Levi Thompson1

1, University of Michigan, Ann Arbor, Michigan, United States

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 potential is limited by the stability window of water. Efforts to increase energy density and reduce cost have focused on non-aqueous chemistries with cell potentials that can approach 5V. Despite their promise, there are significant materials limitations associated with non-aqueous RFBs including the lack of active species that are sufficiently robust to achieve cycling and efficiency targets. Metal coordination complexes (MCCs) offer the possibility of multiple electron transfers, high solubilities in non-aqueous solvents and low cost. This presentation will describe our efforts to correlate experimentally measured standard potentials, solubilities, and cycle lifes, with selected chemical, structural and electronic properties determined using density functional theory (DFT) calculations. A particular focus for our work has been the development of structure-composition-function relationships for complexes including acetylacetonate, terperidine, and bipyridylimino isoindoline ligands based on experimental and computational results. These relationships and associated predictive models have been used to design next generation MCCs. In addition, this presentation will explore a common ion design that holds promise for significantly reducing the cost of RFBs.