Cathodic electrosynthesis of VOx ceramics for supercapacitor applications

The feasibility of electrosynthesis of VO_x by the cathodic electrogenerated base method is demonstrated and advantages of this technique are discussed. The electrogenerated base method results in the fabrication of VO_x 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 VO_x supercapacitors. VO_x material shows capacitive behavior in the positive potential range with a capacitance of 278.6 mF cm⁻². Asymmetric device containing VO_x 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.