PREPARATION METHOD OF FLUOROCARBON-COATED VSE2 COMPOSITE (VSe2@CF) ANODE ELECTRODE MATERIAL

Abstract

A preparation method of fluorocarbon-coated VSe.sub.2 composite (VSe.sub.2@CF) anode electrode material, including: weighting and dissolving an acetylacetone oxovanadium (VO(acac).sub.2) and a selenium dioxide in a solvent to prepare a first solution with a concentration of 0.5-2 mol/L, and stirring the first solution for 0.5 h to obtain a dark green solution; adding the dark green solution with an organic acid to obtain a second solution; transferring the second solution to a polytetrafluoroethylene-lined high-pressure hydrothermal reactor, and holding at a heat insulation temperature for 15-30 h to obtain a third solution; after the third solution is cooled, suction filtering the cooled third solution, and washing the filtered third solution repeatedly to obtain a precipitate; drying the precipitate to obtain a black powder; co-mixing a citric acid solution with the black powder, stirring, ball milling, and drying; and heating up, holding, and finally cooling naturally to room temperature under inert atmosphere.

Claims

1. A preparation method of a fluorocarbon-coated VSe.sub.2 composite (VSe.sub.2@CF) anode electrode material, comprising: weighting and dissolving a vanadium oxide and a selenium oxide in a solvent to prepare a first solution with a concentration of 0.5-2 mol/L, and stirring the first solution for 0.5 h to obtain a dark green solution; adding the dark green solution with an organic acid, and continuing stirring for 0.5 h to obtain a second solution; transferring the second solution to a polytetrafluoroethylene-lined high-pressure hydrothermal reactor, and holding at a heat insulation temperature for a heat insulation time to obtain a third solution; after the third solution is cooled, suction filtering the cooled third solution with deionized water and anhydrous ethanol, and washing the filtered third solution repeatedly to obtain a black precipitate with metallic luster; drying the black precipitate with metallic luster to obtain a black powder; preparing a citric acid solution, co-mixing the citric acid solution with the black powder, and stirring for 24 h to obtain a fourth solution; adding a certain amount of polyvinylidene fluoride (PVDF) to the fourth solution and continuing stirring to obtain a fifth solution; putting the fifth solution into a ball mill and milling to obtain a sixth solution; drying the sixth solution to obtain a brownish grey powder; and performing heating process on the brownish gray powder to obtain the VSe.sub.2@CF anode electrode material.

2. The preparation method according to claim 1, wherein a mass fraction of VSe.sub.2 in the VSe.sub.2@CF anode electrode material is 60% and a mass fraction of carbon quantum dots/carbon is 40%.

3. The preparation method according to claim 1, wherein the vanadium oxide is acetylacetonate oxovanadium; the selenium oxide is selenium dioxide; the solvent is N-Methyl-Pyrrolidone.

4. The preparation method according to claim 1, wherein the organic acid is formic acid.

5. The preparation method according to claim 1, wherein in the transferring the second solution to the polytetrafluoroethylene-lined high-pressure hydrothermal reactor, and holding at the heat insulation temperature for the heat insulation time to obtain the third solution, the heat insulation temperature is in a range of 180-220° C.; the heat insulation time is in a range of 20-24 h.

6. The preparation method according to claim 1, wherein after the third solution is cooled, in the suction filtering the cooled third solution with deionized water and anhydrous ethanol, and washing the filtered third solution repeatedly to obtain the black precipitate with metallic luster, the cooled third solution is suction filtered with the deionized water and washed three times; the cooled third solution is suction filtered with the anhydrous ethanol and washed three times.

7. The preparation method according to claim 1, wherein in the drying the black precipitate with metallic luster to obtain the black powder, the black precipitate with metallic luster is dried at 80-100° C. for 18-24 h.

8. The preparation method according to claim 1, wherein in the co-mixing the citric acid solution with the black powder, and stirring for 24 h to obtain the fourth solution, the citric acid solution is co-mixed and stirred with the black powder at 25-30° C.

9. The preparation method according to claim 1, wherein in the adding a certain amount of PVDF to the fourth solution and continuing stirring to obtain the fifth solution, the stirring is performed for 30 mins.

10. The preparation method according to claim 1, wherein in the putting the fifth solution into the ball mill and milling to obtain the sixth solution, the milling is performed 18-24 h.

11. The preparation method according to claim 1, wherein in the drying the sixth solution to obtain the brownish grey powder, the sixth solution is dried at 50-120° C. for 12-24 h.

12. The preparation method according to claim 1, wherein in the performing heating process on the brownish gray powder to obtain the VSe.sub.2@CF anode electrode material, the brownish gray powder is raised from 25° C. to 180-250° C. at 1-5° C./min and held for 1-5 h under inert atmosphere, 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 VSe.sub.2@CF anode electrode material.

13. The preparation method according to claim 9, wherein in the putting the fifth solution into the ball mill and milling to obtain the sixth solution, the milling is performed 18-24 h.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] 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.

[0030] FIG. 1 is an X-ray diffraction (XRD) pattern obtained from XRD analysis of a fluorocarbon-coated VSe.sub.2 composite (VSe.sub.2@CF) and a pure VSe.sub.2 material prepared in an Embodiment 1 of the present disclosure, wherein a indicates the XRD pattern of the VSe.sub.2@CF anode electrode material prepared in the Embodiment 1, and b indicates the XRD pattern of a pure phase laminate VSe.sub.2 material prepared in the Embodiment 1.

[0031] FIG. 2 is a scanning electron microscope (SEM) image of the VSe.sub.2@CF prepared in the Embodiment 1 of the present disclosure.

[0032] FIG. 3 a SEM image of the pure phase laminate VSe.sub.2 material prepared in the Embodiment 1 of the present disclosure.

[0033] FIG. 4 is a transmission electron microscope (TEM) image of the VSe.sub.2@CF prepared in the Embodiment 1 of the present disclosure.

[0034] FIG. 5 is a TEM image of the pure phase laminate VSe.sub.2 material prepared in the Embodiment 1 of the present disclosure.

[0035] FIG. 6 illustrates charge/discharge cycle performance charts of a button batterie made of the VSe.sub.2@CF prepared in the Embodiment 1 and a button batterie made of a pure phase laminate VSe.sub.2 material prepared in a Comparison 1, at 100 mAg.sup.−1 current density.

[0036] FIG. 7 illustrates charge/discharge multiplicity performance charts of a button batterie made of the VSe.sub.2@CF prepared in the Embodiment 1 and a button batterie made of a pure phase laminate VSe.sub.2 material prepared in a Comparison 1, at 100-1000 mAg.sup.−1 current density.

[0037] FIG. 8 illustrates charge/discharge long cycle performance charts of a button batterie made of the VSe.sub.2@CF prepared in the Embodiment 1 and a button batterie made of a pure phase laminate VSe.sub.2 material prepared in a Comparison 1, at 500 mAg.sup.−1 current density.

[0038] FIG. 9 is a charge/discharge cycle performance chart of a button batterie made of a VSe.sub.2@CF prepared in an Embodiment 2 of the present disclosure at 100 mAg.sup.−1 current density.

[0039] FIG. 10 is a charge/discharge cycle performance chart of a button batterie made of a VSe.sub.2@CF prepared in an Embodiment 3 of the present disclosure at 100 mAg.sup.−1 current density.

DETAILED DESCRIPTION

[0040] The present disclosure is further described below based on the VSe.sub.2@CF as specific embodiments, but the present disclosure is not limited to these embodiments.

Embodiment 1

[0041] 1. Acetylacetone oxovanadium (VO(acac).sub.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.

[0042] 2. The dark green solution is added with formic acid and continued to be stirred for 20 mins to obtain a second solution.

[0043] 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.

[0044] 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.

[0045] 5. The black precipitate with metallic luster is dried at 80° C. for 24 h to obtain a black powder.

[0046] 6. Citric acid solution is prepared, co-mixed with the black powder and stirred for 24 h to obtain a fourth solution.

[0047] 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.

[0048] 8. The fifth solution is put into a ball mill and milled for 24 h to obtain a sixth solution.

[0049] 9. The sixth solution is dried at 50-120° C. for 12-24 h to obtain a brownish grey powder.

[0050] 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 VSe.sub.2@CF anode electrode material.

[0051] XRD analysis and SEM/TEM analysis are performed on the VSe.sub.2@CF obtained in the Embodiment 1 and a pure phase laminate VSe.sub.2 material obtained in the Embodiment 1. According to the XRD patterns, diffraction peaks of the carbon quantum dot/carbon coated VSe.sub.2 composite are consistent with those of the laminate VSe.sub.2 material before modification, indicating that the carbon quantum dot/carbon coating does not change the physical phase structure of the laminate VSe.sub.2 material. The SEM image of the carbon quantum dot/carbon coated VSe.sub.2 composite (VSe.sub.2@CQD) obtained in the Embodiment 1 is shown in FIG. 2, and the SEM image of the pure phase laminate VSe.sub.2 material in the Embodiment 1 is shown in FIG. 3. As seen from the comparison of FIG. 2 and FIG. 3, after the fluorocarbon coating, the laminar microstructure of the material does not change significantly but the surface is rougher and full of granularity. The TEM image of the VSe.sub.2@CF obtained in the Embodiment 1 is shown in FIG. 4, and the TEM image of the pure phase laminate VSe.sub.2 material in the Embodiment 1 is shown in FIG. 5. As seen from the comparison of FIG. 4 and FIG. 5, after the fluorocarbon coating, a large amount of 2-3 nm fluorocarbon in size is coated on the laminate VSe.sub.2 material, indicating that the fluorocarbon is successfully coated on the VSe.sub.2 material.

[0052] The VSe.sub.2@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 VSe.sub.2@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.

[0053] The charge/discharge cycle performance charts of the button batterie made of the VSe.sub.2@CF prepared in the Embodiment 1 and a button batterie made of a pure phase laminate VSe.sub.2 material prepared in a Comparison 1, at 100 mAg.sup.−1 current density are shown in FIG. 6. As can be seen from FIG. 6, the capacity of the VSe.sub.2@CF prepared in the Embodiment 1 is 409.0 mAhg.sup.−1 after 100 cycles, but the capacity of the pure laminate VSe.sub.2 material is only 208.9 mAhg.sup.−1 after 100 cycles. From the above results, the reversible capacity and cyclic stability can be effectively improved using the VSe.sub.2@CF.

[0054] The charge/discharge multiplicity performance charts of the button batterie made of the VSe.sub.2@CF prepared in the Embodiment 1 and the button batterie made of the pure phase laminate VSe.sub.2 material prepared in the Comparison 1, at 100-1000 mAg.sup.−1 current density are shown in FIG. 7, respectively. As can be seen from FIG. 7, the reversible capacities obtained for the VSe.sub.2@CQD in the Embodiment 1 at 100, 200, 300, 500, and 1000 mAg.sup.−1 current densities are 698.7, 501.2, 401.3, 300.2, and 99 mAhg.sup.−1. However, the capacities of the pure laminate VSe.sub.2 material at the same multiplicative current densities are 500, 400.2, 300.2, 200.3 and 99.2 mAhg.sup.−1. From the above results, the capacity of the material at high current densities may be effectively improved using the VSe.sub.2@CQD.

[0055] The charge/discharge long cycle performance charts of the button batterie made of the VSe.sub.2@CQD prepared in the Embodiment 1 and the button batterie made of the pure phase laminate VSe.sub.2 material prepared in the Comparison 1, at 500 mAg.sup.−1 current density are shown in FIG. 8. As can be seen from FIG. 8, the VSe.sub.2@CQD prepared in the Embodiment 1 has the capacity maintained 200.2 mAhg.sup.−1 after 1000 cycles. From the above results, the long cycle stability and the stability of the structure can be effectively improved using the VSe.sub.2@CF.

Embodiment 2

[0056] 1. VO(acac).sub.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.

[0057] 2. The dark green solution is added with formic acid and continued to be stirred for 30 mins to obtain a second solution.

[0058] 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.

[0059] 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.

[0060] 5. The black precipitate with metallic luster is dried at 80° C. for 24 h to obtain a black powder.

[0061] 6. Citric acid solution is prepared, co-mixed with the black powder and stirred for 24 h to obtain a fourth solution.

[0062] 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.

[0063] 8. The fifth solution is put into a ball mill and milled for 24 h to obtain a sixth solution.

[0064] 9. The sixth solution is dried at 50-120° C. for 12-24 h to obtain a brownish grey powder.

[0065] 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 VSe.sub.2@CF anode electrode material.

[0066] The VSe.sub.2@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 VSe.sub.2@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 VSe.sub.2@CF prepared in the Embodiment 2 has excellent multiplicative performance and cycling stability.

Embodiment 3

[0067] 1. VO(acac).sub.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.

[0068] 2. The dark green solution is added with formic acid and continued to be stirred for 30 mins to obtain a second solution.

[0069] 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.

[0070] 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.

[0071] 5. The black precipitate with metallic luster is dried at 80° C. for 24 h to obtain a black powder.

[0072] 6. Citric acid solution is prepared, co-mixed with the black powder and stirred for 24 h to obtain a fourth solution.

[0073] 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.

[0074] 8. The fifth solution is put into a ball mill and milled for 24 h to obtain a sixth solution.

[0075] 9. The sixth solution is dried at 50-120° C. for 12-24 h to obtain a brownish grey powder.

[0076] 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 VSe.sub.2@CF anode electrode material.

[0077] The VSe.sub.2@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 VSe.sub.2@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 VSe.sub.2@CF prepared in the Embodiment 3 has excellent multiplicative performance and cycling stability.

Embodiment 4

[0078] 1. VO(acac).sub.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.

[0079] 2. The dark green solution is added with formic acid and continued to be stirred for 20 mins to obtain a second solution.

[0080] 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.

[0081] 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.

[0082] 5. The black precipitate with metallic luster is dried at 80° C. for 24 h to obtain a black powder.

[0083] 6. Citric acid solution is prepared, co-mixed with the black powder and stirred for 24 h to obtain a fourth solution.

[0084] 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.

[0085] 8. The fifth solution is put into a ball mill and milled for 24 h to obtain a sixth solution.

[0086] 9. The sixth solution is dried at 50-120° C. for 12-24 h to obtain a brownish grey powder.

[0087] 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 VSe.sub.2@CF anode electrode material.

[0088] The VSe.sub.2@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 VSe.sub.2@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 VSe.sub.2@CF prepared in the Embodiment 4 has excellent multiplicative performance and cycling stability.

Embodiment 5

[0089] 1. VO(acac).sub.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.

[0090] 2. The dark green solution is added with formic acid and continued to be stirred for 20 mins to obtain a second solution.

[0091] 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.

[0092] 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.

[0093] 5. The black precipitate with metallic luster is dried at 80° C. for 24 h to obtain a black powder.

[0094] 6. Citric acid solution is prepared, co-mixed with the black powder and stirred for 24 h to obtain a fourth solution.

[0095] 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.

[0096] 8. The fifth solution is put into a ball mill and milled for 24 h to obtain a sixth solution.

[0097] 9. The sixth solution is dried at 50-120° C. for 12-24 h to obtain a brownish grey powder.

[0098] 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 VSe.sub.2@CF anode electrode material.

[0099] The VSe.sub.2@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 VSe.sub.2@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 VSe.sub.2@CF prepared in the Embodiment 5 has excellent multiplicative performance and cycling stability.

[0100] The preparation method of the VSe.sub.2@CF belongs to the field of potassium-ion battery anode materials and preparation technologies. By compounding carbon, PVDF, and VSe.sub.2, 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 VSe.sub.2. 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.