A rechargeable zinc–air battery with decoupled metal oxidation and oxygen reduction reactions

Abstract

Rechargeable metal–air batteries are a subject of interest for many years because of their high theoretical capacity. However, certain fundamental challenges remain that make it difficult to achieve true long term rechargeability. In the present work, a battery configuration is proposed which employs a third redox couple in the form of two auxiliary electrodes. The purpose of the auxiliary electrodes is to isolate the metal electrode and air electrode reactions by accepting the Zn2+ ions in one cell and releasing them in the other cell. This opens the possibility of using a non-aqueous electrolyte in the presence of zinc electrode that ensures good coulombic efficiency while maintaining an aqueous environment with the air electrode. The present work demonstrates fabrication of a Zn–air battery based on this concept. The auxiliary electrode material is chosen to be Copper Hexacyanoferrate (CuHCF). The battery shows a discharge voltage plateau at about 1.5 V, which is much higher than traditional Zn–air batteries. Along with the charge–discharge behavior of the battery, extensive studies on CuHCF and crucial insights on the electrochemical reactions are presented.