Stability of Alizarin for Aqueous Organic Redox Flow Batteries

Abstract

The intermittent nature of renewable energy sources like solar and wind requires suitable large-scale energy storage technologies to properly respond supply and demand of energy. Aqueous organic redox flow batteries (AORFBs) have demonstrated great potential to revolutionize grid-scale energy storage as a result of their low-cost, safety and ability to separate energy and power1. However, most of the organic compounds suffer from lack of sufficient long-term stability.Alizarin (1,2-dihydroxyanthraquinone) is a low-cost, nontoxic, and industrially accessible dye which could potentially be used as an affordable redox-active negative electrolye (negolyte)2. Here, we present an in-depth investigation on the long-term cycling stability of Alizarin. Furthermore, we implement an aggressive cycling conditions to investigate the degradation of the cycled negolyte within just a single day, achieving an equivalent capacity fade percentage as electrolyte cycled for over two weeks3. The capacity fade of alizarin was partially mitigated by the employment of a SOC restriction strategy which was able to decrease the capacity fade rate by more than 60 %.4 Capacity fade measured via cycling is corroborated by ex situ chemical analysis methods.