A sulfur and nitrogen co-doped copper-iron-manganese cathode material in-situ and its preparation method

Abstract

The present invention relates to the field of sodium-ion batteries, and particularly to a sulfur and nitrogen co-doped copper-iron-manganese cathode material in-situ and a preparation method thereof, which are used to solve the problem of poor electrochemical performance of existing copper-iron-manganese-based cathode materials; in this preparation method, an in-situ dopant is added and polymerized to wrap the copper-iron-manganese precipitate, so that the outer surface of the sintered product of the copper-iron-manganese precipitate is wrapped with a carbon layer, and a large number of nitrogen atoms and sulfur atoms are doped in the carbon layer. Carbon coating can improve the conductivity of the material, and the doped nitrogen atoms can make the material have more active defects and improve the sodium-ion diffusion ability. In addition, the sulfur-doped carbon material will have more excellent electrochemical performance because the edges and defect positions of the carbon lattice will be occupied by sulfur atoms, and the degree of defect of the carbon-based material will increase with the doping of sulfur elements, thereby greatly improving the performance of the copper-iron-manganese cathode material.

Description

Technical Field

[0001] The present invention relates to the field of sodium-ion batteries, and particularly to a sulfur-nitrogen in-situ co-doped copper-iron-manganese cathode material and a preparation method thereof. Background Art

[0002] Lithium-ion batteries have been widely used in portable electronic devices and electric vehicles due to their advantages such as high energy density, high power density, and long cycle life. However, due to the limited and uneven distribution of lithium reserves and the rapid increase in lithium consumption in recent years with the booming development of the global electric vehicle industry, the price of lithium has soared, which limits the application of lithium-ion batteries in large-scale energy storage.

[0003] Sodium-ion batteries have a similar electrochemical deintercalation mechanism to lithium-ion batteries, and sodium-ion batteries have advantages such as rich sodium resources, excellent high and low temperature performance, and high safety, and are considered ideal devices in the field of large-scale energy storage. In the sodium-ion battery system, the cathode material plays a decisive role in the energy density, cycle life, and cost of the battery. Therefore, finding a suitable cathode material is crucial for the development and application of sodium-ion batteries.

[0004] Copper-iron-manganese-based cathode materials for sodium-ion batteries have attracted extensive attention from researchers due to advantages such as rich raw materials, environmental friendliness, and good air stability. However, currently existing copper-iron-manganese-based cathode materials have defects such as low product purity and large particle size, resulting in poor cycle performance and rate performance.

[0005] How to improve the poor electrochemical performance of existing copper-iron-manganese-based cathode materials is the key of the present invention. Therefore, there is an urgent need for a sulfur-nitrogen in-situ co-doped copper-iron-manganese cathode material and a preparation method thereof to solve the above problems. Summary of the Invention

[0006] In order to overcome the above technical problems, the purpose of the present invention is to provide a sulfur-nitrogen in-situ co-doped copper-iron-manganese cathode material and a preparation method thereof: by adding copper sulfate pentahydrate, ferrous sulfate heptahydrate, manganese sulfate monohydrate, and deionized water into a three-necked flask and stirring evenly, then adding an in-situ doping agent and continuing to stir to obtain a copper-iron-manganese solution, adding sodium hydroxide solution and ammonium persulfate solution dropwise into the copper-iron-manganese solution, continuing to stir and react after dropping, cooling the reaction product to room temperature after the reaction, then vacuum filtering, washing and drying the filter cake to obtain a doped copper-iron-manganese precursor, and adding the doped copper-iron-manganese precursor into a quartz glass tube for sintering to obtain the sulfur-nitrogen in-situ co-doped copper-iron-manganese cathode material, solving the problem of poor electrochemical performance of existing copper-iron-manganese-based cathode materials.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] A preparation method of a sulfur and nitrogen co-doped copper-iron-manganese cathode material in-situ, comprising the following steps:

[0009] Step 1: Add copper sulfate pentahydrate, ferrous sulfate heptahydrate, manganese sulfate monohydrate and deionized water into a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, stir evenly under the conditions of a temperature of 55-60 °C and a stirring rate of 550-650 r / min, and then add an in-situ dopant and continue stirring to obtain a copper-iron-manganese solution;

[0010] Step 2: While stirring, gradually add a sodium hydroxide solution and an ammonium persulfate solution dropwise into the copper-iron-manganese solution, control the dropping rate to be 1-2 drops / s, after the dropping is completed, raise the temperature to 85-90 °C and continue stirring and reacting for 8-10 h, after the reaction is completed, cool the reaction product to room temperature, then carry out vacuum filtration, wash the filter cake with distilled water 3-5 times, and then add it to a vacuum drying oven and dry it at a temperature of 60-65 °C for 20-30 h to obtain a doped copper-iron-manganese precursor;

[0011] Step 3: Add the doped copper-iron-manganese precursor into a quartz glass tube, introduce argon for protection, sinter at a temperature of 350-360 °C for 5-6 h, then raise the temperature to 750-780 °C and sinter for 8-10 h, control the heating rate to be 5-8 °C / min, and then cool with the furnace to obtain the sulfur and nitrogen co-doped copper-iron-manganese cathode material in-situ.

[0012] As a further scheme of the present invention: the dosage ratio of copper sulfate pentahydrate, ferrous sulfate heptahydrate, manganese sulfate monohydrate, deionized water, in-situ dopant, sodium hydroxide solution and ammonium persulfate solution is 10 mmol: 10 mmol: 10 mmol: 40-50 mL: 0.6-2.2 g: 15-20 mL: 15-20 mL, the mass fraction of the sodium hydroxide solution is 30-35%, and the mass fraction of the ammonium persulfate solution is 2-3%.

[0013] As a further scheme of the present invention: the in-situ dopant is prepared by the following steps:

[0014] Step s1: Add p-nitrobenzaldehyde, benzene and 10% palladium-carbon into a reaction kettle, introduce nitrogen to displace the air in the reaction kettle 2-3 times, and then while stirring, introduce hydrogen at a temperature of 100-110 °C and a stirring rate of 550-650 r / min, maintain the pressure in the reaction kettle at 1.6-1.8 MPa and stir and react for 6-7 h, after the reaction is completed, cool the reaction product to room temperature, and then rotate and evaporate the reaction product to remove the solvent to obtain intermediate 1;

[0015] The reaction principle is as follows:

[0016]

[0017] Step s2: Add p - hydroxyacetophenone and N,N - dimethylacetamide into a three - necked flask equipped with a stirrer and a thermometer. Stir and react for 30 - 50 min under the conditions of a temperature of 20 - 25°C and a stirring rate of 550 - 650 r / min. Then add 2 - bromoisobutyramide and continue to stir and react for 5 - 6 h. Then add sodium hydroxide and raise the temperature to 50 - 55°C and continue to stir and react for 1 - 1.5 h. Then add deionized water and continue to stir and react for 20 - 30 min to precipitate crystals. Then carry out vacuum filtration. Place the filter cake in a vacuum drying oven and dry it for 3 - 5 h under the condition of a temperature of 65 - 75°C to obtain Intermediate 2;

[0018] The reaction principle is as follows:

[0019]

[0020] Step s3: Add Intermediate 2, sodium hydroxide solution and N,N - dimethylacetamide into a three - necked flask equipped with a stirrer, a thermometer and a reflux condenser. Stir and heat to reflux at a stirring rate of 550 - 650 r / min, controlling the heating rate at 2 - 3°C / min. Then continue to stir and react for 2 - 3 h. After the reaction is completed, add the reaction product into distilled water to precipitate crystals. Then carry out vacuum filtration. Place the filter cake in a vacuum drying oven and dry it for 2 - 3 h under the condition of a temperature of 70 - 80°C to obtain Intermediate 3;

[0021] The reaction principle is as follows:

[0022]

[0023] Step s4: Add Intermediate 1, Intermediate 3 and absolute ethanol into a three - necked flask equipped with a stirrer and a thermometer. Stir and react for 30 - 50 min under the conditions of a temperature of 20 - 25°C and a stirring rate of 550 - 650 r / min. Then add sodium hydroxide solution and continue to stir and react for 10 - 15 h. After the reaction is completed, cool the reaction product to 0 - 5°C. Then adjust the pH to 5 - 6 with hydrochloric acid solution to precipitate crystals. Then carry out vacuum filtration. Place the filter cake in a vacuum drying oven and dry it for 8 - 10 h under the condition of a temperature of 45 - 50°C to obtain Intermediate 4;

[0024] The reaction principle is as follows:

[0025]

[0026] Step s5: Add intermediate 4 and absolute ethanol into a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser and a constant pressure dropping funnel. Stir and react for 30 - 50 min under the conditions of a temperature of 45 - 50 °C and a stirring rate of 550 - 650 r / min. Then, while stirring, gradually add formic acid aqueous solution dropwise, control the dropping rate at 1 - 2 drops / s. After the addition is complete, while stirring, gradually add formaldehyde aqueous solution dropwise, control the dropping rate at 1 - 2 drops / s. After the addition is complete, raise the temperature to reflux and continue stirring and reacting for 10 - 12 h. After the reaction is completed, cool the reaction product to room temperature, then adjust the pH to 9 - 10 with sodium hydroxide solution, then extract with ethyl acetate 2 - 3 times, combine the extracts and dry with anhydrous sodium sulfate, then perform vacuum filtration, and rotary evaporate the filtrate to remove the solvent to obtain intermediate 5;

[0027] The reaction principle is as follows:

[0028]

[0029] Step s6: Add intermediate 5, 2-thiophenesulfonyl chloride, potassium carbonate and absolute acetonitrile into a three-necked flask equipped with a stirrer, a thermometer and a reflux condenser. While stirring, heat up to reflux at a stirring rate of 550 - 650 r / min, control the heating rate at 2 - 3 °C / min, then continue stirring and reacting for 10 - 15 h. After the reaction is completed, add the reaction product into ice water, then extract with ethyl acetate 2 - 3 times, combine the extracts and dry with anhydrous sodium sulfate, then perform vacuum filtration, and rotary evaporate the filtrate to remove the solvent to obtain the in-situ dopant.

[0030] The reaction principle is as follows:

[0031]

[0032] As a further scheme of the present invention: The dosage ratio of p-nitrobenzaldehyde, benzene and 10% palladium-carbon in step s1 is 0.1 mol: 80 - 100 mL: 0.15 - 0.3 g.

[0033] As a further scheme of the present invention: The dosage ratio of p-hydroxyacetophenone, N,N-dimethylacetamide, 2-bromo-2-methylpropionamide, sodium hydroxide and deionized water in step s2 is 0.1 mol: 80 - 100 mL: 0.3 - 0.35 mol: 35 - 40 g: 120 - 150 mL.

[0034] As a further scheme of the present invention: The dosage ratio of intermediate 2, sodium hydroxide solution and N,N-dimethylacetamide in step s3 is 0.1 mol: 100 - 120 mL: 100 - 120 mL, and the mass fraction of the sodium hydroxide solution is 35 - 40%.

[0035] As a further solution of the present invention: the dosage ratio of the intermediate 1, intermediate 3, absolute ethanol and sodium hydroxide solution in step s4 is 0.1 mol: 0.12 - 0.15 mol: 30 - 40 mL: 35 - 45 mL, the mass fraction of the sodium hydroxide solution is 5 - 8%, and the mass fraction of the hydrochloric acid solution is 15 - 20%.

[0036] As a further solution of the present invention: the dosage ratio of the intermediate 4, absolute ethanol, formic acid aqueous solution and formaldehyde aqueous solution in step s5 is 0.1 mol: 50 - 60 mL: 70 - 75 g: 50 - 55 g, the mass fraction of the formic acid aqueous solution is 88%, the mass fraction of the formaldehyde aqueous solution is 36%, and the mass fraction of the sodium hydroxide solution is 30 - 35%.

[0037] As a further solution of the present invention: the dosage ratio of the intermediate 5, 2 - thiophenesulfonyl chloride, potassium carbonate and absolute acetonitrile in step s6 is 0.1 mol: 0.22 - 0.25 mol: 0.25 - 0.3 mol: 120 - 150 mL.

[0038] As a further solution of the present invention: a sulfur - nitrogen in - situ co - doped copper - iron - manganese cathode material, and the sulfur - nitrogen in - situ co - doped copper - iron - manganese cathode material is prepared according to the preparation method of the sulfur - nitrogen in - situ co - doped copper - iron - manganese cathode material.

[0039] The beneficial effects of the present invention:

[0040] A sulfur and nitrogen in-situ co-doped copper-iron-manganese cathode material and a preparation method thereof according to the present invention. Copper sulfate pentahydrate, ferrous sulfate heptahydrate, manganese sulfate monohydrate and deionized water are added to a three-necked flask and stirred evenly. Then, an in-situ dopant is added and stirring is continued to obtain a copper-iron-manganese solution. Sodium hydroxide solution and ammonium persulfate solution are added dropwise to the copper-iron-manganese solution. After the addition is complete, stirring and reaction are continued. After the reaction is completed, the reaction product is cooled to room temperature, and then vacuum filtration is carried out. The filter cake is washed and dried to obtain a doped copper-iron-manganese precursor. The doped copper-iron-manganese precursor is added to a quartz glass tube and sintered to obtain the sulfur and nitrogen in-situ co-doped copper-iron-manganese cathode material; in this preparation method, copper sulfate pentahydrate, ferrous sulfate heptahydrate, and manganese sulfate monohydrate are used as the main raw materials for precipitation to obtain a copper-iron-manganese precipitate. Then, adding an in-situ dopant can make the copper-iron-manganese precipitate disperse evenly and adhere to the surface of the copper-iron-manganese precipitate. Then, under the initiation of ammonium persulfate, the in-situ dopant is polymerized to wrap the copper-iron-manganese precipitate to form a doped copper-iron-manganese precursor. Finally, the doped copper-iron-manganese precursor is sintered so that the outer surface of the copper-iron-manganese precipitate sintered product is wrapped with a carbon layer, and a large number of nitrogen atoms and sulfur atoms are doped in the carbon layer. Carbon coating is the most commonly used method to improve the conductivity of materials, but the effect of improving the conductivity of materials only by coating carbon is limited. The doped nitrogen atoms can make the material have more active defects and improve the sodium ion diffusion ability. In addition, the doped sulfur atoms in the carbon material will have more excellent electrochemical performance because the edges and defect positions of the carbon lattice will be occupied by sulfur atoms, and the defect degree of the carbon-based material will increase with the doping of sulfur elements. Therefore, not only can the diffusion rate of sodium ions in the carbon layer be effectively increased, but also the electronic conductivity of the carbon layer can be significantly improved, thereby greatly improving the performance of the copper-iron-manganese cathode material;

[0041] In the process of preparing the sulfur-nitrogen in-situ co-doped copper-iron-manganese cathode material, an in-situ dopant is first prepared. First, the nitro group on p-nitrobenzaldehyde is reduced to an amino group by hydrogen to obtain intermediate 1. Then, 4'-hydroxyacetophenone and 2-bromo-2-methylpropionamide react through the Williamson ether synthesis method to synthesize an ether, and then undergo a Smiles rearrangement reaction to generate intermediate 2. Then, intermediate 2 undergoes a hydrolysis reaction to generate intermediate 3. Then, intermediate 1 and intermediate 3 react to obtain intermediate 4 containing an alkenyl group. Then, intermediate 4 is treated with formic acid and formic acid to introduce 2 methyl groups into the amino group to obtain intermediate 5. Then, intermediate 5 undergoes a nucleophilic substitution reaction with 2-thiophenesulfonyl chloride to form a quaternary ammonium group while introducing a sulfone group and a thiophene ring to obtain the in-situ dopant; the molecular structure of the in-situ dopant contains an alkenyl group and a thiophene ring, which can polymerize to form a polymer under the action of initiation to fully wrap the copper-iron-manganese precipitate, and provide a carbon source. After sintering, a sintered product of the copper-iron-manganese precipitate wrapped with a carbon layer can be formed. Moreover, the quaternary ammonium group, sulfone group, and thiophene ring can provide nitrogen atoms and sulfur atoms, enabling the carbon layer to be doped with nitrogen and sulfur heteroatoms to improve its conductivity. Moreover, the in-situ dopant has good surface activity, can promote the dispersion of the copper-iron-manganese precipitate and avoid its agglomeration, reduce its particle size, and further improve the compactness of the prepared copper-iron-manganese cathode material and further improve the electrochemical performance of the copper-iron-manganese cathode material. Detailed implementation mode

[0042] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0043] Example 1:

[0044] This example is a preparation method of an in-situ dopant, including the following steps:

[0045] Step s1: Add 0.1 mol of p-nitrobenzaldehyde, 80 mL of benzene, and 0.15 g of 10% palladium-carbon to the reaction kettle, introduce nitrogen to displace the air in the reaction kettle 2 times, and then while stirring, introduce hydrogen at a temperature of 100 °C and a stirring rate of 550 r / min, maintain the pressure in the reaction kettle at 1.6 MPa and stir for 6 h. After the reaction is completed, cool the reaction product to room temperature, and then rotate and evaporate the reaction product to remove the solvent to obtain intermediate 1;

[0046] Step s2: Add 0.1 mol of 4-hydroxyacetophenone and 80 mL of N,N-dimethylacetamide into a three-necked flask equipped with a stirrer and a thermometer. Stir and react for 30 min at a temperature of 20 °C and a stirring rate of 550 r / min. Then add 0.3 mol of 2-bromo-2-methylpropanamide and continue to stir and react for 5 h. Then add 35 g of sodium hydroxide and raise the temperature to 50 °C and continue to stir and react for 1 h. Then add 120 mL of deionized water and continue to stir and react for 20 min to precipitate crystals. Then perform vacuum filtration. Place the filter cake in a vacuum drying oven and dry it for 3 h at a temperature of 65 °C to obtain Intermediate 2;

[0047] Step s3: Add 0.1 mol of Intermediate 2, 100 mL of a 35% sodium hydroxide solution, and 100 mL of N,N-dimethylacetamide into a three-necked flask equipped with a stirrer, a thermometer, and a reflux condenser. Stir and heat to reflux at a stirring rate of 550 r / min, controlling the heating rate at 2 °C / min. Then continue to stir and react for 2 h. After the reaction is completed, add the reaction product to distilled water to precipitate crystals. Then perform vacuum filtration. Place the filter cake in a vacuum drying oven and dry it for 2 h at a temperature of 70 °C to obtain Intermediate 3;

[0048] Step s4: Add 0.1 mol of Intermediate 1, 0.12 mol of Intermediate 3, and 30 mL of absolute ethanol into a three-necked flask equipped with a stirrer and a thermometer. Stir and react for 30 min at a temperature of 20 °C and a stirring rate of 550 r / min. Then add 35 mL of a 5% sodium hydroxide solution and continue to stir and react for 10 h. After the reaction is completed, cool the reaction product to 0 °C. Then adjust the pH to 5 with a 15% hydrochloric acid solution to precipitate crystals. Then perform vacuum filtration. Place the filter cake in a vacuum drying oven and dry it for 8 h at a temperature of 45 °C to obtain Intermediate 4;

[0049] Step s5: Add 0.1 mol of Intermediate 4 and 50 mL of absolute ethanol into a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a constant pressure dropping funnel. Stir and react for 30 min at a temperature of 45 °C and a stirring rate of 550 r / min. Then, while stirring, gradually add dropwise 70 g of an 88% formic acid aqueous solution, controlling the dropping rate at 1 drop / s. After the dropping is completed, while stirring, gradually add dropwise 50 g of a 36% formaldehyde aqueous solution, controlling the dropping rate at 1 drop / s. After the dropping is completed, raise the temperature to reflux and continue to stir and react for 10 h. After the reaction is completed, cool the reaction product to room temperature. Then adjust the pH to 9 with a 30% sodium hydroxide solution. Then extract with ethyl acetate twice, combine the extraction solutions and dry them with anhydrous sodium sulfate. Then perform vacuum filtration. Rotate and evaporate the filtrate to remove the solvent to obtain Intermediate 5;

[0050] Step s6: Add 0.1 mol of intermediate 5, 0.22 mol of 2-thiophenesulfonyl chloride, 0.25 mol of potassium carbonate, and 120 mL of anhydrous acetonitrile into a three-necked flask equipped with a stirrer, a thermometer, and a reflux condenser. While stirring at a stirring rate of 550 r / min, heat up to reflux, control the heating rate at 2 °C / min, then continue stirring and reacting for 10 h. After the reaction is completed, add the reaction product into ice water, then extract it twice with ethyl acetate, combine the extraction liquid and dry it with anhydrous sodium sulfate, then perform vacuum filtration, and rotary evaporate the filtrate to remove the solvent to obtain the in-situ dopant.

[0051] Example 2:

[0052] The preparation method of an in-situ dopant in this example includes the following steps:

[0053] Step s1: Add 0.1 mol of p-nitrobenzaldehyde, 100 mL of benzene, and 0.3 g of 10% palladium-carbon into a reaction kettle, displace the air in the reaction kettle with nitrogen 3 times, then while stirring at a temperature of 110 °C and a stirring rate of 650 r / min, introduce hydrogen gas while stirring, maintain the pressure in the reaction kettle at 1.8 MPa and stir and react for 7 h. After the reaction is completed, cool the reaction product to room temperature, then rotary evaporate the reaction product to remove the solvent to obtain intermediate 1;

[0054] Step s2: Add 0.1 mol of p-hydroxyacetophenone and 100 mL of N,N-dimethylacetamide into a three-necked flask equipped with a stirrer and a thermometer. While stirring at a temperature of 25 °C and a stirring rate of 650 r / min, react for 50 min, then add 0.35 mol of 2-bromo-2-methylpropionamide and continue stirring and reacting for 6 h. Then add 40 g of sodium hydroxide and heat up to 55 °C and continue stirring and reacting for 1.5 h. Then add 150 mL of deionized water and continue stirring and reacting for 30 min to precipitate crystals. Then perform vacuum filtration, place the filter cake in a vacuum drying oven, and dry it at a temperature of 75 °C for 5 h to obtain intermediate 2;

[0055] Step s3: Add 0.1 mol of intermediate 2, 120 mL of a sodium hydroxide solution with a mass fraction of 40%, and 120 mL of N,N-dimethylacetamide into a three-necked flask equipped with a stirrer, a thermometer, and a reflux condenser. While stirring at a stirring rate of 650 r / min, heat up to reflux, control the heating rate at 3 °C / min, then continue stirring and reacting for 3 h. After the reaction is completed, add the reaction product into distilled water to precipitate crystals. Then perform vacuum filtration, place the filter cake in a vacuum drying oven, and dry it at a temperature of 80 °C for 3 h to obtain intermediate 3;

[0056] Step s4: Add 0.1 mol of intermediate 1, 0.15 mol of intermediate 3, and 40 mL of absolute ethanol into a three-necked flask equipped with a stirrer and a thermometer. Stir and react for 50 min under the conditions of a temperature of 25 °C and a stirring rate of 650 r / min. Then add 45 mL of a sodium hydroxide solution with a mass fraction of 8% and continue to stir and react for 15 h. After the reaction is completed, cool the reaction product to 5 °C, then adjust the pH to 6 with a hydrochloric acid solution with a mass fraction of 20% to precipitate crystals. Then perform vacuum filtration, place the filter cake in a vacuum drying oven, and dry it at a temperature of 50 °C for 10 h to obtain intermediate 4;

[0057] Step s5: Add 0.1 mol of intermediate 4 and 60 mL of absolute ethanol into a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a constant pressure dropping funnel. Stir and react for 50 min under the conditions of a temperature of 50 °C and a stirring rate of 650 r / min. Then, while stirring, gradually add dropwise 75 g of a formic acid aqueous solution with a mass fraction of 88%, control the dropping rate at 2 drops / s. After the addition is complete, while stirring, gradually add dropwise 55 g of a formaldehyde aqueous solution with a mass fraction of 36%, control the dropping rate at 2 drops / s. After the addition is complete, raise the temperature to reflux and continue to stir and react for 12 h. After the reaction is completed, cool the reaction product to room temperature, then adjust the pH to 10 with a sodium hydroxide solution with a mass fraction of 35%. Then extract with ethyl acetate 3 times, combine the extraction solutions and dry with anhydrous sodium sulfate. Then perform vacuum filtration, and rotary evaporate the filtrate to remove the solvent to obtain intermediate 5;

[0058] Step s6: Add 0.1 mol of intermediate 5, 0.25 mol of 2-thiophenesulfonyl chloride, 0.3 mol of potassium carbonate, and 150 mL of absolute acetonitrile into a three-necked flask equipped with a stirrer, a thermometer, and a reflux condenser. While stirring, heat up to reflux at a stirring rate of 650 r / min, control the heating rate at 3 °C / min. Then continue to stir and react for 15 h. After the reaction is completed, add the reaction product into ice water, then extract with ethyl acetate 3 times, combine the extraction solutions and dry with anhydrous sodium sulfate. Then perform vacuum filtration, and rotary evaporate the filtrate to remove the solvent to obtain the in-situ dopant.

[0059] Example 3:

[0060] This example is a preparation method of a sulfur and nitrogen in-situ co-doped copper iron manganese cathode material, including the following steps:

[0061] Step 1: Add 10 mmol of copper sulfate pentahydrate, 10 mmol of ferrous sulfate heptahydrate, 10 mmol of manganese sulfate monohydrate, and 40 mL of deionized water into a three-necked flask equipped with a stirrer, a thermometer, and a constant-pressure dropping funnel. Stir evenly under the conditions of a temperature of 55 °C and a stirring rate of 550 r / min. Then add 0.6 g of the in-situ dopant from Example 1 and continue stirring to obtain a copper-iron-manganese solution;

[0062] Step 2: While stirring, gradually add 15 mL of a 20% sodium hydroxide solution and 15 mL of a 2% ammonium persulfate solution dropwise into the copper-iron-manganese solution at a dropping rate of 1 drop / s. After the addition is complete, continue stirring and reacting at a temperature of 85 °C for 8 h. After the reaction is completed, cool the reaction product to room temperature, then perform vacuum filtration. Wash the filter cake 3 times with distilled water, and then add it to a vacuum drying oven and dry it at a temperature of 60 °C for 20 h to obtain a doped copper-iron-manganese precursor;

[0063] Step 3: Add the doped copper-iron-manganese precursor into a quartz glass tube, introduce argon for protection, sinter at a temperature of 350 °C for 5 h, then raise the temperature to 750 °C and sinter for 8 h, controlling the heating rate at 5 °C / min, and then cool with the furnace to obtain the sulfur-nitrogen in-situ co-doped copper-iron-manganese cathode material.

[0064] Example 4:

[0065] This example is a preparation method of a sulfur-nitrogen in-situ co-doped copper-iron-manganese cathode material, including the following steps:

[0066] Step 1: Add 10 mmol of copper sulfate pentahydrate, 10 mmol of ferrous sulfate heptahydrate, 10 mmol of manganese sulfate monohydrate, and 50 mL of deionized water into a three-necked flask equipped with a stirrer, a thermometer, and a constant-pressure dropping funnel. Stir evenly under the conditions of a temperature of 60 °C and a stirring rate of 650 r / min. Then add 2.2 g of the in-situ dopant from Example 2 and continue stirring to obtain a copper-iron-manganese solution;

[0067] Step 2: While stirring, gradually add 20 mL of a 25% sodium hydroxide solution and 20 mL of a 3% ammonium persulfate solution dropwise into the copper-iron-manganese solution at a dropping rate of 2 drops / s. After the addition is complete, continue stirring and reacting at a temperature of 90 °C for 10 h. After the reaction is completed, cool the reaction product to room temperature, then perform vacuum filtration. Wash the filter cake 5 times with distilled water, and then add it to a vacuum drying oven and dry it at a temperature of 65 °C for 30 h to obtain a doped copper-iron-manganese precursor;

[0068] Step 3: Add the doped copper-iron-manganese precursor into a quartz glass tube, introduce argon for protection, sinter at 360 °C for 6 h, then raise the temperature to 780 °C and sinter for 10 h, control the heating rate at 8 °C / min, and then cool with the furnace to obtain the sulfur-nitrogen in-situ co-doped copper-iron-manganese cathode material.

[0069] Comparative Example 1:

[0070] The difference between Comparative Example 1 and Example 4 is that no in-situ dopant and ammonium persulfate solution are added.

[0071] Comparative Example 2:

[0072] The difference between Comparative Example 2 and Example 4 is that no ammonium persulfate solution is added.

[0073] Mix the sulfur-nitrogen in-situ co-doped copper-iron-manganese cathode material, acetylene black, and polyvinylidene fluoride in Example 3-4 and Comparative Example 1-2 evenly according to the mass ratio of 8:1:1, then add N-methyl-2-pyrrolidone and mix evenly to form a copper-iron-manganese cathode slurry with a solid content of 47%. Then, use a scraper to evenly coat the copper-iron-manganese cathode slurry on the pre-laid and complete aluminum foil, place it in an oven, dry at 120 °C for 4 h, roll the dried electrode sheet with a roller press, and then punch it into a circular electrode sheet with a diameter of 14 mm to obtain the copper-iron-manganese cathode sheet;

[0074] Assemble the copper-iron-manganese cathode sheet into a CR2016 type button cell in a glove box filled with argon, use 1M NaClO4 / PC solution as the electrolyte, WhatMan DF / D as the separator, and metallic sodium as the anode;

[0075] Detect the performance of the CR2016 type button cell, the test conditions are 25 °C, the voltage range is 2.8 - 4.0 V, and the rate is 0.1C. The test results are shown in the following table:

[0076] Sample <![CDATA[Initial charge specific capacity, mAh·g -1 > <![CDATA[Initial discharge specific capacity, mAh·g -1 > Coulomb efficiency, % Example 3 189.2 169.1 89.4 Example 4 193.8 181.2 93.5 Comparative Example 1 132.8 106.0 79.8 Comparative Example 2 175.6 151.4 86.2

[0077] Referring to the data in the above table and comparing according to Example 3-4 and Comparative Example 1-2, it can be known that adding the in-situ dopant can significantly improve the electrochemical performance of the copper-iron-manganese cathode material, and adding ammonium persulfate after adding the in-situ dopant can further improve the electrochemical performance of the copper-iron-manganese cathode material. The finally prepared sulfur-nitrogen in-situ co-doped copper-iron-manganese cathode material has good charge-discharge capacity and high Coulomb efficiency.

[0078] In the description of this specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0079] The above content is only an example and illustration of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar ways to substitute, as long as they do not deviate from the invention or exceed the scope defined by this claim book, they should all fall within the protection scope of the present invention.

Claims

1. A preparation method of a sulfur and nitrogen co-doped copper-iron-manganese cathode material in-situ, characterized in that, It includes the following steps: Step 1: Add copper sulfate pentahydrate, ferrous sulfate heptahydrate, manganese sulfate monohydrate, and deionized water into a three-necked flask, stir evenly, and then add the in-situ dopant and continue to stir to obtain a copper-iron-manganese solution; Step 2: Dropwise add sodium hydroxide solution and ammonium persulfate solution into the copper-iron-manganese solution. After the addition is completed, continue to stir and react. After the reaction ends, cool the reaction product to room temperature, then conduct vacuum filtration. Wash and dry the filter cake to obtain a doped copper-iron-manganese precursor; Step 3: Add the doped copper-iron-manganese precursor into a quartz glass tube for sintering to obtain the sulfur-nitrogen in-situ co-doped copper-iron-manganese cathode material; The in-situ dopant is prepared by the following steps: Step s1: Add p-nitrobenzaldehyde, benzene, and 10% palladium-carbon into a reaction kettle, stir while introducing hydrogen and stir to react. After the reaction ends, cool the reaction product to room temperature, and then rotary evaporate the reaction product to obtain Intermediate 1; Step s2: Add p-hydroxyacetophenone and N,N-dimethylacetamide into a three-necked flask and stir to react. Then, successively add 2-bromo-isobutyramide, sodium hydroxide, and deionized water and continue to stir to react to precipitate crystals. Then conduct vacuum filtration. Dry the filter cake to obtain Intermediate 2; Step s3: Add Intermediate 2, sodium hydroxide solution, and N,N-dimethylacetamide into a three-necked flask and stir to react. After the reaction ends, add the reaction product into distilled water to precipitate crystals. Then conduct vacuum filtration. Dry the filter cake to obtain Intermediate 3; Step s4: Add Intermediate 1, Intermediate 3, and absolute ethanol into a three-necked flask and stir to react. Then add sodium hydroxide solution and continue to stir to react. After the reaction ends, cool the reaction product, then adjust the pH to precipitate crystals. Then conduct vacuum filtration. Dry the filter cake to obtain Intermediate 4; Step s5: Add Intermediate 4 and absolute ethanol into a four-necked flask and stir to react. Then, successively dropwise add formic acid aqueous solution and formaldehyde aqueous solution. After the addition is completed, continue to stir to react. After the reaction ends, cool the reaction product to room temperature, then adjust the pH, then conduct extraction. Dry the extract, then conduct vacuum filtration. Rotary evaporate the filtrate to obtain Intermediate 5; Step s6: Add Intermediate 5, 2-thiophenesulfonyl chloride, potassium carbonate, and absolute acetonitrile into a three-necked flask and stir to react. After the reaction ends, add the reaction product into ice water, then conduct extraction. Dry the extract, then conduct vacuum filtration. Rotary evaporate the filtrate to obtain the in-situ dopant.

2. The preparation method of a sulfur and nitrogen in-situ co-doped copper-iron-manganese cathode material according to claim 1, characterized in that The dosage ratios of the copper sulfate pentahydrate, ferrous sulfate heptahydrate, manganese sulfate monohydrate, deionized water, in-situ dopant, sodium hydroxide solution, and ammonium persulfate solution are 10 mmol: 10 mmol: 10 mmol: 40 - 50 mL: 0.6 - 2.2 g: 15 - 20 mL: 15 - 20 mL. The mass fraction of the sodium hydroxide solution is 30 - 35%, and the mass fraction of the ammonium persulfate solution is 2 - 3%.

3. The preparation method of a sulfur and nitrogen co-doped copper-iron-manganese cathode material in-situ according to claim 1, characterized in that, The dosage ratios of the p-nitrobenzaldehyde, benzene, and 10% palladium-carbon in Step s1 are 0.1 mol: 80 - 100 mL: 0.15 - 0.3 g.

4. The preparation method of a sulfur and nitrogen in-situ co-doped copper iron manganese cathode material according to claim 1, characterized in that, The dosage ratio of the p-hydroxyacetophenone, N,N-dimethylacetamide, 2-bromo-2-methylpropionamide, sodium hydroxide and deionized water in step s2 is 0.1 mol: 80 - 100 mL: 0.3 - 0.35 mol: 35 - 40 g: 120 - 150 mL.

5. The preparation method of a sulfur and nitrogen co-doped copper-iron-manganese cathode material in-situ according to claim 1, characterized in that, The dosage ratio of the intermediate 2, sodium hydroxide solution and N,N-dimethylacetamide in step s3 is 0.1 mol: 100 - 120 mL: 100 - 120 mL, and the mass fraction of the sodium hydroxide solution is 35 - 40%.

6. The preparation method of a sulfur and nitrogen in-situ co-doped copper-iron-manganese cathode material according to claim 1, characterized in that The dosage ratio of the intermediate 1, intermediate 3, absolute ethanol and sodium hydroxide solution in step s4 is 0.1 mol: 0.12 - 0.15 mol: 30 - 40 mL: 35 - 45 mL, and the mass fraction of the sodium hydroxide solution is 5 - 8%.

7. The preparation method of a sulfur and nitrogen co-doped copper iron manganese cathode material according to claim 1, characterized in that, The dosage ratio of the intermediate 4, absolute ethanol, formic acid aqueous solution and formaldehyde aqueous solution in step s5 is 0.1 mol: 50 - 60 mL: 70 - 75 g: 50 - 55 g, the mass fraction of the formic acid aqueous solution is 88%, and the mass fraction of the formaldehyde aqueous solution is 36%.

8. The preparation method of a sulfur and nitrogen in-situ co-doped copper-iron-manganese cathode material according to claim 1, wherein, The dosage ratio of the intermediate 5, 2-thiophenesulfonyl chloride, potassium carbonate and anhydrous acetonitrile in step s6 is 0.1 mol: 0.22 - 0.25 mol: 0.25 - 0.3 mol: 120 - 150 mL.

9. A sulfur and nitrogen co-doped copper-iron-manganese cathode material in situ, characterized in that, The sulfur and nitrogen in-situ co-doped copper iron manganese cathode material is prepared according to the preparation method of the sulfur and nitrogen in-situ co-doped copper iron manganese cathode material according to any one of claims 1 - 8.

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