Biomass hard carbon negative electrode material and preparation method and application thereof

Abstract

The invention relates to the technical field of battery materials, and discloses a biomass hard carbon negative electrode material and a preparation method and application thereof. The biomass hard carbon negative electrode material is prepared from the following raw materials: biomass charcoal, acid liquor and a coating agent. According to the biomass hard carbon negative electrode material provided by the invention, biomass charcoal is used as a carbon source, the raw material source is wide, and the cost is low; according to the preparation method of the biomass hard carbon negative electrode material, only the biomass charcoal needs to be subjected to ball milling, acid pickling, coating and carbonization, the steps are simple, and the preparation method is suitable for industrial application; during preparation, through ball milling, the particle size of the biomass charcoal can be reduced, the specific surface area can be increased, the crystallinity can be reduced, lattice defects can be increased, and physical properties such as porosity and conductivity can be improved; inorganic impurities and part of organic impurities can be removed through acid pickling, biomass is activated, pores of biomass charcoal are regulated and controlled, and a basis is provided for subsequent preparation of porous materials; open pores can be converted into closed pores through coating of the coating agent, and the conductivity and the ion diffusion rate of the hard carbon negative electrode material are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and in particular to a biomass hard carbon negative electrode material and a preparation method and application thereof. Background Art

[0002] In order to change the energy structure, it is necessary to develop cheap and efficient large-scale energy storage technology. Lithium-ion batteries (LIBs) dominate various battery energy storage technologies due to their high energy density, excellent cycle performance, long life, and high output power. However, the global lithium resources are unevenly distributed and high-grade lithium ore is scarce, resulting in an increasing cost of raw materials for lithium-ion batteries. Since sodium resources are much higher than lithium and sodium-ion batteries (SIBs) have similar electrochemical properties to lithium-ion batteries (LIBs), sodium-ion batteries are expected to become an important supplement to lithium-ion batteries in the field of energy storage.

[0003] Reported negative electrode materials for sodium-ion batteries include carbon-based materials, titanium-based compounds, alloy materials, metal compounds and organic compounds. Among them, hard carbon is a material composed of a graphite-like microcrystalline structure and open angular microcrystals. It has a higher specific capacity than graphite and can provide more sites. It also has the advantages of diverse structures, low prices, high sodium storage capacity, small volume deformation after sodium insertion, environmental friendliness and low redox potential.

[0004] Biomass is an organic waste from plants or animals. It is abundant in resources and can retain its natural structure well after carbonization. It is a green, low-cost, and excellent electrochemical performance sodium ion battery negative electrode material. However, in the prior art, when biomass hard carbon is used as a negative electrode material for sodium ion batteries, there are defects such as complex preparation process and poor conductivity of the material. Summary of the invention

[0005] The present invention aims to solve at least one of the above-mentioned technical problems existing in the prior art. To this end, one of the purposes of the present invention is to provide a biomass hard carbon negative electrode material; the second purpose of the present invention is to provide a method for preparing the biomass hard carbon negative electrode material; the third purpose of the present invention is to provide a negative electrode plate; the fourth purpose of the present invention is to provide a sodium ion battery.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A first aspect of the present invention provides a biomass hard carbon negative electrode material, comprising the following preparation raw materials: biomass carbon, acid solution and a coating agent.

[0008] Preferably, the biomass charcoal includes at least one of bamboo charcoal, coconut shell charcoal, bagasse biochar, and corn cob biochar; more preferably, the biomass charcoal is bamboo charcoal.

[0009] Preferably, the particle size of the biochar is 100-500 mesh.

[0010] Preferably, the concentration of the acid solution is 3-6 mol / L; further preferably, the concentration of the acid solution is 4-6 mol / L.

[0011] Preferably, the acid solution includes at least one of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid; further preferably, the acid solution is sulfuric acid.

[0012] Preferably, the mass ratio of the biochar to the coating agent is (15-35):1; further preferably, the mass ratio of the biochar to the coating agent is (18-22):1.

[0013] Preferably, the coating agent includes at least one of asphalt, glucose and sucrose; further preferably, the coating agent is asphalt.

[0014] The second aspect of the present invention provides a method for preparing the biomass hard carbon negative electrode material according to the first aspect of the present invention, comprising the following steps:

[0015] S1, ball milling the biochar;

[0016] S2, pickling the ball-milled biochar with an acid solution to obtain an acid-washed product;

[0017] S3, coating the pickling product with a coating agent to obtain a coated product;

[0018] S4. Carbonizing the coated product under an inert atmosphere to obtain the biomass hard carbon negative electrode material.

[0019] Preferably, in step S1, the rotation speed of the ball mill is 100-600 r / min; further preferably, the rotation speed of the ball mill is 100-300 r / min.

[0020] Specifically, the purpose of ball milling is to subject biochar particles to strong mechanical force, reduce particle size and increase specific surface area, and control the particle size within 100-500 mesh; increase the contact area between biochar and other substances, enhance its adsorption performance, catalytic activity or reaction efficiency; reduce the crystallinity of biochar and increase lattice defects, thereby changing its density, porosity, conductivity and other physical properties.

[0021] Preferably, in the step S1, a drying step is further included after the ball milling is completed.

[0022] Preferably, the drying temperature is 70-90°C; more preferably, the drying temperature is 75-85°C.

[0023] Preferably, the drying time is 10-15 hours; further preferably, the drying time is 10-12 hours.

[0024] Preferably, in step S2, the pickling time is 2-24 hours; further preferably, the pickling time is 6-12 hours.

[0025] Preferably, in step S2, after the pickling is completed, washing and drying steps are also included.

[0026] Preferably, in step S3, the coating temperature is 20-100°C; further preferably, the coating temperature is 30-50°C.

[0027] Preferably, in step S3, the coating time is 0.5-5 h; further preferably, the coating time is 0.5-1 h.

[0028] Preferably, in step S3, the specific operation of coating is: dissolving the coating agent in an organic solvent to form a mixed solution, and then mixing it with the acid-washed product for coating.

[0029] Preferably, the solid-liquid ratio of the coating agent to the organic solvent is 1 g:(60-100) mL; further preferably, the solid-liquid ratio of the coating agent to the organic solvent is 1 g:(70-90) mL.

[0030] Preferably, the organic solvent comprises tetrahydrofuran.

[0031] Preferably, in step S4, the carbonization temperature rising program is: the initial temperature is 18-22°C, the temperature is increased to 1000-1500°C at a rate of 0.5-10°C / min, and the temperature is kept for 1-4h; further preferably, the carbonization temperature rising program is: the initial temperature is 18-22°C, the temperature is increased to 1200-1400°C at a rate of 1.5-2.5°C / min, and the temperature is kept for 1-3h.

[0032] Preferably, in step S4, the inert gas includes one of argon and nitrogen.

[0033] The third aspect of the present invention provides a negative electrode plate, comprising the biomass hard carbon negative electrode material described in the first aspect of the present invention.

[0034] Preferably, the negative electrode plate further includes a conductive agent, an adhesive and a solvent.

[0035] Preferably, the mass ratio of the biomass hard carbon negative electrode material, the conductive agent and the adhesive is (7-9):(0.8-1.2):1.

[0036] Preferably, the conductive agent includes carbon black (Super-P).

[0037] Preferably, the binder comprises carboxymethyl cellulose (CMC).

[0038] Preferably, the solvent comprises deionized water.

[0039] Preferably, the negative electrode sheet is prepared by a method comprising the following steps: stirring and mixing the biomass hard carbon negative electrode material, conductive agent, adhesive and solvent, coating the resulting slurry on a copper foil current collector, drying, rolling and punching to obtain the negative electrode sheet.

[0040] Preferably, the stirring and mixing time is 2-6 hours; more preferably, the stirring and mixing time is 3-5 hours.

[0041] Preferably, the drying temperature is 110-130°C; further preferably, the drying temperature is 115-125°C.

[0042] Preferably, the drying time is 10-15 hours; further preferably, the drying time is 10-12 hours.

[0043] Preferably, the diameter of the negative electrode plate is 10-15 mm; further preferably, the diameter of the negative electrode plate is 11-13 mm.

[0044] The fourth aspect of the present invention provides a sodium ion battery, comprising the negative electrode sheet described in the third aspect of the present invention.

[0045] Preferably, the sodium ion battery uses metallic sodium as the counter electrode and the reference electrode.

[0046] Preferably, the electrolyte of the sodium ion battery includes sodium hexafluorophosphate electrolyte.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] 1) The biomass hard carbon negative electrode material provided by the present invention uses biomass charcoal as a carbon source, and has a wide range of raw material sources and low cost;

[0049] 2) The preparation method of the biomass hard carbon negative electrode material provided by the present invention only requires ball milling, acid washing, coating and carbonization of the biomass carbon, with simple steps and suitable for industrial use; ball milling during the preparation process can reduce the particle size of the biomass carbon, increase the specific surface area, reduce the crystallinity, increase the lattice defects, and improve the porosity, conductivity and other physical properties; acid washing can remove inorganic impurities and some organic impurities, activate the biomass, and regulate the pores of the biomass carbon, providing a basis for the subsequent preparation of porous materials; coating with a coating agent can convert open pores into closed pores, thereby improving the conductivity and ion diffusion rate of the hard carbon negative electrode material.

[0050] 3) The sodium ion battery assembled from the negative electrode sheet prepared with the participation of biomass hard carbon negative electrode material has high specific capacity and first coulomb efficiency, high charge and discharge efficiency, good cycle stability and good electrochemical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 Schematic diagram of the capacity and first efficiency of the biomass hard carbon anode material corresponding to the sodium ion battery at a current density of 0.1C in implementation case 1;

[0052] Figure 2 Schematic diagram of the capacity and first efficiency of the biomass hard carbon negative electrode material corresponding to the sodium ion battery at a current density of 0.1C in implementation case 2;

[0053] Figure 3 Schematic diagram of the capacity and first efficiency of the biomass hard carbon negative electrode material corresponding to the sodium ion battery at a current density of 0.1C in implementation case 3;

[0054] Figure 4 Schematic diagram of the capacity and first efficiency of the biomass hard carbon negative electrode material corresponding to the sodium ion battery at a current density of 0.1C in implementation case 4. DETAILED DESCRIPTION

[0055] The present invention is further described in detail below by specific examples. Unless otherwise specified, the raw materials, reagents or devices used in the examples and comparative examples can be obtained from conventional commercial sources or can be obtained by prior art methods. Unless otherwise specified, the experiments or test methods are conventional methods in the art.

[0056] Example 1

[0057] This embodiment provides a biomass hard carbon negative electrode material, which is prepared by the following steps:

[0058] S1. 10 g of bamboo charcoal was crushed and then ball-milled at a speed of 200 r / min to control the particle size to 100-500 mesh. The ball-milled sample was dried at 80 °C for 12 h.

[0059] S2. Add 5 mol / L sulfuric acid to the dried sample for pickling and activation, treat at room temperature for 6 h, then wash with deionized water until neutral, and dry to obtain a pickling product;

[0060] S3, dissolving 0.05 g of asphalt in 40 mL of tetrahydrofuran to obtain a mixed solution, adding the acid-washed product, and stirring at 40° C. for 0.5 h to obtain a coated product;

[0061] S4. Place the coated product in a tubular furnace, introduce a nitrogen atmosphere, set the initial temperature at 20°C, increase the temperature to 1300°C at 2°C / min, keep the temperature for 2h, and then cool to room temperature to obtain a biomass hard carbon negative electrode material.

[0062] Example 2

[0063] This embodiment provides a biomass hard carbon negative electrode material, which is prepared by the following steps:

[0064] S1. 10 g of bamboo charcoal was crushed and then ball-milled at a speed of 200 r / min to control the particle size to 100-500 mesh. The ball-milled sample was dried at 80 °C for 12 h.

[0065] S2. Add 5 mol / L sulfuric acid to the dried sample for pickling and activation, treat at room temperature for 8 h, then wash with deionized water until neutral, and dry to obtain a pickling product;

[0066] S3, dissolving 0.05 g of asphalt in 40 mL of tetrahydrofuran to obtain a mixed solution, adding the acid-washed product, and stirring at 40° C. for 0.5 h to obtain a coated product;

[0067] S4. Place the coated product in a tubular furnace, introduce a nitrogen atmosphere, set the initial temperature at 20°C, increase the temperature to 1300°C at 2°C / min, keep the temperature for 2h, and then cool to room temperature to obtain a biomass hard carbon negative electrode material.

[0068] Example 3

[0069] This embodiment provides a biomass hard carbon negative electrode material, which is prepared by the following steps:

[0070] S1. 10 g of bamboo charcoal was crushed and then ball-milled at a speed of 200 r / min to control the particle size to 100-500 mesh. The ball-milled sample was dried at 80 °C for 12 h.

[0071] S2. Add 5 mol / L sulfuric acid to the dried sample for pickling and activation, treat at room temperature for 10 h, then wash with deionized water until neutral, and dry to obtain a pickling product;

[0072] S3, dissolving 0.05 g of asphalt in 40 mL of tetrahydrofuran to obtain a mixed solution, adding the acid-washed product, and stirring at 40° C. for 0.5 h to obtain a coated product;

[0073] S4. Place the coated product in a tubular furnace, introduce a nitrogen atmosphere, set the initial temperature at 20°C, increase the temperature to 1300°C at 2°C / min, keep the temperature for 2h, and then cool to room temperature to obtain a biomass hard carbon negative electrode material.

[0074] Example 4

[0075] This embodiment provides a biomass hard carbon negative electrode material, which is prepared by the following steps:

[0076] S1. 10 g of bamboo charcoal was crushed and then ball-milled at a speed of 200 r / min to control the particle size to 100-500 mesh. The ball-milled sample was dried at 80 °C for 12 h.

[0077] S2. Add 5 mol / L sulfuric acid to the dried sample for pickling and activation, treat at room temperature for 12 h, then wash with deionized water until neutral, and dry to obtain a pickling product;

[0078] S3, dissolving 0.05 g of asphalt in 40 mL of tetrahydrofuran to obtain a mixed solution, adding the acid-washed product, and stirring at 40° C. for 0.5 h to obtain a coated product;

[0079] S4. Place the coated product in a tubular furnace, introduce a nitrogen atmosphere, set the initial temperature at 20°C, increase the temperature to 1300°C at 2°C / min, keep the temperature for 2h, and then cool to room temperature to obtain a biomass hard carbon negative electrode material.

[0080] Comparative Example 1

[0081] This comparative example provides a biomass hard carbon negative electrode material, which is different from Example 1 in that no acid washing is performed, and the preparation steps are as follows:

[0082] S1. 10 g of bamboo charcoal was crushed and then ball-milled at a speed of 200 r / min to control the particle size to 100-500 mesh. The ball-milled sample was dried at 80 °C for 12 h.

[0083] S2, dissolving 0.05 g of asphalt in 40 mL of tetrahydrofuran to obtain a mixed solution, adding the ball-milled sample, and stirring at 40° C. for 0.5 h to obtain a coated product;

[0084] S3. Place the coated product in a tubular furnace, introduce a nitrogen atmosphere, set the initial temperature at 20°C, increase the temperature to 1300°C at 2°C / min, keep the temperature for 2h, and then cool to room temperature to obtain a biomass hard carbon negative electrode material.

[0085] Comparative Example 2

[0086] This comparative example provides a biomass hard carbon negative electrode material, which is different from Example 1 in that no ball milling treatment is performed, and the preparation steps are as follows:

[0087] S1. Crush 10g of bamboo charcoal and then dry it at 80°C for 12h;

[0088] S2. Add 5 mol / L sulfuric acid to the dried sample for pickling and activation, treat at room temperature for 6 h, then wash with deionized water until neutral, and dry to obtain a pickling product;

[0089] S3, dissolving 0.05 g of asphalt in 40 mL of tetrahydrofuran to obtain a mixed solution, adding the acid-washed product, and stirring at 40° C. for 0.5 h to obtain a coated product;

[0090] S4. Place the coated product in a tubular furnace, introduce a nitrogen atmosphere, set the initial temperature at 20°C, increase the temperature to 1300°C at 2°C / min, keep the temperature for 2h, and then cool to room temperature to obtain a biomass hard carbon negative electrode material.

[0091] Preparation of negative electrode sheets and assembly of sodium-ion batteries

[0092] Take the biomass hard carbon negative electrode material in Example 1-4 and Comparative Example 1-2, use carbon black (Super-P) as a conductive agent and carboxymethyl cellulose (CMC) as a binder, mix them in a mass ratio of biomass hard carbon negative electrode material: conductive agent: binder = 8:1:1, add deionized water to form a slurry, stir the slurry at high speed for 4 hours, and then evenly coat it on the copper foil current collector with a coater, dry the obtained electrode sheet at 120°C for 12 hours, roll it after cooling, and then use a slicer to punch it to obtain a negative electrode sheet with a diameter of 12 mm.

[0093] The above negative electrode was used as the working electrode, metallic sodium was used as the counter electrode, and sodium hexafluorophosphate electrolyte 1MNaPF6 inEC:DMC (1:1 vol) was used as the electrolyte to assemble button half-cells. All cells were assembled in an argon-filled glove box (oxygen and moisture contents were both less than 1 ppm).

[0094] Performance Testing

[0095] The electrochemical performance test was carried out using a battery testing system, Xinwei CT-4008Tn, at 25°C, 0-2.5V working voltage, and 0.1C current density. The charging specific capacity, discharge specific capacity, and first coulombic efficiency of the sodium ion button half-cell assembled with the negative electrode sheets made of the biomass hard carbon negative electrode materials in the test examples 1-4 and comparative examples 1-2 were tested at a current density of 0.1C. The performance test results are shown in Table 1:

[0096] Table 1 Electrochemical performance test results of sodium ion button half-cell

[0097]

[0098] Table 1 shows the electrochemical performance test results of sodium ion button half-cells. Figure 1This is a schematic diagram of the capacity and first efficiency of the biomass hard carbon negative electrode material corresponding to the sodium ion battery at a current density of 0.1C in the implementation case 1. Figure 2 This is a schematic diagram of the capacity and first efficiency of the biomass hard carbon negative electrode material corresponding to the sodium ion battery at a current density of 0.1C in the implementation case 2. Figure 3 This is a schematic diagram of the capacity and first efficiency of the biomass hard carbon anode material corresponding to the sodium ion battery at a current density of 0.1C in the implementation case 3. Figure 4 This is a schematic diagram of the capacity and first efficiency of the biomass hard carbon negative electrode material corresponding to the sodium ion battery at a current density of 0.1C in implementation case 4. From Table 1, Figure 1 , Figure 2 , Figure 3 and Figure 4 It can be seen that the sodium ion button half-cell assembled with the negative electrode sheet made of the hard carbon negative electrode material in Examples 1-4 can reach a charge capacity of 278.22 mAh·g at a current density of 0.1C. -1 , the discharge capacity can reach 323.86mAh·g -1 The first coulombic efficiency can reach 85.91%, the battery has high charge and discharge efficiency and good cycle stability, indicating that the biomass hard carbon negative electrode material provided by the present invention has good conductivity, the resistance encountered by sodium ions during the embedding and extraction process is small, and the structural changes of the negative electrode material caused by the embedding and extraction of sodium ions are small.

[0099] The difference between Comparative Example 1 and Example 1 is that the ball-milled bamboo charcoal is not subjected to acid washing. It can be seen that the charging capacity of the biomass hard carbon negative electrode material corresponding to the sodium ion battery at a current density of 0.1C in Comparative Example 1 is only 231.37 mAh·g -1 , the discharge capacity is only 294.85mA·g -1 The first coulombic efficiency is only 78.47%, which is somewhat lower than the electrochemical performance of the battery corresponding to the biomass hard carbon negative electrode material in Example 1. This shows that the preparation method of the biomass hard carbon negative electrode material provided by the present invention can not only remove inorganic impurities and some organic impurities and activate biomass by acid washing, but also regulate the pores of biomass carbon by acid washing, providing a basis for the subsequent preparation of porous materials.

[0100] The difference between Comparative Example 2 and Example 1 is that the bamboo charcoal is not ball-milled. It can be seen that the charging capacity of the biomass hard carbon negative electrode material corresponding to the sodium ion battery at a current density of 0.1C in Comparative Example 2 is only 171.66 mAh·g -1 , the discharge capacity is only 245.11 mA g -1The first coulombic efficiency was only 70.03%, and the electrochemical performance of the sodium ion button half-cell was seriously reduced, indicating that the biomass carbon was not ball-milled, its crystallinity was not reduced, the lattice defects were few, and the physical properties such as porosity and conductivity were not good, which affected the conductivity of the biomass hard carbon negative electrode material and further affected the electrochemical performance of the sodium ion button half-cell.

[0101] The biomass hard carbon negative electrode material provided by the present invention uses bamboo charcoal, coconut shell charcoal, etc. as carbon sources, realizes high added value utilization of biomass charcoal, can reduce environmental pollution caused by combustion of biomass charcoal, and has easy-to-obtain raw materials, low cost, and is green and environmentally friendly. By ball milling, pickling, coating and carbonizing the biomass charcoal, a biomass hard carbon negative electrode material with good conductive performance can be obtained. The preparation method is simple, the product quality is high, and the negative electrode plate is prepared and used to assemble a sodium ion battery. The battery has high specific capacity and first coulomb efficiency, and good electrochemical performance.

Claims

1. A biomass hard carbon negative electrode material, It is characterized in that The preparation method comprises the following raw materials: biomass charcoal, acid liquid and coating agent.

2. The biomass hard carbon negative electrode material according to claim 1, It is characterized in that The biomass charcoal includes at least one of bamboo charcoal, coconut shell charcoal, bagasse biochar, and corn cob biochar.

3. The biomass hard carbon negative electrode material according to claim 1, It is characterized in that The particle size of the biochar is 100-500 meshes.

4. The biomass hard carbon negative electrode material according to claim 1, It is characterized in that The concentration of the acid solution is 3-6 mol / L; Preferably, the acid solution includes at least one of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid.

5. The biomass hard carbon negative electrode material according to claim 1, It is characterized in that The mass ratio of the biochar to the coating agent is (15-35):1; Preferably, the coating agent includes at least one of asphalt, glucose and sucrose.

6. The method for preparing the biomass hard carbon negative electrode material according to any one of claims 1 to 5, It is characterized in that The following steps are involved: S1, ball milling the biochar; S2, pickling the ball-milled biochar with an acid solution to obtain an acid-washed product; S3, coating the pickling product with a coating agent to obtain a coated product; S4. Carbonizing the coated product under an inert atmosphere to obtain the biomass hard carbon negative electrode material.

7. The preparation method according to claim 6, It is characterized in that In the step S1, the rotation speed of the ball mill is 100-600 r / min; And / or, in step S2, the pickling time is 2-24h; And / or, in step S3, the coating temperature is 20-100° C. and the coating time is 0.5-5 h.

8. The preparation method according to claim 6, It is characterized in that In step S4, the carbonization temperature raising procedure is as follows: the initial temperature is 18-22°C, the temperature is raised to 1000-1500°C at a rate of 0.5-10°C / min, and the temperature is kept for 1-4h.

9. A negative electrode sheet, It is characterized in that The invention comprises the biomass hard carbon negative electrode material as described in any one of claims 1 to 5.

10. A sodium ion battery, It is characterized in that Including the negative electrode sheet as described in claim 9.

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