A Rechargeable Battery with an Iron Metal Anode

Abstract To date, tremendous efforts of the battery community are devoted to batteries that employ Li + , Na + , and K + as charge carriers and nonaqueous electrolytes. However, aqueous batteries hold great promise for stationary energy storage due to their inherent low cost and high safety. Among metal batteries that use aqueous electrolytes, zinc metal batteries are the focus of attention. In this study, iron as an anode candidate in aqueous batteries is investigated because iron is undoubtedly the most earth‐abundant and cost‐effective metal anode. Reversible iron plating/stripping in a FeSO 4 electrolyte is demonstrated on the anode side and reversible topotactic (de)insertion of Fe 2+ in a Prussian blue analogue cathode is showcased. Furthermore, it is revealed that LiFePO 4 can pair up with the iron metal anode in a hybrid cell, delivering stable performance as well.