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.