Flow batteries offer the ability to store large amounts of electrical energy at low cost because they permit the power (electrode area) and energy (electrolyte volume) components of the system to be independently scaled. We have developed flow battery chemistries based on aqueous organic quinone-hydroquinone redox couples that can significantly reduce electrical energy storage costs. Paired with the bromine-bromide redox couple, a hydroquinone-bromine flow cell was constructed using carbon electrodes and a Nafion membrane separator. We observed power densities exceeding 125 mW cm�2 at 80% round-trip energy efficiency (> 600 mW cm�2 peak power) and coulombic efficiencies over 95%.The absence of active metal components in both redox chemistry and catalysis represents a significant shift away from modern batteries. The impressive cell performance is in part due to the rapid and reversible two-electron, two-proton quinone-hydroquinone redox chemistry that does not require electrocatalysts. In addition, organic functionalization of the quinone has permitted further optimization of the solubility and redox properties. Metal-free batteries represent a new and promising direction for cost-effective, large-scale energy storage.

Quinone-bromide flow battery

248th National Meeting (2014)

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