Preparation method and application of mesoporous spherical hard carbon material

Abstract

The invention relates to the field of sodium ion batteries, in particular to a preparation method and application of a mesoporous spherical hard carbon material. Carbohydrate is used as a carbon source of a sodium ion battery negative electrode material, and mesoporous spherical hard carbon is prepared through a simple hydrothermal-oxidation-carbonization process. And the precursor is wide in source, low in price and environment-friendly. The obtained hard carbon negative electrode material realizes high capacity, high surface load and high volume capacity of the hard carbon negative electrode material due to the special spherical morphology and the rich pore structure of the hard carbon negative electrode material.

Description

Technical Field

[0001] The invention relates to the field of negative electrode materials for sodium ion batteries, and in particular to a preparation method of a mesoporous spherical hard carbon material, and also to an application of the mesoporous spherical hard carbon material. Background Art

[0002] With the continuous improvement of energy density and power density requirements for energy storage systems, the research and development of negative electrode materials for lithium-ion batteries and sodium-ion batteries has received great attention. Among the many negative electrode materials, hard carbon materials are the most commercially promising negative electrode materials because of their advantages such as stable structure, good specific capacity, controllable morphology and low cost.

[0003] Biomass hard carbon materials are diverse in microstructure, such as spherical, granular, fibrous, tubular, etc. Different microstructures have great differences in pore structure, specific surface area, functional groups, etc. Reasonable hard carbon microstructure can facilitate the transmission and diffusion of sodium ions, which is beneficial to the improvement of the electrochemical performance of sodium ion batteries. For electrode materials, porosity and pore size distribution have a great influence on ion transmission. Mesopores are beneficial to shorten the ion diffusion path and improve rate performance. How to achieve a comprehensive improvement in electrochemical performance, especially the simultaneous improvement of rate performance and high energy density, is still a huge challenge. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing mesoporous spherical hard carbon in response to existing problems. The method has the advantages of low cost, controllable morphology and size, and environmental friendliness. The method can be used to prepare hard carbon materials with high capacity, high surface loading, and high volume capacity.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: A preparation and application of mesoporous spherical hard carbon, comprising the following steps: Step (1): Dissolve the carbon source in deionized water, add an organic solvent, and stir for a period of time.

[0006] Step (2): pouring the uniformly mixed solution into a hydrothermal reactor to prepare hydrothermal carbon under high temperature and high pressure.

[0007] Step (3): Carbonize the hydrothermal carbon at low temperature in an air atmosphere for a period of time, and then switch to an inert atmosphere for high temperature carbonization to obtain a hard carbon negative electrode material.

[0008] Furthermore, the organic solution containing the carbon source is prepared by the following steps: Accurately weigh a certain mass of sucrose, glucose, and maltose, dissolve them in a certain volume of deionized water, measure a certain volume of acetic acid, valeric acid, ethanol, and amyl alcohol, add them into a beaker, and stir to mix evenly.

[0009] Preferably, the carbon source is sucrose, the organic solvent is acetic acid, the preparation concentration is 45-55%, and the stirring time is 1-3h.

[0010] Furthermore, the hydrothermal carbonization reaction adopts the following steps: The mixed solution containing the carbon source is poured into a hydrothermal reactor, and placed in a forced air oven for heating at 140°C-200°C for 6-24 hours.

[0011] Preferably, the hydrothermal temperature is 160°C-180°C, and the time is 10-12h.

[0012] Furthermore, the hydrothermal carbon pre-oxidation and secondary carbonization adopt the following steps: The hydrothermal carbon is placed in an air atmosphere for pre-oxidation for a certain period of time, and then replaced with an inert atmosphere for high-temperature carbonization.

[0013] Preferably, the pre-oxidation conditions are: temperature of 200-400°C, holding time of 1-3h, gas flow rate of 150-300ml / min; high temperature carbonization conditions are: temperature of 1000-1400°C, holding time of 1-6h, heating rate of 1-10°C / min.

[0014] Compared with the prior art, the method for preparing a mesoporous spherical hard carbon material described in the present invention has the following advantages: The hard carbon negative electrode material described in the present invention has a simple synthesis process, low cost, abundant raw material sources, and regular morphology and structure. The hard carbon material is applied to the negative electrode of a sodium ion battery, which can take into account high capacity, high initial efficiency, and high surface load / high volume capacity performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 These are the SEM and TEM images of hard carbon microstructure regulated by hydrothermal-carbonization using different solvents as negative electrode materials for sodium ion batteries.

[0016] Figure 2 This is a comparison chart of the first cycle charge and discharge curves of hard carbon as the negative electrode material of sodium ion batteries at a current density of 20mA / g using different solvents through hydrothermal-carbonization regulation.

[0017] Figure 3 This is the XRD diagram of using different solvents to regulate the hard carbon structure as the negative electrode material for sodium ion batteries.

[0018] Figure 4 This is the Raman diagram of using different solvents to regulate the hard carbon structure as a negative electrode material for sodium ion batteries.

[0019] Figure 5 It is the Raman fitting data of implementing different solvents to regulate the hard carbon structure as the negative electrode material of sodium ion battery.

[0020] Figure 6 It is the implementation of the best solvent-regulated hard carbon structure as the negative electrode material and Prussian blue matching full battery, the electrolyte is a flame retardant electrolyte, and the first cycle charge and discharge curve at a current density of 20mAg-1.

[0021] Figure 7 It is a soft-pack battery that implements the best solvent regulation of hard carbon structure as the negative electrode material and matches it with Prussian blue. The electrolyte is a flame-retardant electrolyte, and the first cycle charge and discharge curve at a current density of 20mAg-1. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0023] The preparation and application of a mesoporous spherical hard carbon provided in this experiment include the following steps: Step (1): Dissolve 15 g of sucrose in 37.5 ml of deionized water, add 37.5 ml of acetic acid solution, and stir for 1 hour.

[0024] Step (2): Pour 75 ml of the mixed solution into a hydrothermal reactor, heat it in a forced air oven at 160°C for 12 hours, and cool it naturally to room temperature. Filter the solid-liquid mixture, wash it to neutrality, and bake it in a forced air oven at 90°C for 12 hours to obtain hydrothermal carbon.

[0025] Step (3): Place the hydrothermal carbon in a tubular furnace, first introduce air, with a gas flow rate of 200 ml / min, and a heating rate of 5°C / min, a carbonization temperature of 250°C, and a holding time of 1 hour. Then switch to a nitrogen atmosphere, with a gas flow rate of 100 ml / min, a heating rate of 10°C / min, and raise the temperature to 1000°C. Then raise the temperature to 1400°C at 5°C / min, and hold the temperature for 3 hours. Obtain mesoporous spherical carbon.

[0026] The hard carbon material was prepared into a slurry according to the mass ratio of active material: conductive carbon: binder (sodium alginate colloid 2% concentration) of 93:2:5. It was evenly coated on aluminum foil and dried in a vacuum oven at 90°C for 12 hours. The electrode was cut with a 10mm circular grinder, and the electrode was weighed and stored in a glove box filled with argon (Ar).

[0027] Metallic sodium was used as the counter electrode, 1M / L NaPF6 (EC+DMC volume ratio 1:1) was used as the electrolyte, and the diaphragm was a glass fiber diaphragm (GF / A). The half-cell was assembled in a glove box filled with argon (Ar). The assembled battery was left to stand in a constant temperature box for 12 hours.

[0028] The cycle and rate performance of the half-cell were tested using a LAND battery testing system (LAND CT2001A).

[0029] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a mesoporous spherical hard carbon material, characterized in that: The steps include: Step (1): dissolving sugar in deionized water and stirring; Step (2): pouring the solution into a hydrothermal reaction kettle, placing it in a blast oven for heating, reacting under high temperature and high pressure, and after completion, washing, filtering and drying the generated hydrothermal carbon; Step (3): The hydrothermal carbon prepared in step (2) is first calcined at low temperature in an air atmosphere, and then switched to an inert gas for high-temperature carbonization to obtain a mesoporous spherical hard carbon.

2. The method for preparing a mesoporous spherical hard carbon material according to claim 1, characterized in that: In step (1), sugar is dissolved in deionized water, and then an organic solvent is added and stirred.

3. The method for preparing a mesoporous spherical hard carbon material according to claim 2, characterized in that: In step (1), the biomass derivative raw material is one or more of sucrose, glucose and maltose.

4. The method for preparing a mesoporous spherical hard carbon material according to claim 2, characterized in that: In step (1), the organic solvent is one or more of acetic acid, valeric acid, ethanol and pentanol.

5. The method for preparing a mesoporous spherical hard carbon material according to claim 2, characterized in that: The concentration of the organic solvent in step (1) is 0.1-75%.

6. The method for preparing a mesoporous spherical hard carbon material according to claim 2, characterized in that: The stirring time in step (1) is 1-3h.

7. The method for preparing a mesoporous spherical hard carbon material according to claim 2, characterized in that: In step (2), the heating temperature of the blast oven is 120-180° C., the heating time is 6-12 h, the hydrothermal carbon is washed with deionized water until the pH is neutral, vacuum filtered, and the blast drying temperature is 60-90° C., and the drying time is 6-12 h.

8. The method for preparing a mesoporous spherical hard carbon material according to claim 2, characterized in that: In step (3), the heat treatment heating rate is 1°C / min-10°C / min, the low-temperature carbonization temperature is 200°C-400°C, the insulation time is 0-3h, the temperature during ventilation is 200°C-400°C, the inert atmosphere includes at least one of nitrogen and argon, the heating rate is 1-10°C / min, the carbonization temperature is 1000°C-1400°C, and the insulation time is 1-6h.

9. The mesoporous spherical hard carbon negative electrode material obtained by the method for preparing a mesoporous spherical hard carbon material according to any one of claims 1 to 8, characterized in that: The material has a regular mesoporous spherical structure, which helps to improve the compaction density and mechanical strength of the material, while also facilitating electron transport and ion diffusion in electrochemical applications.

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