Coal-based composite sodium battery negative electrode material and preparation method thereof

Abstract

The invention relates to the technical field of sodium batteries, and discloses a coal-based composite sodium battery negative electrode material and a preparation method thereof.The preparation method comprises the following steps that S1, anthracite is subjected to supercritical CO2 treatment, and a treated body is obtained and mixed with nano antimony oxide; s2, heating the mixture to obtain coal-based graphite; s3, the coal-based graphite is treated through a Hummers method, and the composite material is obtained. According to the method, the pore structure of the anthracite is regulated and controlled in a supercritical CO2 mode, then the nano antimony oxide is doped into pores of the anthracite, the anthracite is charred during subsequent firing and can better wrap antimony, meanwhile, the pore structure and connectivity of the coal are improved by the supercritical CO2, and the volume expansion of the antimony oxide can be greatly relieved. After the treatment, the graphene / Sb composite material formed by oxidation reduction and ultrasonic exfoliation of the graphite can enable the combination of graphene and antimony to be tighter, so that the electrochemical performance is better.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium batteries, and in particular to a coal-based composite sodium battery negative electrode material and a preparation method thereof. Background Art

[0002] Graphene, an emerging two-dimensional carbon nanomaterial, is widely used in energy storage and conversion, electronic devices, sensors, and biomedicine due to its low mass density, large specific surface area, excellent conductivity, and high flexibility. Currently, the raw materials for graphene production primarily rely on natural graphite or carbon-containing gases such as CH₄ and C₂H₄, which are costly and unfavorable for large-scale production. In contrast, coal, with its abundant reserves, low price, rich variety of aromatic groups, and structural characteristics of long-range disorder and short-range order, is an ideal carbon source for the development of graphene or graphene oxide. In my country, coal utilization is characterized by high pollution, high energy consumption, and low efficiency. Over 50% of coal is directly used for combustion in industrial boilers and kilns, causing serious environmental pollution. Less than 20% of coal is converted into low-pollution energy sources such as gas or liquid through coal chemical technologies. Therefore, my country urgently needs to transform its coal consumption mechanism. Processing coal into high-value-added coal-based new carbon material products with broad application prospects, especially coal-based graphene and composite materials, is of great significance to the clean and efficient use of coal and the transformation and upgrading of the industry.

[0003] For example, patent publication number CN116031392A discloses a method for preparing a nano-antimony / graphene composite material. This patent uses grinding alone to obtain the antimony / graphene composite material. However, the bond between antimony and graphene in the composite material is not very tight, which may cause the antimony to fall off, thus affecting recyclability. Summary of the Invention

[0004] Technical problems solved by the present invention: This technology addresses the current problem of loose bonding between antimony and graphene in antimony / graphene composites produced through grinding and mixing, which impacts electrochemical performance. Supercritical CO2 treatment improves the pore structure and connectivity of coal, allowing antimony oxide to better bond with the coal and effectively mitigating its volume expansion. Traditional Hummers methods for preparing graphene oxide use sulfuric acid, potassium permanganate, and sodium nitrate. This mixing produces toxic gases like NO2 and N2O4, and the reaction temperature is divided into three stages: low, medium, and high, making it difficult to control.

[0005] The technical solution adopted in the present invention is: In response to the above technical problems, the present invention aims to provide a coal-based composite sodium battery negative electrode material and a preparation method thereof. The specific contents are as follows: The present invention provides a method for preparing a negative electrode material for a coal-composite sodium battery and application of the negative electrode material in a sodium ion battery.

[0006] The method for preparing the aforementioned coal composite sodium battery negative electrode material comprises the following steps: 1. Grind the anthracite coal in a ball mill until it passes a 200-mesh sieve. Take a sample of the ground and sieved mixture, then acid-wash and place it in a pressure vessel. The specific steps are: Place the sample in a reactor, heat it to 50-100°C, then introduce supercritical CO2 at a pressure of 10-20 MPa for 10-15 hours to control the coal's pore structure. Allow it to cool. After cooling, mix it with nano-antimony oxide.

[0007] 2. Place the treated anthracite in a graphite crucible in a graphitization furnace, introduce nitrogen, and heat the mixture to 2500-3000°C at a heating rate of 10-25°C / min. Keep the temperature for 1-4 hours, and then cool the mixture to room temperature under circulating water. The resulting sample is coal-based graphite.

[0008] 3. Synthesis of coal-based graphene oxide: The specific method is as follows: ① The first stage: take a dry three-necked flask, add concentrated sulfuric acid first, slowly add coal-based graphite powder under ice bath conditions while stirring continuously, and then slowly add potassium permanganate and H3PO4 and maintain for 1 hour; ② The second stage: After the reaction is completed, remove the three-necked flask from the ice water bath and quickly transfer it to a constant temperature water bath. The reaction temperature is raised to about 50°C and maintained at a constant temperature for 15 hours.

[0009] After the reaction, deionized water at 0°C was slowly added dropwise to the three-necked flask. After the addition of deionized water was completed, an appropriate amount of H2O2 was added dropwise to the three-necked flask. The termination signal was when the suspension turned bright yellow.

[0010] After standing for 5-10 hours, the supernatant was decanted and filtered to retain the precipitate. The precipitate was repeatedly washed with 5% hydrochloric acid and then with high-purity water until it could no longer be filtered. The precipitate was then centrifuged and washed several times at 4000 rpm until the pH of the solution was approximately 7, thereby obtaining a graphene oxide / Sb composite material.

[0011] 4. Preparation of composite materials: The obtained graphene oxide / Sb composite material is ground and mixed with a reducing agent, and then calcined at 200°C-500°C, washed with water, and dried to obtain a graphene / Sb composite material.

[0012] The technical mechanism and beneficial effects adopted by the present invention are: The present invention uses supercritical CO2 to improve the pore structure and connectivity of coal, facilitating subsequent combination with antimony oxide. During subsequent firing, the anthracite is carbonized to better wrap the antimony. After this treatment, the graphite is then subjected to oxidation-reduction and ultrasonic exfoliation to form a graphene / Sb composite material, which can make the combination of graphene and antimony tighter, thereby improving the electrochemical performance.

[0013] During the preparation of the graphene / Sb composite material, toxic gas emissions can be reduced, and the reaction temperature is set at a low mid-range, making it easy to control. The resulting graphene oxide has a larger interlayer spacing, which is conducive to ultrasonic exfoliation, and can produce graphene oxide with fewer layers. DETAILED DESCRIPTION

[0014] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0015] 1. Example Example 1 A preparation step of a coal-based composite sodium battery negative electrode material is as follows: (1) 10g of anthracite was ground to 200 mesh, and then acid-washed with 100ml of 4mol / L HCl and 100ml of 10wt% HF to remove ash. The sample obtained above was washed with deionized water to remove Cl - and F - The neutral sample was placed in a reactor, heated to 100°C, and then supercritical CO2 was introduced at a pressure of 15 MPa for 12 hours. After the heat preservation was completed, the CO2 pressure was released and the mixture was allowed to cool. After cooling, it was mixed with 0.5g of nano-antimony oxide to obtain a mixture.

[0016] The mixture was placed in a graphite crucible of a graphitization furnace, nitrogen was introduced, and the temperature was raised to 2800°C at a heating rate of 20°C / min, kept warm for 2 hours, and cooled to room temperature under circulating water conditions. The obtained sample was coal-based graphite.

[0017] (2) Synthesis of coal-based graphene oxide: The modified Hummers method is used. The specific method is as follows: ① Low temperature stage: Take a dry three-necked flask, first add 130ml of concentrated sulfuric acid with a volume fraction of 98%, slowly add 3g of coal-based graphite powder under continuous stirring under ice bath conditions, then slowly add 10g of potassium permanganate and 20ml of H3PO4 with a concentration of 60% and maintain for 1h.

[0018] ②Medium temperature stage: After the low temperature reaction is completed, remove the three-necked flask from the ice water bath and quickly transfer it to a constant temperature water bath. The reaction temperature is raised to about 50°C and maintained at a constant temperature for 15 hours.

[0019] After the reaction at medium temperature, slowly drop 260 ml of ionized water at 0°C into the three-necked flask. After the addition of deionized water is completed, add an appropriate amount of H2O2 into the three-necked flask. The termination signal is when the suspension turns bright yellow.

[0020] After standing for 5 hours, the supernatant was decanted and filtered to retain the precipitate. The precipitate was repeatedly washed with 5% hydrochloric acid and then with high-purity water until it could no longer be filtered. The precipitate was then centrifuged and washed several times at 4000 rpm until the pH of the solution was approximately 7, thereby obtaining a graphene oxide / Sb composite material.

[0021] (3) Preparation of redox graphene / Sb composite material: The obtained graphene oxide / Sb composite material was ground and mixed with 3 g of sodium borohydride, calcined at 400 °C for 2-3 h, washed with water, and dried to obtain a graphene / Sb composite material. Example 2 The difference between this embodiment and embodiment 1 is that the mass ratio of anthracite to antimony oxide is 40:1.

[0022] Example 3 The difference between this embodiment and embodiment 1 is that the amount of sodium borohydride added is 2 g.

[0023] Example 4 The difference between this embodiment and embodiment 1 is that, in the preparation of the redox graphene / Sb composite material, the calcination temperature is 300°C.

[0024] 2. Comparative Example Comparative Example 1 The difference between this comparative example and Example 1 is that the anthracite is not acid-washed.

[0025] Comparative Example 2 The difference between this comparative example and Example 1 is that the anthracite and antimony oxide are blended but not treated with supercritical CO2.

[0026] Comparative Example 3 The difference between this comparative example and Example 1 is that the synthesis of coal-based graphene oxide is different.

[0027] Specifically: ① Low-temperature blending stage: Assemble a 250 mL reaction flask in an ice-water bath and add 80 mL of 98% concentrated sulfuric acid. Add a solid mixture of 2 g of graphite powder and 1 g of sodium nitrate. Add 5 g of potassium permanganate three times, controlling the reaction temperature to no more than 20°C, and stir for 2 hours.

[0028] ②Medium temperature reaction stage: Remove the ice water bath, raise the temperature to about 35°C, and continue stirring for 30 minutes.

[0029] ③ High-temperature reaction and termination stage: Slowly add 80ml of deionized water and continue stirring for 20 minutes. Then, add an appropriate amount of hydrogen peroxide to reduce the residual oxidant, turning the solution bright yellow. Filter while hot and wash with 5% HCl solution and deionized water until no sulfate is detected in the filtrate. Finally, dry the filter cake thoroughly in a vacuum drying oven at 60°C and store for future use.

[0030] 3. Test Examples The samples prepared in Examples 1-4 and Comparative Examples 1-3 were used for the measurement.

[0031] The active material: conductive agent SP: binder (CMC, SBR) are fully stirred in water at a ratio of 8:1:1 and evenly coated on copper foil. After drying, they are cut into circular pole pieces and assembled into a battery according to the positive electrode shell-pole piece-electrolyte-diaphragm-electrolyte-negative electrode piece (Na piece)-foam nickel-negative electrode shell.

[0032] Test method: Constant current charge and discharge tests were performed at a constant temperature (25°C) within a potential range of 0.001-2.5V.

[0033] The measurement results are shown in Table 1.

[0034]

[0035] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a negative electrode material for a coal-based composite sodium battery, characterized in that: The steps include: S1 Anthracite is treated with supercritical CO2 to obtain a treated body mixed with nano antimony oxide; S2 heating the mixture to obtain coal-based graphite; S3 Coal-based graphite is treated by Hummers method to obtain a composite material.

2. The method for preparing the negative electrode material of a coal-based composite sodium battery according to claim 1, characterized in that: In S1, anthracite is ball-milled and pickled.

3. The method for preparing the negative electrode material of a coal-based composite sodium battery according to claim 1, characterized in that: In S2, heating: under nitrogen atmosphere, heat to 2500~3000℃ at a heating rate of 10~25℃ / min, and keep warm for 1~4h.

4. The method for preparing a negative electrode material for a coal-based composite sodium battery according to claim 1, wherein: In S3, Hummers' treatment includes stages 1, 2, and 3; T 阶段一 <T 阶段二 <T 阶段三 ; Hummers method processing includes at least one of features (S3-1) to (S3-3): (S3-1) Stage 1: Under ice bath conditions, the reaction system includes concentrated sulfuric acid, coal-based graphite, potassium permanganate, and phosphoric acid; (S3-2) Stage 2: After stage 1, the reaction system is subjected to constant temperature treatment. After completion, deionized water and H2O2 are gradually added dropwise. After standing and stratification, the precipitate is collected; (S3-3) Stage three: After stage two, the composite material is calcined with a reducing agent to obtain a composite material.

5. The method for preparing the negative electrode material of a coal-based composite sodium battery according to claim 4, characterized in that: In (S3-1), the mass ratio of coal-based graphite, concentrated sulfuric acid, potassium permanganate, and phosphoric acid is 1:70~90:2~10:3~12.

6. The method for preparing the negative electrode material of a coal-based composite sodium battery according to claim 4, characterized in that: (S3-2) Constant temperature treatment: raising the temperature from room temperature to 45~60℃ and maintaining it for 10~20h.

7. The method for preparing the negative electrode material of a coal-based composite sodium battery according to claim 4, characterized in that: In (S3-3), the reducing agent includes at least one of sodium borohydride, lithium aluminum hydride, and borane; and the calcination temperature is 200-500° C. for 2-3 hours.

8. The method for preparing a negative electrode material for a coal-based composite sodium battery according to any one of claims 1 to 7, characterized in that: In S1, anthracite is placed in a reaction vessel and treated under a supercritical CO2 atmosphere at 50-100°C and a pressure of 10-20 MPa for 10-15 hours to obtain a treated body.

9. The method for preparing the negative electrode material of a coal-based composite sodium battery according to claim 8, characterized in that: The mass ratio of anthracite to antimony oxide is 10:1-40:

1.

10. A coal-based composite sodium battery negative electrode material obtained by the preparation method according to any one of claims 1 to 9.

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