Solvation chemistry tailored via dielectric constant engineering for stable low-temperature aqueous zinc batteries

Aqueous zinc-metal batteries are promising candidates for sustainable energy storage; but their practical viability is severely limited by poor cryogenic performance caused by kinetic sluggishness and interfacial instability. Here we show a strategy for low-temperature ZMBs based on tailoring the Zn²⁺ solvation environment by engineering the dielectric constant (ε). By incorporating ethyl acetate, a low-ε co-solvent, into a Zn(ClO₄)₂ electrolyte, we strategically weaken water's hydrogen-bond network and increase cation-anion pairing. This modified solvation structure accelerates Zn²⁺ transport and desolvation, promotes the formation of a protective solid electrolyte interphase rich in organic and inorganic components, and inhibits parasitic hydrogen evolution. Consequently, the optimized electrolyte enhances Zn plating/stripping stability, with Zn||Zn cells operating at 0.2 mA cm^-2 for 10 months (25 °C) and 1 mA cm^-2 for 4,000 hours (-50 °C), and Zn||PANI batteries at 1 A g^-1 sustaining 10,000 cycles with negligible degradation (-50 °C). This work highlights the critical importance of dielectric constant engineering in electrolyte design and paves the way for high-performance, low-temperature aqueous batteries.