Metallic-phase MoS2 nanosheets boost polysulfide redox kinetics to high-performance polysulfide-based flow batteries

The development of low-cost and durable electrodes in aqueous polysulfide-based flow batteries for grid-scale energy storage remains a critical challenge for renewable energy integration. Here, we report a metallic-phase molybdenum disulfide (1T-MoS 2 ) electrocatalyst that fundamentally enhances polysulfide (S 2 2− /S 2− ) redox kinetics and simultaneously catalyzes the I − /I 3 − redox couple. By extending its application from polysulfide/ferricyanide (S Fe) to polysulfide/iodine (S I) flow batteries (FBs), we demonstrate its notable versatility. This dual functionality represents a critical advancement for dual-species systems. The basal plane of 1T-MoS 2 exhibits strong adsorption affinity for polysulfide (S 2 2− to S 8 2− ) species. Moreover, it shifts the Gibbs free energy change of the rate-determining step toward more favorable values by 28% compared to commercial carbon felt electrode (CF), and establishes efficient electron-transfer pathways. The S Fe FB with 1T-MoS 2 modified carbon felt (1T-MoS 2 /CF) electrode achieves an inspiring 68% increasement in energy efficiency (EE) at a big current density of 100 mA cm ‐2 and a 14% increase in peak power density compared to the pristine CF-based counterpart. Remarkably, the 1T-MoS 2 /CF electrode sustains 2500 cycles (960 h) with an ultralow capacity decay rate of 0.002% per cycle. In S I FBs, the 1T-MoS 2 /CF electrode achieves a breakthrough peak power density of 135 mW cm −2 (62.7% higher than CF) and sustains an average EE of 83.7% over 200 cycles at 20 mA cm −2 , outperforming the cells assembled with 2H-MoS 2 /CF (78.1%) and pristine CF (73.5%). By resolving the long-standing trade-off between efficiency and durability across multiple redox systems, we establish 1T-MoS 2 /CF as a universal electrocatalytic platform, paving the way for high-performance, multi-chemistry compatible flow batteries as grid-scale storage technologies.