Carbon felt electrode coated with WS₂ enables a high-performance polysulfide/ferricyanide flow battery

Polysulfide/ferricyanide flow batteries (S/Fe RFBs), with the advantages of abundant earth reservation, low cost, high safety, and environmental friendliness, have attracted significant interest and demonstrated noteworthy potential for practical applications. However, the battery performance, including the energy efficiency (EE), voltage efficiency (VE), and power density of the S/Fe RFBs, remains low owing to the slow redox kinetics of polysulfide ions. To address these concerns, WS₂ was selected as the booster and deposited on a commercial carbon felt electrode (WS₂–CF) to stimulate the redox reactions of polysulfide ions. With better hydrophilicity and smaller charge-transfer resistance, WS₂–CF exhibits enhanced electrochemical activity toward polysulfide redox reactions. Consequently, the battery performance of S/Fe RFB with WS₂–CF as the anode has been improved, with EE of 84%, VE of 84%, and a peak power density of 175.7 mW·cm⁻², which are all higher than the cell only with the bare carbon felt (CF) as electrodes (76%, 77%, and 155.8 mW·cm⁻², respectively). Furthermore, the cycling life of the S/Fe RFB with WS₂–CF has been prolonged to 2200 cycles with a capacity retention of 96% at 40 mA·cm⁻² because of the good stability of WS₂–CF as the anode. Contrarily, under the same conditions, the S/Fe RFB without WS₂–CF terminated after 1500 cycles with a fast capacity decay. The successful utilization of WS₂ as a booster on an electrode provides an efficient strategy for obtaining advanced S/Fe RFBs for practical applications.