Dynamic Homogeneous Catalysis Enables Stable and Efficient Aqueous Organosulfur Redox Flow Batteries

Stable and affordable organic active molecules that can enable redox flow batteries (RFBs) with long life for grid energy storage are desirable. However, most existing organic molecules face challenges in energy density, cycling stability, and synthesis, which are critical for practical applications. Here, we show an aqueous organosulfur RFB (OSRFB) that utilizes a low-cost, industrial-scale RSSR (R denotes sodium sulfopropyl) as the anolyte material. Dynamic homogeneous catalysis, generated in situ from elemental selenium, is applied to accelerate the redox kinetics of RSSR. It lowers more than one-third of the electrochemical activation energy barrier of RSSR (from 38.8 to below 25 kcal mol^-1), leading to a highly active anolyte. High energy density (53 Wh L^-1_anolyte), high energy efficiency (74.5%), exceptional Coulombic efficiency (>99.97%), and unprecedented ultralong life (134.7 days with a capacity decay rate of 0.037% per day for 0.25 M RSSR and 113.9 days with a capacity decay rate of 0.027% per day for 1.1 M RSSR) are demonstrated in the OSRFB, revealing its significant potential for use in ultralong-duration energy storage.