Sodium-ion battery rosin-based nitrogen-doped hard carbon anode material and its preparation method

Abstract

This invention discloses a rosin-based nitrogen-doped hard carbon anode material for sodium-ion batteries and its preparation method, comprising the following steps: heat-treating a hard carbon precursor material and pulverizing it using an air jet mill to obtain hard carbon powder; uniformly mixing a nitrogen source, rosin, and deionized water, heat-treating the mixture, cooling it, and then pulverizing and sieving it using a sand mill to obtain rosin-based nitrogen-doped powder; uniformly mixing the hard carbon powder and the rosin-based nitrogen-doped powder, adding sodium carboxymethyl cellulose, and stirring until uniform to obtain a mixture; carbonizing the mixture, cooling it, transferring it to an acidic solution, washing, drying, grinding, and sieving it to obtain the anode material. The rosin-based nitrogen-doped hard carbon anode material of this invention has an average volumetric particle size (Dv50) of 4.3–6.1 μm and a specific surface area of ​​4.8–11.7 m². 2 / g, 0.1C first reversible capacity ≥320.9mAh / g, up to 460.4Ah / g, 0.1C first charge-discharge coulombic efficiency ≥81.9%, up to 90.3%.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery materials, and in particular to rosin-based nitrogen-doped hard carbon anode materials for sodium-ion batteries and their preparation methods. Background Technology

[0002] With the rapid development of large-scale smart grids and the widespread application of electric vehicles, lithium resources cannot meet the huge demand for lithium-ion batteries, making it essential to develop energy storage technologies that can replace lithium-ion batteries.

[0003] Currently, commonly used anode materials for sodium-ion batteries include carbon materials, metal oxides / sulfides, or alloys. Hard carbon materials are effective in increasing battery output power due to their stable structure, long cycle life, high lithium intercalation potential, high safety, and microcrystalline structure that facilitates sodium ion movement. However, hard carbon materials are not widely used and their development is challenging. A significant reason is their low energy density; the capacity of most prepared hard carbon materials is between 250 mAh / g and 300 mAh / g, with an initial efficiency typically between 75% and 80%. A balance between cost and performance cannot be achieved, significantly limiting the mass production of hard carbon materials. Summary of the Invention

[0004] To overcome the shortcomings mentioned above, this invention provides a rosin-based nitrogen-doped hard carbon anode material for sodium-ion batteries and its preparation method, solving the problems of low energy density and poor first charge-discharge coulombic efficiency of hard carbon anode materials for sodium-ion batteries.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A rosin-based nitrogen-doped hard carbon anode material for sodium-ion batteries and its preparation method include the following steps:

[0007] (1) The hard carbon precursor material is heat-treated in an inert atmosphere, cooled and then pulverized by air jet milling to obtain hard carbon powder.

[0008] (2) Mix nitrogen source, rosin and deionized water evenly, then heat treat, cool and then crush in a sand mill and sieve to obtain rosin-based nitrogen doped powder;

[0009] (3) Mix the hard carbon powder and rosin-based nitrogen-doped powder evenly, add sodium carboxymethyl cellulose, stir evenly to obtain a mixture; carbonize the mixture under an inert atmosphere, cool it and transfer it to an acidic solution, stir, wash and filter until neutral, dry, grind and sieve to obtain rosin-based nitrogen-doped hard carbon anode material for sodium-ion batteries.

[0010] Preferably, the hard carbon material in step (1) is one or more of cellulose, hemicellulose, and lignin.

[0011] Preferably, the hard carbon material in step (1) is cellulose, hemicellulose and lignin, and the mass ratio of the cellulose to the total mass of the hemicellulose and lignin is 0.1 to 0.9.

[0012] Preferably, the heat treatment in step (1) is performed at a heating temperature of 200℃~700℃ for 2~6 hours; the average volumetric particle size Dv50 of the hard carbon powder is controlled at 4~10μm, and the specific surface area is 5.4~18.4m². 2 / g.

[0013] Preferably, the heat treatment in step (2) is drying at 200°C for 12 hours under a nitrogen atmosphere; the mass ratio of the nitrogen source to the rosin is 0.1 to 0.9; and the average volume particle size Dv50 of the rosin-based nitrogen-doped powder is controlled at 4 to 10 μm.

[0014] Preferably, the rosin in step (2) is resin rosin, wood rosin, or floating oil rosin; the nitrogen source is one or more of urea, melamine, biuret, and aniline.

[0015] Preferably, in step (3), the mass ratio of the hard carbon powder to the rosin-based nitrogen-doped powder is 0.1 to 0.9, and the mass ratio of the added sodium carboxymethyl cellulose to the total mass of the hard carbon powder and the rosin-based nitrogen-doped powder is 0.11 to 0.43.

[0016] Preferably, in step (3), the carbonization of the mixture is carried out at a temperature of 900℃~1500℃ for 2~6h; the acidic solution is an acetic acid solution, hydrochloric acid solution, sulfuric acid solution or nitric acid solution.

[0017] Preferably, the inert atmosphere is nitrogen or argon gas, and the gas flow rate is 1-5 L / min.

[0018] This invention also provides a rosin-based nitrogen-doped hard carbon anode material for sodium-ion batteries. The rosin-based nitrogen-doped hard carbon anode material is prepared using the method described above. The average volumetric particle size Dv50 of the rosin-based nitrogen-doped hard carbon anode material is 4.3–6.1 μm, and the specific surface area is 4.8–11.7 m². 2 / g, 0.1C initial reversible capacity ≥320.9mAh / g, 0.1C initial charge / discharge coulombic efficiency ≥81.9%.

[0019] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention uses hard carbon material as the main body and a specially selected nitrogen source mixed with rosin as the coating. The coated hard carbon material has chemical stability, high mechanical strength, and a large specific surface area. The coating layer can provide a large number of electroactive sites, forming a short ion channel and generating high conductivity, resulting in significantly improved electrochemical performance. The average volumetric particle size Dv50 of the material is 4.3–6.1 μm, and the specific surface area is 4.8–11.7 μm. 2 / g, 0.1C initial reversible capacity ≥320.9mAh / g, up to 460.4Ah / g, 0.1C initial charge-discharge coulombic efficiency ≥81.9%, up to 90.3%; Rosin-based nitrogen-doped hard carbon materials can effectively inhibit the aggregation of nanoparticles, thereby inhibiting the reduction of specific surface area, increasing the attachment sites of sodium ions, and thus improving the capacity of hard carbon. Attached Figure Description

[0020] Figure 1 The first charge-discharge curve of the hard carbon anode material prepared in Example 1 is shown.

[0021] Figure 2 The first charge-discharge curve of the hard carbon anode material prepared in Example 2 is shown.

[0022] Figure 3 The first charge-discharge curve of the hard carbon anode material prepared in Example 3 is shown.

[0023] Figure 4 The first charge-discharge curve of the hard carbon anode material prepared in Example 4 is shown.

[0024] Figure 5 The first charge-discharge curve of the hard carbon anode material prepared in Example 5 is shown.

[0025] Figure 6 The first charge-discharge curve of the hard carbon anode material prepared in Example 6 is shown.

[0026] Figure 7 The first charge-discharge curve of the hard carbon anode material prepared in Example 7 is shown.

[0027] Figure 8 The first charge-discharge curve of the hard carbon anode material prepared in Example 8 is shown.

[0028] Figure 9 The first charge-discharge curve of the hard carbon anode material prepared in Example 9 is shown.

[0029] Figure 10 The first charge-discharge curve of the hard carbon anode material prepared in Example 10 is shown. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to specific implementation methods. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] (1) Weigh 1 kg of cellulose and place it in a corundum crucible. Place the corundum crucible in a heating furnace and keep it at 350°C for 4 hours with a nitrogen flow rate of 1 L / min. After the temperature inside the heating furnace drops to room temperature, take out the crucible and remove the material inside the crucible. Then, use an air jet mill to pulverize the material and sieve it to control the average volume particle size Dv50 of the output material to 4 μm to obtain hard carbon powder.

[0033] (2) Urea and rosin were placed into a 1000ml beaker at mass ratios of 9.5g and 90.5g respectively. 500ml of deionized water was added and stirred evenly. The mixture was then placed in a nitrogen oven and dried at 200℃ for 12h. After cooling, it was pulverized by a sand mill and sieved to control the average volume particle size Dv50 of the output to 10μm. The rosin-based nitrogen-doped powder was obtained by passing it through a 500-mesh sieve.

[0034] (3) Take 9.5g of hard carbon powder and mix it evenly with 90.5g of rosin-based nitrogen doped powder. Then add 11g of sodium carboxymethyl cellulose. After stirring the mixture evenly, put it into a corundum crucible and place it in a tube furnace. Carbonize it in an environment with a nitrogen flow rate of 3L / min. The carbonization temperature is 900℃ and the carbonization holding time is 6 hours. After the temperature inside the tube furnace drops to room temperature, take it out and immerse it in acetic acid solution. Stir it thoroughly and then rinse it with deionized water until it is neutral. Dry it, grind it and pass it through a 500-mesh sieve to obtain the sodium-ion battery rosin-based nitrogen doped coated hard carbon anode material.

[0035] Example 2

[0036] (1) Weigh 1 kg of hemicellulose and place it in a corundum crucible. Place the corundum crucible in a heating furnace and keep it at 350°C for 6 hours with a nitrogen flow rate of 1.5 L / min. After the temperature inside the heating furnace drops to room temperature, take out the crucible and remove the material inside the crucible. Then, use an air jet mill to pulverize the material and sieve it to control the average volume particle size Dv50 of the output to 10 μm to obtain hard carbon powder.

[0037] (2) Urea and rosin were placed into a 1000ml beaker at mass of 20g and 80g respectively. 500ml of deionized water was added and stirred evenly. The mixture was then placed in a nitrogen oven and dried at 200℃ for 12h. After cooling, it was pulverized by a sand mill and sieved to control the average volume particle size Dv50 of the output to 6μm. The rosin-based nitrogen-doped powder was obtained by passing it through a 500-mesh sieve.

[0038] (3) Take 20g of hard carbon powder and mix it evenly with 80g of rosin-based nitrogen doped powder. Then add 27.5g of sodium carboxymethyl cellulose. After stirring the mixture evenly, put it into a corundum crucible and place it in a tube furnace. Carbonize it in an environment with a nitrogen flow rate of 5L / min. The carbonization temperature is 900℃ and the carbonization holding time is 6 hours. After the temperature inside the tube furnace drops to room temperature, take it out and immerse it in acetic acid solution. Stir it thoroughly and then rinse it with deionized water until it is neutral. Dry it, grind it and pass it through a 500-mesh sieve to obtain the sodium-ion battery rosin-based nitrogen doped coated hard carbon anode material.

[0039] Example 3

[0040] (1) Weigh 1 kg of lignin and place it in a corundum crucible. Place the corundum crucible in a heating furnace and keep it at 700℃ for 2 hours under the conditions of nitrogen flow rate of 1.5 L / min and heating temperature of 700℃. After the temperature inside the heating furnace drops to room temperature, take out the crucible and remove the material inside the crucible. Then, use an air jet mill to pulverize the material and sieve it to control the average volume particle size Dv50 of the output material to 6 μm to obtain hard carbon powder.

[0041] (2) Melamine and rosin were loaded into a 1000ml beaker at a ratio of 30g and 70g by mass, 500ml of deionized water was added and stirred evenly. The mixture was then placed in a nitrogen oven and dried at 200℃ for 12h. After cooling, it was pulverized by a sand mill and sieved to control the average volume particle size Dv50 of the output to 10μm. The rosin-based nitrogen-doped powder was obtained by passing it through a 500-mesh sieve.

[0042] (3) Take 30g of hard carbon powder and 70g of rosin-based nitrogen doped powder and mix them evenly. Then add 43g of sodium carboxymethyl cellulose. After stirring the mixture evenly, put it into a corundum crucible and place it in a tube furnace. Carbonize it in an environment with a nitrogen flow rate of 5L / min. The carbonization temperature is 900℃ and the carbonization holding time is 5 hours. After the temperature inside the tube furnace drops to room temperature, take it out and immerse it in hydrochloric acid solution. Stir it thoroughly and then rinse it with deionized water and filter it until neutral. Dry it, grind it and pass it through a 500-mesh sieve to obtain the sodium-ion battery rosin-based nitrogen doped coated hard carbon anode material.

[0043] Example 4

[0044] (1) Weigh 0.1 kg of cellulose, 0.4 kg of hemicellulose and 0.5 kg of lignin and place them in a corundum crucible. Place the corundum crucible in a heating furnace and keep it at 200°C for 6 hours with a nitrogen flow rate of 1 L / min. After the temperature inside the heating furnace drops to room temperature, take out the crucible and remove the material inside. Then, use an air jet mill to pulverize the material and sieve it to control the average volume particle size Dv50 of the output to 4 μm to obtain hard carbon powder.

[0045] (2) Urea and floating rosin were loaded into a 1000ml beaker at a ratio of 40g and 60g by mass, 500ml of deionized water was added and stirred evenly. The mixture was then placed in a nitrogen oven and dried at 200℃ for 12h. After cooling, it was pulverized by a sand mill and sieved to control the average volume particle size Dv50 of the output to 4μm. The rosin-based nitrogen-doped powder was obtained by passing it through a 500-mesh sieve.

[0046] (3) Take 40g of hard carbon powder and 60g of rosin-based nitrogen doped powder and mix them evenly. Then add 30g of sodium carboxymethyl cellulose. After stirring the mixture evenly, put it into a corundum crucible and place it in a tube furnace. Carbonize it in an environment with a nitrogen flow rate of 5L / min. The carbonization temperature is 900℃ and the carbonization holding time is 6 hours. After the temperature inside the tube furnace drops to room temperature, take it out and immerse it in sulfuric acid solution. Stir it thoroughly and then rinse it with deionized water and filter it until neutral. Dry it, grind it and pass it through a 500-mesh sieve to obtain the sodium-ion battery rosin-based nitrogen doped coated hard carbon anode material.

[0047] Example 5

[0048] (1) Weigh 0.47 kg of cellulose, 0.3 kg of hemicellulose and 0.23 kg of lignin and place them in a corundum crucible. Place the corundum crucible in a heating furnace and keep it at 450°C for 6 hours with a nitrogen flow rate of 1 L / min. After the temperature inside the heating furnace drops to room temperature, take out the crucible and remove the material inside. Then, use an air jet mill to pulverize the material and sieve it to control the average volume particle size Dv50 of the output to 4 μm to obtain hard carbon powder.

[0049] (2) Aniline and rosin were loaded into a 1000ml beaker at a ratio of 45g and 55g by mass, respectively. 500ml of deionized water was added and stirred evenly. The mixture was then placed in a nitrogen oven and dried at 200℃ for 12h. After cooling, it was pulverized by a sand mill and sieved to control the average volume particle size Dv50 of the output to 8μm. The rosin-based nitrogen-doped powder was obtained by passing it through a 500-mesh sieve.

[0050] (3) Take 45g of hard carbon powder and 55g of rosin-based nitrogen doped powder and mix them evenly. Then add 11g of sodium carboxymethyl cellulose. After stirring the mixture evenly, put it into a corundum crucible and place it in a tube furnace. Carbonize it in an environment with a nitrogen flow rate of 5L / min. The carbonization temperature is 1300℃ and the carbonization holding time is 2 hours. After the temperature inside the tube furnace drops to room temperature, take it out and immerse it in nitric acid solution. Stir it thoroughly and then rinse it with deionized water and filter it until neutral. Dry it, grind it and pass it through a 500-mesh sieve to obtain the sodium-ion battery rosin-based nitrogen doped coated hard carbon anode material.

[0051] Example 6

[0052] (1) Weigh 0.2 kg of cellulose, 0.5 kg of hemicellulose and 0.3 kg of lignin and place them in a corundum crucible. Place the corundum crucible in a heating furnace and keep it at 450°C for 6 hours under the conditions of nitrogen flow rate of 1 L / min and heating temperature of 450°C. After the temperature inside the heating furnace drops to room temperature, take out the crucible and remove the material inside the crucible. Then, use an air jet mill to pulverize the material and sieve it to control the average volume particle size Dv50 of the output material to 4 μm to obtain hard carbon powder.

[0053] (2) Aniline and floating rosin were loaded into a 1000ml beaker at a mass ratio of 47g and 53g respectively. 500ml of deionized water was added and stirred evenly. The mixture was then placed in a nitrogen oven and dried at 200℃ for 12h. After cooling, it was pulverized by a sand mill and sieved to control the average volume particle size Dv50 of the output to 4μm. The rosin-based nitrogen-doped powder was obtained by passing it through a 500-mesh sieve.

[0054] (3) Take 47g of hard carbon powder and 53g of rosin-based nitrogen doped powder and mix them evenly. Then add 16.5g of sodium carboxymethyl cellulose. After stirring the mixture evenly, put it into a corundum crucible and place it in a tube furnace. Carbonize it in an environment with a nitrogen flow rate of 5L / min. The carbonization temperature is 1300℃ and the carbonization holding time is 5 hours. After the temperature inside the tube furnace drops to room temperature, take it out and immerse it in acetic acid solution. Stir it thoroughly and then rinse it with deionized water and filter it until neutral. Dry it, grind it and pass it through a 500-mesh sieve to obtain the sodium-ion battery rosin-based nitrogen doped coated hard carbon anode material.

[0055] Example 7

[0056] (1) Weigh 0.3 kg of cellulose, 0.4 kg of hemicellulose and 0.3 kg of lignin and place them in a corundum crucible. Place the corundum crucible in a heating furnace and keep it at 450°C for 6 hours with a nitrogen flow rate of 1 L / min. After the temperature inside the heating furnace drops to room temperature, take out the crucible and remove the material inside. Then, use an air jet mill to pulverize the material and sieve it to control the average volume particle size Dv50 of the output to 4 μm to obtain hard carbon powder.

[0057] (2) Biuret and rosin were loaded into a 1000ml beaker at a ratio of 20g and 80g by mass, 500ml of deionized water was added and stirred evenly. The mixture was then placed in a nitrogen oven and dried at 200℃ for 12h. After cooling, it was pulverized by a sand mill and sieved to control the average volume particle size Dv50 of the output to 4μm. The rosin-based nitrogen-doped powder was obtained by passing it through a 500-mesh sieve.

[0058] (3) Take 47g of hard carbon powder and 53g of rosin-based nitrogen doped powder and mix them evenly. Then add 39g of sodium carboxymethyl cellulose. After stirring the mixture evenly, put it into a corundum crucible and place it in a tube furnace. Carbonize it in an environment with a nitrogen flow rate of 5L / min. The carbonization temperature is 1300℃ and the carbonization holding time is 3 hours. After the temperature inside the tube furnace drops to room temperature, take it out and immerse it in acetic acid solution. Stir it thoroughly and then rinse it with deionized water and filter it until neutral. Dry it, grind it and pass it through a 500-mesh sieve to obtain the sodium-ion battery rosin-based nitrogen doped coated hard carbon anode material.

[0059] Example 8

[0060] (1) Weigh 0.4 kg of cellulose, 0.3 kg of hemicellulose and 0.3 kg of lignin and place them in a corundum crucible. Place the corundum crucible in a heating furnace and keep it at 450°C for 6 hours with a nitrogen flow rate of 1 L / min. After the temperature inside the heating furnace drops to room temperature, take out the crucible and remove the material inside. Then, use an air jet mill to pulverize the material and sieve it to control the average volume particle size Dv50 of the output material to 4 μm to obtain hard carbon powder.

[0061] (2) Biuret and rosin were placed in a 1000ml beaker at a ratio of 47g and 53g by mass, respectively. 500ml of deionized water was added and stirred evenly. The mixture was then placed in a nitrogen oven and dried at 200℃ for 12h. After cooling, it was pulverized by a sand mill and sieved to control the average volume particle size Dv50 of the output to 4μm. The rosin-based nitrogen-doped powder was obtained by passing it through a 500-mesh sieve.

[0062] (3) Take 20g of hard carbon powder and mix it evenly with 80g of rosin-based nitrogen doped powder. Then add 25.6g of sodium carboxymethyl cellulose. After stirring the mixture evenly, put it into a corundum crucible and place it in a tube furnace. Carbonize it in an environment with an argon flow rate of 5L / min. The carbonization temperature is 1500℃ and the carbonization holding time is 2 hours. After the temperature inside the tube furnace drops to room temperature, take it out and immerse it in acetic acid solution. Stir it thoroughly and then rinse it with deionized water until it is neutral. Dry it, grind it and pass it through a 500-mesh sieve to obtain the sodium-ion battery rosin-based nitrogen doped coated hard carbon anode material.

[0063] Example 9

[0064] (1) Weigh 0.3 kg of cellulose, 0.3 kg of hemicellulose and 0.4 kg of lignin and place them in a corundum crucible. Place the corundum crucible in a heating furnace and keep it at 450°C for 6 hours with a nitrogen flow rate of 1 L / min. After the temperature inside the heating furnace drops to room temperature, take out the crucible and remove the material inside. Then, use an air jet mill to pulverize the material and sieve it to control the average volume particle size Dv50 of the output material to 4 μm to obtain hard carbon powder.

[0065] (2) Melamine and rosin were loaded into a 1000ml beaker at a ratio of 20g and 80g by mass, 500ml of deionized water was added and stirred evenly. The mixture was then placed in a nitrogen oven and dried at 200℃ for 12h. After cooling, it was pulverized by a sand mill and sieved to control the average volume particle size Dv50 of the output material to 4μm. The material was then passed through a 500-mesh sieve to obtain rosin-based nitrogen-doped powder.

[0066] (3) Take 47.3g of hard carbon powder and 52.7g of rosin-based nitrogen doped powder and mix them evenly. Then add 11g of sodium carboxymethyl cellulose. After stirring the mixture evenly, put it into a corundum crucible and place it in a tube furnace. Carbonize it in an environment with a nitrogen flow rate of 5L / min. The carbonization temperature is 1500℃ and the carbonization holding time is 3 hours. After the temperature inside the tube furnace drops to room temperature, take it out and immerse it in acetic acid solution. Stir it thoroughly and then rinse it with deionized water and filter it until neutral. Dry it, grind it and pass it through a 500-mesh sieve to obtain the sodium-ion battery rosin-based nitrogen doped coated hard carbon anode material.

[0067] Example 10

[0068] (1) Weigh 0.4 kg of cellulose, 0.5 kg of hemicellulose and 0.1 kg of lignin and place them in a corundum crucible. Place the corundum crucible in a heating furnace and keep it at 450°C for 6 hours with a nitrogen flow rate of 1 L / min. After the temperature inside the heating furnace drops to room temperature, take out the crucible and remove the material inside. Then, use an air jet mill to pulverize the material and sieve it to control the average volume particle size Dv50 of the output to 4 μm to obtain hard carbon powder.

[0069] (2) Melamine and rosin were loaded into a 1000ml beaker at a ratio of 47.3g and 52.7g by mass, respectively. 500ml of deionized water was added and stirred evenly. The mixture was then placed in a nitrogen oven and dried at 200℃ for 12h. After cooling, it was pulverized by a sand mill and sieved to control the average volume particle size Dv50 of the output to 4μm. The rosin-based nitrogen-doped powder was obtained by passing it through a 500-mesh sieve.

[0070] (3) Take 20g of hard carbon powder and mix it evenly with 80g of rosin-based nitrogen doped powder. Then add 16.5g of sodium carboxymethyl cellulose. After stirring the mixture evenly, put it into a corundum crucible and place it in a tube furnace. Carbonize it in an environment with a nitrogen flow rate of 5L / min. The carbonization temperature is 1500℃ and the carbonization holding time is 5 hours. After the temperature inside the tube furnace drops to room temperature, take it out and immerse it in acetic acid solution. Stir it thoroughly and then rinse it with deionized water until it is neutral. Dry it, grind it and pass it through a 500-mesh sieve to obtain the sodium-ion battery rosin-based nitrogen doped coated hard carbon anode material.

[0071] Electrochemical performance testing:

[0072] The preparation and testing method of the half-cell is as follows: A polyvinylidene fluoride (PVDF) solution with a mass fraction of 6-7% was prepared using N-methylpyrrolidone as a solvent. The sodium-ion battery rosin-based nitrogen-doped hard carbon anode material prepared in Examples 1-10, PVDF, and conductive carbon black were mixed uniformly at a mass ratio of 90:5:5 and coated onto copper foil. The coated electrode was then placed in a vacuum drying oven at 110°C and vacuum dried for 4 hours for later use. It was then punched into small discs with a diameter of 14 mm. These discs were then transferred to an argon-filled glove box in Micron, Germany, and assembled into 2430 coin cells. A three-component mixed solvent of 1 mol / L NaPF6 at a volume ratio of EC:DMC:EMC = 1:1:1 was used as the electrolyte. A sodium metal sheet was used as the counter electrode, and a 16 μm thick Ube membrane was used as the separator. The electrochemical performance of the assembled half-cell was tested using an Arbin electrochemical detection system in the United States. The charge / discharge voltage range was 0 V to 2.0 V, and the rate was 0.1 C. Figures 1-10 Examples 1-10 present rosin-based nitrogen-doped hard carbon anode materials for sodium-ion batteries.

[0073] Particle size testing: Malvern MS2000 laser particle size analyzer;

[0074] Specific surface area test: Konta specific surface area determination NOVA2000e.

[0075] The test results are shown in Table 1:

[0076] Table 1

[0077]

[0078] As shown in Table 1, the average volumetric particle size Dv50 of the rosin-based nitrogen-doped coated hard carbon anode material prepared by this invention is 4.3–6.1 μm, and the specific surface area is 4.8–11.7 m². 2 / g, 0.1C first reversible capacity ≥320.9mAh / g, up to 460.4Ah / g, 0.1C first charge-discharge coulombic efficiency ≥81.9%, up to 90.3%.

[0079] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing a rosin-based nitrogen-doped hard carbon anode material for sodium-ion batteries, characterized in that: Includes the following steps: (1) Cellulose, hemicellulose, and lignin are heat-treated under an inert atmosphere, wherein the mass ratio of cellulose to the total mass of hemicellulose and lignin is 0.1–0.

9. After cooling, the mixture is pulverized by an air jet mill to obtain hard carbon powder. The average volumetric particle size Dv50 of the hard carbon powder is controlled at 4–10 μm, and the specific surface area is 5.4–18.4 m². 2 / g; (2) Mix nitrogen source, rosin and deionized water evenly, then heat treat, cool and then crush in a sand mill and sieve to obtain rosin-based nitrogen doped powder; (3) Mix hard carbon powder and rosin-based nitrogen doped powder evenly, wherein the mass ratio of hard carbon powder to rosin-based nitrogen doped powder is 0.1 to 0.

9. Add sodium carboxymethyl cellulose and stir evenly to obtain a mixture. Carbonize the mixture under an inert atmosphere, cool it and transfer it to an acidic solution, stir, wash and filter until neutral, dry, grind and sieve to obtain sodium-ion battery rosin-based nitrogen doped coated hard carbon anode material.

2. The method for preparing the rosin-based nitrogen-doped hard carbon anode material for sodium-ion batteries according to claim 1, characterized in that: The heat treatment in step (1) is a heating temperature of 200℃~700℃ and a holding time of 2~6h.

3. The method for preparing the rosin-based nitrogen-doped hard carbon anode material for sodium-ion batteries according to claim 1, characterized in that: The heat treatment in step (2) is drying at 200°C for 12 hours under a nitrogen atmosphere; the mass ratio of the nitrogen source to the rosin is 0.1 to 0.9; and the average volume particle size Dv50 of the rosin-based nitrogen-doped powder is controlled at 4 to 10 μm.

4. The method for preparing the rosin-based nitrogen-doped hard carbon anode material for sodium-ion batteries according to claim 3, characterized in that: The rosin mentioned in step (2) is resin rosin, wood rosin or floating oil rosin; the nitrogen source is one or more of urea, melamine, biuret and aniline.

5. The method for preparing the rosin-based nitrogen-doped hard carbon anode material for sodium-ion batteries according to claim 1, characterized in that: The mass ratio of sodium carboxymethyl cellulose in step (3) to the total mass of the hard carbon powder and rosin-based nitrogen-doped powder is 0.11 to 0.

43.

6. The method for preparing the rosin-based nitrogen-doped hard carbon anode material for sodium-ion batteries according to claim 1, characterized in that: In step (3), the carbonization process involves holding the mixture at a temperature of 900℃ to 1500℃ for 2 to 6 hours; the acidic solution is an acetic acid solution, hydrochloric acid solution, sulfuric acid solution, or nitric acid solution.

7. The method for preparing the rosin-based nitrogen-doped hard carbon anode material for sodium-ion batteries according to claim 1, characterized in that: The inert atmosphere is nitrogen or argon gas, with a gas flow rate of 1–5 L / min.

8. A rosin-based nitrogen-doped hard carbon anode material for sodium-ion batteries, characterized in that: The sodium-ion battery rosin-based nitrogen-doped coated hard carbon anode material is prepared by the preparation method of sodium-ion battery rosin-based nitrogen-doped coated hard carbon anode material according to any one of claims 1-7. The average volumetric particle size Dv50 of the rosin-based nitrogen-doped coated hard carbon anode material is 4.3-6.1 μm, and the specific surface area is 4.8-11.7 m². 2 / g, 0.1C first reversible capacity ≥320.9mAh / g, 0.1C first charge-discharge coulombic efficiency ≥81.9%.

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