Electrolyte engineering for efficient and stable vanadium redox flow batteries

The vanadium redox flow battery (VRFB), regarded as one of the most promising large-scale energy storage systems, exhibits substantial potential in the domains of renewable energy storage, energy integration, and power peaking. In recent years, there has been increasing concern and interest surrounding VRFB and its key components. Electrolytes, serving as the energy storage medium, play a key role in determining the performance and cost of the battery. Despite a great deal of research and development devoted to vanadium-based electrolytes over the years, the solubility of vanadium and its adaptability to varying temperatures have yet to meet the requirements, and the in-situ monitoring and recovery methods still need to be developed for high energy density, long cycle life, and cost-effective VRFB. This paper provides a review of electrolyte properties, supporting electrolytes, electrolyte additives, synthesis methods, and their impact on battery performance. Moreover, electrolyte monitoring and capacity recovery methods are summarized and discussed. This review aims to guide the development, optimization, and application of electrolytes for further improvement of flow batteries.