Investigations on new Fe–Mn redox couple based aqueous redox flow battery

A new class of redox flow batteries involving Fe3+/Fe2+ and Mn3+/Mn2+ redox couples in the anolyte and catholyte, respectively being investigated. The proposed novel design of Fe–Mn redox flow battery exhibits significant Coulombic efficiency of around 96%, at a current density of 7 mA cm−2. The Fe–Mn cell shows good capacity retention even after 100 cycles with the coulombic efficiency retaining at ∼95%. Further, high concentration anolyte and catholyte was used which helps to improve the practical energy density of the system (>40 Wh L−1). The overall cost of the system is expected to be significantly lower than the existing redox flow battery systems. Thus, the low-cost and eco-friendly nature of these active species make this flow battery to be a potential candidate for large scale electricity storage applications which further facilitates the full utilisation of the intermittent renewable energy resources. [Display omitted] •Fe-Mn redox flow system reporting very first time.•Fe2+/Fe3+ and Mn2+/Mn3+ both redox couple are active at positive potential window in aqueous electrolyte.•High coulombic efficiency >96%.•Good cycle life upto 100 cycles.•Low-cost electrolyte with higher concentration.