Abstract: Stable solutions comprising high concentrations of charged coordination complexes, including iron hexacyanides are described, as are methods of preparing and using same in chemical energy storage systems, including flow battery systems. The use of these compositions allows energy storage densities at levels unavailable by other iron hexacyanide systems.

Abstract: This invention is directed to aqueous redox flow batteries comprising ionically charged redox active materials and ionomer membranes, wherein the charge of the redox active materials is of the same sign as that of the ionomer, so as to confer specific improvements.

Abstract: The invention concerns flow batteries comprising: a first half-cell comprising: (i) a first aqueous electrolyte comprising a first redox active material; and a first carbon electrode in contact with the first aqueous electrolyte; (ii) a second half-cell comprising: a second aqueous electrolyte comprising a second redox active material; and a second carbon electrode in contact with the second aqueous electrolyte; and (iii) a separator disposed between the first half-cell and the second half-cell; the first half-cell having a half-cell potential equal to or more negative than about ?0.3 V with respect to a reversible hydrogen electrode; and the first aqueous electrolyte having a pH in a range of from about 8 to about 13, wherein the flow battery is capable of operating or is operating at a current density at least about 25 mA/cm2.

Abstract: This invention is directed to aqueous redox flow batteries comprising redox-active metal ligand coordination compounds. The compounds and configurations described herein enable flow batteries with performance and cost parameters that represent a significant improvement over that previous known in the art.

Abstract: This invention is directed to aqueous redox flow batteries comprising ionically charged redox active materials and separators, wherein the separator is about 100 microns or less and the flow battery is capable of (a) operating with a current efficiency of at least 85% with a current density of at least about 100 mA/cm2; (b) operating with a round trip voltage efficiency of at least 60% with a current density of at least about 100 mA/cm2; and/or (c) giving rise to diffusion rates through the separator for the first active material, the second active material, or both, of about 1×10?7 mol/cm2-sec or less.