Influence of the Concentration of Electrolyte on the Capacitive Properties of Vanadium Nitride Electrode for Electrochemical Capacitors

Cyclic voltammetry and electrochemical impedance spectroscopy were applied to investigate the effect of the concentration of KOH solution on the capacitive performance of the nanostructured vanadium nitride. The results reveal that the required overpotential for the transformation of V2+ to V3+ in concentrated KOH solutions is much lower than that in diluted solutions, indicating that concentrated solutions are kinetically more favorable than diluted solutions. Additionally, a marked decrease in charge transfer resistance and electrolyte series resistance were observed as the concentration of KOH solution increased. Thus, the specific capacitance and the rate capability of the vanadium nitride electrode are improved with increasing of the concentration of KOH solution. Moreover, the specific capacitance of the vanadium nitride material in 6 M KOH solution is the highest, and the vanadium nitride material exhibits great long term stability in KOH solution. (C) 2018 The Electrochemical Society.