Triflate anion chemistry for enhanced four-electron zinc–iodine aqueous batteries

Abstract

I⁺ hydrolysis, sluggish iodine redox kinetics and the instability of Zn anodes are the primary challenges for aqueous four-electron zinc-iodine batteries (4eZIBs). Herein, the OTf^- anion chemistry in aqueous electrolyte is essential for developing advanced 4eZIBs. It is elucidated that OTf^- anions establish weak hydrogen bonds (H bonds) with water to stabilize I⁺ species while optimizing a water-lean Zn²⁺ coordination structure to mitigate Zn dendrites and corrosion. Moreover, the interaction of the OTf^- anions with the iodine species results in an increased equilibrium average intermolecular bond length of the iodine species, facilitating the 4e redox kinetics of iodine with improved reversibility.