A ferrocyanide-polysulfide redox flow battery with homogeneous catalysis for high-performance energy storage

作者：Chao Qin, Xi Xu, Zhizhao Xu, Chunhui Gao, Bo Lu, Mei Ding, Chuankun Jia · 发表于：Energy Materials · 年份：2026 · DOI：10.20517/energymater.2026.150 · 研究领域：Advanced battery technologies research、Membrane-based Ion Separation Techniques、Electrocatalysts for Energy Conversion

Aqueous ferrocyanide-polysulfide redox flow batteries (Fe-S RFBs) are promising for grid-scale energy storage yet suffer from slow polysulfide kinetics, membrane crossover, and supporting-electrolyte mismatch, which increase polarization and undermine cycling durability. Although riboflavin sodium phosphate (FMN-Na) has been used as a homogeneous catalyst to promote polysulfide conversion, previous formulations relied on externally added KOH, creating an OH-/Cl- imbalance and placing greater demands on membrane selectivity. Herein, we construct a KOH-free Fe-S RFB using KCl as the common supporting electrolyte and FMN-Na as a homogeneous molecular catalyst. The system utilizes the alkalinity generated by K2S hydrolysis, removing the need for added KOH while providing a suitable pH environment for FMN-Na electrocatalysis. Whereas earlier work focused on long-chain polysulfide reduction, FMN-Na facilitates polysulfide conversion dominated by the S22-/S2- couple through electron shuttling, reducing polarization and improving reversibility. The optimized Fe-S RFB delivers outstanding cyclability with 5,000 stable cycles at 40 mA cm-2 and a peak power density of 197.2 mW cm-2. With a high-concentration catholyte, the cell yields an initial energy efficiency (EE) of 83.07% and retains 77.34% after 440 cycles. Tailoring the electrolyte compositions extends operation from -20 to 60 °C. Furthermore, Prussian blue-mediated redox targeting and increased active-material concentrations yi...