A method for preparing and applying fluorinated carbon materials with a high fluorine-to-carbon ratio

Abstract

This invention discloses a method for preparing and applying a high fluorine-to-carbon ratio fluorinated carbon material, belonging to the field of fluorinated carbon material preparation. The method for preparing a high fluorine-to-carbon ratio fluorinated carbon material includes the following steps: S1: Crush tea stems and filter to separate the tea stem fragments; S2: Stir the dried tea stem fragments with an acid solution at 100℃-130℃ for 2-4 hours, and wash the tea stem fragments until the pH of the aqueous solution is 6-8; S3: Heat the tea stem fragments to 140℃-160℃ under an inert gas atmosphere. The mixture is heated to ℃ and maintained at that temperature for 1.5-2.5 hours, then carbonized at 1100℃-1400℃ for 2-4 hours. After cooling, pyrolytic carbon material is obtained. S4: The pyrolytic carbon material is washed with water until neutral, dried, and ground into powder. S5: The powder is placed in a container and evacuated. Fluorine-containing gas is introduced, maintaining a pressure of 0.3-0.7 MPa, and reacted at 280℃-360℃ for 12-72 hours. After the reaction, the temperature is lowered to room temperature to obtain a high fluorine-to-carbon ratio fluorinated carbon material. This invention uses tea stems as raw material and utilizes a high-pressure, low-temperature fluorination process to obtain a high fluorine-to-carbon ratio fluorinated carbon material with a fluorine-to-carbon ratio ≥1.0.

Description

Technical Field

[0001] This invention belongs to the field of fluorinated carbon material preparation, and particularly relates to a method for preparing and applying fluorinated carbon materials with a high fluorine-to-carbon ratio. Background Technology

[0002] Fluorinated carbon is a carbon derivative with C-F bonds formed by the fluorination reaction of carbonaceous materials and fluorinating reagents under certain conditions. The chemical formula of fluorinated carbon is CFx, where x is the fluorine-to-carbon atomic ratio, typically between 0 and 1. Fluorinated carbon materials are currently one of the hottest research topics in high-tech, high-performance, and high-efficiency novel carbon-based materials internationally, possessing excellent performance, unique qualities, and many distinctive properties. Initially widely used in the field of solid lubricants, fluorinated carbon materials have seen further development in recent years as a component of lithium-ion batteries.

[0003] Carbon source and fluorination process are two important factors affecting the performance of fluorinated carbon. Therefore, the selection of carbon source, the structural design of biomass carbon materials, and the combination of fluorination technology are crucial for the preparation of high-performance biomass carbon-based fluorinated carbon cathode materials, and none of them can be omitted. Currently used biomass carbon materials have widely varying structures and morphologies, resulting in inconsistent performance. Fluorination processes also suffer from shortcomings such as poor fluorination effect and uneven fluorination degree of fluorinated products. Therefore, it is difficult for fluorinated biomass carbon materials developed with current technology to achieve excellent performance and stable preparation. For example, patent CN 110875475 A discloses a method of preparing biomass carbon using fruit shells and then performing fluorination. The resulting material has a low yield, which cannot meet the requirements of kilogram-level production. This is related to the biomass carbon materials used and the fluorination process.

[0004] Tea stems are the leaf stalks of tea trees. Currently, my country does not yet possess competitive fluorinated carbon cathode material products, mainly because the fluorinated carbon produced has low fluorination degree and low specific energy. Many currently prepared biomass hard carbons have poor performance, lacking high specific surface area and suitable pore size, thus failing to meet the current demand for high-fluorination-degree fluorinated carbon materials. Traditional low-temperature, low-pressure fluorination processes cannot and are difficult to produce high-fluorination-degree fluorinated carbon materials; generally, a fluorination degree (CFx) ≥ 1.0 is considered a high fluorination degree. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing and applying fluorinated carbon materials with a high fluorine-to-carbon ratio, so as to overcome at least one of the above-mentioned defects in the prior art.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] This invention provides a method for preparing a high-fluorine-to-carbon fluoride material, comprising the following steps: S1: Crush tea stems, then filter to separate the tea stem fragments, and wash and dry them; S2: Stir the dried tea stem fragments with an acid solution at 100℃-130℃ for 2-4 hours, then wash the tea stem fragments until the pH of the aqueous solution is 6-8; S3: Heat the tea stem fragments washed in step S2 to 140℃-160℃ under an inert gas atmosphere, and maintain this temperature for 1.5-2 hours. 0.5h, then carbonize at 1100℃-1400℃ for 2-4h, cool to obtain pyrolytic carbon material, S4: wash the pyrolytic carbon material obtained in step S3 with water until neutral, dry and grind into powder, S5: put the powder obtained in step S4 into a container and evacuate, then introduce fluorine-containing gas, maintain the pressure at 0.3-0.7MPa, react at 280℃-360℃ for 12-72h, after the reaction is completed, cool to room temperature to obtain high fluorine-to-carbon ratio fluorinated carbon material.

[0008] Preferably, in step S1: a high-speed blender is used for pulverization, a sieve with a mesh size of 0.2-0.5mm is used for filtration, and deionized water and ethanol are used for cleaning.

[0009] Preferably, in step S2: the acid solution is 0.8-1.2 mol / L hydrochloric acid, and deionized water is used to wash the broken tea stems.

[0010] Preferably, in step S3, the inert gas is one or more of nitrogen, argon, neon, and helium.

[0011] Preferably, in step S3: the tea stem fragments are heated to 140℃-160℃ at a heating rate of 4-6℃ / min in a flowing inert gas atmosphere.

[0012] Preferably, in step S4: the drying temperature is 70℃-90℃, the drying time is 2-4h, and deionized water is used for washing.

[0013] Preferably, in step S5: the powder reacts with a fluorinated gas in a fluorination furnace, wherein the fluorinated gas is one or more of xenon difluoride, nitrogen trifluoride, fluorine, boron trifluoride, or a mixture of fluorine and argon.

[0014] Preferably, the process further includes step S6: grinding the high fluorocarbon ratio fluorinated carbon material obtained in step S5 to a particle size of 30-250 mesh.

[0015] The present invention also provides an application of the high fluorine-to-carbon ratio fluorinated carbon material prepared by the above-mentioned high fluorine-to-carbon ratio fluorinated carbon material preparation method in battery cathode materials.

[0016] The beneficial effects of this invention are as follows:

[0017] 1. Using tea stems as raw material, a new high-pressure, low-temperature fluorination process is used to produce high-fluorine-carbon fluorinated carbon materials with a fluorine-carbon ratio ≥1.0 and a discharge specific energy of up to 2298Wh / kg (discharged to 1.5V at a current density of 0.01C).

[0018] 2. Biomass carbon materials prepared from tea stems have abundant pore size and appropriate active sites, which can effectively improve the degree of fluorination, thereby enhancing the electrochemical performance of fluorinated carbon.

[0019] 3. Using tea stems as a raw material for biochar is an effective utilization of renewable resources. It is inexpensive and easy to operate, which is conducive to large-scale, low-cost production and can achieve kilogram-level preparation. It provides the fluorocarbon industry with a renewable biochar material and solves the raw material problem of fluorocarbon.

[0020] 4. High-pressure low-temperature fluorination technology has solved the problem of preparing fluorinated carbon materials with high fluorine-to-carbon ratio, and has produced fluorinated carbon material products that break through the F / C atomic ratio limit, which are highly competitive. Attached Figure Description

[0021] Figure 1 This is a scanning electron microscope image of the Tea-1100 biomass carbon material from Embodiment 1 of the present invention.

[0022] Figure 2 This is a pore size distribution diagram of the Tea-1100 biomass carbon material in Embodiment 1 of the present invention.

[0023] Figure 3 This is the adsorption curve of the Tea-1100 biomass carbon material in Embodiment 1 of the present invention.

[0024] Figure 4 This is a scanning electron microscope image of the Tea-1100 high fluorocarbon ratio fluorinated carbon material from Embodiment 1 of the present invention.

[0025] Figure 5 This is the XPS image of the Tea-1100 high fluorocarbon ratio fluorinated carbon material from Embodiment 1 of the present invention.

[0026] Figure 6 This is the XRD pattern of the Tea-1100 high fluorocarbon ratio fluorinated carbon material from Embodiment 1 of the present invention.

[0027] Figure 7 This is a pore size distribution diagram of the Tea-1100 high fluorocarbon ratio fluorinated carbon material in Embodiment 1 of the present invention.

[0028] Figure 8 This is the adsorption curve of the Tea-1100 high fluorocarbon ratio fluorinated carbon material in Embodiment 1 of the present invention.

[0029] Figure 9This is the voltage-discharge specific energy curve of the Tea-1100 high fluorocarbon ratio fluorinated carbon material in Embodiment 1 of the present invention.

[0030] Figure 10 This is the voltage-discharge specific capacity curve of the Tea-1100 high fluorocarbon ratio fluorinated carbon material in Embodiment 1 of the present invention. Detailed Implementation

[0031] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0032] Example 1:

[0033] This embodiment provides a method for preparing a high fluorocarbon ratio fluorinated carbon material, comprising the following steps:

[0034] S1: Crush the tea stems with a high-speed blender, then filter them through a sieve with a mesh size of 0.3mm to separate the tea stem fragments. Wash the tea stems with deionized water and ethanol, and then dry them.

[0035] S2: The dried tea stem fragments were stirred with 1 mol / L hydrochloric acid at 120°C for 3 hours to remove impurities. Then, the tea stem fragments were washed with deionized water until the pH of the aqueous solution was 7.

[0036] S3: The tea stem fragments cleaned in step S2 are heated to 150°C at a rate of 5°C / min under a flowing argon atmosphere and held at 150°C for 2 hours to remove free water. Then, they are carbonized at 1100°C for 3 hours and naturally cooled to obtain pyrolytic carbon material, which serves as biomass carbon material (Tea-1100). The Tea-1100 biomass carbon material obtained from the calcined tea stems has a porous structure. Acid treatment removes impurities and increases the number of pores and active sites, improving the specific surface area and thus enhancing performance after fluorination.

[0037] S4: Wash the pyrolytic carbon material obtained in step S3 with deionized water until neutral, dry it at 80°C for 3 hours, and then grind it into powder.

[0038] S5: Take 1 kg of the powder obtained in step S4 and put it into a fluorination furnace. After evacuation, introduce fluorine-containing gas NF3 and maintain a pressure of 0.7 MPa. React at 280℃ for 72 h. After the reaction is completed, let it cool naturally to room temperature to obtain Tea-1100 (milky white) high fluorine-to-carbon fluoride material.

[0039] S6: Grind the high fluorocarbon ratio fluorinated carbon material obtained in step S5 to a particle size of 150 mesh.

[0040] This embodiment also provides an application of the high fluorine-to-carbon ratio fluorinated carbon material prepared by the above-mentioned high fluorine-to-carbon ratio fluorinated carbon material preparation method in battery cathode materials.

[0041] The physical and chemical properties of the prepared Tea-1100 biomass carbon material and Tea-1100 high fluorocarbon ratio fluorinated carbon material were characterized:

[0042] from Figure 1 It can be seen that the surface of Tea-1100 biomass carbon material has a porous structure. From Figure 2 It can be seen that Tea-1100 biomass carbon material has abundant mesopores and micropores, with pore sizes mainly of 0.524nm, 0.785nm, 1.029nm, 1.232nm, and 1.409nm. Figure 3 This is the adsorption curve of Tea-1100 biomass carbon material, with a measured specific surface area of ​​623.104 m². 2 / g.

[0043] from Figure 4 It can be seen that Tea-1100, a high-fluorinated carbon material obtained by fluorination of biomass carbon, also exhibits a porous structure on its surface compared to fluorinated carbon materials. From... Figure 5 It can be seen that the peak positions of CF (289.8 eV) and C-F2 (292.0 eV) are distinct. From... Figure 6 Two broad diffraction peaks at 13.8° and 42.8°, corresponding to interlayer (001) and intralayer (100) reflections, can be clearly observed, consistent with highly disordered fluorinated carbon. From Figure 7 It can be seen that Tea-1100 high fluorocarbon ratio fluorinated carbon material has abundant mesopores and micropores, with pore sizes mainly of 0.567nm, 1.057nm, 3.20nm, 4.07nm, and 4.84nm. Figure 8 This is the adsorption curve of Tea-1100 high fluorocarbon ratio fluorinated carbon material, with a measured specific surface area of ​​183.752 m². 2 / g.

[0044] To assemble coin cell lithium batteries, an active material:conductive carbon:binder (CMC) ratio of 85:8:7 was thoroughly moistened with alcohol, followed by the addition of a suitable amount of purified water. The mixture was ball-milled at 200 rpm for 30 min, then at 400 rpm for 4 h. The resulting material was coated onto conductive carbon aluminum foil using a 200 μm scraper and allowed to air dry. After drying, the surface was kept at 80℃ for 3 h in a forced-air oven. Following drying, the foil was cut using a 14 mm cutting machine and then assembled into coin cells. The electrochemical performance was then tested by discharging the material to 1.5V at a current density of 0.01C.

[0045] from Figure 9 and Figure 10 As can be seen, up to 1.5V, the specific capacity is 955mAh / g and the specific energy is 2298Wh / kg.

[0046] Comparative Example 1:

[0047] This example uses commercial-grade fluorinated carbon material from Daikin Industries, Japan, and is tested under the same electrochemical performance conditions as in Example 1. It discharges to 1.5V at a discharge density of 0.01C, and its specific capacity and specific energy are 848mAh / g and 2184Wh / kg, respectively.

[0048] Example 2:

[0049] The difference between this embodiment and Example 1 is that the biomass carbon material was prepared at a temperature of 1400℃, and Tea-1400 high fluorine-to-carbon ratio fluorinated carbon material was prepared. The same electrochemical performance test conditions as in Example 1 were used. It was discharged to 1.5V at a discharge density of 0.01C, and the specific capacity and specific energy were 866mAh / g and 2177Wh / kg, respectively.

[0050] Example 3:

[0051] The difference between this embodiment and Example 1 is that the fluorination temperature is 360℃, and the Tea-1100 high fluorine-to-carbon fluorinated carbon material prepared is tested under the same electrochemical performance conditions as in Example 1. It discharges to 1.5V at a discharge density of 0.01C, and its specific capacity and specific energy are 870mAh / g and 2190Wh / kg, respectively.

[0052] Example 4:

[0053] The difference between this embodiment and Example 1 is that the fluorination temperature is 330℃, and the Tea-1100 high fluorine-to-carbon fluorinated carbon material prepared is tested under the same electrochemical performance conditions as in Example 1. It discharges to 1.5V at a discharge density of 0.01C, and its specific capacity and specific energy are 878mAh / g and 2205Wh / kg, respectively.

[0054] Example 5:

[0055] The difference between this embodiment and Example 1 is that the fluorination pressure is 0.3 MPa, and the prepared Tea-1100 high fluorine-to-carbon fluorinated carbon material is tested under the same electrochemical performance conditions as in Example 1. It discharges to 1.5V at a discharge density of 0.01C, and its specific capacity and specific energy are 893 mAh / g and 2269 Wh / kg, respectively.

[0056] Example 6:

[0057] The difference between this embodiment and Example 1 is that the fluorination pressure is 0.4 MPa, and the prepared Tea-1100 high fluorine-to-carbon fluorinated carbon material is tested under the same electrochemical performance conditions as in Example 1. It discharges to 1.5V at a discharge density of 0.01C, and its specific capacity and specific energy are 895 mAh / g and 2289 Wh / kg, respectively.

[0058] Example 7:

[0059] The difference between this embodiment and Example 1 is that the fluorination time is 12h. The Tea-1100 high fluorine-to-carbon fluorinated carbon material prepared is tested under the same electrochemical performance conditions as in Example 1. It discharges to 1.5V at a discharge density of 0.01C, and its specific capacity and specific energy are 865mAh / g and 2133Wh / kg, respectively.

[0060] Example 8:

[0061] The difference between this embodiment and Example 1 is that the fluorination time is 48h. The Tea-1100 high fluorine-to-carbon fluorinated carbon material prepared is tested under the same electrochemical performance conditions as in Example 1. It discharges to 1.5V at a discharge density of 0.01C, and its specific capacity and specific energy are 878mAh / g and 2213Wh / kg, respectively.

[0062] Table 1 shows the performance data of Examples 1-8 and Comparative Example 1 discharged to 1.5V at a current density of 0.01C:

[0063] Calculate the fluorine-to-carbon ratio Specific capacity (mAh / g) Specific energy (Wh / kg) Example 1 1.10 955 2298 Comparative Example 1 0.98 848 2184 Example 2 1.00 866 2177 Example 3 1.00 870 2190 Example 4 1.02 878 2205 Example 5 1.03 893 2269 Example 6 1.03 895 2289 Example 7 1.00 865 2133 Example 8 1.02 878 2213

[0064] Table 1

[0065] As shown in Table 1, the fluorine-to-carbon ratios of Examples 1-8 all reached ≥1.0. The high-pressure, low-temperature fluorination technology proposed in this invention solves the problem of preparing high fluorine-to-carbon ratio fluorinated carbon materials, producing fluorinated carbon material products that break through the F / C atomic ratio limit, exhibiting strong competitiveness. Biomass carbon materials prepared from tea stems possess abundant pore size and appropriate active sites, which can effectively increase the degree of fluorination, thereby enhancing the electrochemical performance of fluorinated carbon. Using tea stems as a raw material for biomass carbon materials is an effective utilization of renewable resources, with low cost and simple operation, facilitating large-scale, low-cost production, achieving kilogram-level production. This provides the fluorinated carbon industry with a renewable biomass carbon material, solving the raw material problem for fluorinated carbon. Furthermore, the novel high-pressure, low-temperature fluorination process further enhances the fluorination degree of biomass hard carbon (CFx, x≥1), achieving a discharge specific energy of 2298Wh / kg (discharged to 1.5V at a current density of 0.01C).

[0066] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a high fluorine-to-carbon ratio fluorinated carbon material, characterized in that, Includes the following steps: S1: Crush the tea stems, then filter to separate the tea stem fragments, and wash and dry them; S2: Stir the dried tea stem fragments with acid solution at 100℃-130℃ for 2-4 hours, then wash the tea stem fragments until the pH of the aqueous solution is 6-8; S3: The tea stem fragments cleaned in step S2 are heated to 140℃-160℃ in an inert gas atmosphere and held at this temperature for 1.5-2.5h. Then, they are carbonized at 1100℃-1400℃ for 2-4h and cooled to obtain pyrolytic carbon material. S4: Wash the pyrolytic carbon material obtained in step S3 with water until neutral, dry it and grind it into powder; S5: After placing the powder obtained in step S4 into a container and evacuating it, introduce fluorine-containing gas and maintain a pressure of 0.3-0.7 MPa. React at 280℃-360℃ for 12-72 hours. After the reaction is completed, cool down to room temperature to obtain a high fluorine-to-carbon fluoride material.

2. The method for preparing high fluorine-to-carbon ratio fluorinated carbon materials according to claim 1, characterized in that, In step S1: Use a high-speed blender to pulverize the materials; Filtration is performed using a sieve with a mesh size of 0.2-0.5 mm; Cleaning was performed using deionized water and ethanol.

3. The method for preparing high fluorine-to-carbon ratio fluorinated carbon materials according to claim 1, characterized in that, In step S2: The acid solution is 0.8-1.2 mol / L hydrochloric acid; Use deionized water to wash the broken tea stems.

4. The method for preparing high fluorine-to-carbon ratio fluorinated carbon materials according to claim 1, characterized in that, In step S3: The inert gas is one or more of nitrogen, argon, neon, and helium.

5. The method for preparing high fluorine-to-carbon ratio fluorinated carbon materials according to claim 1, characterized in that, In step S3: Tea stem fragments were heated to 140℃-160℃ at a heating rate of 4-6℃ / min in a flowing inert gas atmosphere.

6. The method for preparing high fluorine-to-carbon ratio fluorinated carbon materials according to claim 1, characterized in that, In step S4: The drying temperature is 70℃-90℃, the drying time is 2-4 hours, and deionized water is used for washing.

7. The method for preparing high fluorine-to-carbon ratio fluorinated carbon materials according to claim 1, characterized in that, In step S5: The powder reacts with a fluorinated gas in a fluorination furnace. The fluorinated gas is one or more of the following: xenon difluoride, nitrogen trifluoride, fluorine, boron trifluoride, or a mixture of fluorine and argon.

8. The method for preparing high fluorine-to-carbon ratio fluorinated carbon materials according to claim 1, characterized in that: Also includes S6: The high fluorocarbon ratio fluorinated carbon material obtained in step S5 is ground to a particle size of 30-250 mesh.

9. The application of a high fluorine-to-carbon ratio fluorinated carbon material prepared by the method according to any one of claims 1-8 in battery cathode materials.

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