Pyromellitic diimide based bipolar molecule for total organic symmetric redox flow battery

Non-aqueous redox flow batteries based on total organic electrolytes, consisting of earth-abundant elements, i.e., C, H, N, O, are regarded as a promising technology for sustainable and large-scale energy storage. In particular, bipolar redox-active organic materials (BROMs) are distinctly fascinating as electroactive species because they have multiple oxidation states and can undergo multiple redox processes . By virtue of this unique characteristic, BROMs can be utilized as both anolyte and catholyte in symmetric flow batteries, consequently, helping alleviate cross-contamination issues. Herein we report an all-organic symmetric redox flow battery based on diimide molecule as a bipolar electroactive material. The potential interval between the cathodic peak and the inner and outer anodic peaks led to a promising cell voltage of 2.22 V. The symmetric battery can be operated at a current density of 20 mA cm −2 , with a coulombic efficiency of 90% for over 100 cycles. This work proposes an alternative approach to designing multi-electron organic redox active materials to facilitate the advancement of high-density symmetric flow batteries.