On the Electrolyte Volume Change during Constant-Current Cycles of the Diaphragm-type Fe/Cr Redox Flow Cell

Abstract

The electrolyte volume change at the Cr-compartment of a diaphragm-type Fe/Cr redox flow cell during constant-current cycles was measured at room temperature. The electrolyte volume at the Cr-compartment increased for the charging process and decreased for the discharging process. The observed volume change was ca.0.5 cm³⋅A^-1⋅h^-1 based on the electricity passed both against and toward the Cr-compartment, which indicated that ca. O.75mol of water was reversibly transferred for each 1 F of the electricity passed. From the observed values, the maximum fluctuations of Cr- and Fe-concentrations in the electrolytes during cycles were estimated to be ca.1.3%.