2, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Redox flow batteries (RFBs) are promising candidates for grid storage, with a few large-scale systems currently in operation. However, current systems have not met the stringent cost and/or safety requirements needed for widespread implementation. Replacing vanadium with organic compounds may lower materials costs, and utilizing non-aqueous (aprotic) electrolyte solvents, in place of water, could enable an increase in operating voltage. Both features make non-aqueous RFBs candidates for large-scale stationary storage. A limited number of organic compounds have been reported as stable electron donors and acceptors, with even fewer materials being studied as small-molecule two-electron donors and/or two-electron acceptors. Our recent efforts have focused on the development of highly soluble electron donors and acceptors with stable oxidized and reduced states. This presentation will focus on design strategies utilized to increase solubility as well as molecular stability in all relevant states of charge. In particular, we highlight the design, synthesis, and electrochemical analysis of posolyte materials with high oxidation potentials. Molecular solubility and stability in various electrolytes will be considered. Spectroscopic, electrochemical, and flow battery results will be presented.