Advanced electrolytes for low-temperature zinc-ion batteries.

Aqueous zinc-ion batteries (ZIBs) are attractive for safe and sustainable energy storage, but their operation in cold environments remains constrained by the temperature sensitivity of water-based electrolytes. When cooled, the strengthening and ordering of the hydrogen-bond (HB) network, together with slowed ion diffusion and altered solvation/desolvation equilibria, can simultaneously reduce conductivity and destabilize electrode interfaces. These coupled effects translate into pronounced polarization, poor zinc plating/stripping reversibility and accelerated performance decay. This mini-review discusses electrolyte advances for low-temperature ZIBs from a physicochemical perspective. We first outline how HB reorganization, Zn2+ solvation structure and ion-solvent interactions collectively govern freezing behaviour, transport kinetics and interfacial reactions. We then survey representative design strategies, including concentration-driven electrolytes, organic co-solvents, eutectic systems and anti-freeze hydrogels, to show how distinct routes can reduce water activity, maintain liquid-like dynamics and promote stable interphases under sub-zero conditions. Finally, we highlight emerging concepts, such as solvation-entropy regulation, chaotropic/kosmotropic ion effects and field- or cycling-induced interphase formation, and discuss the remaining gaps towards transferable design descriptors and practical all-climate zinc batteries. This article is part of the theme issue 'Electrolytes within the domain of electrochemistry and electrochemical energy storage'.