2, University at Buffalo, State University of New York, Buffalo, New York, United States
Non-aqueous redox-flow batteries have emerged as promising systems for large-capacity, reversible energy storage capable of meeting the variable demands of the electrical grid. Here, we investigate the potential for a Lindqvist polyoxovanadate-alkoxide (POV-alkoxide) clusters to serve as the electroactive species for a symmetric, non-aqueous redox-flow battery. POV-alkoxides display four quasi-reversible redox events, and demonstrate significant solubility and stability in acetonitrile across all charge-states. Using the POV-alkoxide cluster in acetonitrile as the electrolyte solution at both the anode and cathode of a static H-cell, we obtain coulombic efficiencies of nearly 100% for over 500 charge-discharge cycles. This application of hexavanadate clusters as electrolytes in organic media demonstrates that the remarkable redox properties of multi-metallic metal-oxide assemblies can be harnessed for non-aqueous energy storage applications, and represents an important new direction for the generation of high performance non-aqueous redox-flow batteries.