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

Sun, Wei; Wang, Fei; Zhang, Bao; Zhang, Mengyi; Küpers, Verena; Ji, Xiao; Theile, Claudia; Bieker, Peter et al. · Science · 2021

basic_science · Level V

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Abstract

Rechargeable alkaline zinc-air batteries promise high energy density and safety but suffer from the sluggish 4 electron (e<sup>-</sup>)/oxygen (O<sub>2</sub>) 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<sub>2</sub>/zinc peroxide (ZnO<sub>2</sub>) chemistry that proceeds through a 2e<sup>-</sup>/O<sub>2</sub> process in nonalkaline aqueous electrolytes, which enables highly reversible redox reactions in zinc-air batteries. This ZnO<sub>2</sub> chemistry was made possible by a water-poor and zinc ion (Zn<sup>2+</sup>)-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.