Cathodic electrosynthesis of VOx ceramics for supercapacitor applications

The feasibility of electrosynthesis of VOx by the cathodic electrogenerated base method is demonstrated and advantages of this technique are discussed. The electrogenerated base method results in the fabrication of VOx material, containing V3+, V4+ and V5+ species from VOSO4 solutions. The deposition yield is studied in-situ at a constant voltage or constant current conditions using a quartz crystal microbalance. The method allows rigid control of the deposition yield. The results of X-ray photoelectron spectroscopy, thermogravimetic and differential thermal analyses allow the development of the new electrosynthesis mechanism. For the first time electric discharge machining (EDM) is used for the fabrication of patterned Ni current collectors for VOx supercapacitors. VOx material shows capacitive behavior in the positive potential range with a capacitance of 278.6 mF cm−2. Asymmetric device containing VOx cathodes and γ-Fe2O3 anodes shows a capacitance of 27.1 mF cm−2 in a voltage window of 1.5 V in Na2SO4 electrolyte. The approach developed in this investigation opens an avenue for the fabrication of advanced patterned ceramic asymmetric supercapacitors with enlarged voltage windows.