Polyoxometalate-based electrolyte materials in redox flow batteries: Current trends and emerging opportunities

Redox flow batteries have received wide attention for electrochemical energy conversion and storage devices due to their specific advantage of uncoupled power and energy devices, and therefore potentially to reduce the capital costs of energy storage. Terrific structural features of polyoxometalates exhibit unique advantages in redox flow batteries, such as, stable chemical properties, multi-electron reaction, good redox reversibility, low permeability, etc, which furnishes a novel perspective for settling various problems of redox flow batteries. This was a comprehensive and critical review of this type of batteries, focusing mainly on the chemistry of polyoxometalate electrolyte materials and introducing a systematic classification. Finally, challenges and perspectives of polyoxometalate electrolyte materials and polyoxometalate redox flow batteries are discussed.