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A redox-flow battery with an alloxazine-based organic electrolyte


Redox-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.

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Figure 1: Cyclic voltammogram and cell schematic.
Figure 2: Cell performance.
Figure 3: Theoretical calculation and cyclic voltammetry of alloxazines.


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This work was funded by the US DOE ARPA-E award no. DE-AR0000348, NSF no. NSF-CBET-1509041, the Massachusetts Clean Energy Technology Center, and the Harvard John A. Paulson School of Engineering and Applied Sciences. We thank C. Qian for designing the Fig. 1d scheme. We appreciate support from the Odyssey Cluster and Research Computing of Harvard University’s Faculty of Arts and Sciences.

Author information




K.L., R.G.G. and M.J.A. formulated the project. K.L. and L.T. synthesized the compounds. K.L., E.S.B. and L.T. collected and analysed the NMR data. K.L., Q.C., E.S.B. and A.V. collected and analysed the electrochemical data. K.L. and A.V. measured solubility. R.G.-B. and A.A.-G. performed theoretical analysis. K.L., R.G.G. and M.J.A. wrote the paper, and all authors contributed to revising the paper.

Corresponding authors

Correspondence to Michael J. Aziz or Roy G. Gordon.

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The authors declare no competing financial interests.

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Supplementary Information

Supplementary Figures 1–13, Supplementary Table 1–2. (PDF 946 kb)

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Lin, K., Gómez-Bombarelli, R., Beh, E. et al. A redox-flow battery with an alloxazine-based organic electrolyte. Nat Energy 1, 16102 (2016).

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