A rechargeable zinc-air battery based on zinc peroxide chemistry.

Rechargeable alkaline zinc-air batteries promise high energy density and safety but suffer from the sluggish 4 electron (e)/oxygen (O) chemistry that requires participation of water and from the electrochemical irreversibility originating from parasitic reactions caused by caustic electrolytes and atmospheric carbon dioxide. Here, we report a zinc-O/zinc peroxide (ZnO) chemistry that proceeds through a 2e/O process in nonalkaline aqueous electrolytes, which enables highly reversible redox reactions in zinc-air batteries. This ZnO chemistry was made possible by a water-poor and zinc ion (Zn)-rich inner Helmholtz layer on the air cathode caused by the hydrophobic trifluoromethanesulfonate anions. The nonalkaline zinc-air battery thus constructed not only tolerates stable operations in ambient air but also exhibits substantially better reversibility than its alkaline counterpart.