Development of Non-Aqueous Redox Flow Batteries for Grid-Scale Energy Storage
Among the grid-scale energy storage options such as pumped hydroelectric, compressed air and lithium ion batteries, redox flow batteries (RFBs) offer a number of attractive features including long cycle lives, and improved energy management as a consequence of the decoupling of power and energy. They also hold promise for significantly reducing cost. Commercially available RFBs are based on aqueous electrolytes, consequently the cell voltage is limited by the stability window of water. Efforts to increase energy density and reduce cost have focused on non-aqueous chemistries with cell voltages that can approach 5V. Despite their promise, there are significant limitations associated with non-aqueous RFBs including the lack of active species that are sufficiently robust to achieve cycling and efficiency targets. This presentation will describe our efforts to correlate experimentally measured standard potentials, solubilities, and cycle lifes, with selected chemical, structural and electronic properties from spectroscopic characterization and density functional theory calculations. A particular focus has been the development of structure-composition-function relationships for metal coordination complexes and alkoxybenzene compounds. These relationships and associated predictive models are being used to design next generation active species for non-aqueous RFBs. In addition, this presentation will explore a common ion design that holds promise for significantly reducing the cost of RFBs.