Effect of carbon dioxide additive on the characteristics of a deep eutectic solvent (DES) electrolyte for non-aqueous redox flow batteries

The effects of CO 2 on physical and electrochemical properties of deep eutectic solvent (DES) containing Fe(II)/Fe(III) redox couple were studied. At 25 °C, the viscosity of the DES decreased from 690.4 cP to 620 cP (10.1% decrease), and the ohmic resistance reduced from 1867 Ω to 1409 Ω (24.5% decrease) with saturated CO 2 . The magnitude of the changes reduces with the increase of temperature. Moreover, the cyclic voltammetry curve shows that the addition of CO 2 has no remarkable influence on the reaction kinetics of redox couple in DES. The results reported here imply that CO 2 has positive effects on the physicochemical characteristics of DES, while further studies are needed for being used in a DES electrolyte flow battery.