Nonaqueous redox flow batteries (NRFB) have emerged as a promising next-generation grid-scale energy storage solution because of their wide voltage window and hence potential higher energy densities.^1-4 The development of redox active materials is essential to enable extensive deployments of such technology. Catholyte (high potential) molecules have been extensively investigated and reported,^5,6 while in contrast there is still a dearth of anolyte (low potential) counterparts.

In this presentation, we report the design of a new anolyte molecule series. The materials, for both pristine and modified forms, are composed of aromatic heterocyles. These molecules exhibit low electrochemical potentials and high solubilities in organic solvents. Coupling with catholyte molecules, high cell voltages around 2.4 V could be achieved, as shown from cyclic voltammetry (CV) results of the pristine form in Fig. 1a. Flow cell performances are evaluated at a concentration of 0.5 M. As shown in Fig. 1b, excellent efficiencies are observed at a current density of 10 mA/cm², with columbic efficiency (CE) ~ 93%, voltage efficiency (VE) ~ 77%, and energy efficiency ~ 72%. Influences of solvents and supporting electrolytes are also covered.

References:

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2. K. Gong, Q. Fang, S. Gu, S. Li, Y. Yan, Energ. Environ. Sci. 2015, DOI: 10.1039/C5EE02341F.

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4. X. Wei, W. Xu, J. Huang, L. Zhang, E. Walter, C. Lawrence, M. Vijayakumar, W. A. Henderson, T. Liu, L. Cosimbescu, B. Li, V. Sprenkle, W. Wang, Angew. Chem. Int. Ed. 2015, 54, 8684.

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6. J. Huang, L. Su, J. A. Kowalski, J. L. Barton, M. Ferrandon, A. K. Burrell, F. R. Brushett, L. Zhang, J. Mater. Chem. A 2015, 3, 14971-14976.