An aqueous organic flow battery integrating a high-capacity hexaazatrinaphthylene anode with a phenazine anolyte for hybrid energy storage

Abstract

Aqueous organic redox flow batteries (AORFBs) are promising in large-scale energy storage applications due to their environmental friendliness, decoupled energy and power, high efficiency, long lifespan, and safety. However, achieving both high accessible specific capacity and reliable cycling performance simultaneously remains challenging, primarily because concentrated organic electrolytes typically suffer from reduced diffusion coefficients, diminished interfacial redox kinetics, and increased undesirable side reactions. In this study, to circumvent these limitations, we propose a novel AORFB design combining a high-capacity hexaazatrinaphthylene (HATN) anode with a phenazine anolyte, which is further paired with a highly stable Li₄[Fe(CN)₆] catholyte for hybrid energy storage. This innovative AORFB cell demonstrates high energy efficiency, remarkable capacity utilization and outstanding cycling stability, attributed to the fast redox kinetics and excellent stability of both HATN and BHPC, a synergistic effect between the two, and the high mass-loading of HATN at the anode. Furthermore, a prototype three-cell AORFB stack incorporating high-loading HATN anodes is successfully constructed, achieving a power density exceeding 400 mW cm⁻², a high capacity utilization of 82.3 %, and excellent cycling durability with a capacity retention of 99.953 % per cycle, showcasing its potential for large-scale energy storage.