All-Liquid Electroactive Materials for High Energy Density Organic Flow Battery

Nonaqueous redox flow batteries (RFBs) are a promising energy storage technology that enables increased cell voltage and high energy capacity compared to aqueous RFBs. Herein, we first report a novel approach to substantially increase the energy density based on the miscible liquid redox materials 2,5-di-tert-butyl-1-methoxy-4-[2′-methoxyethoxy]benzene catholyte and 2-methylbenzophenone anolyte. This system has a high theoretical cell voltage of 2.97 V and a calculated energy density of 223 Wh L–1 that is much higher than those of previously reported nonaqueous organic RFBs. Our reported redox flow chemistry displays excellent electrochemical performance and stability under cyclic voltammetry, bulk electrolysis, and flow cell conditions. A proof-of-principle RFB delivers a coulombic efficiency of 95% and energy efficiency of 70% and represents significant progress toward high energy density RFBs.