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

Graphical Redox flow battery : A Zn−Ce redox flow battery based on choline chloride ethylene glycol deep eutectic solvent was studied. The open-circuit voltage of the battery reaches 2.2 V, and the coulombic efficiency of the battery is stable at about 84 %, which may provide theoretical support for the development of large-scale energy storage system. 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 was tested at different current densities. In addition, battery performance was evaluated at different temperatures and concentrations of cerium in the 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 %.