Green preparation method and application of biomass / sugar composite derived high platform capacity hard carbon material

Abstract

The invention relates to the technical field of sodium ion batteries, in particular to a green preparation method and application of a biomass / sugar composite derived high platform capacity hard carbon material. A green preparation method of a biomass / sugar composite derived high platform capacity hard carbon material comprises the following steps: S1, pretreating a biomass raw material to obtain solid powder; s2, uniformly mixing the solid powder with a sugar solution, and sequentially performing stirring, temperature control and drying treatment to obtain a mixed solid; s3, performing pre-oxidation treatment on the mixed solid, and performing low-temperature carbonization to obtain a pre-carbonized product; and S4, adding the pre-carbonized product into a solvent, heating, stirring and purifying, and sequentially carrying out drying and high-temperature sintering treatment to obtain the hard carbon material. No chemical reagent such as acid, alkali and salt is used in the preparation process, and the synthesis process is environment-friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium-ion batteries, and particularly relates to a green preparation method and application of a biomass / sugar composite-derived high plateau capacity hard carbon material. Background Art

[0002] Sodium-ion batteries are increasingly becoming the focus of attention in the new energy field due to their relatively low production costs, as well as many advantages such as good low-temperature performance, rate performance, and safety performance.

[0003] As the core component of sodium-ion batteries, the anode material plays a decisive role in the overall performance and cost structure of sodium-ion batteries. Generally speaking, the cost-effectiveness and large-scale application potential of hard carbon materials are restricted by the supply of hard carbon precursor raw materials. At present, the available precursors mainly include biomass raw materials, chemical raw materials such as synthetic resins, and fossil raw materials such as coal and pitch.

[0004] Among various precursors, biomass such as coconut shells, wood chips, peanut shells, and bamboo is regarded as an ideal raw material for large-scale production of hard carbon due to its wide sources, low price, sufficient supply, and easy regeneration. However, due to the usually very dense structure of biomass precursors, the hard carbon obtained by direct calcination has fewer closed pores, and the plateau capacity (corresponding to a voltage of 0.001 - 0.1 V) during sodium storage is often low (<100 mAh / g).

[0005] In order to improve the plateau sodium storage capacity of biomass hard carbon, researchers widely use methods such as chemical etching and hard templates to construct closed pores, but there are problems such as cumbersome processes, high production costs, or difficulty in mass production. Moreover, the extensive use of chemical reagents is also likely to cause environmental pollution and other problems.

[0006] Therefore, developing a synthetic strategy that is easy to operate, low-cost, and environmentally friendly to obtain a high plateau capacity biomass hard carbon anode material is one of the key challenges currently faced in the field of sodium-ion batteries. Summary of the Invention

[0007] The main objective of the present invention is to provide a high-capacity and high first-cycle efficiency hard carbon anode material, its preparation method, and a sodium-ion battery, so as to solve the technical problem that it is difficult to obtain a biomass hard carbon material with rich closed pores and high plateau capacity at low cost and high efficiency by existing processes.

[0008] In the present invention, a preparation method of a biomass hard carbon anode material includes the following steps: S1. After pre-treating the biomass raw material, a solid powder is obtained; S2. After uniformly mixing the solid powder and the sugar solution, perform stirring, temperature control, and drying treatments in sequence to obtain a mixed solid; wherein, the sugar solution is a combination of one or more of glucose, sucrose, maltose, or fructose. S3. After subjecting the mixed solid to a pre-oxidation treatment, perform low-temperature carbonization to obtain a pre-carbonized product. S4. Add the pre-carbonized product to a solvent, and after heating and stirring for purification, perform drying and high-temperature sintering treatments in sequence to obtain a biomass hard carbon material for the negative electrode of a sodium-ion battery.

[0009] Further, in step S1, the biomass raw material is one or more of coconut shells, wood chips, peanut shells, and bamboo.

[0010] Further, in step S1, the steps for pre-treating the biomass raw material are as follows: S11. Weigh an appropriate amount of the washed and dried biomass raw material and perform crushing and sieving treatments; wherein, the particle size of the biomass raw material is 75 - 150 mesh sieve. S12. Disperse a certain mass of the sieved biomass raw material in deionized water, heat and stir it, remove the supernatant and dry it to obtain a solid powder; wherein, the dosage of the biomass raw material is 20 - 50 g, the dosage of deionized water is 200 - 500 ml, the heating temperature condition is 80 - 100 °C, and the time is 6 - 12 h; the drying method is air drying, and the drying temperature is 60 - 100 °C.

[0011] Further, in step S2, the mass concentration of the sugar solution is 0.2 - 0.6 g / mL, and the solid-liquid ratio of the mixed solid powder and the sugar solution is 0.2 - 1 g / mL; after mixing, perform temperature control treatment and stirring at 50 - 100 °C, and the treatment time is 5 - 10 h.

[0012] Further, in step S3, the pre-oxidation temperature is 200 - 270 °C, the heating rate is 3 - 10 °C / min, and the heat preservation time is 2 - 5 h; the low-temperature carbonization is carried out by heating in an inert gas atmosphere, wherein the inert gas is argon or nitrogen, the gas flow rate is 60 - 100 ml / min, the heating rate is 3 - 10 °C / min, the carbonization temperature is 500 - 800 °C, and the heat preservation is 2 - 5 h.

[0013] Further, in step S4, the solvent is one or a combination of two solvents of absolute ethanol, deionized water, or acetone, the heating temperature is 50 - 100 °C, and the heat treatment time is 5 - 10 h.

[0014] Further, in step S4, the high-temperature sintering is carried out in an inert gas atmosphere, and the inert gas is argon or nitrogen, and the gas flow rate is 60 - 100 mL / min. The heating program for high-temperature sintering includes two stages. Stage 1: Heat at a heating rate of 3 - 10 °C / min to 700 - 900 °C and hold for 0.5 - 2 h. Stage 2: Heat at a heating rate of 2 - 5 °C / min to 1200 - 1600 °C and hold for 2 - 6 h.

[0015] The biomass hard carbon anode material obtained by the above preparation method.

[0016] The application of the above biomass hard carbon anode material as an anode material for sodium-ion batteries.

[0017] The present invention has the following advantages and beneficial effects compared with the prior art: 1. The present invention uses biomass raw materials, and the raw materials used are widely sourced and can be biomass waste materials, which helps to achieve large-scale and low-cost production of hard carbon.

[0018] 2. The present invention can efficiently construct a large number of closed pores inside the hard carbon through the way of biomass-sugar composite derivation and in combination with a simple solvent treatment process, so as to obtain a high plateau capacity on the basis of a high first-cycle efficiency.

[0019] 3. The present invention does not use any chemical reagents such as acids, alkalis, and salts, and the synthesis process is environmentally friendly. Description of the Drawings

[0020] Figure 1 Electrochemical performance test of the biomass hard carbon material prepared in Example 1.

[0021] Figure 2 Electrochemical performance test of the biomass hard carbon material prepared in Example 2.

[0022] Figure 3 Electrochemical performance test of the biomass hard carbon material prepared in Example 3.

[0023] Figure 4 Electrochemical performance test of the biomass hard carbon material prepared in Comparative Example 1.

[0024] Figure 5 Electrochemical performance test of the biomass hard carbon material prepared in Comparative Example 2.

[0025] Figure 6 Electrochemical performance test of the biomass hard carbon material prepared in Comparative Example 3.

[0026] Figure 7 HTEM image of the biomass hard carbon material prepared in Example 2.

[0027] Figure 8 HTEM image of the biomass hard carbon material prepared in Comparative Example 1. Detailed Embodiments

[0028] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings. For those not specified in the embodiments in terms of specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in this field or according to the product specifications. For the reagents or instruments not specified in terms of the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0029] The first thing the present invention aims to protect is to provide a green preparation method for a biomass / sugar composite-derived high-platform-capacity hard carbon material, including the following steps: S1. Weigh an appropriate amount of washed and dried biomass raw materials and perform crushing and sieving treatments; wherein, the biomass raw materials are one or a combination of coconut shells, wood chips, peanut shells, and bamboo, and the particle size of the powder after crushing is 75-150 mesh sieve. S2. Heat and stir a certain mass of the biomass raw materials after sieving in deionized water, remove the supernatant and dry to obtain solid powder A; wherein, 20-50 g of the biomass raw materials are taken, 200-500 ml of deionized water is added, the reaction temperature is 80-100 °C, the time is 6-12 h, the drying method is air drying, and the drying temperature is 60-100 °C.

[0030] S3. Mix solid powder A evenly with sugar solutions of different concentrations, then stir and perform temperature control treatment, and dry to obtain mixed solid B; in step S3, the sugar solution is one or a combination of glucose, sucrose, maltose, or starch, the mass concentration of the sugar solution is 0.2-0.6 g / mL, and the solid-liquid ratio of the mixture of the solid powder and the sugar solution is 0.2-1 g / mL; after mixing, perform temperature control treatment and stir at 50-100 °C, and the treatment time is 5-10 h.

[0031] S4. Perform pre-oxidation treatment on mixed solid B in a muffle furnace to obtain precursor material C; wherein, the pre-oxidation temperature in the muffle furnace is 200-270 °C, the heating rate is 3-10 °C / min, and the holding time is 2-5 h.

[0032] S5. Heat and perform low-temperature carbonization on precursor material C in an inert gas atmosphere to obtain pre-carbonized product D; wherein, the inert gas is argon or nitrogen, the gas flow rate is 60-100 ml / min, the heating rate is 3-10 °C / min, the carbonization temperature is 500-800 °C, and keep warm for 2-5 h.

[0033] S6. Perform temperature-controlled solvent heat treatment on pre-carbonized product D and dry to obtain solid E; the solvent for the heat treatment is one or a combination of anhydrous ethanol, deionized water, or acetone, the heating temperature is 50-100 °C, and the treatment time is 5-10 h.

[0034] S7. Sinter the solid E at high temperature in an inert gas atmosphere to obtain a biomass / sugar composite-derived hard carbon material with a high plateau capacity. Among them, the inert gas is argon or nitrogen, and the gas flow rate is 60-100 mL / min. The heating program for high-temperature sintering includes two stages. Stage 1: Heat up to 700-900 °C at a heating rate of 3-10 °C / min and hold for 0.5-2 h. Stage 2: Heat up to 1200-1600 °C at a heating rate of 2-5 °C / min and hold for 2-6 h.

[0035] The second thing the present invention wants to protect is the biomass / sugar composite-derived hard carbon material with a high plateau capacity prepared by the above preparation method.

[0036] The third thing the present invention wants to protect is a sodium-ion battery biomass hard carbon negative electrode material, and this negative electrode material is the biomass / sugar composite-derived hard carbon material with a high plateau capacity prepared by the above preparation method.

[0037] <Example 1> A green preparation method of a biomass / sugar composite-derived hard carbon material with a high plateau capacity, including the following steps: S1. Weigh an appropriate amount of washed and dried wood chip raw materials, crush them, and sieve them through a 150-mesh sieve. S2. Add 20 g of the sieved wood chip raw materials to 250 ml of deionized water, heat them in an oil bath to 85 °C for 6 h, filter and dry them by blowing air, and the drying temperature is 80 °C. S3. Take 5 g of the wood chip raw materials processed in step S2, add 20 ml of a 0.3 g / mL glucose solution, react in an oil bath at 85 °C for 6 h, transfer them to an oven for drying treatment to obtain a solid powder with glucose and wood chip raw materials mixed evenly. S4. Heat the solid powder obtained in step S3 to 210 °C at a rate of 5 °C / min in a muffle furnace for pre-oxidation for 3 h to obtain a pre-oxidized precursor material with wood chip raw materials and glucose mixed evenly. S5. Heat the precursor material obtained in step S4 to 500 °C at a rate of 5 °C / min in an argon atmosphere with an air flow rate of 100 mL / min, hold for 2 h for low-temperature carbonization; stir the material after low-temperature carbonization with absolute ethanol and heat it to 60 °C for heat treatment for 6 h, and then transfer it to a drying oven for drying to obtain a solid. S6. Heat the solid obtained in step S5 to 900 °C at a rate of 5 °C / min in an argon atmosphere with an air flow rate of 100 mL / min, hold for 1.5 h, then heat it to 1500 °C at a rate of 3 °C / min for carbonization, and hold for 5 h to obtain a biomass / sugar composite-derived hard carbon material with low ash content and rich closed pores and a high plateau capacity.

[0038] <Example 2> A green preparation method of a biomass / sugar composite-derived high plateau capacity hard carbon material, comprising the following steps: S1. Weigh an appropriate amount of washed and dried peanut shell raw materials, crush them, and sieve them through a 150-mesh sieve; S2. Add 30 g of the sieved peanut shell raw materials to 400 ml of deionized water, heat them in an oil bath to 95 °C for 3 h, filter and dry them by blowing air, and the drying temperature is 80 °C; S3. Take 10 g of the peanut shell raw materials treated in step S2, add 30 ml of a 0.4 g / mL glucose solution, heat them in an oil bath to 75 °C and react for 6 h, transfer them to an oven for drying, and obtain a solid powder with glucose and peanut shell raw materials evenly mixed; S4. Heat the solid powder obtained in step S3 in a muffle furnace at a rate of 3 °C / min to 230 °C for pre-oxidation for 4 h to obtain a pre-oxidized precursor material with peanut shell raw materials and glucose evenly mixed; S5. Heat the precursor material obtained in step S4 in an argon atmosphere with an air flow rate of 80 mL / min at a rate of 3 °C / min to 700 °C, keep it warm for 3.5 h, and carry out low-temperature carbonization; stir the material after low-temperature carbonization with deionized water / absolute ethanol = 1:1 (volume ratio), heat it to 70 °C, carry out heat treatment for 8 h, and then transfer it to a drying oven for drying to obtain a solid; S6. Heat the solid obtained in step S5 in a nitrogen atmosphere with an air flow rate of 80 mL / min first at a rate of 8 °C / min to 700 °C, keep it warm for 2.5 h, and then heat it at a rate of 5 °C / min to 1300 °C for carbonization and keep it warm for 6 h to obtain a biomass / sugar composite-derived high plateau capacity hard carbon material with low ash content and abundant closed pores.

[0039] Obtain the HTEM image of the biomass / sugar composite-derived high plateau capacity hard carbon material prepared in this example, as Figure 7 shown. From Figure 7 it can be seen that the biomass / sugar composite-derived high plateau capacity hard carbon material prepared in this example has the characteristics of low ash content and abundant closed pores.

[0040] <Example 3> A green preparation method of a biomass / sugar composite-derived high plateau capacity hard carbon material, comprising the following steps: S1. Weigh an appropriate amount of washed and dried coconut shell raw materials, crush them, and sieve them through a 100-mesh sieve; S2. Add 30 g of the sieved coconut shell raw materials to 250 ml of deionized water, heat them in an oil bath to 95 °C for 3 h, filter and dry them; S3. Take 7 g of the coconut shell raw material processed in step S2, add it to 10 ml of a solution of sucrose / glucose = 1:1 (mass ratio) with a concentration of 0.5 g / mL, heat it in an oil bath to 75 °C and react for 8 h, then transfer it to an oven for drying treatment to obtain a solid powder with uniformly mixed sucrose / glucose and coconut shell raw material; S4. Heat the solid powder obtained in step S3 in a muffle furnace at a rate of 4 °C / min to 250 °C for pre-oxidation for 3 h to obtain a precursor material with uniformly mixed coconut shell raw material and sucrose / glucose after pre-oxidation; S5. Heat the precursor material obtained in step S4 in an argon atmosphere with a ventilation rate of 90 mL / min at a rate of 2 °C / min to 600 °C, hold for 3 h for low-temperature carbonization. Stir the material after low-temperature carbonization with deionized water and heat it to 80 °C, conduct heat treatment for 10 h, and then transfer it to a drying oven for drying to obtain a solid; S6. Heat the solid obtained in step S5 in an argon atmosphere with a ventilation rate of 60 mL / min first at a rate of 5 °C / min to 800 °C, hold for 2 h, then at a rate of 5 °C / min to 1500 °C for carbonization, hold for 4 h to obtain a biomass / sugar composite-derived high-platform-capacity hard carbon material with low ash content and abundant closed pores.

[0041] <Comparative Example 1> A preparation method of a biomass hard carbon material, comprising the following steps: S1. Weigh an appropriate amount of washed and dried bamboo raw material, crush it, and sieve it through a 100-mesh sieve; S2. Add 15 g of the sieved bamboo raw material to 350 ml of deionized water, heat it in an oil bath to 75 °C for 8 h, filter and dry; S3. Take 7 g of the bamboo raw material processed in step S2, add it to 20 ml of a glucose solution with a concentration of 0.3 g / mL, heat it in an oil bath to 85 °C and react for 7 h, then transfer it to an oven for drying treatment to obtain a solid powder with uniformly mixed glucose and bamboo raw material; S4. Heat the solid obtained in step S3 in an argon atmosphere with a ventilation rate of 80 mL / min first at a rate of 5 °C / min to 700 °C, hold for 1.5 h, then at a rate of 5 °C / min to 1500 °C for carbonization, hold for 4 h to obtain a biomass hard carbon material with low ash content and abundant closed pores as the negative electrode of a sodium-ion battery.

[0042] Obtain the HTEM image of the biomass hard carbon material prepared in this comparative example, as Figure 8 shown. It can be seen from Figure 8 that the biomass hard carbon material prepared in this comparative example only has a small number of closed pores.

[0043] <Comparative Example 2> A preparation method of a biomass hard carbon material, comprising the following steps: S1. Weigh an appropriate amount of washed and dried wood chip raw materials, crush them, and sieve them through a 150-mesh sieve; S2. Add 15 g of the sieved wood chip raw materials to 250 ml of deionized water, heat them in an oil bath to 85 °C for 6 h, filter and dry; S3. Take 7 g of the wood chip raw materials treated in step S2, add 20 ml of a 0.4 g / mL glucose solution, heat them in an oil bath to 85 °C and react for 5 h, transfer them to an oven for drying treatment to obtain a solid powder with uniformly mixed glucose and wood chip raw materials; S4. Heat the solid powder obtained in step S3 in a muffle furnace at a rate of 5 °C / min to 270 °C for pre-oxidation for 3 h to obtain a pre-oxidized precursor material with uniformly mixed wood chip raw materials and glucose; S5. Heat the precursor material obtained in step S4 in an argon atmosphere with a ventilation rate of 70 mL / min first at a rate of 5 °C / min to 700 °C, hold for 3.5 h, then heat at a rate of 4 °C / min to 1400 °C for carbonization, hold for 6 h to obtain a sodium-ion battery negative electrode biomass hard carbon material with low ash content and abundant closed pores.

[0044] <Comparative Example 3> A preparation method of a biomass hard carbon material, comprising the following steps: S1. Weigh an appropriate amount of washed and dried coconut shell raw materials, crush them, and sieve them through a 100-mesh sieve; S2. Add 20 g of the sieved coconut shell raw materials to 250 ml of deionized water, heat them in an oil bath to 85 °C for 6 h, filter and dry; S3. Take 10 g of the coconut shell raw materials treated in step S2, add 20 ml of a 0.3 g / mL sucrose solution, heat them in an oil bath to 75 °C and react for 6 h, transfer them to an oven for drying treatment to obtain a solid powder with uniformly mixed sucrose and coconut shell raw materials; S4. Heat the solid powder obtained in step S3 in an argon atmosphere with a ventilation rate of 100 mL / min at a rate of 6 °C / min to 700 °C, hold for 2 h for low-temperature carbonization. Stir the low-temperature carbonized material with deionized water and heat to 65 °C, perform heat treatment for 8 h, and then transfer it to a drying oven for drying; S5. Heat the solid obtained in step S4 in an argon atmosphere with a ventilation rate of 80 mL / min first at a rate of 5 °C / min to 800 °C, hold for 0.5 h, then heat at a rate of 4 °C / min to 1400 °C for carbonization, hold for 5 h to obtain a sodium-ion battery negative electrode biomass hard carbon material with low ash content and abundant closed pores.

[0045] Test Example 1: Electrochemical Performance Test Battery Assembly: The hard carbon materials obtained in Examples 1-3 and Comparative Examples 1-3 were used as active materials respectively. After being mixed into a homogeneous slurry according to the mass ratio of active material: ultrafine carbon powder (SP): sodium carboxymethyl cellulose (CMC): styrene-butadiene rubber (SBR) of 91:3:2:4, the black slurry was coated on copper foil using a 60 μm four-sided coater, and baked in a vacuum drying oven at 120 °C for 12 h to obtain the negative electrode sheets. The electrode membranes were punched into circular discs with a diameter of 11 mm using a punching machine. A sodium metal sheet was used as the counter electrode, and glass fiber (Waterman) was used as the separator. The commercial electrolyte NP-035 (1M NaPF6, with ethylene glycol dimethyl ether as the solvent) was selected as the electrolyte, and 2025 coin-type sodium-ion batteries were assembled in an argon-protected glove box. In addition, the assembled 2025 coin-type batteries were subjected to constant current charge-discharge tests on a Neware battery test system. The test voltage range was 0.001-2.5 V, and the test results are shown in Table 1 and the appendix Figures 1 - 6 as follows.

[0046] Table 1 Performance Comparison of Batteries Obtained in Examples and Comparative Examples

[0047] Through comparative analysis of the examples and comparative examples, it can be seen that the first-cycle charge specific capacities of the half-cells assembled from the negative electrode sheets prepared from the hard carbon materials of Examples 1-3 are all higher than those of the comparative examples. It is particularly noteworthy that the plateau capacity of Example 2 is as high as 245 mAh / g. After biomass and sugar are compounded and derived under optimized conditions and ratios, and combined with a simple solvent treatment process, a large number of closed pores can be efficiently constructed inside the hard carbon, thereby obtaining a high plateau capacity.

[0048] For those not covered above, the prior art applies.

[0049] Although some specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are only for illustration purposes and not for limiting the scope of the present invention. Those skilled in the technical field to which the present invention pertains can make various modifications or supplements to the described specific embodiments or use similar methods for substitution, but will not deviate from the direction of the present invention or exceed the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc. made based on the technical essence of the present invention to the above embodiments should be included in the protection scope of the present invention.

Claims

1. A green preparation method of a biomass / sugar composite-derived high-capacity hard carbon material, characterized in that, It includes the following steps: S1. After pretreating the biomass raw material, a solid powder is obtained. S2. After uniformly mixing the solid powder with the sugar solution, stirring, temperature control, and drying treatments are carried out in sequence to obtain a mixed solid; wherein, the sugar solution is one or several of glucose, sucrose, maltose, or fructose. S3. After subjecting the mixed solid to pre-oxidation treatment, low-temperature carbonization is carried out to obtain a pre-carbonized product. S4. The pre-carbonized product is added to a solvent, and after heating, stirring, and purification, drying and high-temperature sintering treatments are carried out in sequence to obtain a biomass / sugar composite-derived high plateau capacity hard carbon material.

2. The green preparation method of a biomass / sugar composite-derived high-capacity hard carbon material according to claim 1, characterized in that, In step S1, the biomass raw material is one or several of coconut shells, wood chips, peanut shells, and bamboo.

3. The green preparation method of a biomass / sugar composite-derived high specific capacity hard carbon material according to claim 2, wherein, In step S1, the steps for pretreating the biomass raw material are: S11. Weigh an appropriate amount of the washed and dried biomass raw material, and carry out crushing and sieving treatments; wherein, the particle size of the sieved biomass raw material is 75 - 150 mesh sieve. S12. Disperse a certain mass of the sieved biomass raw material in deionized water, heat and stir, remove the supernatant and dry to obtain a solid powder; wherein, the dosage of the biomass raw material is 20 - 50 g, the dosage of deionized water is 200 - 500 ml, the heating temperature condition is 80 - 100 °C, the time is 6 - 12 h; the drying method is air drying, and the drying temperature is 60 - 100 °C.

4. The green preparation method of a biomass / sugar composite-derived high-capacity hard carbon material according to claim 1, characterized in that, In step S2, the mass concentration of the sugar solution is 0.2 - 0.6 g / mL, and the mixing solid-liquid ratio of the solid powder to the sugar solution is 0.2 - 1 g / mL; after mixing, temperature control treatment and stirring are carried out at 50 - 100 °C, and the treatment time is 5 - 10 h.

5. The green preparation method of a biomass / sugar composite-derived high-capacity hard carbon material according to claim 1, characterized in that In step S3, the pre-oxidation temperature is 200 - 270 °C, the heating rate is 3 - 10 °C / min, and the heat preservation time is 2 - 5 h; the low-temperature carbonization is carried out by heating in an inert gas atmosphere, wherein, the inert gas is argon or nitrogen, the gas flow rate is 60 - 100 ml / min, the heating rate is 3 - 10 °C / min, the carbonization temperature is 500 - 800 °C, and the heat preservation is 2 - 5 h.

6. The green preparation method of a biomass / sugar composite-derived high platform capacity hard carbon material according to claim 1, characterized in that, In step S4, the solvent is one or a combination of two solvents of anhydrous ethanol, deionized water, or acetone, the heating temperature is 50 - 100 °C, and the heat treatment time is 5 - 10 h.

7. The green preparation method of a biomass / sugar composite-derived high-capacity hard carbon material according to claim 6, characterized in that, In step S4, the high-temperature sintering is carried out in an inert gas atmosphere, and the inert gas is argon or nitrogen, and the gas flow rate is 60 - 100 mL / min; The heating program of the high-temperature sintering includes two stages: Stage 1: Heat up to 700 - 900 °C at a heating rate of 3 - 10 °C / min and keep the temperature for 0.5 - 2 h. Stage 2: Heat up to 1200 - 1600 °C at a heating rate of 2 - 5 °C / min and keep the temperature for 2 - 6 h.

8. The biomass / sugar composite-derived high plateau capacity hard carbon material obtained by the preparation method according to any one of claims 1 - 7.

9. The application of the biomass / sugar composite-derived high plateau capacity hard carbon material according to claim 8 as a negative electrode material for sodium ion batteries.

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