An Asymmetric Viologen-Based Negolyte with a Low Redox Potential for Neutral Aqueous Redox Flow Batteries

Aqueous redox flow batteries (ARFBs) with neutral electrolytes show promise for large-scale energy storage owing to their relatively low cost and inherent safety. However, the performance of these ARFBs has been limited by solubility electroactive species and/or cell voltages. In this study, an asymmetric viologen-based compound called MMV (1-Methyl-4,4'-bipyridylium iodide) was assessed as active in negolyte ARFBs. Inexpensive starting materials a simple synthesis route yielded at cost. exhibited ?3 M water, electrochemical measurements confirmed that reaction involves transfer single electron fast kinetics. Importantly, structure demonstrated potential ?1.05 V vs SCE, one most negative potentials reported organic electrolytes. MMV, however, showed poor cycling high concentrations. Signs dimerization precipitation were observed, resulting measured capacities significantly lower than theoretical values rapid fade rate. It should be possible avoid problems synthesizing derivatives higher charge preserve potential.