REDOX BATTERY

"A rechargeable battery with two redox electrodes contained in compartments typically separated by an ion-exchange membrane E.g., a battery with iron and chromium redox couples in the two compartments. During discharge, ""ferric"" (trivalent iron) cations are reduced to ""ferrous"" (divalent iron) ions at one of the redox electrodes, while ""chromous"" (divalent chromium) ions are oxidized to ""chromic"" (trivalent chromium) ions at the other electrode. The reverse reactions occur during charging. An advantage of this system is that the polarization losses are relatively small because the redox reactions are typically fast and no solid phases are being formed during the reaction. Also, the solutions containing the iron and chromium salts can be stored in separate large tanks and circulated to a small ""battery,"" permitting the storage of large amounts of energy. "