We introduce a highly stable quinone as the redox-active material in a negative potential electrolyte (negolyte) for aqueous redox flow batteries operating at nearly neutral pH. This new negolyte has a high solubility at pH 9 and above and chemical stability studies demonstrate high stability at both pH 9 and 12. By pairing the quinone with a potassium ferri/ferrocyanide positive electrolyte across an inexpensive, non-fluorinated permselective polymer membrane, this near-neutral quinone flow battery exhibits an open-circuit voltage of 1.0 V and a capacity fade rate of 0.00036% / cycle and 0.014% / day, which is the lowest ever reported for any flow battery in the absence of rebalancing processes (Figure 1). We further demonstrate that the negolyte pH drifts upward upon atmospheric oxygen penetration but, when oxygen is excluded, oscillates reversibly between 9 and 12 during cycling (Figure 2). These results enhance the suitability of aqueous-soluble redox-active organics for use in large-scale energy storage, potentially enabling massive penetration of intermittent renewable electricity.

Quinone redox flow battery with record stability at near-neutral pH

2019 Spring National Meeting

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