Organic redox-active molecules for alkaline aqueous redox flow batteries

Redox flow batteries (ARFBs) have emerged as a promising technology for large-scale energy storage, enabling the efficient utilization of intermittent renewable energy sources. Recently, aqueous organic redox flow batteries (AORFBs) have been garnered attention due to the metal-free composition of organic molecules, offering favorable characteristics like earth-abundant elements, electrochemical reversibility, and adaptable molecular design. This review focuses on recent progress in using organic redox-active molecules as anolytes in alkaline AORFBs, specifically anthraquinones and phenazines. Molecular engineering strategies are explored to enhance solubility, increase capacity, and improve stability of the organic redox-active molecules. Moreover, the utilization of solid organic substances with high energy density, either as anode active materials or capacity booster, is outlined and discussed Overall, this review showcases the versatility and prospects of organic redox-active molecules for AORFBs.