The Use of the Mannich Reaction toward Amino-Based Anthraquinone Applied in Aqueous Redox Flow Battery

Abstract

A water-soluble anthraquinone derived from alizarin, 3HAAQ, is introduced as the redox-active material in a negative potential electrolyte (anolyte) for aqueous redox flow batteries operating at pH 14. The synthesis of 3HAAQ is carried out using the Mannich reaction, which significantly improves the solubility of the new compound, an important factor for its use in RFB. Pairing with potassium ferri/ferrocyanide positive electrolyte, this flow battery exhibits an open-circuit voltage of 1.24 V and maintains nearly 80% of the theoretical capacity at 40 mA cm−2 current density.