powder. 18 g of sodium chloride powder and 6 g of coconut shell powder were added to a ball mill jar and ball-milled for 1 hour. The milled material was then added to a corundum crucible and heated to 1100 °C at a heating rate of 6 °C / min under a nitrogen atmosphere for high-temperature carbonization and matrix modification to obtain a crude product. The crude product was washed with deionized water and finally dried at 80 °C to obtain bio-based carbon black.

[0063] The difference between Comparative Example 5 and Example 1 is that Comparative Example 5 uses coconut shells as a carbon source, while Example 1 uses peanut shells as a carbon source.

[0064] Bio-based carbon black prepared in Examples 1-8 and Comparative Examples 1-5 were used as conductive agents for lithium-ion batteries, lithium iron phosphate (brand: Kejing; product number: P198-DF5) was used as the positive electrode material, and PVDF (brand: Arkema; ​​product model: MA-EN-BI-01) was used as the binder to prepare electrodes, and button cells were assembled. The discharge specific capacity (mAh / g) of the button half-cell after 1000 cycles at a current density of 100 mA / g, as well as the initial coulombic efficiency (%) and initial discharge specific capacity (mAh / g) of the button half-cell at a current density of 100 mA / g, were tested. The test results are shown in Table 1.

[0065] LiFePO4, carbon black, and PVDF were mixed in a mass ratio of 94:3:3 and stirred into a slurry using N-methylpyrrolidone (brand: KELUD; product model: MA-EN-OT-01) as a solvent. The slurry was then coated onto aluminum foil (brand: KELUD; product model: MA-EN-CU-0N) and thoroughly dried to form the positive electrode. A lithium metal sheet was used as the negative electrode, a Celgard 2500 polypropylene porous membrane (brand: KELUD; product model: MA-EN-SE-07) as the separator, and 1.0 M LiPF6 / EC-DMC-EMC=1:1:1 Vol% with 1.0% VC (brand: Duoduo Chemical Reagent Network; product model: LB-092) as the electrolyte. The battery was assembled in an argon-protected glove box. After 24 hours of resting, the battery cycle performance was tested using a battery testing system from Wuhan Landian Electronics Co., Ltd.

[0066] Table 1

[0067] As shown in Table 1, when the bio-based carbon black prepared in Example 1 is used as a conductive agent in lithium-ion batteries, the initial coulombic efficiency is 98% at a current density of 100 mA / g, the initial discharge specific capacity is above 167 mAh / g, and the discharge specific capacity after 1000 cycles is 159 mAh / g. This indicates that the bio-based carbon black prepared using peanut shells as a carbon source according to the method described in this invention exhibits excellent cycle performance and high specific capacity as a conductive agent in lithium-ion batteries.

[0068] When the bio-based carbon black prepared in Examples 1 and 2-5 is used as a conductive agent in lithium-ion batteries, the analysis revealed that the high-temperature carbonization and matrix modification temperatures have a significant impact on the performance of the bio-based carbon black. The initial coulombic efficiency, initial discharge specific capacity, and discharge specific capacity after 1000 cycles of the bio-based carbon black in Examples 2-5 are much lower than those of the bio-based carbon black in Example 1. This indicates that in the process of preparing bio-based carbon black using the method described in this invention, the selection of high-temperature carbonization and matrix modification temperatures plays an important role in whether the prepared bio-based carbon black has excellent cycle performance when used as a conductive agent in lithium-ion batteries. When the high-temperature carbonization and matrix modification temperature is selected as 1100 ℃, the prepared bio-based carbon black exhibits excellent cycle performance, high initial coulombic efficiency, and high initial discharge specific capacity when used as a conductive agent in lithium-ion batteries. The main reason is that when the high-temperature carbonization and matrix modification temperature is below 1100 ℃, the carbonization and matrix modification of the synthesized material are insufficient, while when the high-temperature carbonization and matrix modification temperature is above 1100 ℃, the synthesized material undergoes structural collapse, resulting in an imperfect matrix structure, which is not conducive to the rapid diffusion of lithium ions.

[0069] When the bio-based carbon black prepared in Examples 1 and 6-8 is used as a conductive agent in lithium-ion batteries, the analysis revealed that the heating rate has a significant impact on the performance of the bio-based carbon black. The initial coulombic efficiency, initial discharge specific capacity, and discharge specific capacity after 1000 cycles of the bio-based carbon black in Examples 6-8 are much smaller than those of the bio-based carbon black in Example 1. This indicates that in the process of preparing bio-based carbon black using the method described in this invention, both excessively slow and excessively fast heating rates are not conducive to constructing a perfect bio-based carbon black structure. A heating rate of 6 °C / min is beneficial for the bio-based carbon black to obtain excellent lithium storage performance.

[0070] Studies in Example 1 and Comparative Example 1 revealed that the bio-based carbon black prepared using sodium chloride powder as a matrix modifier exhibited significantly better initial coulombic efficiency, initial discharge specific capacity, and discharge specific capacity after 1000 cycles compared to bio-based carbon black prepared without sodium chloride powder as a matrix modifier. Studies in Example 1 and Comparative Examples 2-3 further showed that the bio-based carbon black prepared using sodium chloride powder as a matrix modifier had significantly higher initial coulombic efficiency, initial discharge specific capacity, and discharge specific capacity after 1000 cycles than bio-based carbon black prepared using lithium chloride powder or potassium chloride powder as matrix modifiers. This indicates that the matrix modifier has a significant impact on the performance of the prepared bio-based carbon black; the addition of a matrix modifier helps improve the structure of the bio-based carbon black, and a more optimized bio-based carbon black structure facilitates the insertion and extraction of lithium ions.

[0071] The studies in Examples 1 and Comparative Examples 4-5 revealed that the initial coulombic efficiency, initial discharge specific capacity, and discharge specific capacity after 1000 cycles of bio-based carbon black prepared using peanut shells as a carbon source were significantly higher than those prepared using bamboo or coconut shells as carbon sources. This indicates that the carbon source has a significant impact on the performance of the prepared bio-based carbon black, and a suitable carbon source is beneficial for obtaining structurally stable carbon black.

[0072] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the ideas of this invention.

Claims

1. A method for preparing bio-based carbon black, a conductive agent suitable for batteries, characterized in that, include: The mixing step includes mixing a carbon source with a matrix modifier to obtain a mixture; wherein, by mass, the matrix modifier:the carbon source = 3:1; the matrix modifier is sodium chloride, and the carbon source is peanut shell; The heating step includes carbonizing the mixture under heating conditions to obtain the bio-based carbon black; wherein, in the heating step, the mixture is heated to 1100℃-1200℃.

2. The preparation method according to claim 1, characterized in that, It also includes a washing step, which involves washing and drying the bio-based carbon black to obtain dried bio-based carbon black.

3. The preparation method according to claim 1, characterized in that, In the heating step, the heating is carried out in an inert gas atmosphere.

4. The preparation method according to claim 3, characterized in that, The inert gas is selected from at least one of nitrogen, helium, neon, and argon.

5. The preparation method according to claim 1, characterized in that, In the mixing step, the mixture is in powder form.

6. The preparation method according to claim 1, characterized in that, In the mixing step, the particle size of the mixture is 200-300 mesh.

7. The preparation method according to claim 1, characterized in that, The carbon source is in powder form.

8. The preparation method according to claim 1, characterized in that, The matrix modifier is in powder form.

9. The preparation method according to claim 1, characterized in that, In the mixing step, the particle size of the carbon source is 200-300 mesh.

10. The preparation method according to claim 1, characterized in that, In the mixing step, the particle size of the matrix modifier is 200-300 mesh.

11. The preparation method according to claim 1, characterized in that, In the heating step, the heating rate of the mixture is 2-8 °C / min.

Images