Advancing anti-freezing hydrogel electrolyte based on deep eutectic solvent for wide temperature range aqueous zinc-ion battery.

Hydrogels based on Deep Eutectic Solvents (DES) demonstrate remarkable anti-freezing, resilience, and toughness, presenting a promising avenue to the operation of aqueous zinc-ion batteries under extreme conditions. A gel electrolyte capable of operating over a wide temperature range is developed based on a DES comprising 1 mol/kg (m) Zn(ClO) + 3.5 m Mg(ClO). Spectral characterization confirms the synergistic influence of both anions and cations on the freezing point of the DES. With four hydrogen bond (HB) acceptors, Mg exhibits strong electrostatic attraction towards the O atoms of HO, while ClO forms numerous HBs with HO molecules. This dual interaction allows for precise adjustment of the chemical environment around the H and O atoms of HO, resulting in an exceptionally low freezing point of -116.92 °C for the DES. The gel electrolyte derived from this DES demonstrates an impressive ionic conductivity of 0.285 mS/cm at -70 °C. Leveraging its excellent low-temperature performance and compatibility with a zinc anode, the flexible Zn-Mn battery constructed with this electrolyte exhibits robust electrochemical performance at low temperatures. Specifically, at -70 °C, it achieves a high specific capacity of 76.83 mAh/g, displays excellent rate capability, and maintains stable cycling performance. Moreover, the Zn-Mn battery operates reliably across a broad temperature range from -70 to 80 °C. This study presents innovative insights for advancing Zn-Mn batteries capable of efficient operation across diverse environmental conditions, thereby opening new avenues for their development.