Cell Performance of a Diaphragm-type Fe/Cr Redox Flow Cell

Abstract

A diaphragm-type Fe/Cr redox flow cell equipped with a rebalance cell and state of charge monitors has been developed. The electrolyte used was 1 M FeCl₂-1 M CrCl₃-2 M HCl solution for both Fe- and Cr-compartments. A 100 cycle-life test using the single cell without catalyst loading was carried out at 30°C. The system was evaluated in terms of working voltage, discharge capacity, charge/discharge coulombic efficiency, hydrogen gas evolution rate and cross-mixing rate. The average charge/discharge coulombic efficiency during 100 cycles was 96.7%. The losses of electricity due to hydrogen gas evolution and cross mixing were calculated to be 1.5% and 1.8%, respectively, based on the electricity used for charging. The possibility of application to an electrical energy storage system is discussed in terms of the reliability and the cycle life of the system.