Method for repairing defects of pyrolytic carbon materials using coupling agents

Abstract

The present invention discloses a method for repairing defects in pyrolytic carbon materials using a coupling agent. The method comprises the following steps: sintering a carbon material in an inert atmosphere to obtain a primary calcined carbon material; obtaining an embedded carbon material by electrochemical oxidation or chemical oxidation; obtaining an expanded carbon material by instant high-temperature sintering; performing radiation treatment under plasma or corona conditions, and treating the material with a mixed solution of a newly prepared coupling agent solution and an acid solution or an alkaline solution by spraying and soaking; treating the obtained filter residue with high pressure to obtain a fully grafted carbon material; and post-processing and sintering to obtain a hard carbon material embedded with nano-silicon-carbon microcrystals. The method of the present invention can achieve tight coating of the hard carbon material, and the prepared product has few surface pores, high charge and discharge coulomb efficiency, and good charge and discharge cycle stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery electrode material preparation, and specifically relates to a method for repairing defects in pyrolytic carbon materials using a coupling agent that can be used in lithium batteries, lithium ion batteries, sodium batteries, sodium ion batteries and supercapacitors. Background Art

[0002] Sodium-ion batteries (SIBs) offer advantages such as abundant resources and excellent low-temperature performance. Commercial SIBs commonly use hard carbon materials as their negative electrode materials. The charge-discharge performance and first-cycle Coulombic efficiency of these hard carbon anode materials play a crucial role in the electrochemical performance of SIBs. The discharge curve of SIBs consists of a slope region and a low-voltage discharge plateau. Currently, there are differing views on the intercalation and deintercalation mechanisms of sodium ions in SIBs, suggesting that the key factors influencing the charge-discharge performance of SIBs remain unidentified.

[0003] Compared to lithium-ion batteries, sodium-ion batteries suffer from a low energy density, making them a significant disadvantage in high-energy-density systems (e.g., electric vehicle powertrains). To address this issue, developing anode materials for high-energy-density sodium-ion batteries is crucial. To address the low specific capacity of hard carbon materials, silicon-based materials with high theoretical specific capacity hold great promise for application in sodium-ion battery systems.

[0004] Silicon is one of the most abundant elements in the Earth's crust. In lithium-ion batteries, silicon's theoretical lithium storage capacity (~4200 mAh / g) is over 10 times that of graphite. During charge-discharge cycling, silicon's voltage plateau is slightly higher than that of graphite, making lithium deposition less likely on the silicon anode surface during charging, thus improving safety. Alloying and dealloying of silicon with lithium (discharge / charge) causes volume expansion and contraction of the silicon material. After several cycles of charge and discharge, the silicon material can pulverize, causing the active silicon anode to detach from the current collector, significantly reducing its cycling performance. After years of continuous improvement, the performance of the developed silicon-carbon anode material has significantly improved, leading to its widespread application in lithium-ion batteries. Compared to lithium ions, sodium ions have a larger ionic radius and experience a higher volume expansion rate when alloying and dealloying with silicon (discharge / charge). Conventional silicon-carbon has poor cycling performance in sodium-ion batteries, which explains the limited reports on the application of silicon in sodium-ion batteries.

[0005] Artificial graphite and natural graphite are widely used anode materials for lithium-ion batteries. However, their performance in sodium-ion battery systems is inferior to that of hard carbon materials. Therefore, further research on hard carbon anode materials is necessary.

[0006] Research has shown that the sintering of anthracite to produce conventional electric carbon coal produces primarily large, flake-like particles with thicker flakes. As the sintering temperature increases, especially above 2500°C, the size and thickness of the flake particles decrease significantly, and the size distribution narrows. Yan Zhengguo et al. believe that the graphitization process of anthracite requires sufficiently high temperatures and duration to increase the atomic activity of the coal's chaotic layer structure, facilitate the cleavage of covalent bonds, and rearrange the carbon structure into a more oriented graphite crystal structure. Rouzaud et al. and Beny-Bassez et al. propose that the graphitization process can be divided into four stages, corresponding to four graphitization products: pre-graphitization (aromatic layer graphite), primary graphitization (microcolumnar graphite), intermediate graphitization (flexible graphite), and high graphitization (flat graphite). Zheng Zhe et al. believe that high-temperature graphitization is often used to increase the degree of graphitization of carbon materials and improve their crystal structure. When sintered below 1000°C, coal is difficult to transform into flexible graphite. To transform coal into flat graphite close to ideal graphite, it must be treated at temperatures above 2000-2500°C to undergo decomposition and ultimately form flat graphite. Pyrolytic carbon can be produced using two carbonization processes: limited oxygen supply and air-isolated carbonization. This can be achieved by using low-temperature sintering furnaces such as carbon kilns, carbonization furnaces, spiral furnaces, fluidized bed furnaces, and multi-layer carbonization furnaces, followed by high-temperature sintering in an air-isolated or inert atmosphere.

[0007] China has abundant coal resources, and it has been reported that the performance of the coal is improved by initially pyrolyzing it and then coating the pyrolyzed coal with phenolic resin. However, pyrolyzed coal contains a large number of internal pores and holes, and predecessors have been unable to make the phenolic resin penetrate into the inner layer and internal pores of the coal particles. The hard carbon prepared by this method cannot cover the pores and holes in the pyrolyzed coal particles. As the charge and discharge cycle proceeds, sodium ions are embedded in and out of the coal microcrystals, causing the nanopores and holes inside the coal-based hard carbon particles to be exposed to the electrolyte of the battery system, and side reactions occur with the electrolyte, reducing the charge and discharge coulombic efficiency and charge and discharge cycle stability. The hard carbon materials prepared from coal by this method also have problems such as low coulombic efficiency, low discharge capacity, low cycle life, and slow reaction kinetics, which hinder their practical application. Although a variety of modification methods have been reported, the improvement effect is still not obvious.

[0008] Hard carbon materials are composed of short-range ordered microdomains of curved, graphene-like sheets. These microdomains are randomly stacked, with large interlayer spacing (typically greater than 0.37 nm). Hard carbon particles are characterized by numerous nanopores and defects. When used as anode materials for sodium-ion batteries, the large ionic radius of sodium ions results in poor kinetics for sodium ion insertion and deintercalation, resulting in poor rate performance. Summary of the Invention

[0009] In order to solve the above problems, the present invention provides a method for preparing high-capacity modified hard carbon by using a coupling agent to repair defects in pyrolytic carbon materials.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0011] The method for repairing defects of pyrolytic carbon materials using a coupling agent comprises the following steps:

[0012] 1) Preliminary sintering of the carbon material in an inert atmosphere to obtain a pre-sintered carbon material;

[0013] 2) embedding high-temperature unstable ions into the microcrystalline structure of the calcined carbon material by electrochemical oxidation or chemical oxidation to obtain an embedded carbon material; the high-temperature unstable ions are sulfur, oxygen, hydrogen, chlorine or nitrogen ions;

[0014] 3) The embedded carbon material is subjected to instant high-temperature sintering in an inert atmosphere or an air-tight reactor, and then washed and dried to obtain the expanded carbon material;

[0015] 4) Under controlled atmosphere, the expanded carbon material is placed in a low-temperature plasma or corona condition and irradiated for 10 seconds to 20 minutes; then, the aerosol formed by the freshly prepared mixed solution A is sprayed into the material at 40 to 90°C and reacted for 10 seconds to 10 minutes; the freshly prepared mixed solution A is then added and allowed to soak and react for 10 seconds to 10 minutes, and the solution is filtered to remove the solution to obtain a filter residue;

[0016] The mixed solution A is a mixed solution of a coupling agent solution and an acid solution or an alkaline solution; the weight percentage of the coupling agent to the weight percentage of the initially fired carbon material is 1 to 10 wt%;

[0017] 5) placing the filter residue in a high-pressure reactor, pressurizing it at 5 to 100 atmospheres for 5 minutes to 10 hours, and drying it at 90 to 150° C. to obtain a fully grafted carbon material;

[0018] 6) The fully grafted carbon material is placed in an inert atmosphere or a weak reducing atmosphere for post-processing and sintering to obtain a hard carbon material embedded with nano-silicon-carbon microcrystals.

[0019] The preliminary sintering is preliminary programmed temperature sintering, in which the carbon material from which metal impurities have been removed is heated from room temperature to 700-1000°C at a heating rate of 15°C / min-40°C / min in a nitrogen atmosphere, and sintered at this temperature for 2-10 hours to cause a pyrolysis reaction in the carbon material, and then cooled to room temperature to obtain a pre-burned carbon material; the carbon material is anthracite, bituminous coal, lignite, petroleum coke, coke, natural graphite or lignin material.

[0020] The electrochemical oxidation method is to use an inert electrode as cathode and a pre-burned carbon material as anode in an acid solution at 2-50 mA / cm2 Electrolysis is performed for 0.1 to 6 hours at a current density to obtain an electrolytic carbon material; the electrolytic carbon material is washed and dried to obtain an embedded carbon material; the inert electrode is a graphite, activated carbon or titanium-manganese alloy electrode.

[0021] The chemical oxidation method comprises adding a mixed solution of potassium permanganate, potassium chlorate, potassium dichromate, ammonium persulfate, potassium persulfate, sodium persulfate or hydrogen peroxide and solution B at a volume of 0.01 to 0.3 times the volume of the calcined carbon material under freezing conditions, then reacting at 5 to 50° C. for 1 to 20 minutes, washing and drying to obtain an embedded carbon material; the freezing conditions are freezing conditions in the temperature range of -20 to 5° C.; and the solution B is an aqueous solution of any one of the following: sulfuric acid, a mixed acid of sulfuric acid and phosphoric acid, a mixed acid of nitric acid and phosphoric acid, acetic acid, or ammonium sulfate.

[0022] The instantaneous high-temperature sintering is to place the embedded carbon material directly in an inert atmosphere or an air-isolated reactor at a temperature range of 200 to 600°C and sinter it for 5 to 50 seconds, or to heat the embedded carbon material from room temperature to 200 to 600°C at a heating rate of 70°C / min to 150°C / min, maintain the temperature and sinter for 5 to 50 seconds, and then cool it to room temperature to obtain the expanded carbon material.

[0023] Furthermore, the mixed solution A is a mixed solution of 0.1-10 wt% acid solution or alkaline solution and 90-99.9 wt% coupling agent solution; the pH of the acid solution is 3-6, and the pH of the alkaline solution is 8.5-12; the coupling agent solution is a silane coupling agent solution; the silane coupling agent solution is a mixed solution prepared by 0.1-7 wt% silane coupling agent, 20-87 wt% alcohol, 0-0.2 wt% non-ionic surfactant and water; the alcohol is a solution of ethanol or methanol with 0-50 wt% isopropanol added; the non-ionic surfactant is lauryl oleyl alcohol, palmityl alcohol, stearyl alcohol, cyclohexanol, terpene alcohol, lauryl diethanolamine, glycerol, pentaerythritol, glucose or sorbitol.

[0024] The silane coupling agent is silane-polyethylene glycol-silane, vinyl triethoxysilane, methyl trioxysilane, vinyl trioxysilane, propenyl trioxysilane, methyl vinyl dioxysilane, methacryl dioxysilane or dimethyl dioxysilane.

[0025] The acid solution is one or a mixture of two or more of an aqueous solution of sulfuric acid, hydrochloric acid, nitric acid or acetic acid; the alkali solution is an aqueous solution of sodium hydroxide, potassium hydroxide, lithium hydroxide or ammonia water.

[0026] The post-processing sintering is a post-processing programmed temperature sintering. The post-processing programmed temperature sintering is to heat the fully grafted carbon material to 1100-1700°C at a heating rate in the range of 3°C / min-30°C / min in an inert atmosphere or a weak reducing atmosphere, keep it warm for 2-10 hours, and cool it to room temperature to obtain a hard carbon material embedded with nano-silicon-carbon microcrystals.

[0027] The controlled environment atmosphere is an atmosphere of methane, ethane, formaldehyde, oxygen, air or water vapor. The inert atmosphere is an atmosphere of nitrogen or argon; and the weak reducing atmosphere is a mixed atmosphere of hydrogen and nitrogen or argon.

[0028] The present invention has the following advantages:

[0029] First, the present invention utilizes a transient high-temperature sintering method to expand the interlayer distance of the initially calcined carbon material's microcrystals. Next, through radiation exposure to a specific atmosphere, grafted groups are formed on the surface of the prepared expanded carbon material and on the inner surface of the particles. These grafted groups form silicon-oxygen-carbon chains with a silane coupling agent, which can repair the nanopores within the expanded carbon material's microcrystals and the imperfect surfaces within the expanded nanopores of the expanded carbon material's microcrystals. The hard carbon material embedded with nano-silicon-carbon microcrystals prepared by this method significantly reduces the size of the solid electrolyte interphase (SEI) membrane formed in the battery system, thereby improving the coulombic efficiency of charge and discharge. Second, through coating with a silane coupling agent, the silicon-carbon layer embedded in the nanopores of the hard carbon microcrystals prevents the imperfect inner surface of the expanded nanopores from contacting the battery electrolyte, significantly reducing side reactions with the electrolyte and improving the sample's cycling performance. Third, the silicon-carbon layer embedded within the nanopores of the hard carbon microcrystals is confined to a small volume by the nanopores and cavities within the hard carbon inner layer, reducing the volume expansion of the silicon-carbon during charge and discharge, thereby improving cycling stability. Fourth, the silicon-carbon layer embedded within the carbon microcrystals significantly increases the charge and discharge capacity of the hard carbon system.

[0030] Compared with the prior art, the present invention greatly reduces the sintering temperature and sintering time for preparing the primary fired carbon material, and has a significant energy-saving and emission-reduction effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 1 is the morphology of the sample prepared in Example 1 of the present invention and the corresponding energy spectrum.

[0032] Figure 2 is the XRD diffraction pattern of the sample prepared in Example 1 of the present invention.

[0033] Figure 3 This is the cycle performance curve of the sample prepared in Example 1 of the present invention. Implementation Method

[0034] The present invention will be further described below with reference to the following examples, which are intended only to further supplement and illustrate the present invention, rather than to limit the present invention. Example

[0035] The method for repairing defects of pyrolytic carbon materials using a coupling agent comprises the following steps:

[0036] 1) In a nitrogen atmosphere, anthracite from which metal impurities have been removed is heated from room temperature to 800°C at a heating rate of 20°C / min, sintered for 5 hours to cause pyrolysis of the carbon material, and then cooled to room temperature to obtain a calcined carbon material;

[0037] 2) adding a mixed solution of hydrogen peroxide (0.15 times the volume of the calcined carbon material) and concentrated sulfuric acid and concentrated nitric acid (1:1:1 by weight) to the calcined carbon material at 5°C, reacting at 30°C for 5 minutes, washing, and drying to obtain an embedded carbon material;

[0038] 3) In a nitrogen atmosphere, the embedded carbon material was directly sintered at 350°C for 15 seconds, cooled to room temperature, washed and dried to obtain an expanded carbon material;

[0039] 4) The expanded carbon material was irradiated in a low-temperature plasma in a water vapor atmosphere for 10 minutes, and then an aerosol formed by a freshly prepared mixed solution of 6 wt% sulfuric acid solution (pH = 3) and 94 wt% silane coupling agent solution was sprayed into the expanded carbon material at 70°C for 30 seconds. Subsequently, a mixed solution of 6 wt% sulfuric acid solution (pH = 3) and 94 wt% silane coupling agent solution was added, and the mixture was immersed and reacted for 20 seconds. The solution was filtered to remove the solution to obtain a filter residue;

[0040] The silane coupling agent is vinyl trisilane, the weight percentage of the silane coupling agent to the weight percentage of the calcined carbon material is 3wt%, and the silane coupling agent solution is a mixed solution of 3wt% vinyl trisilane, 70wt% ethanol and water;

[0041] 5) placing the filter residue in a high-pressure reactor, pressurizing it at 8 atmospheres for 0.5 h, and drying it at 120° C. to obtain a fully grafted carbon material;

[0042] 6) In an argon atmosphere, the fully grafted carbon material was heated from room temperature to 1550°C at a heating rate of 5°C / min, kept at this temperature for 5 hours, and cooled to room temperature to obtain a hard carbon material embedded with nano-silicon carbon microcrystals.

[0043] Figure 1 is the morphology of the sample prepared in Example 1 and the corresponding energy spectrum, Figure 1 This indicates that nano-silicon carbon has been embedded in the hard carbon material. Figure 2 is the XRD diffraction pattern of the sample prepared in Example 1, Figure 2 It shows that the prepared sample has a Hexagonal structure. Figure 3 is the cycle performance curve of the sample prepared in Example 1, Figure 3 It shows that the prepared samples have excellent charge and discharge performance. Example

[0044] The method for repairing defects of pyrolytic carbon materials using a coupling agent comprises the following steps:

[0045] 1) Under a nitrogen atmosphere, the lignin material from which metal impurities were removed was heated from room temperature to 1000°C at a heating rate of 40°C / min, and sintered at this temperature for 10 hours to cause a pyrolysis reaction of the carbon material. The carbon material was then cooled to room temperature to obtain a calcined carbon material.

[0046] 2) adding a mixed solution of sulfuric acid and ammonium persulfate in a weight ratio of 1:0.1 in an amount 0.3 times the volume of the calcined carbon material to the calcined carbon material at -5°C, reacting at 50°C for 20 minutes, washing and drying to obtain an embedded carbon material;

[0047] 3) In a nitrogen atmosphere, the embedded carbon material was directly sintered at 600°C for 50 seconds, cooled to room temperature, washed and dried to obtain an expanded carbon material;

[0048] 4) In a formaldehyde atmosphere, the expanded carbon material was subjected to low-temperature plasma radiation treatment for 20 minutes; at 90°C, an aerosol formed by a freshly prepared mixed solution of 10 wt% acetic acid solution (pH = 4) and 90 wt% silane coupling agent solution was sprayed into the material and reacted for 10 minutes; then, a mixed solution of 10 wt% acetic acid solution (pH = 4) and 90 wt% silane coupling agent solution was added, and the material was immersed in the mixture for reaction for 10 minutes, and the solution was removed by filtration to obtain a filter residue;

[0049] The silane coupling agent is methyltrisilane, the weight percentage of the silane coupling agent to the weight percentage of the calcined carbon material is 10wt%, and the silane coupling agent solution is a mixed solution of 7wt% methyltrisilane, 87wt% alcohol and water, and the alcohol is a mixed solution of 50wt% isopropyl alcohol and 50% methanol;

[0050] 5) placing the filter residue in a high-pressure reactor, pressurizing it at 100 atmospheres for 10 hours, and drying it at 150° C. to obtain a fully grafted carbon material;

[0051] 6) In a mixed atmosphere of nitrogen and hydrogen with a volume ratio of 1:0.08, the fully grafted carbon material was heated to 1700°C at a heating rate of 30°C / min, kept at this temperature for 10 hours, and cooled to room temperature to obtain a hard carbon material embedded with nano-silicon-carbon microcrystals. Example

[0052] The method for repairing defects of pyrolytic carbon materials using a coupling agent comprises the following steps:

[0053] 1) In a nitrogen atmosphere, the petroleum coke from which metal impurities were removed was heated from room temperature to 700°C at a heating rate of 15°C / min, sintered for 2 hours to cause a pyrolysis reaction of the carbon material, and cooled to room temperature to obtain a calcined carbon material;

[0054] 2) adding a mixed solution of sulfuric acid and sodium persulfate (weight ratio 1:0.05) in an amount 0.01 times the volume of the calcined carbon material to the calcined carbon material at -20°C, reacting at 50°C for 1 minute, washing and drying to obtain an embedded carbon material;

[0055] 3) In a nitrogen atmosphere, the embedded carbon material is directly sintered at 200°C for 5 seconds, cooled to room temperature, washed and dried to obtain an expanded carbon material;

[0056] 4) In a formaldehyde atmosphere, the expanded carbon material was subjected to low-temperature plasma radiation treatment for 10 seconds; at 90°C, an aerosol formed by a mixture of a freshly prepared 0.1wt% hydrochloric acid solution (pH = 6) and a 99.9wt% silane coupling agent solution was sprayed into the expanded carbon material, reacted for 2 minutes, and then a freshly prepared mixture of a 0.1wt% hydrochloric acid solution (pH = 6) and a 99.9wt% silane coupling agent solution was added, and the mixture was immersed in the solution for 5 minutes. The solution was then filtered to remove the solution to obtain a filter residue;

[0057] The silane coupling agent is propylene trisilane, and the weight percentage of the silane coupling agent to the weight percentage of the initially fired carbon material is 1wt%.

[0058] The silane coupling agent solution is a mixed solution of 2 wt% acryltrisilane, 20 wt% ethanol, 0.2 wt% cyclohexanol (non-ionic surfactant) and water;

[0059] 5) placing the obtained filter residue in an autoclave, pressurizing it at 30 atmospheres for 5 minutes, and drying it at 150°C to obtain a fully grafted carbon material;

[0060] 6) The fully grafted carbon material was placed in a mixed gas atmosphere with an argon to hydrogen volume ratio of 1:0.1, and the fully grafted carbon material was heated to 1700°C at a heating rate of 3°C / min, kept at this temperature for 2 hours, and cooled to room temperature to obtain a hard carbon material embedded with nano-silicon carbon microcrystals. Example

[0061] The method for repairing defects of pyrolytic carbon materials using a coupling agent comprises the following steps:

[0062] 1) In a nitrogen atmosphere, anthracite from which metal impurities have been removed is heated from room temperature to 900°C at a heating rate of 25°C / min, sintered for 8 hours to cause pyrolysis of the carbon material, and cooled to room temperature to obtain a calcined carbon material;

[0063] 2) In a solution of sulfuric acid and acetic acid in a weight ratio of 1:1, with a graphite electrode as the cathode and a pre-burned carbon material as the anode, the 2 Electrolyze for 6 hours at a current density of 0.5 to obtain an electrolytic carbon material; wash and dry the electrolytic carbon material to obtain an embedded carbon material;

[0064] 3) In a nitrogen reactor, the embedded carbon material is directly sintered at 400°C for 30 seconds, cooled to room temperature, washed and dried to obtain an expanded carbon material;

[0065] 4) The expanded carbon material was subjected to corona radiation treatment under methane atmosphere for 20 minutes; an aerosol formed by a mixture of a freshly prepared 7 wt% sodium hydroxide solution (pH = 12) and a 93 wt% silane coupling agent solution was sprayed into the material at 40°C and reacted for 5 minutes; a mixture of a freshly prepared 7 wt% sodium hydroxide solution (pH = 12) and a 93 wt% silane coupling agent solution was then added and allowed to soak and react for 5 minutes, and the solution was filtered to remove the solution to obtain a filter residue;

[0066] The silane coupling agent is methyl acryloyldioxysilane, the weight percentage of the silane coupling agent to the weight percentage of the calcined carbon material is 3wt%, the silane coupling agent solution is a mixed solution of 7wt% methyl acryloyldioxysilane, 30wt% alcohol, 0.1wt% glycerol (non-ionic surfactant) and water, and the alcohol is a mixed solution of 5wt% isopropyl alcohol and 95wt% ethanol;

[0067] 5) placing the obtained filter residue in a high-pressure reactor, pressurizing it at 5 atmospheres for 5 minutes, and drying it at 90° C. to obtain a fully grafted carbon material;

[0068] 6) The fully grafted carbon material was placed in an argon atmosphere and heated to 1100°C at a heating rate of 5°C / min, kept at this temperature for 10 hours, and cooled to room temperature to obtain a hard carbon material embedded with nano-silicon-carbon microcrystals. Example

[0069] The method for repairing defects of pyrolytic carbon materials using a coupling agent comprises the following steps:

[0070] 1) Under a nitrogen atmosphere, the lignin material from which metal impurities were removed was heated from room temperature to 1000°C at a heating rate of 15°C / min, sintered at this temperature for 10 hours to cause pyrolysis of the carbon material, and cooled to room temperature to obtain a calcined carbon material;

[0071] 2) In sulfuric acid solution, with titanium-manganese alloy electrode as cathode and pre-burned carbon material as anode, at 50mA / cm 2 Electrolysis was performed at a current density of 0.1 h to obtain an electrolytic carbon material, and the electrolytic carbon material was washed and dried to obtain an embedded carbon material;

[0072] 3) In a nitrogen atmosphere, the embedded carbon material was heated from room temperature to 600°C at a heating rate of 70°C / min, maintained at the temperature for 25 seconds, cooled to room temperature, washed, and dried to obtain an expanded carbon material;

[0073] 4) Under methane atmosphere, the expanded carbon material was subjected to corona radiation treatment for 5 minutes; at 80°C, an aerosol formed by a mixture of a freshly prepared 10wt% ammonia solution (pH = 8.5) and a 90wt% silane coupling agent solution was sprayed into the material and reacted for 1 minute; then, a freshly prepared mixture of a 10wt% ammonia solution (pH = 8.5) and a 90wt% silane coupling agent solution was added and allowed to soak and react for 5 minutes, and the solution was filtered to remove the solution to obtain a filter residue;

[0074] The silane coupling agent is methylvinyldioxysilane, the weight percentage of the silane coupling agent to the weight percentage of the calcined carbon material is 9wt%, and the silane coupling agent solution is a mixed solution of 5wt% methylvinyldioxysilane, 87wt% alcohol and water, wherein the alcohol is a mixed solution of 20wt% isopropyl alcohol and 80wt% ethanol;

[0075] 5) placing the filter residue in a high-pressure reactor, pressurizing it at 50 atmospheres for 2 hours, and drying it at 120° C. to obtain a fully grafted carbon material;

[0076] 6) In a nitrogen atmosphere, the fully grafted carbon material was heated from room temperature to 1100°C at a heating rate of 10°C / min and kept at that temperature for 2 hours; then cooled to room temperature to obtain a hard carbon material embedded with nano-silicon carbon microcrystals. Example

[0077] The method for repairing defects of pyrolytic carbon materials using a coupling agent comprises the following steps:

[0078] 1) In a nitrogen atmosphere, the coke from which metal impurities have been removed is heated from room temperature to 950°C at a heating rate of 18°C / min, sintered at this temperature for 10 hours to cause a pyrolysis reaction of the carbon material, and then cooled to room temperature to obtain a calcined carbon material;

[0079] 2) In acetic acid solution, with graphite electrode as cathode and pre-burned carbon material as anode, at 30mA / cm 2 Electrolysis was performed at a current density of 0.5 h to obtain an electrolytic carbon material, and the electrolytic carbon material was washed and dried to obtain an embedded carbon material;

[0080] 3) In an air-tight reactor, the embedded carbon material is heated from room temperature to 200°C at a heating rate of 100°C / min, maintained at this temperature for 40 seconds, cooled to room temperature, washed, and dried to obtain an expanded carbon material;

[0081] 4) In an air atmosphere, the expanded carbon material was subjected to corona radiation treatment for 5 minutes; at 50°C, an aerosol formed by a mixture of a freshly prepared 3wt% potassium hydroxide solution (pH = 10) and a 97wt% silane coupling agent solution was sprayed into the material, reacted for 10 seconds, and then a freshly prepared mixture of a 3wt% potassium hydroxide solution (pH = 10) and a 97wt% silane coupling agent solution was added, and the material was immersed in the material for reaction for 8 minutes. The solution was then filtered to remove the solution to obtain a filter residue;

[0082] The silane coupling agent is vinyl trisilane, the weight percentage of the silane coupling agent to the weight percentage of the calcined carbon material is 5wt%, and the silane coupling agent solution is a mixed solution of 1wt% vinyl trisilane, 20wt% alcohol, 0.2wt% lauryl alcohol (non-ionic surfactant) and water, and the alcohol is a mixed solution of 50wt% isopropyl alcohol and 50wt% ethanol;

[0083] 5) placing the obtained filter residue in a high-pressure reactor, pressurizing it at 5 atmospheres for 10 hours, and drying it at 90° C. to obtain a fully grafted carbon material;

[0084] 6) In a nitrogen atmosphere, the fully grafted carbon material was heated from room temperature to 1600°C at a heating rate of 30°C / min, kept at this temperature for 8 hours, and cooled to room temperature to obtain a hard carbon material embedded with nano-silicon carbon microcrystals. Example

[0085] The method for repairing defects of pyrolytic carbon materials using a coupling agent comprises the following steps:

[0086] 1) In a nitrogen atmosphere, anthracite from which metal impurities have been removed is heated from room temperature to 920°C at a heating rate of 25°C / min, sintered for 9 hours to cause pyrolysis of the carbon material, and then cooled to room temperature to obtain a calcined carbon material;

[0087] 2) adding a mixed solution of sulfuric acid and phosphoric acid in a weight ratio of 1:1 and 10 wt% hydrogen peroxide to the calcined carbon material at -10°C, reacting at 10°C for 10 minutes, washing, and drying to obtain an embedded carbon material;

[0088] 3) In an air-tight atmosphere, the embedded carbon material is directly sintered at 450°C for 30 seconds, cooled to room temperature, washed and dried to obtain an expanded carbon material;

[0089] 4) In a water vapor atmosphere, the expanded carbon material was subjected to low-temperature plasma radiation treatment for 50 seconds; at 50°C, an aerosol formed by a freshly prepared mixed solution of 5wt% sulfuric acid (pH = 3) and 95wt% silane coupling agent solution was sprayed into the material and reacted for 10 minutes; then, a freshly prepared mixed solution of 5wt% sulfuric acid (pH = 3) and 95wt% silane coupling agent solution was added, and the material was immersed in the mixture for reaction for 10 seconds, and the solution was filtered to remove the solution to obtain a filter residue;

[0090] Wherein, the silane coupling agent is acryltrisilane, the weight percentage of the silane coupling agent to the weight percentage of the calcined carbon material is 10wt%, the silane coupling agent solution is a mixed solution of 7wt% acryltrisilane, 25wt% alcohol and water, and the alcohol is a mixed solution of 20wt% isopropyl alcohol and 80wt% methanol;

[0091] 5) placing the filter residue in a high-pressure reactor, pressurizing it at 10 atmospheres for 10 minutes, and drying it at 100° C. to obtain a fully grafted carbon material;

[0092] 6) In an argon atmosphere, the fully grafted carbon material was heated to 1500°C at a heating rate of 10°C / min, kept at this temperature for 10 hours, and cooled to room temperature to obtain a hard carbon material embedded with nano-silicon carbon microcrystals.

Claims

1. A method for repairing defects in pyrolytic carbon materials using a coupling agent, characterized in that: The following steps are involved: 1) Preliminary sintering of the carbon material in an inert atmosphere to obtain a pre-sintered carbon material; 2) embedding high-temperature unstable ions into the microcrystalline structure of the calcined carbon material by electrochemical oxidation or chemical oxidation to obtain an embedded carbon material; the high-temperature unstable ions are sulfur, oxygen, hydrogen, chlorine or nitrogen ions; 3) The embedded carbon material is subjected to instant high-temperature sintering in an inert atmosphere or an air-tight reactor, and then washed and dried to obtain the expanded carbon material; 4) Under controlled atmosphere, the expanded carbon material is placed in a low-temperature plasma or corona condition and irradiated for 10 seconds to 20 minutes; then, the aerosol formed by the freshly prepared mixed solution A is sprayed into the material at 40 to 90°C and reacted for 10 seconds to 10 minutes; the freshly prepared mixed solution A is then added and allowed to soak and react for 10 seconds to 10 minutes, and the solution is filtered to remove the solution to obtain a filter residue; The mixed solution A is a mixed solution of a silane coupling agent solution and an acid solution or an alkaline solution; the weight percentage of the coupling agent to the weight percentage of the initially fired carbon material is 1 to 10 wt%; 5) placing the filter residue in a high-pressure reactor, pressurizing it at 5 to 100 atmospheres for 5 minutes to 10 hours, and drying it at 90 to 150° C. to obtain a fully grafted carbon material; 6) The fully grafted carbon material is placed in an inert atmosphere or a weak reducing atmosphere for post-processing and sintering to obtain a hard carbon material embedded with nano-silicon-carbon microcrystals.

2. The method for repairing defects in pyrolytic carbon materials using a coupling agent according to claim 1, characterized in that: The preliminary sintering is preliminary programmed temperature sintering, in which the carbon material from which metal impurities have been removed is heated from room temperature to 700-1000°C at a heating rate of 15°C / min-40°C / min in a nitrogen atmosphere, and sintered at this temperature for 2-10 hours to cause a pyrolysis reaction in the carbon material, and then cooled to room temperature to obtain a pre-burned carbon material; the carbon material is anthracite, bituminous coal, lignite, petroleum coke, coke, natural graphite or lignin material.

3. The method for repairing defects in pyrolytic carbon materials using a coupling agent according to claim 1, characterized in that: The electrochemical oxidation method is to use an inert electrode as cathode and a pre-burned carbon material as anode in an acid solution at 2-50 mA / cm 2 Electrolysis is performed for 0.1 to 6 hours at a current density to obtain an electrolytic carbon material; the electrolytic carbon material is washed and dried to obtain an embedded carbon material; the inert electrode is a graphite, activated carbon or titanium-manganese alloy electrode.

4. The method for repairing defects in pyrolytic carbon materials using a coupling agent according to claim 1, wherein: The chemical oxidation method comprises adding a mixed solution of potassium permanganate, potassium chlorate, potassium dichromate, ammonium persulfate, potassium persulfate, sodium persulfate or hydrogen peroxide and solution B to the calcined carbon material under freezing conditions; then reacting at 5 to 50° C. for 1 to 20 minutes, washing and drying to obtain the embedded carbon material; the freezing conditions are freezing conditions in the temperature range of -20 to 5° C.; and the solution B is an aqueous solution of any one of the following: sulfuric acid, a mixed acid of sulfuric acid and phosphoric acid, a mixed acid of nitric acid and phosphoric acid, acetic acid, or ammonium sulfate.

5. The method for repairing defects in pyrolytic carbon materials using a coupling agent according to claim 1, characterized in that: The instantaneous high-temperature sintering is to place the embedded carbon material directly in an inert atmosphere or an air-isolated reactor at a temperature range of 200 to 600°C and sinter it for 5 to 50 seconds, or to heat the embedded carbon material from room temperature to 200 to 600°C at a heating rate of 70°C / min to 150°C / min, maintain the temperature and sinter for 5 to 50 seconds, and then cool it to room temperature to obtain the expanded carbon material.

6. The method for repairing defects in pyrolytic carbon materials using a coupling agent according to claim 1, wherein: The mixed solution A is a mixed solution of 0.1-10 wt% acid solution or alkaline solution and 90-99.9 wt% coupling agent solution; the pH of the acid solution is 3-6, and the pH of the alkaline solution is 8.5-12; the silane coupling agent solution is a mixed solution prepared by 0.1-7 wt% silane coupling agent, 20-87 wt% alcohol, 0-0.2 wt% non-ionic surfactant and water; the alcohol is a solution of ethanol or methanol added with 0-50 wt% isopropyl alcohol; the non-ionic surfactant is lauryl oleyl alcohol, palmityl alcohol, stearyl alcohol, cyclohexanol, terpene alcohol, lauroyl diethanolamine, glycerin, pentaerythritol, glucose or sorbitol.

7. The method for repairing defects in pyrolytic carbon materials using a coupling agent according to claim 6, characterized in that: The silane coupling agent is silane-polyethylene glycol-silane, vinyl triethoxysilane, methyl trioxysilane, vinyl trioxysilane, propenyl trioxysilane, methyl vinyl dioxysilane, methacryl dioxysilane or dimethyl dioxysilane.

8. The method for repairing defects in pyrolytic carbon materials using a coupling agent according to claim 1, characterized in that: The acid solution is one or a mixture of two or more of an aqueous solution of sulfuric acid, hydrochloric acid, nitric acid or acetic acid; the alkaline solution is an aqueous solution of sodium hydroxide, potassium hydroxide, lithium hydroxide or ammonia water.

9. The method for repairing defects in pyrolytic carbon materials using a coupling agent according to claim 1, characterized in that: The post-processing sintering is a post-processing programmed temperature sintering. The post-processing programmed temperature sintering is to heat the fully grafted carbon material from room temperature to 1100-1700°C at a heating rate in the range of 3°C / min-30°C / min in an inert atmosphere or a weak reducing atmosphere, keep it warm for 2-10 hours, and cool it to room temperature to obtain a hard carbon material embedded with nano-silicon-carbon microcrystals.

10. The method for repairing defects of pyrolytic carbon materials using a coupling agent according to claim 1, characterized in that: The controlled environment atmosphere is an atmosphere of methane, ethane, formaldehyde, oxygen, air or water vapor; the inert atmosphere is an atmosphere of nitrogen or argon; and the weak reducing atmosphere is a mixed atmosphere of hydrogen and nitrogen or argon.

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