Long-Term Stability of Quinone Electrolytes in Aqueous Flow Batteries

Quinone-based flow batteries are attractive candidates for large-scale electrical energy storage, as quinones can be inexpensive, exhibit rapid redox kinetics, and require no electrocatalyst [1-3]. We present the evaluation of several quinone negative electrolyte materials for use in a flow battery with a positive electrolyte containing bromine and hydrobromic acid. Several substituted quinones are shown to undergo reversible two-electron reduction and oxidation in acidic aqueous solution, with tunable reduction potentials. Some are found to be stable in the presence of bromine, while others undergo decomposition reactions. One stable substituted quinone is currently being tested in a quinone-bromide flow battery. As of writing this abstract, the cell exhibits a peak galvanic power density above 700 mW/cm², an average round-trip energy efficiency of 70%, and current efficiency of 95% as tested to 30 constant-current charge-discharge cycles at 0.25 A/cm². Further cycling will be reported.

[1] B. Huskinson, M.P. Marshak, C. Suh, S. Er, M.R. Gerhardt, C.J. Galvin, X. Chen, A. Aspuru-Guzik, R.G. Gordon and M.J. Aziz, “A metal-free organic-inorganic aqueous flow battery”, Nature 505, 195 (2014), http://dx.doi.org/10.1038/nature12909

[2] B. Huskinson, M.P. Marshak, M.R. Gerhardt and M.J. Aziz, “Cycling of a quinone-bromide flow battery for large-scale electrochemical energy storage”, ECS Trans. 61, 27 (2014)

[3]  B. Yang, L. Hoober-Burkhardt, F. Wang, G.K. Surya Prakash, and S.R. Narayanan, J. Electrochem. Soc. 161, A1371 (2014).

Figure 1. a. Polarization curves and b. galvanic power density as a function of current density for a substituted quinone – bromide flow battery at three different states of charge (SoC). The peak galvanic power density exceeds 0.7 W/cm²at 90% SoC.

Figure 2. Cell voltage during constant current charge-discharge cycling of a substituted quinone-bromide flow battery at ± 0.25 A/cm². Voltage cutoffs were set at 1.3 V and 0.3 V. The time window chosen shows cycles 14-24 of a 30-cycle experiment.