Redox-active anthraquinone-based π-conjugated polymer anode for high-capacity aqueous organic hybrid flow battery

Organic molecules/polymers are currently investigated as redox species for aqueous low-cost hybrid flow batteries. In this work, a redox-active anthraquinone-based conjugated polymer synthesized via a facile electrochemical polymerization approach is reported, which can be employed as a high-capacity anode material for aqueous hybrid flow batteries. The redox-active anthraquinone polymer displays a two-electron-transfer redox reaction at −0.616 V (versus the standard hydrogen electrode, SHE) with fast redox kinetics in aqueous alkaline electrolytes (pH = 12). Paired with a potassium ferrocyanide catholyte, the aqueous hybrid flow battery employed this redox-active anthraquinone polymer as the anode material in aqueous supporting electrolyte of pH = 12 exhibits an open circuit voltage of about 1.09 V, high specific capacity (103.6 mA h g−1 at 2 A g−1) and large mass power density (9.41 W g−1 at 100 % SOC), along with excellent capacity retention (99.948 % per cycle) and energy efficiency (74.1 %) after 100 cycles.