Dissolution, solvation and diffusion in low-temperature zinc electrolyte design

Aqueous zinc-based batteries have garnered the attention of the electrochemical energy storage community, but they suffer from electrolytes freezing and sluggish kinetics in cold environments. In this Review, we discuss the key parameters necessary for designing anti-freezing aqueous zinc electrolytes. We start with the fundamentals related to different zinc salts and their dissolution and solvation behaviours, by highlighting the effects of anions and additives on salt solubility, ion diffusion and freezing points. We then focus on the complex structures and energetics of cation-anion-solvent interaction. We also evaluate the prevailing strategies to improve the performance of electrolytes at low temperatures, with a discussion on the kinetics of plating and stripping of zinc anodes and charge storage in various cathode materials. Furthermore, we consider the current challenges and envisage future research directions in cold-resistant aqueous electrolyte formulations for zinc batteries.