A Vanadium redox battery consists of a power cell in which two electrolytes are kept separated by an ion exchange membrane, somewhat confusingly, both electrolytes are vanadium based. The electrolyte in the positive half-cell contains VO2+ and VO2+ ions, the electrolyte in the negative half-cell, V3+ and V2+ ions. This electrolyte is typically prepared by electrolytically dissolving vanadium pentoxide (V2O5) in sulphuric acid (H2SO4) and the solution remains strongly acidic in use.