Hydrothermal Synthesis Of VO_x With Special Morphologies For Supercapacitor Electrode

The developing alternative energy storage and conversion devices with high power and energy densities for solving critical energy and environmental issues have been motivated and accelerated intensive research. Supercapacitors have been considered as potential candidates for the next generation of energy storage devices because of their higher power densities and longer cycling lives compared to secondary batteries, and higher energy density than conventional capacitors. In the past decades, vanadium oxides and their derivatives have been received increasing attention due to their layered structures, novel chemical and physical properties. In this work, three kinds of vanadium oxides were synthesized. The products were characterized by the techniques including X-ray powder diffraction, infrared spectroscopy, Raman. The morphology of the products was observed by scanning electron microscopy and transmission electron microscopy tests. The results are as follows:VO₂?B?/C core-shell composites were successfully prepared using commercial V2O5 and glucoses as the starting materials by a facile one-pot hydrothermal method. The products consisted of the crystal VO2?B? phase and the amorphous carbon phase. The amorphous carbon contains lots of organic groups. The morphology of the as-obtained V02?B?/C composites are well-defined nanobelts. Furthermore, the electrochemical properties of V02?B?/C core-shell composites were investigated by cyclic voltammetry ?CV? and galvanostatic charge-discharge ?GCD?. The results showed the specific capacitance of VO2?B?/C is 189 F·g-1, it also shows an excellent energy density of 178.4 W·h·kg-1 at a power density of 2525.9 W·kg-1 and a rapidly reversible redox Faraday response. Higher carbon content results in lower initial specific capacitance but better cyclic stability.V₂O₅ nanoparticles with high specific surface area were prepared using the as obtained V02?B?/C composites by calcination. V2O5 nanoparticles performed a high initial specific capacitance of 385 F·g-1, it also shows an excellent energy density of 231.7 W·h·kg-1 at a power density of 1980 W·kg-1. The effects of the calcination temperature and time on materials' electrochemical properties were studied.LiV₃O₈ nanosheets were successfully synthesized using commercial V2O5, H2O2 and LiOH by a facile hydrothermal approach and subsequent calcination. The pure phase LiV3O8 nanosheets with layered structures were formed. Furthermore, the electrochemical properties of LiV3O8 nanosheets were investigated, the results showed that LiV3O8 nanosheets performed a high initial specific capacitance of 288 F·g-1, and the specific capacitance after 100 cycles was 98 F·g-1[2].