Beyond alkaline and neutral: emerging electrolyte strategies for rechargeable Zn–air batteries

Zinc-air batteries (ZABs) are promising candidates for sustainable energy storage due to their high theoretical energy density (1086 Wh kg -1 ), low cost, and environmental compatibility. However, their practical deployment is hindered by limited rechargeability, arising from electrolyte instability, Zn anode degradation, and sluggish oxygen redox kinetics. Conventional alkaline and near-neutral electrolytes suffer from issues such as carbonation, dendrite formation, parasitic reactions, and poor reaction kinetics, which restrict long-term cycling performance. This Review focuses on emerging electrolyte strategies beyond conventional systems, with particular emphasis on water-in-salt electrolytes (WiSE) and peroxide-mediated reaction pathways. We provide a mechanistic perspective on how electrolyte structure governs Zn 2+ solvation, interfacial behavior, and oxygen reaction pathways, thereby influencing Zn reversibility and overall battery performance. In particular, we discuss how reduced water activity and modified solvation environments in WiSE can suppress parasitic reactions and alter reaction kinetics, while peroxide-based chemistries enable alternative two-electron pathways with improved energy efficiency. By critically comparing these approaches, we highlight key challenges including transport limitations, interfacial stability, and the discrepancy between apparent stability and true Zn reversibility under practical operating conditions. Finally, we outline future research directions toward integrating electrolyte design with realistic performance metrics to enable commercially viable, high-performance rechargeable ZABs.