Method for preparing biomass hard carbon negative electrode material based on advanced oxidation treatment of biomass precursor and application of biomass hard carbon negative electrode material

Abstract

The invention relates to the technical field of sodium ion batteries, in particular to a method for preparing a biomass hard carbon negative electrode material based on advanced oxidation treatment of a biomass precursor and application of the biomass hard carbon negative electrode material. A method for preparing a biomass hard carbon negative electrode material based on advanced oxidation treatment of a biomass precursor comprises the following steps: S1, uniformly mixing a pretreated biomass raw material with a persulfate solution to obtain a mixed solution A; s2, performing temperature control reaction on the mixed solution A, and sequentially washing and drying to obtain a precursor material B; and S3, sintering the precursor material B in a protective atmosphere to obtain the biomass hard carbon negative electrode material. Different from conventional oxidation, the preparation method provided by the invention adopts advanced oxidation to carry out pretreatment on the biomass raw material, the oxidation efficiency is extremely high, the control is easy, and batch operation can be carried out under relatively mild conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to a method for preparing a biomass hard carbon negative electrode material based on advanced oxidation treatment of a biomass precursor and an application thereof. Background Art

[0002] With the continuous expansion of the portable electronic products and electric vehicle markets, the demand for energy storage technology is rising sharply. Compared with traditional energy storage systems, lithium-ion batteries are recognized by the industry as the core energy storage system in the field of efficient electrochemical energy storage due to their outstanding advantages such as high energy density, long cycle life, safety and pollution-free. The electrochemical performance of lithium-ion batteries depends largely on the selection of negative electrode materials. Graphite, as a widely used low-cost commercial negative electrode material, is widely used for its excellent conductivity and excellent reversibility. However, the relatively low theoretical capacity of graphite (372 mAh / g) restricts its further development. Compared with graphite negative electrode, hard carbon has a higher specific surface area and a more developed pore structure, which helps to provide more lithium storage sites, thereby increasing the lithium storage capacity of negative electrode materials. Moreover, hard carbon has a wide range of raw material sources and excellent safety performance. Therefore, hard carbon negative electrode materials have been widely studied in the field of lithium-ion batteries in recent years.

[0003] At present, the raw materials used to prepare hard carbon are mainly biomass, asphalt, resin and organic polymer. Among these raw materials, biomass (starch, sugar, etc.) has become an ideal precursor for preparing hard carbon negative electrode materials due to its wide source, environmental friendliness and low cost. However, the capacity of pure biomass hard carbon materials is still difficult to meet the application needs of high energy density lithium-ion batteries.

[0004] In order to further improve the lithium storage capacity of hard carbon negative electrode materials, researchers have tried to composite silicon with hard carbon. Silicon is a negative electrode material with a high theoretical specific capacity (4200 mAh / g), but its volume expansion during charging and discharging is serious (3~4 times the volume expansion), resulting in poor cycle stability and weak conductivity, which limits its practical application. In principle, the composite of hard carbon and silicon can take advantage of the structural stability and excellent conductivity of the former and the high capacity characteristics of the latter to achieve complementary advantages. However, the current related composite processes (such as carbon-coated silicon, deposition of silicon on porous carbon surfaces, construction of carbon / silicon eggshell-yolk structures, etc.) have problems such as cumbersome processes, high production costs, or uneven silicon distribution and low utilization, which restricts its practical application. Summary of the invention

[0005] In view of the above existing technical problems, the present invention provides a silicon-containing biomass hard carbon anode material, a preparation method thereof, and an application thereof, which are used to overcome the technical problems such as cumbersome operation, high cost, uneven silicon distribution, and low utilization rate existing in the current silicon-carbon composite process. The present invention selects a common mixture of starch and sugar as the biomass precursor, and at the same time, through a simple pretreatment process, a common silane coupling agent is converted into a specific silicon precursor. After mixing the two precursors in a suitable ratio, through further process steps such as pre-oxidation, pulverization, carbonization, and re-pulverization, a kind of silicon-containing biomass hard carbon anode material with high lithium storage capacity and excellent cycle stability is obtained.

[0006] In the present invention, a method for preparing a biomass hard carbon anode material based on advanced oxidation treatment of a biomass precursor includes the following steps: S1. Mix the pretreated biomass raw material with a persulfate solution evenly to obtain a mixed solution A; S2. After carrying out a temperature-controlled reaction on the mixed solution A, wash and dry it in sequence to obtain a precursor material B; S3. Sinter the precursor material B in a protective atmosphere to obtain the biomass hard carbon anode material.

[0007] Further, in the step S1, the pretreatment of the biomass raw material is washing, drying, pulverization, and sieving in sequence.

[0008] Further, in the step S1, the biomass raw material is one or a combination of several of coconut shell, wood chips, peanut shell, or waste bamboo, and the particle size of the biomass raw material after sieving is 75-150 μm.

[0009] Further, in the step S1, the persulfate solution is one or two of sodium persulfate or potassium monopersulfate, and the persulfate solution uses pure water as a solvent.

[0010] Further, in the step S1, the dosage of the biomass raw material is 5-10 g, the concentration of the persulfate solution is 0.1-1 mol / L, and the solid-liquid ratio in the mixed solution A is 10-100 g / L.

[0011] Further, in the step S2, the temperature of the temperature-controlled reaction is 50-90 °C, and the reaction time is 5-20 h. Further, the protective atmosphere in the step S3 is argon or nitrogen, and the gas flow rate is 60-100 mL / min.

[0012] Further, the heating program in step S3 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.

[0013] The biomass hard carbon anode material prepared by the above preparation method.

[0014] Application of the above biomass hard carbon material as the anode material of a sodium-ion battery.

[0015] The present invention has the following advantages and beneficial effects compared with the prior art: (1) The present invention uses biomass waste as the precursor raw material, and the pretreatment steps are simple, which helps to scale up production and reduce production costs.

[0016] (2) Different from conventional oxidation (air oxidation or H2O2 / NaClO / NaClO2 oxidation), the present invention uses advanced oxidation to pretreat the biomass raw material, with extremely high oxidation efficiency and easy control, and can be batch-operated under relatively mild conditions.

[0017] (3) The advanced oxidation adopted by the present invention can effectively break the bonding between different components in the biomass raw material, play the role of adjusting the relative contents of cellulose, hemicellulose and lignin, and further combine with the large number of oxygen-containing groups introduced by oxidation, which helps to form abundant closed pores inside the hard carbon anode material.

[0018] (4) The advanced oxidation adopted by the present invention can also release hydrogen ions synchronously during the treatment of the biomass raw material. Therefore, without additional strong acid purification steps, the ash in the biomass raw material can be effectively removed, and the purity of the biomass hard carbon anode material can be improved. Description of the Drawings

[0019] Figure 1 Electrochemical performance test of the biomass hard carbon anode material prepared in Example 1; Figure 2 Electrochemical performance test of the biomass hard carbon anode material prepared in Example 2; Figure 3 Electrochemical performance test of the biomass hard carbon anode material prepared in Example 3; Figure 4 Electrochemical performance test of the biomass hard carbon anode material prepared in Comparative Example 1; Figure 5 HTEM image of the biomass hard carbon anode material prepared in Example 2; Figure 6HTEM image of the biomass hard carbon anode material prepared in Comparative Example 1. Detailed implementation mode

[0020] 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 examples 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.

[0021] The first object of the present invention is to provide a method for preparing a biomass hard carbon anode material based on the advanced oxidation treatment of biomass precursors, including the following steps: S1. Mix the pretreated biomass raw material with a persulfate solution evenly to obtain a mixed solution A; wherein, the pretreatment of the biomass raw material is successively washing, drying, crushing and sieving; the biomass raw material is one or a combination of coconut shell, wood chips, peanut shell or waste bamboo, and the particle size of the biomass raw material after sieving is 75 - 150 μm.

[0022] The persulfate oxidant is one or a combination of sodium persulfate PS (Na2S2O8) or potassium monopersulfate PMS (KHSO5), and the persulfate solution uses pure water as the solvent.

[0023] The dosage of the biomass raw material is 5 - 10 g, the concentration of the persulfate solution is 0.1 - 1 mol / L, and the solid-liquid ratio in the mixed solution A is 10 - 100 g / L.

[0024] S2. After carrying out a temperature-controlled reaction on the mixed solution A, wash and dry successively to obtain a precursor material B; wherein, the temperature of the temperature-controlled reaction is 50 - 90 °C, and the reaction time is 5 - 20 h. S3. Sinter the precursor material B at high temperature in a protective atmosphere to obtain the biomass hard carbon anode material. Among them, the protective atmosphere in step S3 is argon or nitrogen, and the gas flow rate is 60 - 100 mL / min.

[0025] In this step, the heating program includes two stages. Stage one: heat up to 700 - 900 °C at a heating rate of 3 - 10 °C / min and keep warm for 0.5 - 2 h; Stage two: heat up to 1200 - 1600 °C at a heating rate of 2 - 5 °C / min and keep warm for 2 - 6 h.

[0026] The second object of the present invention is to provide the biomass hard carbon anode material prepared by the above preparation method.

[0027] The third object of the present invention is to provide the above-mentioned biomass hard carbon for use as a negative electrode material in a sodium ion battery.

[0028] <Example 1> This example provides a method for preparing a biomass hard carbon negative electrode material based on advanced oxidation treatment of a biomass precursor, comprising the following steps: S1. Weigh an appropriate amount of washed and dried peanut shell raw material, crush it, and sieve it through a 75-mesh sieve. S2. Add 8 g of the sieved peanut shell raw material to a 0.1 mol / L sodium persulfate solution and mix evenly to obtain a mixed solution, where the solid-liquid ratio in the mixed solution is 40 g / L. S3. Keep the mixed solution in step S2 at 85 °C for a temperature-controlled reaction for 6 h, then wash it with water until it is neutral, and perform a drying treatment to obtain a precursor material subjected to advanced oxidation treatment. S4. Heat the precursor material obtained in step S3 in a nitrogen atmosphere with an air flow rate of 60 mL / min first at a rate of 10 °C / min to 800 °C and hold for 2 h; then heat it at a rate of 5 °C / min to 1300 °C and hold for 3 h to obtain a biomass hard carbon negative electrode material.

[0029] Perform an electrochemical performance test on the biomass hard carbon negative electrode material prepared in this example, and the results are as Figure 1 shown. As Figure 1 can be seen, at a current density of 30 mA / g, the charging specific capacity is 324 mA / g, where the plateau capacity contribution is 216 mA / g, and the first efficiency is 90.1%.

[0030] <Example 2> This example provides a method for preparing a biomass hard carbon negative electrode material based on advanced oxidation treatment of a biomass precursor, comprising the following steps: S1. Weigh an appropriate amount of washed and dried wood chip raw material, crush it, and sieve it through a 100-mesh sieve. S2. Add 8 g of the sieved wood chip raw material to a 0.3 mol / L potassium monopersulfate solution and mix evenly to obtain a mixed solution, where the solid-liquid ratio in the mixed solution is 40 g / L. S3. Keep the uniformly mixed solution obtained in step S2 in an oil bath at 75 °C for a reaction for 15 h, then wash it with water until it is neutral, and perform a drying treatment to obtain a precursor material subjected to advanced oxidation treatment. S4. Heat the precursor material obtained in step S3 in an argon atmosphere with an air flow rate of 70 mL / min first at a rate of 10 °C / min to 800 °C and hold for 1.5 h; then heat it at a rate of 5 °C / min to 1300 °C and hold for 5 h to obtain a biomass hard carbon negative electrode material.

[0031] The electrochemical performance of the biomass hard carbon anode material prepared in this example was tested, and the results are as Figure 2 shown. It can be seen from Figure 2 that at a current density of 30 mA / g, the charge specific capacity is 345 mA / g, of which the plateau capacity contributes 230 mA / g, and the first efficiency is 92.3%.

[0032] Obtain the HTEM image of the biomass hard carbon anode material prepared in this example, as shown in Figure 5 shown. It can be seen from Figure 5 that the biomass hard carbon anode material prepared in this example has rich closed pore characteristics.

[0033] <Example 3> This example provides a method for preparing a biomass hard carbon anode material based on advanced oxidation treatment of biomass precursors, including the following steps: S1. Weigh an appropriate amount of washed and dried sawdust and peanut shell raw materials, crush them according to a mass ratio of 1:1, and pass through a 150-mesh sieve; S2. Add 10 g of the sieved sawdust and peanut shell mixed raw materials into a 1 mol / L persulfate solution and mix evenly to obtain a mixed solution. The solid-liquid ratio in the mixed solution is 50 g / L, and the persulfate solution is a mixed solution of sodium persulfate and potassium monopersulfate with a mass ratio of 1:1; S3. React the mixed solution in step S2 in an oil bath at 80 °C for 20 h, then wash it with water until neutral and dry it to obtain a precursor material treated by advanced oxidation; S4. Heat the precursor material obtained in step S3 in an argon atmosphere with an air flow rate of 80 mL / min from 10 °C / min to 900 °C and hold for 0.5 h; then heat it from 5 °C / min to 1300 °C and hold for 6 h to obtain the biomass hard carbon anode material.

[0034] The electrochemical performance of the biomass hard carbon anode material prepared in this example was tested, and the results are as Figure 3 shown. It can be seen from Figure 3 that at a current density of 30 mA / g, the charge specific capacity is 333 mA / g, of which the plateau capacity contributes 222 mA / g, and the first efficiency is 91.4%.

[0035] <Comparative Example 1> This example provides a method for preparing a biomass hard carbon anode material, including the following steps: S1. Weigh an appropriate amount of washed and dried waste bamboo raw materials, crush them and pass through a 150-mesh sieve; S2. Add 8 g of the sieved waste bamboo raw materials to deionized water and mix evenly, with a solid-liquid ratio of 50 g / L; S3. React the uniformly mixed solution obtained in step S2 in an oil bath at 75 °C for 15 h and perform a drying treatment to obtain a precursor material; S4. Heat the precursor obtained in step S3 from 10 °C / min to 700 °C in an argon atmosphere with a ventilation rate of 80 mL / min and hold for 1.5 h. Then heat it from 5 °C / min to 1500 °C and hold for 4 h to obtain a biomass hard carbon negative electrode material.

[0036] Perform an electrochemical performance test on the biomass hard carbon negative electrode material prepared in this comparative example, and the results are as Figure 4 shown. It can be Figure 4 seen that at a current density of 30 mA / g, the charging specific capacity is 232 mA / g, among which the plateau capacity contribution is 145 mA / g and the first efficiency is 88.4%.

[0037] Obtain the HTEM image of the biomass hard carbon negative electrode material prepared in the comparative example, as Figure 6 shown. It can be Figure 6 seen that the biomass hard carbon negative electrode material prepared in this comparative example only has a small number of closed pores.

[0038] Test Example 1: Electrochemical performance test Battery assembly: Use the hard carbon negative electrode materials obtained in Examples 1 to 3 and Comparative Example 1 as active substances respectively. After mixing them into a homogeneous slurry according to the mass ratio of active substance: superfine carbon powder (SP): sodium carboxymethyl cellulose (CMC): styrene-butadiene rubber (SBR) of 91:3:2:4, use a 60 μm four-sided coater to coat the black slurry on the copper foil and bake it in a vacuum drying oven at 120 o °C for 12 h to obtain a negative electrode sheet. Use a punching machine to punch the electrode film into a round sheet with a diameter of 11 mm, use a sodium metal sheet as the counter electrode, glass fiber (Waterman) as the separator, and select a commercial electrolyte NP-035 (1M NaPF6, with ethylene glycol dimethyl ether as the solvent) to assemble a 2025 coin-type sodium ion battery in an Ar-protected glove box. In addition, perform a constant current charge-discharge test on the assembled 2025 coin-type battery on a Neware battery test system, and the test voltage range is 0.001 - 2.5 V.

[0039] It can be analyzed from Examples 1 to 3 and Comparative Example 1 that the initial charge specific capacities of the half-cells assembled from the negative electrode sheets prepared from the biomass hard carbon negative electrode materials of Examples 1 to 3 are all higher than that of Comparative Example 1. The advanced oxidation pretreatment of biomass raw materials can break the hydrogen bonds and covalent bonds between cellulose, lignin and hemicellulose, adjust the relative contents between cellulose, hemicellulose and lignin, and combine with a large number of oxygen-containing groups introduced by oxidation, which helps to form abundant closed pores inside the hard carbon negative electrode material. When applied to sodium-ion batteries, it can accommodate more sodium ions and improve the specific capacity of sodium-ion batteries. In addition, the hydrogen ions released during the reaction of Examples 1 to 3 with biomass raw materials can effectively remove the ash in the biomass, achieving a purification effect, which helps the material to exhibit high initial efficiency.

[0040] For those not covered above, the prior art shall apply.

[0041] 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 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 ways 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 modification, equivalent substitution, improvement, etc. made to the above embodiments based on the technical essence of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a biomass hard carbon anode material by treating a biomass precursor based on advanced oxidation, characterized in that, It includes the following steps: S1. Mix the pretreated biomass raw material with the persulfate solution evenly to obtain a mixed solution A; S2. After carrying out a temperature-controlled reaction on the mixed solution A, wash and dry it in sequence to obtain a precursor material B; S3. Sinter the precursor material B in a protective atmosphere to obtain the biomass hard carbon negative electrode material.

2. The method for preparing a biomass hard carbon anode material by treating a biomass precursor based on advanced oxidation according to claim 1, wherein In the step S1, the pretreatment of the biomass raw material is washing, drying, crushing and sieving in sequence.

3. A method for preparing a biomass hard carbon anode material from a biomass precursor by advanced oxidation according to claim 2, characterized in that, In the step S1, the biomass raw material is one or more of coconut shell, wood chips, peanut shell or waste bamboo, and the particle size of the biomass raw material after sieving is 75-150 μm.

4. A method for preparing a biomass hard carbon anode material based on the advanced oxidation treatment of biomass precursors according to claim 1, characterized in that: In the step S1, the persulfate solution is one or two of sodium persulfate or potassium monopersulfate, and the persulfate solution uses pure water as a solvent.

5. A method for preparing a biomass hard carbon anode material based on advanced oxidation treatment of biomass precursors according to claim 1, characterized in that: In the step S1, the dosage of the biomass raw material is 5-10 g, the concentration of the persulfate solution is 0.1-1 mol / L, and the solid-liquid ratio in the mixed solution A is 10-100 g / L.

6. A method for preparing a biomass hard carbon anode material by treating a biomass precursor based on advanced oxidation according to claim 1, characterized in that: In the step S2, the temperature of the temperature-controlled reaction is 50-90 °C, and the reaction time is 5-20 h.

7. A method for preparing a biomass hard carbon anode material by treating a biomass precursor based on advanced oxidation according to claim 1, characterized in that: The protective atmosphere in the step S3 is argon or nitrogen, and the gas flow rate is 60-100 mL / min.

8. A method for preparing a biomass hard carbon anode material based on advanced oxidation treatment of biomass precursors according to claim 1, characterized in that: The heating program in the step S3 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.

9. A biomass hard carbon negative electrode material for a sodium ion battery, characterized in that: Prepared by using the method described in any one of claims 1-8.

10. A sodium-ion battery, characterized in that: Using the biomass hard carbon negative electrode material described in claim 9 as the negative electrode material.

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