Subzero Temperature Operation of Aqueous Zn Metal Batteries by Tailoring Electrolyte Solvation Structure

The declining performance of aqueous zinc metal batteries (AZMBs) at colder temperatures, especially due to aqueous electrolyte solidification and reduced capacity retention at subzero temperatures, poses a considerable challenge. Here, we report a cheap and ecofriendly aqueous electrolyte formulation comprising low-concentration zinc chloride salt and a common antifreeze agent. We show that the glycerin antifreeze co-solvent effectively interacts with free water molecules and weakens the zinc-ion primary solvation structures, thereby considerably mitigating their detrimental effect at low temperatures. Consequently, the optimized electrolyte successfully outputs a depressed liquid-glass transition point down to −99.2 °C and a record-high Zn plating/stripping Coulombic efficiency of ∼99.94% at −40 °C, as well as ∼70% of its room-temperature capacity at −40 °C, opening up a new opportunity for practical AZMBs.