Ferrocene/anthraquinone based bi-redox molecule for symmetric nonaqueous redox flow battery

The crossover of anolyte and catholyte during cycling places a serious obstacle for the performance of non-aqueous redox flow batteries (NARFBs). Employing symmetric RFB is an effective strategy to alleviate this issue. A new bi-redox material, 1-(ferrocenylmethyl-amino)-anthraquinone (FcMeAAQ) composed of ferrocene and anthraquinone two moieties, is designed for symmetrical NARFB. Both experimental and density functional theory calculational results show the relatively good stability of FcMeAAQ when one-electron redox reaction is involved. The assembled symmetric NARFB with the Daramic AA-250 porous membrane delivers an open circuit voltage of 1.42 V, Coulombic efficiency of 90.8%, and energy efficiency of 81.8% over 100 cycles at the current density of 2 mA cm−2. Furthermore, a peak power density of ~16 mW cm−2 is achieved at the state of charge of 100%.