Patent Application
20220384784
The present disclosure relates to the field of new ion battery preparation technologies, specifically an anode material for potassium ion batteries, and in particular to a fluorocarbon-coated VSe2 composite (VSe2@CF) anode electrode material and a preparation method thereof.
After decades of development, lithium-ion batteries have been widely applied in digital consumer products, electric vehicles, and energy storage due to high open-circuit voltage, high energy density and long cycle life. Compared to the reserves of sodium (2.36 wt %) and potassium (2.09 wt %) in the earth, the reserves of lithium are about 0.0017 wt %, which is low in nature and expensive, greatly limiting the application of lithium batteries as large-scale energy storage and power batteries. The development of new ion batteries is an inevitable trend in the field of battery energy storage. Due to high storage capacity and wide distribution, potassium becomes an ideal type of ion battery instead of lithium. To improve the energy density, cycle stability and other requirements of potassium-ion batteries, the development of new, stable anode materials for potassium ion batteries has become one of the important methods for potassium ion battery research.
Vanadium diselenide (VSe2), as a typical graphene-like transition metal selenide, is widely applied in energy, electronic components, and photovoltaic research due to its unique graphene-like structure, excellent electrical properties, mechanical properties, etc. As early as 978, Dr. M. Stanley Whittingham did a study on the application of the VSe2 material in lithium-ion batteries. It was pointed out that compared with other transition metal selenide materials, VSe2 has a c/a value of 1.82 and the layer spacing is much greater than other TMDs-like materials. Therefore, VSe2 may be an ideal anode material for lithium-ion batteries. Conventionally, the yield of the VSe2 prepared by solvent thermal method as well as hydrothermal method is high, but the products have more impurities and poorer crystalline structure, which may lead to poor conductivity of VSe2 itself and occurrence of phenomena such as restacking. In this way, capacity may decrease rapidly during battery cycling. A preparation of composites with VSe2 as a substrate may be an effective way to solve the problem. VSe2 composites with amorphous carbon and fluorine-rich base materials may be applied in potassium-ion batteries to greatly improve electrochemical performance.
The present disclosure is to provide a fluorocarbon-coated VSe2 composite (VSe2@CF) anode electrode material and a preparation method thereof. The method is simple and can effectively improve the electronic conductivity of VSe2 synthesized by the solvothermal method and enhance the multiplicative performance of the anode electrode material, while suppressing the volume expansion and side reactions such as agglomeration during the charging and discharging process, thus improving the cycling performance.
The VSe2@CF described in the present disclosure is prepared by a combination of solvent thermal and wet ball milling methods. In the composite, the mass fraction of vanadium diselenide is about 60% and that of the carbon fluoride is about 40%. The method may include operations as followed.
1. VO(acac)2 and selenium dioxide are weighted and dissolved in N-Methyl-Pyrrolidone solvent to prepare a first solution with a concentration of 1 mol/L. The first solution is stirred for 0.5 h to obtain a dark green solution.
2. The dark green solution is added with an organic acid and continued to be stirred for 20 mins to obtain a second solution.
3. The second solution is transferred to a polytetrafluoroethylene-lined high-pressure hydrothermal reactor and is held at 180-220° C. for 20 h to obtain a third solution.
4. After the third solution is cooled, the cooled third solution is suction filtered with deionized water and anhydrous ethanol and washed repeatedly to obtain a black precipitate with metallic luster.
5. The black precipitate with metallic luster is dried at 80° C. to obtain a black powder.
6. Citric acid solution is prepared, co-mixed with the black powder and stirred for 24 h to obtain a fourth solution.
7. A certain amount of PVDF is added to the fourth solution and continued to be stirred for 30 mins to obtain a fifth solution.
8. The fifth solution is put into a ball mill and milled for 24 h to obtain a sixth solution.
9. The sixth solution is dried for 24 h to obtain a brownish grey powder.
10. The brownish gray powder is, under inert atmosphere, raised from 25° C. to 180-250° C. at 1-5° C./min and held for 1-5 h, then raised to 450-600° C. at 1-5° C./min and held for 2-5 h, and naturally cooled to room temperature to obtain the VSe2@CF anode electrode material.
Notes
In the step 1, the vanadium oxide is acetylacetonate oxovanadium; the selenium oxide is selenium dioxide; the solvent is N-Methyl-Pyrrolidone.
In the step 2, the organic acid is formic acid.
In the step 3, the heat insulation temperature is in a range of 180-220° C.; the heat insulation time is preferably in a range of 14-28 h.
In the step 4, the cooled third solution is suction filtered with the deionized water three times; the cooled third solution is suction filtered with the anhydrous ethanol three times.
In step 5, the black precipitate with metallic luster is preferably dried at 80-100° C. for 18-24 h.
In step 6, in the prepared citric acid solution, the mass of citric acid is roughly 3 times the mass of VSe2 powder, the solvent is deionized water and preferably the stirring control time is 18-26 h.
In step 7, the mass of PVDF added to the mixture is about 1-3% of the total mass of the mixture. Preferably the mixing time is 15-45 mins.
In step 8, the preferred time for the fifth solution to enter the ball mill for ball milling is 18-26 h.
In step 9, the sixth solution is preferably dried at 50-120° C. for 12-24 h.
In step 10, the inert atmosphere is one or more of nitrogen or argon, preferably argon. The heating rate is preferably 5° C./min, the first holding temperature is preferably 180-250° C., the holding time is preferably 1-3 h, the second holding temperature is preferably 450-600° C., and the holding time is preferably 2-5 h.
The VSe2@CF prepared by the above method may be applied in potassium-ion batteries as the anode electrode material.
The VSe2@CF described in the present disclosure has excellent multiplicity performance and cycling stability. The carbon fluoride chemical and vanadium diselenide form a synergistic effect effectively inhibiting the vanadium diselenide agglomeration, while increasing the electronic conductivity and lithium-ion diffusion rate, thus effectively improving the material multiplicity performance and cycle stability.
In order to more clearly describe the technical solutions in the embodiments of the present disclosure, the following will briefly introduce the drawings required in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.
The present disclosure is further described below based on the VSe2@CF as specific embodiments, but the present disclosure is not limited to these embodiments.
1. Acetylacetone oxovanadium (VO(acac)2) and selenium dioxide are weighted and dissolved in N-Methyl-Pyrrolidone solvent to prepare a first solution with a concentration of 1 mol/L. The first solution is stirred for 0.5 h to obtain a dark green solution.
2. The dark green solution is added with formic acid and continued to be stirred for 20 mins to obtain a second solution.
3. The second solution is transferred to a polytetrafluoroethylene-lined high-pressure hydrothermal reactor and is held at 200° C. for 24 h to obtain a third solution.
4. After the third solution is cooled, the cooled third solution is suction filtered with deionized water and anhydrous ethanol and washed repeatedly to obtain a black precipitate with metallic luster.
5. The black precipitate with metallic luster is dried at 80° C. for 24 h to obtain a black powder.
6. Citric acid solution is prepared, co-mixed with the black powder and stirred for 24 h to obtain a fourth solution.
7. A certain amount of polyvinylidene fluoride (PVDF) is added to the fourth solution and continued to be stirred for 30 mins to obtain a fifth solution.
8. The fifth solution is put into a ball mill and milled for 24 h to obtain a sixth solution.
9. The sixth solution is dried at 50-120° C. for 12-24 h to obtain a brownish grey powder.
10. The brownish gray powder is, under inert atmosphere, raised from 25° C. to 180-250° C. at 1-5° C./min and held for 1-5 h, then raised to 450-600° C. at 1-5° C./min and held for 2-5 h, and naturally cooled to room temperature to obtain the VSe2@CF anode electrode material.
XRD analysis and SEM/TEM analysis are performed on the VSe2@CF obtained in the Embodiment 1 and a pure phase laminate VSe2 material obtained in the Embodiment 1. According to the XRD patterns, diffraction peaks of the carbon quantum dot/carbon coated VSe2 composite are consistent with those of the laminate VSe2 material before modification, indicating that the carbon quantum dot/carbon coating does not change the physical phase structure of the laminate VSe2 material. The SEM image of the carbon quantum dot/carbon coated VSe2 composite (VSe2@CQD) obtained in the Embodiment 1 is shown in
The VSe2@CF prepared in the Embodiment 1, acetylene black, and binder PVDF were dissolved in N-Methyl-Pyrrolidone in the ratio of 7.5:1.5:1.5 for stirring. The resulting slurry was coated on a copper foil and vacuum dried in a vacuum drying chamber for 12 h to obtain a cathode electrode sheet. Battery assembling is performed in an argon-filled glove box with the VSe2@CF as the cathode, a potassium sheet as the anode, a glass fiber as a diaphragm, and 0.8 M KPF6 in EC:DEC (1:1) as the electrolyte. The assembled button battery is tested for electrochemical performance.
The charge/discharge cycle performance charts of the button batterie made of the VSe2@CF prepared in the Embodiment 1 and a button batterie made of a pure phase laminate VSe2 material prepared in a Comparison 1, at 100 mAg−1 current density are shown in
The charge/discharge multiplicity performance charts of the button batterie made of the VSe2@CF prepared in the Embodiment 1 and the button batterie made of the pure phase laminate VSe2 material prepared in the Comparison 1, at 100-1000 mAg−1 current density are shown in
The charge/discharge long cycle performance charts of the button batterie made of the VSe2@CQD prepared in the Embodiment 1 and the button batterie made of the pure phase laminate VSe2 material prepared in the Comparison 1, at 500 mAg−1 current density are shown in
1. VO(acac)2 and selenium dioxide are weighted and dissolved in N-Methyl-Pyrrolidone solvent to prepare a first solution with a concentration of 1.5 mol/L. The first solution is stirred for 0.5 h to obtain a dark green solution.
2. The dark green solution is added with formic acid and continued to be stirred for 30 mins to obtain a second solution.
3. The second solution is transferred to a polytetrafluoroethylene-lined high-pressure hydrothermal reactor and is held at 200° C. for 24 h to obtain a third solution.
4. After the third solution is cooled, the cooled third solution is suction filtered with deionized water and anhydrous ethanol and washed repeatedly to obtain a black precipitate with metallic luster.
5. The black precipitate with metallic luster is dried at 80° C. for 24 h to obtain a black powder.
6. Citric acid solution is prepared, co-mixed with the black powder and stirred for 24 h to obtain a fourth solution.
7. A certain amount (0.3 g) of PVDF is added to the fourth solution and continued to be stirred for 30 mins to obtain a fifth solution.
8. The fifth solution is put into a ball mill and milled for 24 h to obtain a sixth solution.
9. The sixth solution is dried at 50-120° C. for 12-24 h to obtain a brownish grey powder.
10. The brownish gray powder is raised, under inert atmosphere, from 25° C. to 180-250° C. at 1-5° C./min and held for 1-5 h, then raised to 450-600° C. at 1-5° C./min and held for 2-5 h, and naturally cooled to room temperature to obtain the VSe2@CF anode electrode material.
The VSe2@CF prepared in the Embodiment 2, acetylene black, and binder PVDF were dissolved in N-Methyl-Pyrrolidone in the ratio of 7.5:1.5:1.5 for stirring. The resulting slurry was coated on a copper foil and vacuum dried in a vacuum drying chamber for 12 h to obtain a cathode electrode sheet. Battery assembling is performed in an argon-filled glove box with the VSe2@CF as the cathode, a potassium sheet as the anode, a glass fiber as a diaphragm, and KPF6 as the electrolyte. The assembled button battery is tested for electrochemical performance. Electrochemical performance tests are performed at 25° C. between 0.01 and 3.0 V. The results show that the VSe2@CF prepared in the Embodiment 2 has excellent multiplicative performance and cycling stability.
1. VO(acac)2 and selenium dioxide are weighted and dissolved in N-Methyl-Pyrrolidone solvent to prepare a first solution with a concentration of 1.5 mol/L. The first solution is stirred for 0.5 h to obtain a dark green solution.
2. The dark green solution is added with formic acid and continued to be stirred for 30 mins to obtain a second solution.
3. The second solution is transferred to a polytetrafluoroethylene-lined high-pressure hydrothermal reactor and is held at 200° C. for 24 h to obtain a third solution.
4. After the third solution is cooled, the cooled third solution is suction filtered with deionized water and anhydrous ethanol and washed repeatedly to obtain a black precipitate with metallic luster.
5. The black precipitate with metallic luster is dried at 80° C. for 24 h to obtain a black powder.
6. Citric acid solution is prepared, co-mixed with the black powder and stirred for 24 h to obtain a fourth solution.
7. A certain amount (0.3 g) of PVDF is added to the fourth solution and continued to be stirred for 30 mins to obtain a fifth solution.
8. The fifth solution is put into a ball mill and milled for 24 h to obtain a sixth solution.
9. The sixth solution is dried at 50-120° C. for 12-24 h to obtain a brownish grey powder.
10. The brownish gray powder is, under inert atmosphere, raised from 25° C. to 180-250° C. at 1-5° C./min and held for 1-5 h, then raised to 450-600° C. at 1-5° C./min and held for 2-5 h, and naturally cooled to room temperature to obtain the VSe2@CF anode electrode material.
The VSe2@CF prepared in the Embodiment 23, acetylene black, and binder PVDF were dissolved in N-Methyl-Pyrrolidone in the ratio of 7.5:1.5:1.5 for stirring. The resulting slurry was coated on a copper foil and vacuum dried in a vacuum drying chamber for 12 h to obtain a cathode electrode sheet. Battery assembling is performed in an argon-filled glove box with the VSe2@CF as the cathode, a potassium sheet as the anode, a glass fiber as a diaphragm, and KPF6 as the electrolyte. The assembled button battery is tested for electrochemical performance. Electrochemical performance tests are performed at 25° C. between 0.01 and 3.0 V. The results show that the VSe2@CF prepared in the Embodiment 3 has excellent multiplicative performance and cycling stability.
1. VO(acac)2 and selenium dioxide are weighted and dissolved in N-Methyl-Pyrrolidone solvent to prepare a first solution with a concentration of 1 mol/L. The first solution is stirred for 0.5 h to obtain a dark green solution.
2. The dark green solution is added with formic acid and continued to be stirred for 20 mins to obtain a second solution.
3. The second solution is transferred to a polytetrafluoroethylene-lined high-pressure hydrothermal reactor and is held at 180° C. for 24 h to obtain a third solution.
4. After the third solution is cooled, the cooled third solution is suction filtered with deionized water and anhydrous ethanol and washed repeatedly to obtain a black precipitate with metallic luster.
5. The black precipitate with metallic luster is dried at 80° C. for 24 h to obtain a black powder.
6. Citric acid solution is prepared, co-mixed with the black powder and stirred for 24 h to obtain a fourth solution.
7. A certain amount (0.1 g) of PVDF is added to the fourth solution and continued to be stirred for 30 mins to obtain a fifth solution.
8. The fifth solution is put into a ball mill and milled for 24 h to obtain a sixth solution.
9. The sixth solution is dried at 50-120° C. for 12-24 h to obtain a brownish grey powder.
10. The brownish gray powder is, under inert atmosphere, raised from 25° C. to 180-250° C. at 1-5° C./min and held for 1-5 h, then raised to 450-600° C. at 1-5° C./min and held for 2-5 h, and naturally cooled to room temperature to obtain the VSe2@CF anode electrode material.
The VSe2@CF prepared in the Embodiment 4, acetylene black, and binder PVDF were dissolved in N-Methyl-Pyrrolidone in the ratio of 7.5:1.5:1.5 for stirring. The resulting slurry was coated on a copper foil and vacuum dried in a vacuum drying chamber for 12 h to obtain a cathode electrode sheet. Battery assembling is performed in an argon-filled glove box with the VSe2@CF as the cathode, a potassium sheet as the anode, a glass fiber as a diaphragm, and KPF6 as the electrolyte. The assembled button battery is tested for electrochemical performance. Electrochemical performance tests are performed at 25° C. between 0.01 and 3.0 V. The results show that the VSe2@CF prepared in the Embodiment 4 has excellent multiplicative performance and cycling stability.
1. VO(acac)2 and selenium dioxide are weighted and dissolved in N-Methyl-Pyrrolidone solvent to prepare a first solution with a concentration of 1 mol/L. The first solution is stirred for 0.5 h to obtain a dark green solution.
2. The dark green solution is added with formic acid and continued to be stirred for 20 mins to obtain a second solution.
3. The second solution is transferred to a polytetrafluoroethylene-lined high-pressure hydrothermal reactor and is held at 200° C. for 24 h to obtain a third solution.
4. After the third solution is cooled, the cooled third solution is suction filtered with deionized water and anhydrous ethanol and washed repeatedly to obtain a black precipitate with metallic luster.
5. The black precipitate with metallic luster is dried at 80° C. for 24 h to obtain a black powder.
6. Citric acid solution is prepared, co-mixed with the black powder and stirred for 24 h to obtain a fourth solution.
7. A certain amount of PVDF is added to the fourth solution and continued to be stirred for 30 mins to obtain a fifth solution.
8. The fifth solution is put into a ball mill and milled for 24 h to obtain a sixth solution.
9. The sixth solution is dried at 50-120° C. for 12-24 h to obtain a brownish grey powder.
10. The brownish gray powder is, under inert atmosphere, raised from 25° C. to 180-250° C. at 1-5° C./min and held for 1-5 h, then raised to 450-600° C. at 1-5° C./min and held for 2-5 h, and naturally cooled to room temperature to obtain the VSe2@CF anode electrode material.
The VSe2@CF prepared in the Embodiment 5, acetylene black, and binder PVDF were dissolved in N-Methyl-Pyrrolidone in the ratio of 7.5:1.5:1.5 for stirring. The resulting slurry was coated on a copper foil and vacuum dried in a vacuum drying chamber for 12 h to obtain a cathode electrode sheet. Battery assembling is performed in an argon-filled glove box with the VSe2@CF as the cathode, a potassium sheet as the anode, a glass fiber as a diaphragm, and KPF6 as the electrolyte. The assembled button battery is tested for electrochemical performance. Electrochemical performance tests are performed at 25° C. between 0.01 and 3.0 V. The results show that the VSe2@CF prepared in the Embodiment 5 has excellent multiplicative performance and cycling stability.
The preparation method of the VSe2@CF belongs to the field of potassium-ion battery anode materials and preparation technologies. By compounding carbon, PVDF, and VSe2, a synergistic effect is produced among the three components. The fluorocarbon can increase the electronic conductivity and potassium-ion diffusion rate of the material and can inhibit agglomeration of the active substance VSe2. Therefore, the prepared composites have excellent electrochemical properties and exhibit good multiplicative performance and cycling stability. The process method is simple, low cost, environmentally friendly and suitable for large-scale industrial production.
