Novel vanadium chloride/polyhalide redox flow battery

This paper describes a novel redox flow cell which employs a polyhalide solution in the positive half-cell electrolyte and a vanadium(II)/vanadium(III) chloride redox couple as the negative half-cell electrolyte. During charging, the bromide ions in the positive half-cell are considered to undergo oxidation to the polyhalide ion Br2Cl−; the formal potential of this couple is about 0.8 V versus the saturated calomel electrode (SCE). When combined with a formal potential of around −0.5 V versus SCE for the V(III)/V(III) coupled in the chloride supporting electrolyte, an overall cell potential of approximately 1.3 V would be expected for the vanadium chloride/polyhalide redox flow cell.