Dilute electrolytes for suppressing metal anode corrosion during calendar aging and cycling in aqueous zinc batteries

Abstract While numerous improvements in cycling stability have been demonstrated for next-generation battery chemistries with metallic anodes, their calendar aging (e.g., capacity loss during idle periods of rest) performance painfully lags behind and remains a critical bottleneck hindering their practical deployment. In contrast to their commercial counterparts, metallic anodes exhibit substantial capacity loss during calendar aging. Despite several recent studies exploring the underlying reasons for calendar aging, few solutions have been proposed to mitigate this key issue. Here, we design a low concentration electrolyte (0.1 M ZnSO 4 ) that can reduce calendar aging losses in Zn metal chemistries by more than an order of magnitude (<1.5% capacity fade after 24 hours of aging) while still maintaining improved cycling stability (>3300 cycles at 4 C) with an average Coulombic efficiency of 99.8%. We find that solvated water molecules (rather than unsolvated water molecules) drive Zn corrosion, motivating our effort to minimize these reactive solvated water molecules through a holistic approach centered around concentration reduction, aided by isotopic solvent substitution and targeted additives. This strategy could be applicable to other battery chemistries and provides an approach that can address both calendar aging and cycling stability, both of which are necessary for practical applications.