A high voltage organic redox flow battery with redox couples O<inf>2</inf>/tetrabutylammonium complex and tris(4-bromophenyl)amine as redox active species

Redox flow batteries (RFBs) are considered a vital part of the energy storage system for storing the energy generated from the renewable energy sources such as wind and solar. Limited by the water electrolysis potential window, the aqueous RFBs exhibit low energy density (<25 Wh L−1). In this context a non-aqueous organic solvent based RFB system is very attractive as it offers avenue to expand the operating potential window beyond 1.23 V, which has a direct impact on the RFB’s energy and power densities. In this study, new redox systems based on tris(4-bromophenyl)amine (4-Br-TPA) and oxygen saturated N,N-dimethylformamide (DMF) containing tetra-n-butylammonium hexafluorophosphate (TBAPF6) are utilized as catholyte and anolyte respectively. Here, TBAPF6 performs dual role, both as supporting electrolyte and a stabilizer of superoxide anion radical.