Investigations the effects of some additives on the electrochemical behaviors of positive electrolye of vanadium redox battery

In this study, positive electrolyte solutions of vanadium redox battery consisting of fumed silica, TiO2, B2O3, α-Al2O3, γ-Al2O3, gibbisite, boehmit, asetonitril and TiOSO4 as additive were prepared and the solutions were characterized electrochemically, spectrally and thermally. Optimum amount of additives were determined by electrochemical methods such as cyclic voltammetry and electrochemical impedance spectroscopy. The optimum scanning rate used cyclic voltammetric analysis with pencil graphite electrode was adjusted as 20 mV/s and the mass transfer mechanism on the electrode surface was determined as diffusion and adsorption. Besides, the surface morphology and chemistry of used electrodes were investigated SEM, EDX and XPS analysis. Cyclic charge-discharge tests were performed in the solution having optimum amount of additives and the highest discharge capacities were determined as 91,71; 91,19; 89,09 and 86,19 mAh in the solution consisting of acetonitrile, boroxide, fumed silica and γ-alümina as additive, respectively. The solutions consisting of additives were characterized UV-VIS analysis. The effects of additives on the thermal stability of V(V) solutions were investigated at -20, 25, 40 and 60 °C and the effects of additives on thermal precipitation of V(V) were determined. In this concept, the result was obtained that the additives fumed silica, TiO2, B2O3, γ -Al2O3, gibbsite, boehmite and TiOSO4 can be used as anti-precipitation agents for the positive electrolyte component of vanadium redox battery.