Abstract Aqueous organic redox flow batteries (AORFBs) are promising for large‐scale energy storage due to their low cost, high safety, and lightweight design. Here, this study designs a polymer material, P‐T‐N‐4, based on a hydrophilic polyvinylimidazole backbone, incorporating 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) and quaternary ammonium groups, achieving high‐water‐solubility (39 Ah L −1 in 1.0 m NaCl aqueous solution (NaCl aq )) and low viscosity (6.3 mPa s in 1.0 m NaCl aq at 10 Ah L −1 ). Using P‐T‐N‐4 as the cathode, methyl viologen (MV) as the anode, and 1.0 m NaCl aq as the electrolyte, a series of P‐T‐N‐4/MV AORFBs is assembled and performed charge–discharge tests in air atmosphere. The P‐T‐N‐4/MV AORFB at 20 Ah L −1 demonstrates stable cycling for over 400 cycles at 30 mA cm −2 , exhibiting an average capacity retention of 99.88% per cycle (99.94% per hour), an average Coulombic efficiency of 99.18% (except the first cycle of 87.36%), and material utilization of 83.1%. Furthermore, the assembled P‐T‐N‐4/MV AORFB achieves stable cycling for over 100 cycles even at a higher concentration of 30 Ah L −1 , with a capacity retention rate of 99.96% per cycle during the first 50 cycles.
Ren et al. (Tue,) studied this question.