Aqueous soluble organic (ASO) redox-active materials have recently attracted significant attention as alternatives to traditional transition metal ions in redox flow batteries (RFB). However, reported reversible capacities of ASO are often substantially lower than their theoretical values based on the reported maximum solubilities. Here, we describe a phenazine-based ASO compound with an exceptionally high reversible capacity that exceeds 90% of its theoretical value. By strategically modifying the phenazine molecular structure, we demonstrate an increased solubility from near-zero with pristine phenazine to as much as 1.8 M while also shifting its redox potential by more than 400 mV. An RFB based on a phenazine derivative (7,8-dihydroxyphenazine-2-sulfonic acid) at its near-saturation concentration exhibits an operating voltage of 1.4 V with a reversible anolyte capacity of 67 Ah l⁻¹ and a capacity retention of 99.98% per cycle over 500 cycles.

作为氧化还原液流电池（RFB）中传统过渡金属离子的替代品，水溶性有机（ASO）氧化还原活性材料最近引起了广泛的关注。然而，基于所报道的最大溶解度，所报道的ASO可逆容量通常大大低于其理论值。在这里，我们描述了一种基于吩嗪的ASO化合物，该化合物具有超高的可逆容量，超过其理论值的90％。通过战略性地修改吩嗪分子的结构，我们证明了溶解度从原始的吩嗪几乎从零提高到了1.8 M，同时其氧化还原电位也超过了400 mV。基于吩嗪衍生物（7,8-二羟基吩嗪-2-磺酸）的RFB在其接近饱和浓度时的工作电压为1。^-1，在500个循环中每个循环的容量保持率为99.98％。