Bio-based sodium ion electrode hard carbon negative electrode material and preparation method thereof

Abstract

The invention relates to the field of batteries, in particular to a bio-based sodium ion electrode hard carbon negative electrode material and a preparation method thereof, and the preparation method comprises the following steps: step 1, preparing niobium-hafnium silicide powder; step 2, preparing alkali treatment powder, then mixing the alkali treatment powder, the composite microspheres and the reduced graphene oxide, and carrying out ball milling treatment to obtain a bio-based mixture; and step 4, placing the bio-based mixture in a crucible, placing the crucible in a graphite furnace, and carrying out heat preservation sintering treatment to obtain the negative electrode material. Bamboo powder is used as a bio-based hard carbon precursor material, and the bamboo powder, composite microspheres and reduced graphene oxide are blended and compounded and then sintered to prepare the hard carbon negative electrode material. The negative electrode material prepared by the method is high in initial discharge specific capacity, high in coulombic efficiency and excellent in recyclability.

Description

Technical Field

[0001] The present invention relates to the field of batteries, and particularly to a bio-based sodium-ion electrode hard carbon anode material and a preparation method thereof. Background Art

[0002] Sodium-ion batteries have advantages such as rich resources, low cost, and environmental friendliness, and are considered to be one of the most promising ideal power sources to replace lithium-ion batteries for large-scale energy storage applications. The performance of sodium-ion batteries mainly depends on the sodium storage positive and negative electrode materials, and the sodium storage negative electrode material is an important component among them. Among the currently studied sodium storage negative electrode materials, carbon-based negative electrodes not only have a low sodium intercalation platform, high capacity, and good cycle stability, but also have advantages such as rich resources and simple preparation, and are currently the most promising sodium storage negative electrode materials.

[0003] Currently, the research on bio-based materials as precursors for hard carbon materials in sodium-ion batteries is very popular. Bio-based hard carbon materials are a type of hard carbon materials prepared from bio-based precursors through processes such as pyrolysis and carbonization. Such materials have attracted wide attention due to their wide raw material sources, low cost, environmental friendliness, unique microstructure, and excellent electrochemical performance. However, the initial discharge specific capacity (ICE) of bio-based hard carbon materials is usually low, and the cycle reversibility is poor, which greatly limits their practical applications in sodium-ion batteries. Therefore, it is necessary to develop a bio-based hard carbon material with high first efficiency, high Coulomb efficiency, and good recyclability. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the purpose of the present invention is to provide a bio-based sodium-ion electrode hard carbon anode material and a preparation method thereof.

[0005] The purpose of the present invention is achieved by the following technical solutions: In the first aspect, the present invention provides a preparation method of a bio-based sodium-ion electrode hard carbon anode material, including the following steps: Step 1, preparing niobium hafnium silicide powder: Weigh and mix silicon powder, niobium powder, and hafnium powder. After first performing ball milling treatment, then place it in a graphite furnace for heating treatment to obtain niobium hafnium silicide powder; Step 2, preparing composite microspheres: Mix niobium hafnium silicide powder, nickel acetate, sodium selenite, and deionized water. After heating and stirring treatment, obtain a precursor mixture; drop an aqueous solution of ascorbic acid into the precursor mixture, and then perform treatment in a reaction kettle to obtain composite microspheres; Step 3, preparing a bio-based mixture: Weigh the moso bamboo powder and soak it in the sodium hydroxide solution. After the soaking is completed, wash it with water and dry it to obtain the alkali-treated powder; then mix the alkali-treated powder, composite microspheres and reduced graphene oxide, and perform ball milling treatment to obtain the bio-based mixture. Step 4, prepare the anode material: Place the bio-based mixture in a crucible, place the crucible in a graphite furnace, and perform heat preservation sintering treatment to obtain the anode material.

[0006] Preferably, in the said step 1, the purities of the silicon powder, niobium powder and hafnium powder are all greater than 99%, and the particle size is 50 - 60μm; the mass ratio of hafnium powder, niobium powder and silicon powder is 0.9 - 1.3:0.46 - 0.62:0.56 - 0.74.

[0007] Preferably, in the said step 1, the ball milling speed is 250 - 450r / min, the ball milling time is 3 - 8h, and the ball-to-material ratio is 1 - 5:1.

[0008] Preferably, in the said step 1, the temperature of the graphite furnace is 860 - 1280°C, and the treatment time is 3 - 5h.

[0009] Preferably, in the said step 2, the mass ratio of niobium hafnium silicide powder, nickel acetate, sodium selenite and deionized water is 1:0.12 - 0.24:0.17 - 0.34:20 - 30.

[0010] Preferably, in the said step 2, the temperature of the heating and stirring treatment is 60 - 80°C, and the reaction time is 1 - 5h.

[0011] Preferably, in the said step 2, the aqueous solution of ascorbic acid is obtained by mixing ascorbic acid and deionized water according to a mass ratio of 0.2 - 0.6:10.

[0012] Preferably, in the said step 2, the mass ratio of the aqueous solution of ascorbic acid to the precursor mixture is 0.2 - 0.7:1.

[0013] Preferably, in the said step 2, the dropping speed of the aqueous solution of ascorbic acid is 50 - 80 drops / minute, the reaction temperature in the reaction kettle is 120 - 170°C, and the reaction time is 4 - 10h.

[0014] Preferably, in the said step 3, the moso bamboo powder is first dried in an oven until the moisture content is lower than 10%; the particle size of the moso bamboo powder is 100 - 200μm.

[0015] Preferably, in the said step 3, the mass fraction of the sodium hydroxide solution is 10% - 30%, and the soaking time is 1 - 3h.

[0016] Preferably, in the step 3, the purity of the reduced graphene oxide is ≥99%, the monolayer diameter is 0.5-10 μm, and the carbon-oxygen ratio is 9.89.

[0017] Preferably, in the step 3, the mass ratio of the alkali-treated powder, the composite microspheres and the reduced graphene oxide is 1:0.06-0.16:0.01-0.1.

[0018] Preferably, in the step 3, the ball milling speed is 250-450 r / min, the ball milling time is 3-10 h, and the ball-to-material ratio is 2-8:1.

[0019] Preferably, in the step 4, the heating treatment method in the graphite furnace is as follows: under the protection of nitrogen, first heat up to 450-550 °C, keep warm for 1-3 h, and then heat up to 850-1150 °C, and keep warm for 1-3 h.

[0020] In the second aspect, the present invention provides a bio-based sodium ion electrode hard carbon negative electrode material prepared by the above preparation method.

[0021] The beneficial effects of the present invention are as follows: 1. The present invention uses bamboo powder as a bio-based hard carbon precursor material, which is blended and compounded with composite microspheres and reduced graphene oxide and then sintered to prepare a hard carbon negative electrode material. The negative electrode material prepared by the present invention not only has a high initial discharge specific capacity, but also has a high Coulomb efficiency, and in addition, has excellent recyclability.

[0022] 2. The present invention uses composite microspheres and reduced graphene oxide together as enhancers for the hard carbon negative electrode material. Among them, the composite microspheres use niobium hafnium silicide powder as the matrix material, and a layer of nickel selenide is in-situ formed on its surface, thus forming a composite coated microsphere structure. The composite microspheres and the reduced graphene oxide are co-doped into bamboo powder and carbonized and compounded, and finally a hard carbon negative electrode material is prepared. Compared with conventional hard carbon negative electrode materials, it obviously has higher initial efficiency, sodium storage capacity and cycle life.

[0023] 3. The present invention uses alkali solution immersion treatment before carbonization of bamboo powder to enhance the activity of bamboo charcoal, so that it is easier to combine with composite microspheres and graphene, and the product obtained after ball milling is also combined more tightly and evenly.

[0024] 4. The matrix of the composite microspheres is niobium hafnium silicide, which is obtained by mixing niobium and hafnium with silicon in a suitable ratio and then sintering. After testing, it is found that compared with the composite microspheres obtained from single niobium silicide or hafnium silicide, the composite microspheres prepared by the present invention have a certain promoting effect on the initial efficiency, capacity and cycle life of the electrode, and are particularly excellent in terms of cycle life. Description of the Drawings

[0025] The present invention will be further described with reference to the accompanying drawings. However, the embodiments shown in the drawings do not constitute any limitation to the present invention. For those of ordinary skill in the art, other drawings can be obtained based on the following drawings without creative work.

[0026] Figure 1 It is a SEM schematic diagram of the bio-based sodium ion electrode hard carbon negative electrode material prepared in Example 1 of the present invention. Detailed implementation manners

[0027] To better understand the above technical solutions, the exemplary embodiments of the present invention will be described in more detail below. Although the exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0028] The present invention will be further described below in conjunction with the following embodiments. Example 1

[0029] A preparation method of a bio-based sodium ion electrode hard carbon negative electrode material includes the following steps: Step 1, prepare niobium hafnium silicide powder: Weigh silicon powder, niobium powder and hafnium powder with a purity greater than 99% and a particle size of 50 - 60 μm and mix them. The mass ratio of hafnium powder, niobium powder and silicon powder is 1.1:0.54:0.65. Place them in a ball mill for ball milling. The ball milling speed is 350 r / min, the ball milling time is 5 h, and the ball-to-material ratio is 3:1. After the ball milling is completed, place the product in a graphite furnace and heat it to 1120 °C for 4 h. After cooling to room temperature with the furnace, sieve it through a 400-mesh sieve to obtain niobium hafnium silicide powder; Step 2, prepare composite microspheres: Mix niobium hafnium silicide powder, nickel acetate, sodium selenite and deionized water. The mass ratio of niobium hafnium silicide powder, nickel acetate, sodium selenite and deionized water is 1:0.18:0.25:25. After heating to 70 °C and stirring for 3 h, a precursor mixture is obtained; Mix ascorbic acid and deionized water according to a mass ratio of 0.4:10 to obtain an aqueous solution of ascorbic acid. Drop the aqueous solution of ascorbic acid into the precursor mixture. The mass ratio of the aqueous solution of ascorbic acid and the precursor mixture is 0.5:1. The dropping speed is 50 - 60 drops per minute. After dropping is completed, pour it into a reaction kettle and heat it to 150 °C for 6 h to obtain composite microspheres; Step 3, prepare bio-based mixture: Weigh moso bamboo powder with a moisture content below 10% and a particle size of 100 - 200 μm (Jiangxi Ruimei Bamboo and Wood Technology Co., Ltd.), and then soak it in a 20% sodium hydroxide solution at a solid-liquid ratio of 1:10 for 2 h. After soaking, wash it with water until neutral, and then dry it in an oven to obtain alkali-treated powder; Then take reduced graphene oxide (purity ≥ 99%, single-layer sheet diameter of 0.5 - 10 μm, carbon-oxygen ratio of 9.89). Mix the alkali-treated powder, composite microspheres, and reduced graphene oxide according to a mass ratio of 1:0.11:0.08, and place them in a ball mill for ball milling. The ball milling speed is 350 r / min, the ball milling time is 6 h, and the ball-to-material ratio is 5:1 to obtain a bio-based mixture; Step 4, prepare the anode material: Place the bio-based mixture in a crucible, place the crucible in a graphite furnace, and introduce nitrogen as a protective gas. First, heat it to 500 °C, hold for 2 h, then heat it to 1050 °C, hold for 2 h, and cool it to room temperature with the furnace to obtain the anode material. Example 2

[0030] A preparation method of a bio-based sodium-ion electrode hard carbon anode material, comprising the following steps: Step 1, prepare niobium hafnium silicide powder: Weigh silicon powder, niobium powder, and hafnium powder with a purity greater than 99% and a particle size of 50 - 60 μm and mix them. The mass ratio of hafnium powder, niobium powder, and silicon powder is 0.9:0.62:0.56. Place them in a ball mill for ball milling. The ball milling speed is 250 r / min, the ball milling time is 3 h, and the ball-to-material ratio is 1:1. After ball milling, place the product in a graphite furnace and heat it to 860 °C for 3 h. Cool it to room temperature with the furnace and then screen it through a 200-mesh sieve to obtain niobium hafnium silicide powder; Step 2, prepare composite microspheres: Mix niobium hafnium silicide powder, nickel acetate, sodium selenite, and deionized water. The mass ratio of niobium hafnium silicide powder, nickel acetate, sodium selenite, and deionized water is 1:0.12:0.17:20. Heat it to 60 °C and stir for 1 h to obtain a precursor mixture. Mix ascorbic acid and deionized water according to a mass ratio of 0.2:10 to obtain an aqueous solution of ascorbic acid. Drop the aqueous solution of ascorbic acid into the precursor mixture. The mass ratio of the aqueous solution of ascorbic acid to the precursor mixture is 0.2:1, and the dropping speed is 50 drops / minute. After dropping, pour it into a reaction kettle and heat it to 120 °C for 4 h to obtain composite microspheres; Step 3, prepare a bio-based mixture: Weigh moso bamboo powder with a moisture content of less than 10% and a particle size of 100 - 200 μm, and then soak it in a 10% sodium hydroxide solution for 1 h. After the soaking is completed, wash it with water until neutral, and then dry it in an oven to obtain alkali-treated powder; Then mix the alkali-treated powder, composite microspheres, and reduced graphene oxide in a mass ratio of 1:0.06:0.01, and place them in a ball mill for ball milling. The ball milling speed is 250 r / min, the ball milling time is 3 h, and the ball-to-material ratio is 2:1 to obtain a bio-based mixture; Step 4, prepare the anode material: Place the bio-based mixture in a crucible, place the crucible in a graphite furnace, and introduce nitrogen as a protective gas. First, heat it to 450 °C, keep it warm for 3 h, then heat it to 850 °C, keep it warm for 3 h, and cool it to room temperature with the furnace to obtain the anode material. Example 3

[0031] A preparation method of a bio-based sodium-ion electrode hard carbon anode material includes the following steps: Step 1, prepare hafnium niobium silicide powder: Weigh silicon powder, niobium powder, and hafnium powder with a purity greater than 99% and a particle size of 50 - 60 μm and mix them. The mass ratio of hafnium powder, niobium powder, and silicon powder is 1.3:0.46:0.74. Place them in a ball mill for ball milling. The ball milling speed is 450 r / min, the ball milling time is 8 h, and the ball-to-material ratio is 5:1. After the ball milling is completed, place the product in a graphite furnace and heat it to 1280 °C for 5 h, and cool it to room temperature with the furnace. Then, sieve it through a 500-mesh sieve to obtain hafnium niobium silicide powder; Step 2, prepare composite microspheres: Mix hafnium niobium silicide powder, nickel acetate, sodium selenite, and deionized water. The mass ratio of hafnium niobium silicide powder, nickel acetate, sodium selenite, and deionized water is 1:0.24:0.34:30. Heat it to 80 °C and stir for 5 h to obtain a precursor mixture. Mix ascorbic acid and deionized water in a mass ratio of 0.6:10 to obtain an aqueous solution of ascorbic acid. Drop the aqueous solution of ascorbic acid into the precursor mixture. The mass ratio of the aqueous solution of ascorbic acid and the precursor mixture is 0.7:1, and the dropping speed is 80 drops / min. After dropping, pour it into a reaction kettle and heat it to 170 °C for 10 h to obtain composite microspheres; Step 3, prepare a bio-based mixture: Weigh moso bamboo powder with a moisture content of less than 10% and a particle size of 100 - 200 μm, and then soak it in a 30% sodium hydroxide solution for 3 h. After the soaking is completed, wash it with water until neutral, and then dry it in an oven to obtain alkali-treated powder; Then, the alkali-treated powder, composite microspheres, and reduced graphene oxide are mixed at a mass ratio of 1:0.16:0.1, placed in a ball mill for ball milling treatment. The ball milling speed is 450 r / min, the ball milling time is 10 h, and the ball-to-material ratio is 8:1 to obtain a bio-based mixture; Step 4, preparing the anode material: Place the bio-based mixture in a crucible, place the crucible in a graphite furnace, introduce nitrogen as a protective gas, first heat up to 550 °C, hold for 1 h, then heat up to 1150 °C, hold for 1 h, and cool to room temperature with the furnace to obtain the anode material.

[0032] Comparative Example 1 A bio-based sodium-ion electrode hard carbon anode material, different from the preparation method of Example 1 in that no composite microspheres are added, and moso bamboo powder and reduced graphene oxide are directly used as raw materials for preparation. Specifically: Step 1, preparing the bio-based mixture Take moso bamboo powder with a moisture content lower than 10% and a particle size of 100 - 200 μm, then soak it in a 20% sodium hydroxide solution for 2 h. After soaking, wash it with water until neutral and dry it in an oven to obtain the alkali-treated powder; Then take reduced graphene oxide, mix the alkali-treated powder and reduced graphene oxide at a mass ratio of 1:0.08, place them in a ball mill for ball milling treatment. The ball milling speed is 350 r / min, the ball milling time is 6 h, and the ball-to-material ratio is 5:1 to obtain a bio-based mixture; Step 2, preparing the anode material: Place the bio-based mixture in a crucible, place the crucible in a graphite furnace, introduce nitrogen as a protective gas, first heat up to 500 °C, hold for 2 h, then heat up to 1050 °C, hold for 2 h, and cool to room temperature with the furnace to obtain the anode material.

[0033] Comparative Example 2 A bio-based sodium-ion electrode hard carbon anode material, different from the preparation method of Example 1 in that the composite microspheres are niobium silicide & nickel selenide, and the rest is the same as Example 1. Specifically: Step 1, preparing niobium silicide powder: Weigh silicon powder and niobium powder with a purity greater than 99% and a particle size of 50 - 60 μm and mix them. The mass ratio of niobium powder to silicon powder is 1.64:0.65. Place them in a ball mill for ball milling treatment. The ball milling speed is 350 r / min, the ball milling time is 5 h, and the ball-to-material ratio is 3:1. After ball milling, place the product in a graphite furnace and heat it up to 1120 °C for 4 h. Cool to room temperature with the furnace and pass through a 200-mesh sieve to obtain niobium silicide powder; Step 2, preparing the composite microspheres: Mix niobium silicide powder, nickel acetate, sodium selenite and deionized water. The mass ratio of niobium silicide powder, nickel acetate, sodium selenite and deionized water is 1:0.18:0.25:25. After heating to 70 °C and stirring for 3 h, a precursor mixture is obtained; Mix ascorbic acid and deionized water according to a mass ratio of 0.4:10 to obtain an aqueous solution of ascorbic acid. Dropwise add the aqueous solution of ascorbic acid into the precursor mixture. The mass ratio of the aqueous solution of ascorbic acid to the precursor mixture is 0.5:1. The dropping rate is 50 - 60 drops per minute. After dropping, pour it into a reaction kettle, heat to 150 °C and treat for 6 h to obtain composite microspheres; Step 3, prepare the bio-based mixture, which is the same as in Example 1; Step 4, prepare the negative electrode material, which is the same as in Example 1.

[0034] Comparative Example 3 A bio-based sodium-ion electrode hard carbon negative electrode material, which is different from the preparation method of Example 1 in that the composite microspheres are hafnium silicide & nickel selenide, and the rest is the same as in Example 1. Specifically: Step 1, prepare hafnium silicide powder: Weigh silicon powder and hafnium powder with a purity greater than 99% and a particle size of 50 - 60 μm and mix them. The mass ratio of hafnium powder to silicon powder is 1.64:0.65. Place them in a ball mill for ball milling. The ball milling speed is 350 r / min, the ball milling time is 5 h, and the ball-to-material ratio is 3:1. After ball milling, place the product in a graphite furnace and heat to 1120 °C for 4 h. After cooling to room temperature with the furnace, sieve through a 200-mesh sieve to obtain hafnium silicide powder; Step 2, prepare composite microspheres: Mix hafnium silicide powder, nickel acetate, sodium selenite and deionized water. The mass ratio of hafnium silicide powder, nickel acetate, sodium selenite and deionized water is 1:0.18:0.25:25. After heating to 70 °C and stirring for 3 h, a precursor mixture is obtained; Mix ascorbic acid and deionized water according to a mass ratio of 0.4:10 to obtain an aqueous solution of ascorbic acid. Dropwise add the aqueous solution of ascorbic acid into the precursor mixture. The mass ratio of the aqueous solution of ascorbic acid to the precursor mixture is 0.5:1. The dropping rate is 50 - 60 drops per minute. After dropping, pour it into a reaction kettle, heat to 150 °C and treat for 6 h to obtain composite microspheres; Step 3, prepare the bio-based mixture, which is the same as in Example 1; Step 4, prepare the negative electrode material, which is the same as in Example 1.

[0035] Experimental detection The performance of the hard carbon anode materials prepared in Example 1 and Comparative Examples 1-3 was tested with reference to the standard GB / T 43114-2023. Among them, the preparation of the button battery includes: the anode materials prepared in Example 1 and Comparative Examples 1-3 of the present invention; the separator is a polyethylene-polypropylene (PE-PP) composite membrane with a thickness of 80 μm; the electrolyte is a 1 mol / L LiPF solution; the battery case is CR2032; the counter electrode and the reference electrode are sodium metal sheets; the charge-discharge rate used for the first discharge specific capacity, the first Coulombic efficiency, and the cycling test is 0.1C, and the voltage range is 0.005-1.5V. The test results are shown in Table 1: Table 1 Performance display of different hard carbon anode materials Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Initial discharge specific capacity (mA·h / g) 415.3 339.5 376.4 392.8 Initial Coulombic efficiency (%) 88.2 79.4 81.7 85.6 Capacity retention rate after 200 cycles of use (%) 90.1 82.3 88.5 87.2 It can be seen from Table 1 that the first discharge specific capacity of the hard carbon anode material prepared in Example 1 of the present invention can reach 415.3 mA·h / g, the first Coulombic efficiency can reach 88.2%, and the capacity retention rate can still reach 90.1% after 200 cycles, indicating that the hard carbon anode material prepared in Example 1 of the present invention exhibits excellent initial efficiency, capacity, and cycle life in the application of sodium-ion batteries.

[0036] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means 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 representation of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification.

[0037] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a bio-based sodium ion electrode hard carbon negative electrode material, characterized in that: The following steps are involved: Step 1, weighing silicon powder, niobium powder and hafnium powder, mixing them, first subjecting them to ball milling treatment, and then placing them in a graphite furnace for heating treatment to obtain niobium hafnium silicide powder; Step 2, mixing niobium hafnium silicide powder, nickel acetate, sodium selenite and deionized water, heating and stirring to obtain a precursor mixture; adding an aqueous solution of ascorbic acid to the precursor mixture, and then treating it in a reactor to obtain composite microspheres; Step 3, weighing bamboo powder and soaking it in a sodium hydroxide solution, washing it with water and drying it after soaking to obtain an alkali-treated powder; then mixing the alkali-treated powder, the composite microspheres and the reduced graphene oxide, and performing ball milling to obtain a bio-based mixture; Step 4, placing the bio-based mixture in a crucible, placing the crucible in a graphite furnace, and performing heat preservation and sintering treatment to obtain a negative electrode material.

2. The method for preparing a bio-based sodium ion electrode hard carbon negative electrode material according to claim 1, characterized in that: In step 1, the purity of silicon powder, niobium powder and hafnium powder is greater than 99%, and the particle size is 50-60 μm; the mass ratio of hafnium powder, niobium powder and silicon powder is 0.9-1.3:0.46-0.62:0.56-0.

74.

3. The method for preparing a bio-based sodium ion electrode hard carbon negative electrode material according to claim 1, characterized in that: In the step 1, the ball milling speed is 250-450 r / min, the ball milling time is 3-8 h, and the ball-to-material ratio is 1-5:1; the temperature of the graphite furnace is 860-1280° C., and the processing time is 3-5 h.

4. The method for preparing a bio-based sodium ion electrode hard carbon negative electrode material according to claim 1, characterized in that: In the step 2, the mass ratio of niobium hafnium silicide powder, nickel acetate, sodium selenite and deionized water is 1:0.12-0.24:0.17-0.34:20-30; the aqueous solution of ascorbic acid is obtained by mixing ascorbic acid and deionized water in a mass ratio of 0.2-0.6:

10.

5. The method for preparing a bio-based sodium ion electrode hard carbon negative electrode material according to claim 1, characterized in that: In the step 2, the temperature for the heating and stirring treatment is 60-80° C., and the reaction time is 1-5 hours.

6. The method for preparing a bio-based sodium ion electrode hard carbon negative electrode material according to claim 1, characterized in that: In the step 2, the mass ratio of the aqueous solution of ascorbic acid to the precursor mixture is 0.2-0.7:1; the dripping speed of the aqueous solution of ascorbic acid is 50-80 drops / minute, the reaction temperature in the reactor is 120-170° C., and the reaction time is 4-10 hours.

7. The method for preparing a bio-based sodium ion electrode hard carbon negative electrode material according to claim 1, characterized in that: In the step 3, the mass fraction of the sodium hydroxide solution is 10%-30%, and the immersion time is 1-3h; in the step 3, the mass ratio of the alkali-treated powder, the composite microspheres and the reduced graphene oxide is 1:0.06-0.16:0.01-0.

1.

8. The method for preparing a bio-based sodium ion electrode hard carbon negative electrode material according to claim 1, characterized in that: In the step 3, the ball milling speed is 250-450 r / min, the ball milling time is 3-10 h, and the ball-to-material ratio is 2-8:

1.

9. The method for preparing a bio-based sodium ion electrode hard carbon negative electrode material according to claim 1, characterized in that: In step 4, the temperature in the graphite furnace is first raised to 450-550° C. under the protection of nitrogen, and then heated to 850-1150° C. and kept warm for 1-3 hours.

10. A bio-based sodium ion electrode hard carbon negative electrode material prepared using the preparation method of claim 1.

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