Sodium electricity coal-based hard carbon negative electrode material and preparation method thereof

Abstract

The invention discloses a sodium electric coal-based hard carbon negative electrode material and a preparation method thereof, and belongs to the technical field of preparation of negative electrode materials. The sodium electricity coal-based hard carbon negative electrode material is prepared from the following components in parts by weight: 40-48 parts of anthracite, 1-5 parts of a composite pore-forming agent, 2-4 parts of a modified cross-linking agent and 1-3 parts of potassium permanganate, the composite pore-forming agent is prepared from 3-thiophenecarboxylic acid, pentafluorophenyl trifluoroacetate, N, N-dimethyl-1, 3-propane diamine and 1-bromo-isopentane, and the modified cross-linking agent is prepared from 1-bromo-isopentane. The modified cross-linking agent is prepared from hexamethylcyclotrisiloxane, 1, 3-bis (aminopropyl) tetramethyldisiloxane, N, N '-di-tert-butyl ethylenediamine, triphenylmethane triisocyanate and isophorone diisocyanate, and the negative electrode material prepared by the method has excellent pore size distribution, rate capability and cycle stability.

Description

Technical Field

[0001] The invention belongs to the technical field of negative electrode material preparation, and specifically relates to a sodium electric coal-based hard carbon negative electrode material and a preparation method thereof. Background Art

[0002] With the rapid development of renewable energy, efficient, low-cost, and environmentally friendly energy storage technology has become the key to promoting energy structure transformation and achieving sustainable development. As the current mainstream energy storage technology, the widespread application of lithium-ion batteries is limited by the uneven distribution of lithium resources and limited reserves, resulting in rising costs. Therefore, it is of great strategic significance to explore alternative energy storage technologies, especially sodium-ion batteries based on sodium, which is abundant in the earth's crust and has low costs.

[0003] Sodium-ion batteries and lithium-ion batteries are similar in working principles. Both achieve the storage and release of electrical energy through the embedding and de-embedding of sodium ions (lithium ions) between the positive and negative electrodes. However, compared with lithium-ion batteries, sodium-ion batteries show significant advantages in terms of cost and resource availability. Hard carbon materials, especially coal-based hard carbon, are regarded as one of the ideal choices for negative electrode materials of sodium-ion batteries due to their high theoretical specific capacity, good cycle stability and low cost. Coal-based hard carbon materials use a specific carbonization process to convert carbon-containing raw materials such as coal into hard carbon materials with rich microporous and mesoporous structures. These structures provide abundant active sites for the storage of sodium ions, thereby improving the specific capacity and cycle performance of the battery.

[0004] Patent CN 116169266 A discloses a reed-based hard carbon sodium negative electrode material self-doped with N and S and a preparation method thereof. The preparation method mainly comprises the following steps: first, the dried reed is washed with pure water, and after drying, crushing and screening, the raw material is pyrolyzed at a relatively low temperature, and then the pyrolyzed material is subjected to secondary pyrolysis in a closed container, and then the pyrolyzed material is subjected to secondary pyrolysis at high temperature in a closed container, and then crushed and screened to obtain a reed-based hard carbon negative electrode material self-doped with N and S. The preparation method is simple, low-cost, and has excellent electrochemical properties. However, the pore size distribution, rate performance, and cycle performance of the negative electrode material prepared by this method still have room for improvement. Summary of the invention

[0005] The purpose of the present invention is to provide a sodium electric coal-based hard carbon negative electrode material and a preparation method thereof, so as to solve the technical problems of poor pore size distribution, poor rate performance and poor cycle performance of the negative electrode material in the prior art.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides a sodium electric coal-based hard carbon negative electrode material, which is composed of the following components in parts by weight: 40-48 parts of anthracite, 1-5 parts of a composite pore-forming agent, 2-4 parts of a modified cross-linking agent, and 1-3 parts of potassium permanganate, wherein the composite pore-forming agent is prepared from 3-thiophenecarboxylic acid, pentafluorophenyl trifluoroacetate, N,N-dimethyl-1,3-propylenediamine and 1-bromoisopentane, and the modified cross-linking agent is prepared from hexamethylcyclotrisiloxane, 1,3-bis(aminopropyl)tetramethyldisiloxane, N,N'-di-tert-butylethylenediamine, triphenylmethane triisocyanate and isophorone diisocyanate.

[0007] Preferably, the preparation method of the composite pore-forming agent comprises the following steps: Q1: Tetrahydrofuran and 3-thiophenecarboxylic acid are added to a container, cooled in an ice-water bath to obtain a mixed solution, triethylamine and pentafluorophenyl trifluoroacetate are added dropwise to the mixed solution, stirred at room temperature after the addition is complete, the solvent is removed by rotary evaporation, the product is dissolved with ethyl acetate, washed, the separated organic phase is dried, filtered, rotary evaporated, and purified to obtain compound 1; Q2: Add anhydrous ferric chloride and chloroform to a container, stir under argon protection to obtain a suspension, add compound 1 to chloroform, stir rapidly and then add to the suspension to obtain a mixture, stir under argon protection, then pour into methanol, collect the precipitate by filtration, extract, and vacuum dry to obtain compound 2; Q3: Compound 2 and N,N-dimethylformamide are added to a container, mixed and stirred, and then N,N-dimethyl-1,3-propylenediamine and triethylamine are added. After stirring, the mixture is cooled, dialyzed, filtered, and dried to obtain compound 3; Q4: Add compound 3 and N,N-dimethylformamide to a container, heat and stir until completely dissolved, then add 1-bromoisopentane and continue the reaction. After the reaction is completed, cool, dialyze, and rotary evaporate to obtain a solid. Dissolve the solid with deionized water, filter, and dry to obtain a composite pore-forming agent.

[0008] In the above process, the synthetic reaction formula of the composite pore-forming agent is as follows:

[0009] Preferably, in Q1, the dosage ratio of tetrahydrofuran, 3-thiophenecarboxylic acid, triethylamine and pentafluorophenyl trifluoroacetate is (150-200) mL: (5-6.7) g: (19.6-26.07) mL: (12.1-16.09) mL, the temperature is lowered to 0-1°C, the stirring time is 1-3 h, the mixture is washed with a saturated sodium bicarbonate aqueous solution, and dried with anhydrous sodium sulfate for 20-24 h. The mixed eluent in the purification process is a mixed solution of ethyl acetate and n-hexane in a volume ratio of 10:1.

[0010] Preferably, in Q2, the dosage ratio of anhydrous ferric chloride and compound 1 is (1.94-3.88) g: (0.92-1.84) g, the stirring time is 30-45 min, the stirring time under argon protection is 10-12 h, the extraction is carried out with methanol for 3-5 days, and the vacuum drying time is 20-24 h.

[0011] Preferably, in Q3, the dosage ratio of compound 2, N,N-dimethylformamide, N,N-dimethyl-1,3-propylenediamine and triethylamine is (0.1-0.3) g: (20-60) mL: (65.4-196.2) mL: (44.6-133.8) mL, the mixing and stirring temperature is 50-60°C, the time is 30-45 min, the stirring time is 48-50 h, dialyzed with deionized water for 3-5 days, the molecular retention capacity = 3500 Da, and filtered with a 0.22 μm filter membrane.

[0012] Preferably, in Q4, the dosage ratio of compound 3, N,N-dimethylformamide and 1-bromoisopentane is (0.1-0.3) g: (10-30) mL: (3-9) mL, the heating and stirring temperature is 50-60°C, the reaction time is 6-8h, the reaction is dialyzed with ethanol for 2-3 days, and filtered with a 0.22μm filter membrane.

[0013] Preferably, the method for preparing the modified cross-linking agent comprises the following steps: S1: adding hexamethylcyclotrisiloxane and benzyltrimethylammonium hydroxide to a container, heating and vacuuming to remove water, then adding 1,3-bis(aminopropyl)tetramethyldisiloxane, introducing nitrogen and heating to react, after the reaction is completed, continuing to heat to react, and then continuing to heat and vacuumize to obtain product 1; S2: Add N,N'-di-tert-butylethylenediamine and tetrahydrofuran into a container, introduce nitrogen, slowly dropwise add a mixed solution of triphenylmethane triisocyanate and tetrahydrofuran, raise the temperature to react, and after the reaction is completed, perform rotary evaporation and vacuum rotary evaporation to obtain product 2; S3: vacuum-dry the product 1, then slowly drop tetrahydrofuran containing the product 1 into tetrahydrofuran containing isophorone diisocyanate, slowly heat up after the dropwise addition, then add tetrahydrofuran containing the product 2, continue the reaction, then let the mixed solution stand, heat and react, to obtain a modified cross-linking agent.

[0014] In the above process, hexamethylcyclotrisiloxane is copolymerized and terminated by 1,3-bis(aminopropyl)tetramethyldisiloxane to obtain product 1, which is then reacted with N,N'-di-tert-butylethylenediamine and triphenylmethane triisocyanate to obtain product 2. Product 1 is then chain extended using isophorone diisocyanate and reacted with product 2 to obtain a modified crosslinker.

[0015] Preferably, in S1, the mass ratio of hexamethylcyclotrisiloxane, benzyltrimethylammonium hydroxide and 1,3-bis(aminopropyl)tetramethyldisiloxane is (100-120):(0.51-0.54):(2.55-3.23), the heating temperature is 50-60°C, the vacuum dehydration time is 2-4h, the heating reaction temperature is 80-85°C, the reaction time is 6-8h, the heating reaction temperature is continued to be 170-175°C, the time is 1-1.5h, the heating temperature is continued to be 180-185°C, and the vacuum is drawn for 2-4h.

[0016] Preferably, in S2, the molar ratio of N,N'-di-tert-butylethylenediamine to triphenylmethane triisocyanate is 3:(0.8-1.2), and the temperature rising reaction process is: first react at 30°C for 1h, then increase the temperature by 5°C in 15min, and continue to react at 50°C for 3h; in S3, the vacuum dehydration temperature is 80-85°C, the time is 2-3h, the amount ratio of product 1, isophorone diisocyanate and product 2 is (15-20)g:(0.45-0.89)g:(0.78-1.82)g, and the slow temperature rising process is: from 10°C to 50°C, the temperature rising rate is 10°C / min, the continued reaction time is 1-1.5h, the standing time is 10-12h, the heating reaction temperature is 50-60°C, and the time is 5-8h.

[0017] Preferably, the method for preparing the sodium electric coal-based hard carbon negative electrode material comprises the following steps: Step (1): crushing the anthracite to obtain coal powder with a particle size range of 200-300 nm; Step (2): mixing coal powder with a composite pore-forming agent, a modified cross-linking agent and potassium permanganate to obtain a mixed powder, and then tableting the mixed powder to obtain a sheet material; Step (3): placing the sheet material in a nitrogen atmosphere for carbonization treatment at 60-80°C, washing and removing impurities after the treatment, and then placing it in a high-temperature furnace at 350-550°C for carbonization treatment, crushing, washing, and drying to obtain a sodium electric coal-based hard carbon negative electrode material.

[0018] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. The present invention first uses 3-thiophenecarboxylic acid, pentafluorophenyl trifluoroacetate, N,N-dimethyl-1,3-propylenediamine and 1-bromoisopentane as raw materials to prepare a composite pore-forming agent, and then uses hexamethylcyclotrisiloxane, 1,3-bis(aminopropyl)tetramethyldisiloxane, N,N'-di-tert-butylethylenediamine, triphenylmethane triisocyanate and isophorone diisocyanate as raw materials to prepare a modified cross-linking agent, and the composite pore-forming agent and the modified cross-linking agent are simultaneously added into the preparation process of sodium electric coal-based hard carbon negative electrode material, so that the obtained negative electrode material has uniform pore size distribution, excellent rate performance, cycle stability and service life.

[0019] 2. The present invention uses 3-thiophenecarboxylic acid, pentafluorophenyl trifluoroacetate, N,N-dimethyl-1,3-propylenediamine and 1-bromoisopentane as raw materials to prepare a composite pore-forming agent. The composite pore-forming agent forms a uniform pore structure inside the negative electrode material. These structures are retained during the heat treatment process, thereby improving the overall porosity of the negative electrode material. The obtained structure with high porosity can provide more channels for the diffusion of ions in the negative electrode material, reduce the transmission resistance of ions, and improve the ion transmission performance of the material. The presence of the pore structure can increase the specific surface area of ​​the negative electrode material, expose more active sites, which is beneficial to the adsorption and desorption of ions, and further improves the transmission efficiency of ions. The presence of the pore structure can also provide a buffer space for the volume change occurring during the charge and discharge process, effectively alleviate the volume expansion of the material, and improve the cycle stability. The presence of the aperture structure can shorten the transmission path of ions from the electrolyte to the inside of the material, so that the ions can reach the active sites faster for reaction, thereby improving the rate performance of the material.

[0020] 3. The present invention uses hexamethylcyclotrisiloxane, 1,3-bis(aminopropyl)tetramethyldisiloxane, N,N'-di-tert-butylethylenediamine, triphenylmethane triisocyanate and isophorone diisocyanate as raw materials to prepare a modified crosslinking agent. The siloxane bonds in the modified crosslinking agent have excellent bond energy, so that the obtained network structure can remain stable in an electrochemical environment, thereby effectively enhancing the overall structural stability of the negative electrode material, preventing structural damage caused by volume changes during charging and discharging, improving the structural stability of the negative electrode material, and improving the cycle life; the organic amine group in the modified crosslinking agent can form a charge transfer complex with the electron acceptor in the negative electrode material to improve the electron mobility. At the same time, the polar group in the modified crosslinking agent can promote the wetting and penetration of the electrolyte on the surface of the material, reduce the interface resistance, and further improve the conductivity. DETAILED DESCRIPTION

[0021] The following will be described clearly and completely in conjunction with the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Example 1: This example discloses a method for preparing a composite pore-forming agent, comprising the following steps: Q1: 175 mL of tetrahydrofuran and 5.8 g of 3-thiophenecarboxylic acid were added to a container, and the mixture was cooled to 0°C in an ice-water bath to obtain a mixed solution. 22.84 mL of triethylamine and 14.1 mL of pentafluorophenyl trifluoroacetate were added dropwise to the mixed solution. After the addition was completed, the mixture was stirred at room temperature for 1 h, and the solvent was removed by rotary evaporation. The product was dissolved in ethyl acetate and washed with a saturated sodium bicarbonate aqueous solution. The separated organic phase was dried with anhydrous sodium sulfate for 24 h, filtered, rotary evaporated, and purified. The mixed eluent in the purification process was a mixed solution of ethyl acetate and n-hexane in a volume ratio of 10:1 to obtain compound 1; Q2: 2.91 g of anhydrous ferric chloride and 30 mL of chloroform were added to a container, stirred for 45 min under argon protection to obtain a suspension, 1.38 g of compound 1 was added to 10 mL of chloroform, stirred rapidly and then added to the suspension to obtain a mixture, stirred for 12 h under argon protection, then poured into methanol, filtered to collect the precipitate, extracted with methanol for 3 days, and vacuum dried for 24 h to obtain compound 2; Q3: 0.2 g of compound 2 and 40 mL of N,N-dimethylformamide were added to a container, mixed and stirred at 50°C for 45 min, and then 130.8 mL of N,N-dimethyl-1,3-propylenediamine and 89.2 mL of triethylamine were added. After stirring for 48 h, the mixture was cooled and dialyzed with deionized water for 3 days, with a molecular weight cutoff of 3500 Da. The mixture was filtered with a 0.22 μm filter membrane and dried to obtain compound 3. Q4: Add 0.2 g of compound 3 and 20 mL of N,N-dimethylformamide into a container, heat and stir at 60°C until completely dissolved, then add 6 mL of 1-bromoisopentane and continue the reaction for 8 h. After the reaction is completed, cool and dialyze with ethanol for 3 days. Rotary evaporate to obtain a solid, dissolve the solid with deionized water, filter with a 0.22 μm filter membrane, and dry to obtain a composite pore-forming agent.

[0023] This embodiment discloses a method for preparing a modified cross-linking agent, comprising the following steps: S1: 110 g of hexamethylcyclotrisiloxane and 0.53 g of benzyltrimethylammonium hydroxide were added to a container, and water was removed under vacuum at 60° C. for 4 h. Then, 2.89 g of 1,3-bis(aminopropyl)tetramethyldisiloxane was added, nitrogen was introduced, and the temperature was raised to 85° C. for reaction for 6 h. After the reaction was completed, the temperature was further raised to 175° C. for reaction for 1.5 h, and then the temperature was further raised to 185° C. for vacuumization for 4 h to obtain product 1; S2: 22 mL of N,N'-di-tert-butylethylenediamine and 30 mL of tetrahydrofuran were added to a container, and after nitrogen was introduced, a mixed solution of 12.5 g of triphenylmethane triisocyanate and 20 mL of tetrahydrofuran was slowly added dropwise, and the temperature was raised to react. First, the reaction was carried out at 30°C for 1 h, and then the temperature was raised by 5°C over 15 min, and then the temperature was raised to 50°C and the reaction was continued for 3 h. After the reaction was completed, rotary evaporation was performed under vacuum to obtain product 2; S3: The product 1 was dehydrated in vacuo at 85°C for 3h, and then 20mL of tetrahydrofuran containing 17.5g of the product 1 was slowly added dropwise to 5mL of tetrahydrofuran containing 0.67g of isophorone diisocyanate. After the addition was completed, the temperature was slowly increased from 10°C to 50°C at a rate of 10°C / min, and then 5mL of tetrahydrofuran containing 1.3g of the product 2 was added, and the reaction was continued for 1.5h. The mixed solution was then allowed to stand for 12h and heated at 60°C for 8h to obtain a modified cross-linking agent.

[0024] This embodiment discloses a sodium electric coal-based hard carbon negative electrode material, which is composed of the following components in parts by weight: 44 parts of anthracite, 3 parts of a composite pore-forming agent, 3 parts of a modified cross-linking agent, and 2 parts of potassium permanganate.

[0025] This embodiment discloses a sodium electric coal-based hard carbon negative electrode material, comprising the following steps: Step (1): crushing the anthracite to obtain coal powder with a particle size of 220 nm; Step (2): mixing coal powder with a composite pore-forming agent, a modified cross-linking agent and potassium permanganate to obtain a mixed powder, and then tableting the mixed powder to obtain a sheet material; Step (3): placing the sheet material in a nitrogen atmosphere for carbonization treatment at 80°C. After the treatment, washing and removing impurities, then placing it in a high-temperature furnace at 550°C for carbonization treatment, crushing, washing, and drying to obtain a sodium electric coal-based hard carbon negative electrode material.

[0026] Example 2: This example discloses a method for preparing a composite pore-forming agent, comprising the following steps: Q1: 150 mL of tetrahydrofuran and 5 g of 3-thiophenecarboxylic acid were added to a container, and the mixture was cooled to 0°C in an ice-water bath to obtain a mixed solution. 19.6 mL of triethylamine and 12.1 mL of pentafluorophenyl trifluoroacetate were added dropwise to the mixed solution. After the addition was completed, the mixture was stirred at room temperature for 1 h, and the solvent was removed by rotary evaporation. The product was dissolved in ethyl acetate and washed with a saturated sodium bicarbonate aqueous solution. The separated organic phase was dried with anhydrous sodium sulfate for 24 h, filtered, rotary evaporated, and purified. The mixed eluent in the purification process was a mixed solution of ethyl acetate and n-hexane in a volume ratio of 10:1 to obtain compound 1; Q2: 1.94 g of anhydrous ferric chloride and 30 mL of chloroform were added to a container, stirred for 45 min under argon protection to obtain a suspension, 0.92 g of compound 1 was added to 10 mL of chloroform, stirred rapidly and then added to the suspension to obtain a mixture, stirred for 12 h under argon protection, then poured into methanol, filtered to collect the precipitate, extracted with methanol for 3 days, and vacuum dried for 24 h to obtain compound 2; Q3: 0.1 g of compound 2 and 20 mL of N,N-dimethylformamide were added to a container, mixed and stirred at 50°C for 45 min, and then 65.4 mL of N,N-dimethyl-1,3-propylenediamine and 44.6 mL of triethylamine were added. After stirring for 48 h, the mixture was cooled and dialyzed with deionized water for 3 days, with a molecular weight cutoff of 3500 Da. The mixture was filtered with a 0.22 μm filter membrane and dried to obtain compound 3. Q4: Add 0.1 g of compound 3 and 10 mL of N,N-dimethylformamide into a container, heat and stir at 60°C until completely dissolved, then add 3 mL of 1-bromoisopentane and continue the reaction for 8 h. After the reaction is completed, cool and dialyze with ethanol for 3 days. Rotary evaporate to obtain a solid, dissolve the solid with deionized water, filter with a 0.22 μm filter membrane, and dry to obtain a composite pore-forming agent.

[0027] This embodiment discloses a method for preparing a modified cross-linking agent, comprising the following steps: S1: 100 g of hexamethylcyclotrisiloxane and 0.51 g of benzyltrimethylammonium hydroxide were added to a container, and water was removed under vacuum at 60° C. for 4 h. Then, 2.55 g of 1,3-bis(aminopropyl)tetramethyldisiloxane was added, nitrogen was introduced, and the temperature was raised to 85° C. for reaction for 6 h. After the reaction was completed, the temperature was further raised to 175° C. for reaction for 1.5 h, and then the temperature was further raised to 185° C. for vacuumization for 4 h to obtain product 1; S2: 22 mL of N,N'-di-tert-butylethylenediamine and 30 mL of tetrahydrofuran were added to a container, and after nitrogen was introduced, a mixed solution of 10 g of triphenylmethane triisocyanate and 20 mL of tetrahydrofuran was slowly added dropwise, and the temperature was raised to react. First, the reaction was carried out at 30°C for 1 h, and then the temperature was raised by 5°C over 15 min, and then the temperature was raised to 50°C and the reaction was continued for 3 h. After the reaction was completed, rotary evaporation was performed under vacuum to obtain product 2; S3: The product 1 was dehydrated in vacuo at 85°C for 3h, and then 20mL of tetrahydrofuran containing 15g of the product 1 was slowly added dropwise to 5mL of tetrahydrofuran containing 0.45g of isophorone diisocyanate. After the addition was completed, the temperature was slowly increased from 10°C to 50°C at a rate of 10°C / min, and then 5mL of tetrahydrofuran containing 0.78g of the product 2 was added, and the reaction was continued for 1.5h. The mixed solution was then allowed to stand for 12h and heated at 60°C for 8h to obtain a modified cross-linking agent.

[0028] This embodiment discloses a sodium electric coal-based hard carbon negative electrode material, which is composed of the following components in parts by weight: 40 parts of anthracite, 1 part of a composite pore-forming agent, 2 parts of a modified cross-linking agent, and 1 part of potassium permanganate.

[0029] This embodiment discloses a sodium electric coal-based hard carbon negative electrode material, comprising the following steps: Step (1): crushing the anthracite to obtain coal powder with a particle size of 220 nm; Step (2): mixing coal powder with a composite pore-forming agent, a modified cross-linking agent and potassium permanganate to obtain a mixed powder, and then tableting the mixed powder to obtain a sheet material; Step (3): placing the sheet material in a nitrogen atmosphere for carbonization treatment at 80°C. After the treatment, washing and removing impurities, then placing it in a high-temperature furnace at 550°C for carbonization treatment, crushing, washing, and drying to obtain a sodium electric coal-based hard carbon negative electrode material.

[0030] Example 3: This example discloses a method for preparing a composite pore-forming agent, comprising the following steps: Q1: 200 mL of tetrahydrofuran and 6.7 g of 3-thiophenecarboxylic acid were added to a container, and the mixture was cooled to 0°C in an ice-water bath to obtain a mixed solution. 26.07 mL of triethylamine and 16.09 mL of pentafluorophenyl trifluoroacetate were added dropwise to the mixed solution. After the addition was completed, the mixture was stirred at room temperature for 1 h, and the solvent was removed by rotary evaporation. The product was dissolved in ethyl acetate and washed with a saturated sodium bicarbonate aqueous solution. The separated organic phase was dried over anhydrous sodium sulfate for 24 h, filtered, rotary evaporated, and purified. The mixed eluent in the purification process was a mixed solution of ethyl acetate and n-hexane in a volume ratio of 10:1 to obtain compound 1; Q2: 3.88 g of anhydrous ferric chloride and 30 mL of chloroform were added to a container, stirred for 45 min under argon protection to obtain a suspension, 1.84 g of compound 1 was added to 10 mL of chloroform, stirred rapidly and then added to the suspension to obtain a mixture, stirred for 12 h under argon protection, then poured into methanol, filtered to collect the precipitate, extracted with methanol for 3 days, and vacuum dried for 24 h to obtain compound 2; Q3: 0.3 g of compound 2 and 60 mL of N,N-dimethylformamide were added to a container, mixed and stirred at 50°C for 45 min, and then 196.2 mL of N,N-dimethyl-1,3-propylenediamine and 133.8 mL of triethylamine were added. After stirring for 48 h, the mixture was cooled, dialyzed with deionized water for 3 days, with a molecular weight cutoff of 3500 Da, filtered with a 0.22 μm filter membrane, and dried to obtain compound 3; Q4: Add 0.3 g of compound 3 and 30 mL of N,N-dimethylformamide into a container, heat and stir at 60°C until completely dissolved, then add 8.5 mL of 1-bromoisopentane and continue the reaction for 8 hours. After the reaction is completed, cool and dialyze with ethanol for 3 days. Rotary evaporate to obtain a solid, dissolve the solid with deionized water, filter with a 0.22 μm filter membrane, and dry to obtain a composite pore-forming agent.

[0031] This embodiment discloses a method for preparing a modified cross-linking agent, comprising the following steps: S1: 120 g of hexamethylcyclotrisiloxane and 0.54 g of benzyltrimethylammonium hydroxide were added to a container, and water was removed under vacuum at 60° C. for 4 h. Then, 3.23 g of 1,3-bis(aminopropyl)tetramethyldisiloxane was added, nitrogen was introduced, and the temperature was raised to 85° C. for reaction for 6 h. After the reaction was completed, the temperature was further raised to 175° C. for reaction for 1.5 h, and then the temperature was further raised to 185° C. for vacuumization for 4 h to obtain product 1; S2: 22 mL of N,N'-di-tert-butylethylenediamine and 30 mL of tetrahydrofuran were added to a container, and after nitrogen was introduced, a mixed solution of 15 g of triphenylmethane triisocyanate and 20 mL of tetrahydrofuran was slowly added dropwise, and the temperature was raised to react. First, the reaction was carried out at 30°C for 1 h, and then the temperature was raised by 5°C in 15 min, and then the temperature was raised to 50°C and the reaction was continued for 3 h. After the reaction was completed, rotary evaporation was performed under vacuum to obtain product 2; S3: The product 1 was dehydrated in vacuo at 85°C for 3h, and then 20mL of tetrahydrofuran containing 20g of the product 1 was slowly added dropwise to 5mL of tetrahydrofuran containing 0.89g of isophorone diisocyanate. After the addition was completed, the temperature was slowly increased from 10°C to 50°C at a rate of 10°C / min, and then 5mL of tetrahydrofuran containing 1.82g of the product 2 was added, and the reaction was continued for 1.5h. The mixed solution was then allowed to stand for 12h and heated at 60°C for 8h to obtain a modified cross-linking agent.

[0032] This embodiment discloses a sodium electric coal-based hard carbon negative electrode material, which is composed of the following components in parts by weight: 48 parts of anthracite, 5 parts of a composite pore-forming agent, 4 parts of a modified cross-linking agent, and 3 parts of potassium permanganate.

[0033] This embodiment discloses a sodium electric coal-based hard carbon negative electrode material, comprising the following steps: Step (1): crushing the anthracite to obtain coal powder with a particle size of 220 nm; Step (2): mixing coal powder with a composite pore-forming agent, a modified cross-linking agent and potassium permanganate to obtain a mixed powder, and then tableting the mixed powder to obtain a sheet material; Step (3): placing the sheet material in a nitrogen atmosphere for carbonization treatment at 80°C. After the treatment, washing and removing impurities, then placing it in a high-temperature furnace at 550°C for carbonization treatment, crushing, washing, and drying to obtain a sodium electric coal-based hard carbon negative electrode material.

[0034] Example 4: This example discloses a method for preparing a composite pore-forming agent, comprising the following steps: Q1: 165 mL of tetrahydrofuran and 5.2 g of 3-thiophenecarboxylic acid were added to a container, and the mixture was cooled to 0°C in an ice-water bath to obtain a mixed solution. 21.22 mL of triethylamine and 13.1 mL of pentafluorophenyl trifluoroacetate were added dropwise to the mixed solution. After the addition was completed, the mixture was stirred at room temperature for 1 h, and the solvent was removed by rotary evaporation. The product was dissolved in ethyl acetate and washed with a saturated sodium bicarbonate aqueous solution. The separated organic phase was dried with anhydrous sodium sulfate for 24 h, filtered, rotary evaporated, and purified. The mixed eluent in the purification process was a mixed solution of ethyl acetate and n-hexane in a volume ratio of 10:1, and compound 1 was obtained; Q2: Add 2.43 g of anhydrous ferric chloride and 30 mL of chloroform to a container, stir for 45 min under argon protection to obtain a suspension, add 1.15 g of compound 1 to 10 mL of chloroform, stir rapidly and then add to the suspension to obtain a mixture, stir for 12 h under argon protection, then pour into methanol, collect the precipitate by filtration, extract with methanol for 3 days, and vacuum dry for 24 h to obtain compound 2; Q3: 0.15 g of compound 2 and 30 mL of N,N-dimethylformamide were added to a container, mixed and stirred at 50°C for 45 min, and then 98.1 mL of N,N-dimethyl-1,3-propylenediamine and 66.9 mL of triethylamine were added. After stirring for 48 h, the mixture was cooled and dialyzed with deionized water for 3 days, with a molecular weight cutoff of 3500 Da. The mixture was filtered with a 0.22 μm filter membrane and dried to obtain compound 3. Q4: Add 0.15g of compound 3 and 15mL of N,N-dimethylformamide into a container, heat and stir at 60°C until completely dissolved, then add 4.5mL of 1-bromoisopentane and continue the reaction for 8h. After the reaction is completed, cool and dialyze with ethanol for 3 days. Rotary evaporate to obtain a solid, dissolve the solid with deionized water, filter with a 0.22μm filter membrane, and dry to obtain a composite pore-forming agent.

[0035] This embodiment discloses a method for preparing a modified cross-linking agent, comprising the following steps: S1: 105 g of hexamethylcyclotrisiloxane and 0.52 g of benzyltrimethylammonium hydroxide were added to a container, and water was removed under vacuum at 60° C. for 4 h. Subsequently, 2.72 g of 1,3-bis(aminopropyl)tetramethyldisiloxane was added, nitrogen was introduced, and the temperature was raised to 85° C. for reaction for 6 h. After the reaction was completed, the temperature was further raised to 175° C. for reaction for 1.5 h, and then the temperature was further raised to 185° C. for vacuumization for 4 h to obtain product 1; S2: 22 mL of N,N'-di-tert-butylethylenediamine and 30 mL of tetrahydrofuran were added to a container, and after nitrogen was introduced, a mixed solution of 11 g of triphenylmethane triisocyanate and 20 mL of tetrahydrofuran was slowly added dropwise, and the temperature was raised to react. First, the reaction was carried out at 30°C for 1 h, and then the temperature was raised by 5°C over 15 min, and then the temperature was raised to 50°C and the reaction was continued for 3 h. After the reaction was completed, rotary evaporation was performed under vacuum to obtain product 2; S3: The product 1 was dehydrated in vacuo at 85°C for 3h, and then 20mL of tetrahydrofuran containing 16g of the product 1 was slowly added dropwise to 5mL of tetrahydrofuran containing 0.56g of isophorone diisocyanate. After the addition was completed, the temperature was slowly increased from 10°C to 50°C at a rate of 10°C / min, and then 5mL of tetrahydrofuran containing 1.04g of the product 2 was added, and the reaction was continued for 1.5h. The mixed solution was then allowed to stand for 12h and heated at 60°C for 8h to obtain a modified cross-linking agent.

[0036] The present embodiment discloses a sodium electric coal-based hard carbon negative electrode material, which is composed of the following components in parts by weight: 42 parts of anthracite, 2 parts of a composite pore-forming agent, 1 part of a modified cross-linking agent, and 3 parts of potassium permanganate.

[0037] This embodiment discloses a sodium electric coal-based hard carbon negative electrode material, comprising the following steps: Step (1): crushing the anthracite to obtain coal powder with a particle size of 220 nm; Step (2): mixing coal powder with a composite pore-forming agent, a modified cross-linking agent and potassium permanganate to obtain a mixed powder, and then tableting the mixed powder to obtain a sheet material; Step (3): placing the sheet material in a nitrogen atmosphere for carbonization treatment at 80°C. After the treatment, washing and removing impurities, then placing it in a high-temperature furnace at 550°C for carbonization treatment, crushing, washing, and drying to obtain a sodium electric coal-based hard carbon negative electrode material.

[0038] Comparative Example 1: Compared with Example 1, in the process of preparing the composite pore-forming agent in Comparative Example 1, 3-thiophenecarboxylic acid is not added, and other conditions remain unchanged.

[0039] Comparative Example 2: Compared with Example 1, in Comparative Example 2, during the preparation of the modified cross-linking agent, hexamethylcyclotrisiloxane was not added, and other conditions remained unchanged.

[0040] Comparative Example 3: Compared with Example 1, in the process of preparing the sodium power coal-based hard carbon negative electrode material in Comparative Example 3, no composite pore-forming agent is added, and other conditions remain unchanged.

[0041] Comparative Example 4: Compared with Example 1, in Comparative Example 4, during the process of preparing the sodium power coal-based hard carbon negative electrode material, no modified cross-linking agent is added, and other conditions remain unchanged.

[0042] The performance of the sodium electric coal-based hard carbon negative electrode materials prepared in Examples 1-4 and Comparative Examples 1-4 was tested, and the pore size distribution of the samples was tested using a surface area analyzer NOVA-Touch. The prepared samples, conductive carbon black and polyvinylidene fluoride were mixed in a mass ratio of 91:4:5 to form a slurry, which was then coated on a copper foil. After vacuum drying, the copper foil was cut into electrode sheets with a diameter of 12 mm, and the substrate loading was 5 mg / cm 2 , the electrolyte is 1 mol / L sodium hexafluorophosphate, transferred to a glove box filled with argon to assemble a 2032 button half-cell and then tested, using metallic sodium as the counter electrode and a glass fiber diaphragm. The packaged button half-cell was placed in the glove box for 12 hours and then subjected to a constant current charge and discharge cycle test at a voltage range of 0-2V and a current density of 30mA / g. The test results are shown in Table 1: Table 1

[0043] It can be seen from the test results in Table 1 that the sodium electric coal-based hard carbon negative electrode materials prepared in Examples 1-4 of the present invention have uniform pore size distribution, excellent rate performance and cycle stability. By comparing Comparative Example 1 with Examples 1-4, it can be seen that the addition of 3-thiophenecarboxylic acid can effectively improve the pore size distribution, rate performance and cycle stability of the sodium electric coal-based hard carbon negative electrode materials; by comparing Comparative Example 2 with Examples 1-4, it can be seen that the addition of hexamethylcyclotrisiloxane can effectively improve the cycle stability of the sodium electric coal-based hard carbon negative electrode materials; by comparing Comparative Example 3 with Examples 1-4, it can be seen that the addition of a composite pore-forming agent can effectively improve the pore size distribution, rate performance and cycle stability of the sodium electric coal-based hard carbon negative electrode materials; by comparing Comparative Example 4 with Examples 1-4, it can be seen that the addition of a modified cross-linking agent can effectively improve the cycle stability of the sodium electric coal-based hard carbon negative electrode materials.

[0044] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0045] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. Sodium electric coal-based hard carbon negative electrode material, characterized in that: The invention is composed of the following components in parts by weight: 40-48 parts of anthracite, 1-5 parts of a composite pore-forming agent, 2-4 parts of a modified cross-linking agent, and 1-3 parts of potassium permanganate, wherein the composite pore-forming agent is prepared from 3-thiophenecarboxylic acid, pentafluorophenyl trifluoroacetate, N,N-dimethyl-1,3-propylenediamine and 1-bromoisopentane, and the modified cross-linking agent is prepared from hexamethylcyclotrisiloxane, 1,3-bis(aminopropyl)tetramethyldisiloxane, N,N'-di-tert-butylethylenediamine, triphenylmethane triisocyanate and isophorone diisocyanate.

2. The sodium electric coal-based hard carbon negative electrode material according to claim 1, characterized in that: The preparation method of the composite pore-forming agent, The following steps are involved: Q1: Tetrahydrofuran and 3-thiophenecarboxylic acid are added to a container, cooled in an ice-water bath to obtain a mixed solution, triethylamine and pentafluorophenyl trifluoroacetate are added dropwise to the mixed solution, stirred at room temperature after the addition is complete, the solvent is removed by rotary evaporation, the product is dissolved with ethyl acetate, washed, the separated organic phase is dried, filtered, rotary evaporated, and purified to obtain compound 1; Q2: Add anhydrous ferric chloride and chloroform to a container, stir under argon protection to obtain a suspension, add compound 1 to chloroform, stir rapidly and then add to the suspension to obtain a mixture, stir under argon protection, then pour into methanol, collect the precipitate by filtration, extract, and vacuum dry to obtain compound 2; Q3: Compound 2 and N,N-dimethylformamide are added to a container, mixed and stirred, and then N,N-dimethyl-1,3-propylenediamine and triethylamine are added. After stirring, the mixture is cooled, dialyzed, filtered, and dried to obtain compound 3; Q4: Add compound 3 and N,N-dimethylformamide to a container, heat and stir until completely dissolved, then add 1-bromoisopentane and continue the reaction. After the reaction is completed, cool, dialyze, and rotary evaporate to obtain a solid. Dissolve the solid with deionized water, filter, and dry to obtain a composite pore-forming agent.

3. The sodium electric coal-based hard carbon negative electrode material according to claim 2, characterized in that: In the Q1, the dosage ratio of tetrahydrofuran, 3-thiophenecarboxylic acid, triethylamine and pentafluorophenyl trifluoroacetate is (150-200) mL: (5-6.7) g: (19.6-26.07) mL: (12.1-16.09) mL, the temperature is lowered to 0-1°C, the stirring time is 1-3 h, the mixture is washed with a saturated sodium bicarbonate aqueous solution, and dried with anhydrous sodium sulfate for 20-24 h. The mixed eluent in the purification process is a mixed solution of ethyl acetate and n-hexane in a volume ratio of 10:

1.

4. The sodium electric coal-based hard carbon negative electrode material according to claim 2, characterized in that: In Q2, the dosage ratio of anhydrous ferric chloride and compound 1 is (1.94-3.88) g: (0.92-1.84) g, the stirring time is 30-45 min, the stirring time under argon protection is 10-12 h, the extraction is carried out with methanol for 3-5 days, and the vacuum drying time is 20-24 h.

5. The sodium electric coal-based hard carbon negative electrode material according to claim 2, characterized in that: In Q3, the dosage ratio of compound 2, N,N-dimethylformamide, N,N-dimethyl-1,3-propylenediamine and triethylamine is (0.1-0.3) g: (20-60) mL: (65.4-196.2) mL: (44.6-133.8) mL, the mixing and stirring temperature is 50-60°C, the time is 30-45 min, the stirring time is 48-50 h, and the mixture is dialyzed with deionized water for 3-5 days. The molecular retention capacity is 3500 Da, and the mixture is filtered with a 0.22 μm filter membrane.

6. The sodium electric coal-based hard carbon negative electrode material according to claim 2, characterized in that: In Q4, the dosage ratio of compound 3, N,N-dimethylformamide and 1-bromoisopentane is (0.1-0.3) g: (10-30) mL: (3-9) mL, the heating and stirring temperature is 50-60°C, the reaction time is 6-8h, the reaction is dialyzed with ethanol for 2-3 days, and the reaction is filtered with a 0.22μm filter membrane.

7. The sodium electric coal-based hard carbon negative electrode material according to claim 1, characterized in that: The preparation method of the modified cross-linking agent comprises the following steps: S1: adding hexamethylcyclotrisiloxane and benzyltrimethylammonium hydroxide to a container, heating and vacuuming to remove water, then adding 1,3-bis(aminopropyl)tetramethyldisiloxane, introducing nitrogen and heating to react, after the reaction is completed, continuing to heat to react, and then continuing to heat and vacuumize to obtain product 1; S2: Add N,N'-di-tert-butylethylenediamine and tetrahydrofuran into a container, introduce nitrogen, slowly dropwise add a mixed solution of triphenylmethane triisocyanate and tetrahydrofuran, raise the temperature to react, and after the reaction is completed, perform rotary evaporation and vacuum rotary evaporation to obtain product 2; S3: vacuum-dry the product 1, then slowly drop tetrahydrofuran containing the product 1 into tetrahydrofuran containing isophorone diisocyanate, slowly heat up after the dropwise addition, then add tetrahydrofuran containing the product 2, continue the reaction, then let the mixed solution stand, heat and react, to obtain a modified cross-linking agent.

8. The sodium electric coal-based hard carbon negative electrode material according to claim 7, characterized in that: In the S1, the mass ratio of hexamethylcyclotrisiloxane, benzyltrimethylammonium hydroxide and 1,3-bis(aminopropyl)tetramethyldisiloxane is (100-120):(0.51-0.54):(2.55-3.23), the heating temperature is 50-60°C, the vacuum dehydration time is 2-4h, the heating reaction temperature is 80-85°C, the reaction time is 6-8h, the heating reaction temperature is continued to be 170-175°C, the time is 1-1.5h, the heating temperature is continued to be 180-185°C, and the vacuum is drawn for 2-4h.

9. The sodium electric coal-based hard carbon negative electrode material according to claim 7, characterized in that: In the S2, the molar ratio of N,N'-di-tert-butylethylenediamine and triphenylmethane triisocyanate is 3:(0.8-1.2), and the temperature rising reaction process is: first react at 30°C for 1h, then increase the temperature by 5°C in 15min, and then increase the temperature to 50°C and continue to react for 3h; in the S3, the vacuum dehydration temperature is 80-85°C, the time is 2-3h, the amount ratio of product 1, isophorone diisocyanate and product 2 is (15-20)g:(0.45-0.89)g:(0.78-1.82)g, and the slow heating process is: from 10°C to 50°C, the heating rate is 10°C / min, the continued reaction time is 1-1.5h, the standing time is 10-12h, the heating reaction temperature is 50-60°C, and the time is 5-8h.

10. A method for preparing a sodium electric coal-based hard carbon negative electrode material, characterized in that: The following steps are involved: Step (1): crushing the anthracite to obtain coal powder with a particle size range of 200-300 nm; Step (2): mixing coal powder with a composite pore-forming agent, a modified cross-linking agent and potassium permanganate to obtain a mixed powder, and then tableting the mixed powder to obtain a sheet material; Step (3): placing the sheet material in a nitrogen atmosphere for carbonization treatment at 60-80°C, washing and removing impurities after the treatment, and then placing it in a high-temperature furnace at 350-550°C for carbonization treatment, crushing, washing, and drying to obtain a sodium electric coal-based hard carbon negative electrode material.

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