A Wide-Temperature-Range Electrolyte for all Vanadium Flow Batteries.

The all-vanadium flow battery (VFB) has emerged as a highly promising large-scale, long-duration energy storage technology due to its inherent advantages, including decoupling of power and capacity, high safety, scalability, long cycle life, and environmental compatibility. However, the practical application of VFB systems is hindered by the poor thermal stability of vanadium electrolytes under extreme temperatures, where precipitation occurs at high temperatures (≥40 °C) and low temperatures (≤10 °C), severely limiting their geographical adaptability. This study proposes a wide-temperature-range (WTR) electrolyte by introducing four organic/inorganic additives, comprising benzene sulfonate, phosphate salts, halide salts, and imidazole into the conventional vanadium electrolyte. The operational temperature of vanadium electrolyte was extended to -5∼45 °C. Electrochemical characterization confirmed that WTR-electrolyte has comparable performance to the conventional electrolyte at 100 mA cm-2, while not sacrificing performance. Furthermore, the WTR-electrolyte can not only be stored in the temperature range of -5∼45 °C, but also can stably operate at -5 °C and 45 °C. This work provides a viable strategy for designing WTR vanadium electrolytes, offering critical insights to advance the deployment of vanadium-based energy storage systems in diverse climatic environments.