Preparation Method and Application of a Mesoporous Spherical Hard Carbon Material

Abstract

The present invention relates to the field of sodium-ion batteries, and specifically relates to a preparation method and application of a mesoporous spherical hard carbon material. Using saccharides as the carbon source for the negative electrode material of sodium-ion batteries, mesoporous spherical hard carbon is prepared through a simple hydrothermal-oxidation-carbonization process. The precursor has a wide source, low price, and is environmentally friendly. The obtained hard carbon negative electrode material realizes high capacity, high areal loading, and high volume capacity of the hard carbon negative electrode material due to its special spherical morphology and rich pore structure.

Description

Technical Field

[0001] The present invention relates to the field of anode materials for sodium-ion batteries, and specifically relates to a preparation method of a mesoporous spherical hard carbon material, and also relates to the application of a mesoporous spherical hard carbon material. Background Art

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

[0003] Biomass hard carbon materials show diversity in microstructure, such as spherical, granular, fibrous, tubular, etc. Different microstructures are very different in pore structure, specific surface area, functional groups, etc. Reasonable design of the microstructure of hard carbon can help the transmission and diffusion of sodium ions, and is beneficial to the improvement of the electrochemical performance of sodium-ion batteries. For electrode materials, the porosity and pore size distribution have a great influence on ion transport. Mesopores are beneficial to shortening the ion diffusion path and improving the rate performance. How to comprehensively improve the electrochemical performance, especially the simultaneous improvement of the 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 preparation method of mesoporous spherical hard carbon for existing problems. This method has the advantages of low cost, controllable morphology and size, and environmental friendliness; high-capacity, high areal loading, and high volume capacity hard carbon materials can be prepared by using this method.

[0005] The technical solution adopted by the present invention to achieve the above purpose is:

[0006] A preparation and application of mesoporous spherical hard carbon, comprising the following steps:

[0007] Step (1): Dissolve a carbon source in deionized water, add an organic solvent, and stir for a period of time.

[0008] Step (2): Pour the uniformly mixed solution into a hydrothermal reaction kettle, and prepare hydrothermal carbon under high temperature and high pressure.

[0009] Step (3): Carbonize the hydrothermal carbon at a low temperature in an air atmosphere for a period of time, and then change to an inert atmosphere for high-temperature carbonization to obtain a hard carbon anode material.

[0010] Further, the organic solution containing the carbon source is prepared by the following steps:

[0011] 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 pentanol, and add them to a beaker and stir to mix evenly.

[0012] Preferably, the carbon source is sucrose, the organic solvent is acetic acid, the preparation concentration is 45 - 55%, and the stirring time is 1 - 3 h.

[0013] Furthermore, for the hydrothermal carbonization reaction, the following steps are adopted:

[0014] Pour the mixed solution containing the carbon source into a hydrothermal reaction kettle, place it in a forced-air oven and heat at 140°C - 200°C for 6 - 24 h.

[0015] Preferably, the hydrothermal temperature is 160°C - 180°C and the time is 10 - 12 h.

[0016] Furthermore, for the pre-oxidation and secondary carbonization of the hydrothermal carbon, the following steps are adopted:

[0017] Place the hydrothermal carbon in an air atmosphere for pre-oxidation for a certain time, and then change to an inert atmosphere for high-temperature carbonization.

[0018] Preferably, the pre-oxidation conditions are: temperature 200 - 400°C, holding time 1 - 3 h, gas flow rate 150 - 300 ml / min; the high-temperature carbonization conditions are: temperature 1000 - 1400°C, holding time 1 - 6 h, heating rate 1 - 10°C / min.

[0019] Compared with the prior art, the preparation method of the mesoporous spherical hard carbon material of the present invention has the following advantages:

[0020] For the hard carbon negative electrode material described in the present invention, the synthesis process is simple, the cost is low, the raw material source is rich, and at the same time its morphology and structure are regular. Applying this hard carbon material to the negative electrode of a sodium-ion battery can achieve high capacity, high initial efficiency, high areal / volumetric capacity performance. Description of the Drawings

[0021] Figure 1 are the SEM and TEM images of regulating the microstructure of hard carbon as the negative electrode material of a sodium-ion battery by hydrothermal-carbonization with different solvents.

[0022] Figure 2 is a comparison chart of the first-cycle charge-discharge curves of regulating hard carbon as the negative electrode material of a sodium-ion battery by hydrothermal-carbonization with different solvents at a current density of 20 mA / g.

[0023] Figure 3 is the XRD pattern of regulating the structure of hard carbon as the negative electrode material of a sodium-ion battery with different solvents.

[0024] Figure 4 It is the Raman spectrum of implementing the regulation of the hard carbon structure with different solvents as the anode material for sodium-ion batteries.

[0025] Figure 5 It is the Raman fitting data of implementing the regulation of the hard carbon structure with different solvents as the anode material for sodium-ion batteries.

[0026] Figure 6 It is the first charge-discharge curve of the full battery with the best solvent-regulated hard carbon structure as the anode material matched with Prussian blue, the electrolyte is a flame-retardant electrolyte, and the current density is 20 mA g-1.

[0027] Figure 7 It is the first charge-discharge curve of the soft-pack battery with the best solvent-regulated hard carbon structure as the anode material matched with Prussian blue, the electrolyte is a flame-retardant electrolyte, and the current density is 20 mA g-1. Detailed implementation manners

[0028] The present invention will be further described in detail below in conjunction with embodiments, but the implementation manners of the present invention are not limited thereto.

[0029] A method for preparing and applying mesoporous spherical hard carbon provided in this experiment includes the following steps:

[0030] 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.

[0031] Step (2): Pour 75 ml of the mixed solution into a hydrothermal reaction kettle, heat it in a blast drying oven at 160 °C for 12 hours, and naturally cool it to room temperature. Filter the solid-liquid mixture by suction, wash it until neutral, and dry it in a blast drying oven at 90 °C for 12 h to obtain hydrothermal carbon.

[0032] Step (3): Place the hydrothermal carbon in a tubular furnace, first introduce air with a gas flow rate of 200 ml / min, heat it at a heating rate of 5 °C / min, the carbonization temperature is 250 °C, and the holding time is 1 h. Then change to a nitrogen atmosphere with a gas flow rate of 100 ml / min and a heating rate of 10 °C / min, and heat it to 1000 °C. Then heat it at 5 °C / min to 1400 °C, and the holding time is 3 h. Mesoporous spherical carbon is obtained.

[0033] Prepare the hard carbon material into a slurry according to the mass ratio of active material: conductive carbon: binder (sodium alginate colloid with a concentration of 2%) of 93:2:5. Uniformly coat it on the aluminum foil, dry it in a vacuum drying oven at 90 °C for 12 hours, cut the electrode sheet with a 10 mm circular mold, weigh the electrode sheet and store it in a glove box filled with argon (Ar).

[0034] Using sodium metal as the counter electrode, the electrolyte used was 1 M / L NaPF6 (EC + DMC volume ratio 1:1), the separator was a glass fiber separator (GF / A), and the half-cell was assembled inside a glove box filled with argon (Ar). The assembled battery was left to stand in an incubator for 12 h.

[0035] The cyclic and rate performance of the half-cell was tested using a Blue Power battery test system (LAND CT2001A).

[0036] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A preparation method of a mesoporous spherical hard carbon material, characterized in that, It includes the following steps: Step (1): Dissolve sucrose in deionized water, then add acetic acid and stir. The concentration of acetic acid is 0.1 - 75%; Step (2): Pour the solution into a hydrothermal reaction kettle, place it in a forced-air oven for heating, react under high temperature and high pressure. After the reaction, wash, filter by suction and dry the obtained hydrothermal carbon; Step (3): First calcine the hydrothermal carbon prepared in step (2) at a low temperature in an air atmosphere, and then switch to an inert gas for high-temperature carbonization to obtain mesoporous spherical hard carbon. The low-temperature carbonization temperature is 200°C - 400°C, the heat preservation time is 1 - 3 h, the temperature during gas replacement is 200°C - 400°C, the inert atmosphere includes at least one of nitrogen and argon, the heating rate of high-temperature carbonization is 1 - 10°C / min, the carbonization temperature is 1000°C - 1400°C, and the heat preservation time is 1 - 6 h.

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

3. The preparation method of a mesoporous spherical hard carbon material according to claim 2, characterized in that, In step (2), the heating temperature of the forced-air oven is 120 - 180°C, the heating time is 6 - 12 h, wash the hydrothermal carbon with deionized water until the pH is neutral, filter by vacuum suction, and the drying temperature of forced-air drying is 60 - 90°C, and the drying time is 6 - 12 h.

4. The mesoporous spherical hard carbon negative electrode material obtained by the preparation method of a mesoporous spherical hard carbon material according to any one of claims 1-3, characterized in that, This material has a regular mesoporous spherical structure, which helps to improve the tap density and mechanical strength of the material, and is also beneficial to electron transport and ion diffusion in electrochemical applications.

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