Investigations Into Aqueous Redox Flow Batteries Based on Ferrocene Bisulfonate

The successful implementation of redox flow battery (RFB) technology requires the development of highly stable and soluble catholyte and anolyte materials that could be used in aqueous media. In this work, we investigated a highly soluble derivative of ferrocene—1,1′-bis(sulfonate)ferrocene dianion disodium salt—as a possible catholyte in an all-anionic RFB design. Based on the results of cyclic voltammetry and charge/discharge cycling experiments, we determined that this compound can be unstable and prone to a nucleophilic attack by anions in certain supporting electrolytes. However, it is stable in neutral pH solutions with weak nucleophilic anions like nitrate. These findings are fundamental for the future development of improved RFB materials.