Bipyridinium-based aqueous organic redox flow batteries

Xianzhi Yuan, Kai Wan, Zhipeng Xiang, Wenjin Li, Mingbao Huang, Zhiyong Fu, Zhenxing Liang^*

Abstract: Aqueous organic redox flow batteries (AORFBs) have emerged as a promising medium- to long-term energy storage technology, offering an alternative to metal-dependent lithium-based batteries. AORFBs utilize organic electroactive molecules as the energy storage medium, which has garnered significant attention in the field of electrochemical energy storage. Among the various candidates, bipyridinium salts have gained particular interest due to their excellent electrochemical reversibility and high ionic conductivity in neutral electrolytes. However, challenges persist in improving specific energy, cycling stability, and energy efficiency. To address these issues, our research group has focused on three key areas: molecular design, solution meso-structure analysis, and process intensification. We have investigated the redox mechanisms of electroactive molecules, developed methods to analyze and regulate their aggregation structures, enhanced mass transfer and reaction kinetics, and improved oxygen-resistance stability. This paper reviews the recent advancements in these areas, discusses future directions for overcoming existing challenges, and offers both theoretical insights and practical guidance for advancing AORFB technology.