Lin, KaixiangGómez-Bombarelli, RafaelBeh, EugeneTong, LiuchuanChen, QingValle, AlvaroAspuru-Guzik, AlanAziz, MichaelGordon, Roy2017-07-132016Lin, Kaixiang, Rafael Gómez-Bombarelli, Eugene S. Beh, Liuchuan Tong, Qing Chen, Alvaro Valle, Alán Aspuru-Guzik, Michael J. Aziz, and Roy G. Gordon. 2016. “A Redox-Flow Battery with an Alloxazine-Based Organic Electrolyte.” Nature Energy 1 (9) (July 18): 16102. doi:10.1038/nenergy.2016.102.2058-7546http://nrs.harvard.edu/urn-3:HUL.InstRepos:33439113Redox-flow batteries (RFBs) can store large amounts of electrical energy from variable sources, such as solar and wind. Recently, redox-active organic molecules in aqueous RFBs have drawn substantial attention due to their rapid kinetics and low membrane crossover rates. Drawing inspiration from nature, here we report a high-performance aqueous RFB utilizing an organic redox compound, alloxazine, which is a tautomer of the isoalloxazine backbone of vitamin B2. It can be synthesized in high yield at room temperature by single-step coupling of inexpensive o-phenylenediamine derivatives and alloxan. The highly alkaline-soluble alloxazine 7/8-carboxylic acid produces a RFB exhibiting open-circuit voltage approaching 1.2 V and current efficiency and capacity retention exceeding 99.7% and 99.98% per cycle, respectively. Theoretical studies indicate that structural modification of alloxazine with electron-donating groups should allow further increases in battery voltage. As an aza-aromatic molecule that undergoes reversible redox cycling in aqueous electrolyte, alloxazine represents a class of radical-free redox-active organics for use in large-scale energy storage.en-USJournal Article2016-07-2720162017-07-1310.1038/nenergy.2016.102