A polyelectrolyte membrane-based vanadium/air redox flow battery

A vanadium/air redox flow battery (VARFB) was developed using on one side 2 M V2+/V3+ solution in 3 M H2SO4 and H2O/O2 on the other side as redox couples. The vanadium side is identical to the already available all vanadium redox flow battery. Air is used as the second redox couple in order to decrease the weight and increase the weight specific power output. In the VARFB cell, a membrane electrode assembly (MEA) with a new reversible air electrode is applied. In this short communication, we show that the VARFB operated at 80 °C has a voltage efficiency of 46% and an energy efficiency of 45.7%. Although somewhat lower than for other redox flow batteries like all vanadium, having 81% voltage efficiency and 73% energy efficiency, the weight specific storage capacity is almost doubled here since in our system only one liquid redox couple has to be stored.