A Fluorine‐Free Chaotropic Electrolyte Promoting Zinc Peroxide Chemistry for Non‐Alkaline Zinc–Air Batteries

Rechargeable non-alkaline zinc-air batteries (ZABs) based on highly reversible zinc peroxide chemistry offer high energy density and superior stability under ambient air. However, the unique chemistry is closely related to the inner Helmholtz layer facilitated by the triflate anions, which has not been reported in other dilute fluorine-free electrolytes. There is still a lack of selection criteria for anions and benchmarking two-electron oxygen reduction reaction (2e^- ORR) selectivity. Herein, the Hofmeister series was introduced to depict the hydrophobicity of anions. Integrated spectroscopic and electrochemical analyses demonstrate that chaotropic anions promote 2e^- ORR selectivity by disrupting the hydrogen-bond network and decreasing interfacial water at the electrode-electrolyte interface. As proof of concept, a fluorine-free chaotropic electrolyte, zinc perchlorate (Zn(ClO₄)₂), is proposed to enable efficient zinc peroxide chemistry for ZABs without requiring specialized cell configuration. The ZABs using Zn(ClO₄)₂ electrolyte not only exhibit improved reaction kinetics and higher energy efficiency but also reduced cost compared to fluorine-containing counterparts. This study provides new insights into electrolyte design strategies for developing low-cost and durable ZABs based on zinc peroxide chemistry.