Overcharge protection in aqueous zinc-ion batteries via self-sacrificial additives

In pursuing zinc-ion batteries (ZIBs) with extended lifetimes, considerable research has been devoted to enhancing their stability, specifically cycling stability, by developing stable cathodes and Zn anodes. However, the durability, that is, reliability of ZIBs under abuse operations, particularly overcharge conditions, has long been overlooked in past research. This work investigates the durability of two typical aqueous ZIBs under overcharge conditions (Mn²⁺ expanded hydrated vanadium (MnVO) and manganese dioxide (MnO₂) as cathode materials). Experimental findings highlight the detrimental effects of overcharging on ZIBs, leading to rapid battery failure primarily attributed to electrolyte decomposition and subsequent deterioration of interfacial contact. Subsequently, self-sacrificial electrolytes are developed by introducing bromine-based additives into the electrolyte (tetrabutylammonium and benzyl trimethylammonium bromine). These additives undergo oxidation before the electrolyte decomposition, introducing an additional Br⁻/Br₂ redox couple. Consequently, this approach effectively stabilizes the electrolyte environment. It provides efficient overcharge protection for extended periods, enabling the Zn‖MnVO and Zn‖MnO₂ batteries to sustain for over 650 hours and 550 hours, even under harsh 200% state-of-charge conditions, respectively. © 2024 The Royal Society of Chemistry.