A High-Stability Quinone-Based Homogeneous Catalyst Auxiliary Disulfide Bond Decomposition Enabling High-Efficiency Polysulfide-Ferrocyanide Flow Batteries

Sulfur-based flow batteries (SFBs) attract attention for large-scale energy storage due to the abundance and low cost of sulfur, as well as their simple design; however, they face challenges such as sluggish polysulfide redox kinetics, which cause high overpotentials and low efficiency. Herein, we introduce highly active quinone-based homogeneous molecular catalysts in the SFBs to alter the ionic arrangement around S(0) atoms, reducing the strong binding of disulfide bonds and thereby enhancing the electrochemical activity of polysulfides. The DHBQ catalyst could significantly lessen the overpotential to 280 mV (from 409 mV) at 20 mA cm –2 and increase the capacity to 10.8 Ah L –1 (over three times that of the untreated one). A polysulfide-ferrocyanide flow battery was demonstrated for 200 cycles at 40 mA cm –2 with a 100% capacity retention rate. These improvements highlight the effectiveness of quinone-based homogeneous catalysts in overcoming the bottlenecks of SFBs, offering a promising strategy for their practical application in long-duration and large-scale energy storage systems.