A Sustainable Redox Flow Battery with Alizarin-Based Aqueous Organic Electrolyte

To achieve sustainable development, biomass materials are alternative options for mitigating the problems associated with energy and the environment. Recently, soluble anthraquinones in aqueous redox flow batteries have attracted extensive attention. Inspired by a natural anthraquinone dye named alizarin, here we report an affordable, sustainable, and efficient redox flow battery electrolyte using a derivative of alizarin, namely, alizarin-3-methyliminodiacetic acid, which has been easily synthesized from alizarin on an industrial scale. The battery exhibits an open-circuit voltage of 1.38 V, and the maximum power density exceeds 0.49 W cm(-2). Also, the battery has a stable cycling performance of 350 cycles with a high Coulombic efficiency of 99.6%, energy efficiency of 84.2%, and capacity retention of 99.98% per cycle, 99.97% per hour, and 99.19% per day at 0.1 A cm(-2). Moreover, the battery system is environmentally friendly and provides novel ideas for biomass-derived green energy-storage systems.