A Zn−Ce Redox Flow Battery with Ethaline Deep Eutectic Solvent

Abstract

Compared with conventional aqueous and ionic liquid electrolytes, deep eutectic solvent (DES) are considered as electrolyte for redox flow batteries because they have a wider electrochemical window and relatively low price. In this study, Ce(Ⅳ)/Ce(Ⅲ) and Zn(Ⅱ)/Zn redox couples are used as the positive and negative active materials, respectively, in an electrolyte consisting of choline chloride ethylene glycol (ethaline). The structure of Ce(Ⅲ) in the positive electrolyte is inferred through spectrum detection. Ce(IV)/Ce(III) and Zn(II)/Zn redox couples show a stable potential difference of 2.2 V (vs. Ag) through cyclic voltammetry. The charge and discharge performance of battery were tested at different current densities. In addition, battery performance was evaluated at different temperatures and concentrations of the cerium in electrolyte. Consequently, at a current density of 0.5 mA·cm ‐2 at room temperature and using 1.0 M Ce(III), the battery performance reaches the best coulombic efficiency of 84%.