Synergistic Solvation Strategy for Low-Temperature Alkaline Zinc-Ferricyanide Flow Battery

Alkaline zinc-ferricyanide flow batteries (AZFFBs) emerge as promising candidates for long-duration energy storage. However, at cryogenic temperatures, these systems suffer from electrolyte solidification, anodic zinc dendrite formation, zinc-related side reactions, and cathodic Fe(CN)₆ ^4- precipitation-induced capacity decay. Herein, we propose a synergistic solvation strategy in which Li⁺ and Cl^- jointly inhibit the formation of tetrahedral hydrogen bond networks, thereby lowering the liquid-solid transition peak temperature of both the anolyte and catholyte. Meanwhile, Cl^- is utilized to construct a water-poor solvation structure around Zn(OH)₄ ^2- to optimize zinc deposition and inhibit the side reactions, while Li⁺ enhances the solubility of Fe(CN)₆ ^4- by incorporating additional water molecules into its solvation structure through strong ion-dipole interactions. The optimized AZFFB exhibits outstanding low-temperature performance, achieving stable cycling at -20 °C with an average coulombic efficiency of 99.54%. It also demonstrates excellent stability at room temperature, sustaining over 500 cycles at 28 °C with an average coulombic efficiency of 99.79%, representing more than a 22-fold extension in cycle life. Additionally, the AZFFB exhibits robust stability under fluctuating temperature conditions. These breakthroughs markedly enhance the potential of AZFFBs as viable solutions for extreme-environment energy storage, particularly in polar region microgrids, cold-climate off-grid power systems, and subsea power applications.