阅读说明：本技术 一种绿色制备高比表面积β-碳化硅的方法 (Green preparation method of beta-silicon carbide with high specific surface area ) 是由 郭向云 张同崑 焦志锋 于 2021-09-06 设计创作，主要内容包括：本发明属于碳化硅制备技术领域,涉及一种绿色制备高比表面积β-碳化硅的方法,制备包括如下步骤：将蔗糖、硅溶胶及金属盐或金属氧化物混合,并控制碳硅摩尔比为1:1-10,金属盐或金属氧化物与硅之比为0.1-3(摩尔比)混合均匀后静置5-30分钟,然后放于均相反应器中于150-220℃反应3-6小时得到沉淀物；收集沉淀物干燥后放于氩气氛围中,升温至1000-1500℃进行碳热还原反应3-20小时,反应后自然冷却至室温,最后煅烧,冷却后再用盐酸和氢氟酸的混合溶液浸泡去除反应物中未反应的杂质,最后洗涤、过滤、干燥。本发明具有成本低、工艺简单、绿色、能工业化大规模生产的工艺特点。(The invention belongs to the technical field of silicon carbide preparation, and relates to a green preparation method of beta-silicon carbide with a high specific surface area, which comprises the following steps: mixing cane sugar, silica sol and metal salt or metal oxide, controlling the molar ratio of carbon to silicon to be 1:1-10, and controlling the ratio of the metal salt or metal oxide to the silicon to be 0.1-3 (molar ratio), uniformly mixing, standing for 5-30 minutes, and then placing the mixture into a homogeneous reactor to react for 3-6 hours at the temperature of 150-220 ℃ to obtain a precipitate; collecting the precipitate, drying, placing in an argon atmosphere, heating to 1000-1500 ℃ for carbothermic reduction reaction for 3-20 hours, naturally cooling to room temperature after reaction, finally calcining, soaking in a mixed solution of hydrochloric acid and hydrofluoric acid after cooling to remove unreacted impurities in the reactant, and finally washing, filtering and drying. The invention has the process characteristics of low cost, simple process, greenness and capability of industrial large-scale production.)

1. A green preparation method of beta-silicon carbide with high specific surface area is characterized by comprising the following steps: the method comprises the following steps:

(1) preparing a silicon carbide precursor: mixing cane sugar, silica sol and metal salt or metal oxide, controlling the molar ratio of carbon to silicon to be 1:1-10, and controlling the ratio of the metal salt or metal oxide to the silicon to be 0.1-3 (molar ratio), uniformly mixing, standing for 5-30 minutes, and then placing the mixture into a homogeneous reactor to react for 3-6 hours at the temperature of 150-220 ℃ to obtain a precipitate; the metal salt is iron, cobalt or nickel salt, and the metal oxide is an oxide of iron, cobalt or nickel;

(2) c, carbothermic reduction: collecting the precipitate obtained in the step (1), drying, placing in an argon atmosphere, heating to 1000-1500 ℃ for carbothermic reduction reaction for 3-20 hours, and naturally cooling to room temperature after reaction to obtain a primary reactant;

(3) and (3) post-treatment: and (3) calcining the primary reactant obtained in the step (2) to remove unreacted carbon in the reactant, cooling, soaking in a mixed solution of hydrochloric acid and hydrofluoric acid to remove unreacted impurities in the reactant, and finally washing, filtering and drying to obtain the beta-silicon carbide.

2. The green process for producing high surface area β -silicon carbide according to claim 1, wherein: the metal salt in the step (1) is any one of nickel nitrate, cobalt nitrate, ferric nitrate and ferric sulfate, and the metal oxide is any one of nickel oxide, cobalt oxide or ferric oxide.

3. The green process for producing high surface area β -silicon carbide according to claim 1, wherein: the calcination method in the step (3) is to calcine the primary reactant obtained in the step (2) in an air atmosphere at 600-800 ℃ for 3-7 hours.

4. The green process for producing high surface area β -silicon carbide according to claim 1, wherein: in the step (3), the concentration of the hydrochloric acid in the mixed solution of the hydrochloric acid and the hydrofluoric acid is 0.5M-5M, the concentration of the hydrofluoric acid is 1M-15M, and the soaking time is 12-48 hours.

Technical Field

The invention belongs to the technical field of silicon carbide preparation, and particularly relates to a method for green preparation of beta-silicon carbide with a high specific surface area.

Background

Silicon carbide (SiC) has many excellent properties, such as good mechanical strength, chemical stability, high thermal and electrical conductivity, etc., and thus has wide applications in ceramics, metal composites, wear-resistant materials, catalysis, etc. The porous silicon carbide has the advantages of high temperature resistance, high pressure resistance, acid and alkali corrosion resistance and the like, and is an ideal catalyst carrier material under harsh chemical reaction conditions. However, silicon carbide is a widely used catalyst carrier, and has a problem of too low specific surface area. Therefore, the inexpensive synthesis of silicon carbide with a high specific surface area has been the object of recent efforts. Although there are many methods for producing high surface area silicon carbide, controlling the growth of silicon carbide crystals and forming porous structures at high temperatures remains a significant challenge for researchers.

The nanometer silicon carbide product produced by the silicon carbide cathode material has the characteristics of high purity, good dispersion performance, small particle size, uniform distribution, large specific surface area, high surface activity, low apparent density, good activity and the like. The nano silicon carbide can be compounded with graphite, carbon nano tubes, nano titanium nitride and the like to prepare a negative electrode material of a lithium battery, can improve the capacity and prolong the service life of the lithium battery, is a new-generation photoelectric semiconductor material and has wider gap energy. The negative electrode material is a main component of the lithium ion battery, and the performance of the negative electrode material directly influences the performance of the lithium ion battery. The demand of high-energy portable power sources is increased rapidly, the demand of small lithium ion batteries is increased, and a negative electrode material with large capacity and reliable cyclicity becomes a key point of research of people. The application of high-capacity power batteries increases the demand on battery materials, particularly high-performance cathode materials. The silicon carbide used as the negative electrode material of the battery means that crystals with the crystal size in the range of 0.5-300nm can be in various shapes such as a sphere, a line or a sheet or an irregular shape. Because the specific surface area of the silicon carbide used for the battery cathode material is large and the number of bare leakage atoms is large, the silicon carbide which can be embedded into the lithium ion battery cathode material can be crystalline or amorphous, and the lattice structure can be cubic or hexagonal stacked, so that the silicon carbide can be used as the cathode material of the lithium ion battery. The silicon carbide for the battery negative electrode material has high capacity and good cycle performance. The silicon carbide used as the negative electrode material of the battery can be used for lithium ion intercalation whether dispersed single crystals or arrays. Experiments prove that the performance of the negative electrode material can be improved by adding silicon carbide for the negative electrode material of the battery into other negative electrode materials, and the lithium ion intercalation characteristic can be improved by adding other trace or small amount of metal elements. The application of silicon carbide on the negative electrode material of the battery is the main component of the lithium ion battery, and the performance of the negative electrode material directly influences the performance of the lithium ion battery. The demand of high-energy portable power sources is increased rapidly, the demand of small lithium ion batteries is increased, and a negative electrode material with large capacity and reliable cyclicity becomes a key point of research of people. The application of high-capacity power batteries increases the demand on battery materials, particularly high-performance cathode materials. 1, the silicon carbide used as the negative electrode material of the rechargeable lithium battery is used in the negative electrode material of the rechargeable lithium battery, or the surface of the silicon carbide coated with graphite is used as the negative electrode material of the rechargeable lithium battery, so that the electric capacity and the charging and discharging cycle times of the rechargeable lithium battery are improved by more than 3 times; 2. the silicon carbide used as the negative electrode material of the battery is used in the high-temperature resistant coating and the refractory material.

The silicon carbide is industrially prepared by carbothermic reduction, i.e. by directly mixing powdered carbon with silicon dioxide, heating to above 2000 ℃ and reacting to form silicon carbide, the total package reaction equation is SiO₂(s) +3c(s) → SiC(s) +2co (g) (1) since silicon dioxide, carbon, etc. are in a molten state at a high temperature of 2000 ℃ or higher, the produced silicon carbide is a dense massive solid, the specific surface area is very low, and α -SiC.

Because of the wide application prospect of high specific area silicon carbide, people develop various preparation methods in laboratories, including template methods, sol-gel methods, vapor deposition methods, and the like. (1) Ledoux et al, university of stelas burg, france, first proposed a method for preparing silicon carbide by a gas-solid reaction using gas phase SiO and activated carbon. They use porous active carbon as a template, and gas-phase SiO reacts with the carbonaceous pore walls of the active carbon to generate silicon carbide, thereby obtaining porous silicon carbide with a similar active carbon pore canal structure, and the specific surface area is 20-200m²·g^-1In the meantime. (2) Vix-Guerl et al, silica gel and quartz powder are mixed according to a certain proportion and pressed into thin slices, and then the moisture in the mixture is removed by a freeze-drying method to obtain the porous silica template. Then, phenolic resin is infiltrated into the pore canal of the silicon oxide template, and porous silicon carbide is obtained by carbothermic reductionA specific surface area of 35m²·g^-1This method can obtain silicon carbide having a specific shape. (3) Moene et al propose an improved chemical vapor deposition process for the preparation of high specific surface area silicon carbide. They use hydrogen to react organosilicon precursors such as silicon tetrachloride (SiCl)₄) Brought into a high-temperature reactor (about 1380K) containing activated carbon and reacted to form silicon carbide with a high specific surface area of 25-80m²·g^-1In the meantime. (4) A compound denier university Hoodia Caoyong who is reported in Chinese patent (publication No. CN101177269A) adds organic acid into tetraethoxysilane and organosilicon to form a silicon source, and sucrose is used as a carbon source to prepare silicon carbide. The tetraethoxysilane mentioned in the method belongs to dangerous chemical tube products, has high cost and is harmful to the health of operators, and is difficult to be applied to large-scale industrial application and laboratory application. In general, the existing preparation method of the silicon carbide is complex and has high cost.

Disclosure of Invention

The invention aims to solve the problems of pollution, high cost and the like in the existing preparation method of the high-specific-surface-area silicon carbide, and provides a green and economic preparation method of the high-specific-surface-area beta-silicon carbide by using cheap and environment-friendly sucrose as a carbon source and carrying out hydrothermal treatment on a silica sol and a sucrose solution. The method takes cheap, green and environment-friendly cane sugar as a carbon source, takes silica sol as a silicon source, and adopts inorganic substances as raw materials, so that the method is simple, easy to obtain, more environment-friendly, short in hydrothermal process time consumption and easy to industrialize. Preparing a silicon carbide precursor by a hydrothermal method, and then carrying out carbothermal reduction to obtain the silicon carbide. The main reaction for forming SiC is SiO₂And C, the higher the temperature, the higher the SiC yield. However, high temperatures (about 2000 ℃) cause sintering of SiC, resulting in a decrease in the specific surface area. Therefore, a metal salt or a metal oxide, such as nickel nitrate, iron oxide, etc., is added in the hydrothermal treatment to act as a catalyst in the carbothermic reduction process.

In order to realize the purpose of the invention, the adopted technical scheme is as follows: a green preparation method of beta-silicon carbide with high specific surface area comprises the following steps:

(1) preparing a silicon carbide precursor: mixing cane sugar, silica sol and metal salt or metal oxide, controlling the molar ratio of carbon to silicon to be 1:1-10, and controlling the ratio of the metal salt or metal oxide to the silicon to be 0.1-3 (molar ratio), uniformly mixing, standing for 5-30 minutes, and then placing the mixture into a homogeneous reactor to react for 3-6 hours at the temperature of 150-220 ℃ to obtain a precipitate; the metal salt is iron, cobalt or nickel salt, and the metal oxide is an oxide of iron, cobalt or nickel;

(2) c, carbothermic reduction: collecting the precipitate obtained in the step (1), drying, placing in an argon atmosphere, heating to 1000-1500 ℃ for carbothermic reduction reaction for 3-20 hours, and naturally cooling to room temperature after reaction to obtain a primary reactant;

(3) and (3) post-treatment: calcining the primary reactant obtained in the step (2) to remove unreacted carbon in the reactant, cooling, soaking in a mixed solution of hydrochloric acid and hydrofluoric acid to remove unreacted impurities in the reactant, and finally washing, filtering and drying to obtain beta-silicon carbide; the prepared beta-silicon carbide has smaller grain diameter and presents blue light.

Further, the metal salt in the step (1) is any one of nickel nitrate, cobalt nitrate, ferric nitrate and ferric sulfate, and the metal oxide is any one of nickel oxide, cobalt oxide or ferric oxide.

Further, the calcination method in the step (3) is to calcine the primary reactant obtained in the step (2) in an air atmosphere at 600-800 ℃ for 3-7 hours.

Further, in the step (3), the concentration of the hydrochloric acid in the mixed solution of the hydrochloric acid and the hydrofluoric acid is 0.5M-5M, the concentration of the hydrofluoric acid is 1M-15M, and the soaking time is 12-48 hours.

Compared with the prior art, the method has the following advantages:

1. the cheap and easily obtained silica sol is used for replacing ethyl orthosilicate, so that the preparation cost of the silicon carbide is obviously reduced, and the harm to the body of an operator is reduced;

2. by a principle similar to sol-gel, precursors of silicon oxide and carbon are uniformly mixed on a molecular level, a proper catalyst is used for carbon thermal reduction reaction at a relatively low temperature, porous silicon carbide with high specific surface area can be obtained, and the silica sol and sucrose are directly mixed to prepare a silicon-carbon binary mixture, so that the method has the advantages of simple operation and short preparation period, and is beneficial to rapid large-scale production of the silicon carbide;

3. the method has the advantages of rich raw material sources, low cost, simple required equipment, simple and easy operation process, low production cost, lower reaction temperature, short production period, high product purity and easy realization of large-scale production.

Drawings

FIG. 1 is an XRD pattern of beta-silicon carbide prepared by the present invention.

Detailed Description

The present invention is not limited to the following embodiments, and those skilled in the art can implement the present invention in other embodiments according to the disclosure of the present invention, or make simple changes or modifications on the design structure and idea of the present invention, and fall into the protection scope of the present invention. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

The invention is described in more detail below with reference to the following examples:

silica sol was purchased from Shanghai Michelin corporation, silica content 30%;

the hydrofluoric acid is purchased by chemical reagents of national drug group, the content is more than 40 percent, and the analysis is pure, namely AR is 500 ml;

concentrated hydrochloric acid is purchased from national medicine group chemical reagent limited company, the content is 36-38%, the analysis is pure, and AR is 500 ml.

Example 1

(1) Firstly, dissolving 15.10g of sucrose in 150ml of water, standing for 30 minutes, adding 0.99g of newly prepared iron oxide and 13.21g of silica sol, uniformly mixing, reacting for 4 hours at 180 ℃ in a hydrothermal reaction kettle, collecting precipitate and drying;

(2) dividing the dried product into two parts, putting the two parts into a tubular high-temperature furnace, introducing argon, heating to 1400 ℃ and 1300 ℃ respectively, reacting at constant temperature for 5 hours, and naturally cooling to room temperature under the argon atmosphere to obtain a primary product;

(3) oxidizing the obtained primary product in 700 ℃ air for 3 hours, soaking the primary product in mixed acid of hydrochloric acid and hydrofluoric acid with the volume ratio of 1:3 for 24 hours, and finally washing, filtering and drying the primary product to obtain the product with the specific surface areas of 28m²·g^-1(corresponding to a carbothermic reduction temperature of 1400 ℃) and 21m²·g^-1(corresponding to the carbothermic reduction temperature of 1300 ℃) and the mass is 0.14g (corresponding to the carbothermic reduction temperature of 1400 ℃) and 0.13g (corresponding to the carbothermic reduction temperature of 1300 ℃), and the pore size is mainly concentrated in the porous silicon carbide with the diameter of about 30 nm.

Example 2

Firstly, dissolving 12.47g of sucrose in 100ml of water, standing for 30 minutes, adding 4.32g of ferric nitrate and 12.47g of silica sol, uniformly mixing, and reacting for 4 hours at 180 ℃ in a hydrothermal reaction kettle;

putting the dried product into a tubular high-temperature furnace, introducing argon, heating to 1400 ℃, reacting at constant temperature for 7 hours, and naturally cooling to room temperature under the argon atmosphere;

oxidizing the obtained reaction product in 700 ℃ air for 3 hours, soaking the reaction product in mixed acid of hydrochloric acid and hydrofluoric acid with the volume ratio of 1:3 for 24 hours, and finally washing, filtering and drying the reaction product to obtain the product with the specific surface area of 46m²·g^-1Porous silicon carbide with a mass of 1.06g and a pore size mainly centered around 30 nm.

Example 3

Firstly, dissolving 12.47g of sucrose in 100ml of water, standing for 30 minutes, adding 0.68g of ferric nitrate and 12.47g of silica sol, uniformly mixing, and reacting for 4 hours at 180 ℃ in a hydrothermal reaction kettle;

putting the dried product into a tubular high-temperature furnace, introducing argon, heating to 1450 ℃, reacting at constant temperature for 8 hours, and naturally cooling to room temperature under the argon atmosphere;

oxidizing the obtained reaction product in 700 ℃ air for 3 hours, soaking the reaction product in mixed acid of hydrochloric acid and hydrofluoric acid with the volume ratio of 1:3 for 24 hours, and finally washing, filtering and drying the reaction product to obtain the product with the specific surface area of 108m²·g^-1Porous silicon carbide with a mass of 1.56g and a pore size mainly centered around 20 nm.

Example 4

Firstly, dissolving 14.23g of sucrose in 100ml of water, standing for 30 minutes, adding 0.22g of nickel nitrate and 12.47g of silica sol, uniformly mixing, and reacting for 4 hours at 180 ℃ in a hydrothermal reaction kettle;

putting the dried product into a tubular high-temperature furnace, introducing argon, heating to 1450 ℃, reacting at constant temperature for 8 hours, and naturally cooling to room temperature under the argon atmosphere;

oxidizing the obtained reaction product in air at 700 ℃ for 3 hours, soaking the reaction product in mixed acid of hydrochloric acid and hydrofluoric acid with the volume ratio of 1:3 for 24 hours, and finally washing, filtering and drying the reaction product to obtain the product with the specific surface area of 376m²·g^-1The mass is 0.49g of silicon carbide, and the pore size is mainly concentrated in porous silicon carbide of about 10 nm.

Example 5

Firstly, dissolving 14.23g of sucrose in 100ml of water, standing for 30 minutes, adding 0.28g of nickel nitrate and 12.47g of silica sol, uniformly mixing, and reacting for 4 hours at 180 ℃ in a hydrothermal reaction kettle;

putting the dried product into a tubular high-temperature furnace, introducing argon, heating to 1450 ℃, reacting at constant temperature for 8 hours, and naturally cooling to room temperature under the argon atmosphere;

oxidizing the obtained reaction product in 700 ℃ air for 3 hours, soaking the reaction product in mixed acid of hydrochloric acid and hydrofluoric acid with the volume ratio of 1:3 for 24 hours, and finally washing, filtering and drying the reaction product to obtain the product with the specific surface area of 400m²·g^-1The mass is 0.80g of silicon carbide, and the pore size is mainly concentrated in porous silicon carbide of about 10 nm.

Example 6

Firstly, dissolving 14.23g of sucrose in 100ml of water, standing for 30 minutes, adding 11.10g of ferric nitrate and 12.47g of silica sol, uniformly mixing, and reacting for 4 hours at 180 ℃ in a hydrothermal reaction kettle;

putting the dried product into a tubular high-temperature furnace, introducing argon, heating to 1450 ℃, reacting at constant temperature for 8 hours, and naturally cooling to room temperature under the argon atmosphere;

oxidizing the obtained reaction product in 700 ℃ air for 3 hours, soaking the reaction product in mixed acid of hydrochloric acid and hydrofluoric acid with the volume ratio of 1:3 for 24 hours, and finally washing, filtering and drying the reaction product to obtain the product with the specific surface area of 120m²·g^-1Mass of1.88g of silicon carbide, porous silicon carbide with pore sizes mainly centered around 10 nm.

Example 7

Firstly, dissolving 14.23g of sucrose in 100ml of water, standing for 30 minutes, adding 12.95g of nickel nitrate and 12.47g of silica sol, uniformly mixing, and reacting for 4 hours at 180 ℃ in a hydrothermal reaction kettle;

putting the dried product into a tubular high-temperature furnace, introducing argon, heating to 1450 ℃, reacting at constant temperature for 8 hours, and naturally cooling to room temperature under the argon atmosphere;

oxidizing the obtained reaction product in the air at 700 ℃ for 3 hours, soaking the reaction product in mixed acid of hydrochloric acid and hydrofluoric acid with the volume ratio of 1:3 for 24 hours, and finally washing, filtering and drying the reaction product to obtain the product with the specific surface area of 118m²·g^-1The mass is 1.81g of silicon carbide, and the pore size is mainly concentrated in porous silicon carbide of about 10 nm.

Example 8

Firstly, dissolving 14.23g of sucrose in 100ml of water, standing for 30 minutes, adding 1.14g of nickel nitrate and 12.47g of silica sol, uniformly mixing, and reacting for 4 hours at 180 ℃ in a hydrothermal reaction kettle;

putting the dried product into a tubular high-temperature furnace, introducing argon, heating to 1450 ℃, reacting at constant temperature for 8 hours, and naturally cooling to room temperature under the argon atmosphere;

oxidizing the obtained reaction product in 700 ℃ air for 3 hours, soaking the reaction product in mixed acid of hydrochloric acid and hydrofluoric acid with the volume ratio of 1:3 for 24 hours, and finally washing, filtering and drying the reaction product to obtain the product with the specific surface area of 156m²·g^-1The mass is 1.56g of silicon carbide, and the pore size is mainly concentrated in porous silicon carbide of about 10 nm.

Example 9

Firstly, dissolving 14.23g of sucrose in 100ml of water, standing for 30 minutes, adding 1.81g of nickel nitrate and 12.47g of silica sol, uniformly mixing, and reacting for 4 hours at 180 ℃ in a hydrothermal reaction kettle;

putting the dried product into a tubular high-temperature furnace, introducing argon, heating to 1450 ℃, reacting at constant temperature for 8 hours, and naturally cooling to room temperature under the argon atmosphere;

the obtained reaction product is at 700 DEG COxidizing in air for 3 hours, soaking for 24 hours by using mixed acid of hydrochloric acid and hydrofluoric acid with the volume ratio of 1:3, and finally washing, filtering and drying to obtain the product with the specific surface area of 230m²·g^-1Porous silicon carbide with a mass of 1.05g and a pore size mainly centered around 10 nm.

Example 10

Firstly, dissolving 14.23g of sucrose in 100ml of water, standing for 30 minutes, adding 0.46g of nickel nitrate and 12.47g of silica sol, uniformly mixing, and reacting for 4 hours at 180 ℃ in a hydrothermal reaction kettle;

putting the dried product into a tubular high-temperature furnace, introducing argon, heating to 1450 ℃, reacting at constant temperature for 8 hours, and naturally cooling to room temperature under the argon atmosphere;

oxidizing the obtained reaction product in 700 ℃ air for 3 hours, soaking the reaction product in mixed acid of hydrochloric acid and hydrofluoric acid with the volume ratio of 1:3 for 24 hours, and finally washing, filtering and drying the reaction product to obtain the product with the specific surface area of 268m²·g^-1The mass is 0.89g of silicon carbide, and the pore size is mainly concentrated in porous silicon carbide of about 10 nm.

Example 11

Firstly, 30.78g of sucrose is dissolved in 100ml of water, the mixture is kept stand for 30 minutes, 0.34g of nickel nitrate and 18.9g of silica sol are added, the mixture is uniformly mixed, and the mixture is reacted for 12 hours in a hydrothermal reaction kettle at 180 ℃;

putting the dried product into a tubular high-temperature furnace, introducing argon, heating to 1450 ℃, reacting at constant temperature for 8 hours, and naturally cooling to room temperature under the argon atmosphere;

oxidizing the obtained reaction product in 700 ℃ air for 3 hours, soaking the reaction product in mixed acid of hydrochloric acid and hydrofluoric acid with the volume ratio of 1:3 for 24 hours, and finally washing, filtering and drying the reaction product to obtain the product with the specific surface area of 450m²·g^-1The mass is 1.94g of silicon carbide, and the pore size is mainly concentrated in porous silicon carbide of about 10 nm.

Example 12

Firstly, 30.78g of sucrose is dissolved in 100ml of water, the mixture is kept stand for 30 minutes, 0.34g of nickel nitrate and 18.9g of silica sol are added, the mixture is uniformly mixed, and the mixture is reacted for 12 hours in a hydrothermal reaction kettle at 180 ℃;

putting the dried product into a tubular high-temperature furnace, introducing argon, heating to 1450 ℃, reacting at constant temperature for 8 hours, and naturally cooling to room temperature under the argon atmosphere;

oxidizing the obtained reaction product in 700 ℃ air for 3 hours, soaking the reaction product in mixed acid of hydrochloric acid and hydrofluoric acid with the volume ratio of 1:3 for 24 hours, and finally washing, filtering and drying the reaction product to obtain the product with the specific surface area of 500m²·g^-1The mass is 1.99g of silicon carbide, and the pore size is mainly concentrated in porous silicon carbide of about 20 nm.

Example 13

Firstly, 71.82g of sucrose is dissolved in 300ml of water, the mixture is kept stand for 30 minutes, 0.34g of nickel nitrate and 50.4g of silica sol are added, the mixture is uniformly mixed, and the mixture is reacted for 12 hours in a hydrothermal reaction kettle at 180 ℃;

putting the dried product into a tubular high-temperature furnace, introducing argon, heating to 1450 ℃, reacting at constant temperature for 8 hours, and naturally cooling to room temperature under the argon atmosphere;

oxidizing the obtained reaction product in 700 ℃ air for 3 hours, soaking the reaction product in mixed acid of hydrochloric acid and hydrofluoric acid with the volume ratio of 1:3 for 24 hours, and finally washing, filtering and drying the reaction product to obtain the product with the specific surface area of 500m²·g^-1The mass was 12.93g of silicon carbide, and the pore size was mainly concentrated in porous silicon carbide of about 10 nm.

Example 14

Firstly, dissolving 14.23g of sucrose in 100ml of water, standing for 30 minutes, adding 0.46g of nickel nitrate and 12.47g of silica sol, uniformly mixing, and reacting for 4 hours at 180 ℃ in a hydrothermal reaction kettle;

putting the dried product into a tubular high-temperature furnace, introducing argon, heating to 1400 ℃, reacting at constant temperature for 7 hours, and naturally cooling to room temperature under the argon atmosphere;

oxidizing the obtained reaction product in 700 ℃ air for 3 hours, soaking the reaction product in mixed acid of hydrochloric acid and hydrofluoric acid with the volume ratio of 1:3 for 24 hours, and finally washing, filtering and drying the reaction product to obtain the product with the specific surface area of 180m²·g^-1The mass is 0.69g of silicon carbide, and the pore size is mainly concentrated in porous silicon carbide of about 10 nm.

Example 15

Firstly, dissolving 20g of chopped tea fruit peel in 200ml of potassium hydroxide solution (1M), stirring for 30min, then transferring the mixture into a 250ml reaction kettle, reacting at the temperature of 130-;

putting the dried product into a tubular high-temperature furnace, introducing argon, heating to 600-800 ℃, reacting at constant temperature for 2 hours, and naturally cooling to room temperature at the heating rate of 4 ℃/min under the argon atmosphere; finally, repeatedly washing the reaction product with dilute HCl (0.1-0.5M) and distilled water until the pH value is neutral;

taking 5g of the product, 100ml of water and 12.47g of silica sol, adding 0.46g of nickel nitrate, uniformly mixing, and reacting for 4 hours at 180 ℃ in a hydrothermal reaction kettle;

putting the dried product into a tubular high-temperature furnace, introducing argon, heating to 1450 ℃, reacting at constant temperature for 8 hours, and naturally cooling to room temperature under the argon atmosphere;

oxidizing the obtained reaction product in 700 ℃ air for 3 hours, soaking the reaction product in mixed acid of hydrochloric acid and hydrofluoric acid with the volume ratio of 1:3 for 24 hours, and finally washing, filtering and drying the reaction product to obtain the product with the specific surface area of 480m²·g^-1The mass is 5.23g of silicon carbide, and the pore size is mainly concentrated in porous silicon carbide of about 20 nm.

Example 16

Firstly, 14.23g of sucrose is dissolved in 100ml of water, the mixture is kept stand for 30 minutes, 5.01g of cobalt nitrate and 12.47g of silica sol are added, the mixture is uniformly mixed, and the mixture is reacted for 4 hours at 180 ℃ in a hydrothermal reaction kettle

Putting the dried product into a tubular high-temperature furnace, introducing argon, heating to 1450 ℃, reacting at constant temperature for 8 hours, and naturally cooling to room temperature under the argon atmosphere;

the obtained solid product does not need to be subjected to acid washing and calcination for carbon removal, and the carbon-coated silicon carbide, namely the carbon/silicon carbide cathode material, can be obtained. The specific surface area of the silicon carbide is 350m²·g^-1。

The initial capacity of the silicon carbide for the battery cathode material reaches 3876.3mAh/g through initial tests, the initial coulombic efficiency is larger than or equal to 98%, the capacitance retention rate after 100 cycles is larger than or equal to 97%, and the silicon carbide has capacity and good cycle performance.

Example 17

Firstly, 14.23g of sucrose is dissolved in 100ml of water, the mixture is kept stand for 30 minutes, 3.11g of cobalt nitrate and 12.47g of silica sol are added, the mixture is uniformly mixed, and the mixture is reacted for 4 hours at 180 ℃ in a hydrothermal reaction kettle

Putting the dried product into a tubular high-temperature furnace, introducing argon, heating to 1450 ℃, reacting at constant temperature for 8 hours, and naturally cooling to room temperature under the argon atmosphere;

the obtained solid product does not need to be subjected to acid washing and calcination for carbon removal, and the carbon-coated silicon carbide, namely the carbon/silicon carbide cathode material, can be obtained. The specific surface area of the silicon carbide is 500m²·g^-1。

The initial capacity of the silicon carbide for the battery cathode material reaches 4886.8mAh/g through initial tests, the initial coulombic efficiency is larger than or equal to 98%, the capacitance retention rate after 100 cycles is larger than or equal to 97%, and the silicon carbide has capacity and good cycle performance.

Example 18

Firstly, 14.23g of sucrose is dissolved in 100ml of water, the mixture is kept stand for 30 minutes, 1.23g of cobalt nitrate and 12.47g of silica sol are added, the mixture is uniformly mixed, and the mixture is reacted for 4 hours at 180 ℃ in a hydrothermal reaction kettle

Putting the dried product into a tubular high-temperature furnace, introducing argon, heating to 1450 ℃, reacting at constant temperature for 8 hours, and naturally cooling to room temperature under the argon atmosphere;

the obtained solid product does not need to be subjected to acid washing and calcination for carbon removal, and the carbon-coated silicon carbide, namely the carbon/silicon carbide cathode material, can be obtained. The specific surface area of the silicon carbide is 700m²·g^-1。

The initial capacity of the silicon carbide for the battery cathode material reaches 5300.8mAh/g through initial test, the initial coulombic efficiency is not less than 98%, the capacitance retention rate after 100 times of circulation is not less than 97%, and the silicon carbide has capacity and good circulation performance

Example 19

Firstly, taking 2g of prepared silicon carbide, heating a mixed solution of sucrose, silica sol and nickel nitrate (the molar ratio of carbon to silicon is 8:1, and the molar ratio of nickel to silicon is 0.0154) in a microwave oven to form xerogel, adding 2g of weighed silicon carbide, mixing and stirring;

tabletting the dried product to prepare a sample, then putting the sample into a tubular high-temperature furnace, introducing argon, heating to 1450 ℃, reacting at constant temperature for 8 hours, and naturally cooling to room temperature under the argon atmosphere; finally, the carbon/silicon carbide cathode material can be obtained;

the initial capacity of the silicon carbide for the battery cathode material reaches 5300.8mAh/g through initial tests, the initial coulombic efficiency is larger than or equal to 98%, the capacitance retention rate after 100 cycles is larger than or equal to 97%, and the silicon carbide has capacity and good cycle performance.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and their concepts should be equivalent or changed within the technical scope of the present invention.