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Integrated computational and experimental studies of concentrated redoxmer/electrolyte solutions reveal that charging leads to softening of the solution.

Energy density in nonaqueous redox flow batteries (RFBs) is often limited by the modest solubility of the redox-active organic molecules (ROMs). In addition, the lack of a separator that prevents ROMs from crossing between anolyte and catholyte solutions necessitates the use of 1:1 mixtures of two ROMs in both the anolyte and catholyte solutions in symmetric RFBs, further limiting concentrations. We show that permanently cationic oligomers of viologen, tris(dialkylamino)cyclopropenium, and phenothiazine molecules have high solubility in acetonitrile and cross over an anion exchange membrane at slow to undetectable rates, enabling the creation of asymmetric RFBs with low crossover. No added supporting electrolyte is necessary, with only the PF

Nonaqueous redox flow batteries are a promising technology for grid-scale energy storage, however, their success relies on identifying redox-active materials that exhibit extreme potentials, high solubilities , and long cycling stabilities.

Metal-free redox flow batteries with TEMPO-based polypeptide catholytes and viologen-based polypeptide anolytes were demonstrated. Post-cycling analysis indicated the main source of capacity fade was degradation of the redox-active pendant groups.

Non-aqueous redox flow batteries which can be operated under subzero temperature are significant for applications in cold regions.

The advance non-aqueous redox flow batteries require redox-active organic molecules (ROM) with large solubilities in all states of charge (NMR-spectrometer icon by DBCLS and screen and workstation icons by Simon Duerr licensed under creative commons).