Dual-Salt Chaotropic Eutectic Electrolyte for Enhancing Low-Temperature Zinc-Ion Batteries

Aqueous zinc-ion batteries (ZIBs) exhibit severe performance degradation at low temperatures primarily due to the freezing of water. To mitigate this issue, we engineered a dual-salt super-chaotropic eutectic electrolyte that exploits the strong Hofmeister effect of zinc salts to disrupt the ordered hydrogen-bonding network of the electrolyte, significantly lowering its freezing point. The electrolyte, formulated with Zn(ClO₄)₂·6H₂O, NaClO₄·H₂O, and acetamide, leverages the strong chaotropic properties of ClO₄ ^- ions to dismantle the hydrogen bonding network of water molecules, realizing an ultra-low freezing point of -75.9 °C. Additionally, the electrolyte minimizes water activity, suppresses the hydrogen evolution reaction, and mitigates corrosion through the robust coordination among ClO₄ ^-, acetamide, and Zn²⁺ ions, enabling uniform and compact Zn deposition. The Zn||sodium vanadium phosphate (NVP) battery demonstrates higher redox potential, exceptional low-temperature cycling performance, achieving over 5500 cycles at -20 °C with 81.2% capacity retention and nearly 100% Coulombic efficiency. Furthermore, the pouch cell retains 94.8% of its capacity after 250 cycles at -20 °C. This innovative chaotropic eutectic electrolyte provides a promising pathway for advancing low-temperature ZIBs with extended operational lifespans.