Organic Anolyte Species for Aqueous Redox Flow Batteries

The incorporation of energy storage devices into the grid has garnered increased attention for their potential to mediate energy supply from intermittent renewable sources like solar and wind and also to balance peak power demand. Redox flow batteries are promising candidates for grid-scale energy storage given their simpler scalability relative to traditional secondary batteries based on solid-state electroactive materials. However, current state-of-the-art vanadium based systems are hindered by high material cost.1 The use of low cost organic electrolytes has emerged as a potential alternative to vanadium based systems.2,3 Presented will be our recent efforts in developing water soluble organic anolyte materials for aqueous flow battery systems. For a family of structurally related molecules, substituent effects on solubilities, electrochemical properties, and chemical stability for a select promising candidate will be discussed. Rational optimization of flow cell conditions including the membrane and electrodes has been achieved for performance improvement. The final anolyte candidate exhibits high solubility in the supporting electrolyte, undergoes two electron redox chemistry, and demonstrates good stability. When coupled with the well-established ferricyanide/ferrocyanide catholyte, the flow battery possesses a high OCV of 1.35 V at 50% SOC and yields stable long-term cyclability. References Zhang, M.; Moore, M.; Watson, J.S.; Zawodzinski, T.A.; Counce, R.M. J. Electrochem. Soc. 2012, 159, A1183. Park, M.; Ryu, J.; Wang, W.; Cho, J. Nat. Rev. Mater. 2016, 2, 16080. Soloveichik, G.L. Chem. Rev. 2015, 115, 11533.