Ionic liquid-mediated aqueous redox flow batteries for high voltage applications

Aqueous redox flow batteries with high cell voltages represent a promising approach for low-cost, high safety and high energy density applications. However, water breakdown is a major concern because it limits cell voltage. For the first time, we report the use of a highly concentrated aqueous ionic liquid electrolyte, 1-butyl-3-methylimidazolium chloride (BMImCl)-H2O, in an aqueous flow battery operating with a broad electrochemical stability window of 3 V. The proof-of-concept was demonstrated using 2 V redox couples of metal acetylacetonates and a hybrid Zn/Ce flow battery. (C) 2016 Elsevier B.V. All rights reserved.