Electrochemical Re‐Construction of Dynamic Intermediate Phases to Improve Reduction Kinetics in Lithium‐Sulfur Batteries

Abstract Lithium‐sulfur batteries (LSBs) are still plagued by major challenges, such as the shuttle effect of polysulfides and slow redox kinetics, despite years of rapid development. Although catalyst incorporation mitigates these problems, the constrained electronic structures of conventional catalysts limit their catalytic selectivity. Herein, a dynamically coupled catalytic system composed of Fe ₂ O ₃ and its electrochemically re‐constructed intermediate phase, Li ₃ Fe ₂ S ₄ , is reported, which mediates sulfur reduction reactions and significantly enhances reaction kinetics. Advanced in situ characterizations reveal the dynamic structural evolution mechanism of the Fe ₂ O ₃ in electrochemical process. Theoretical calculations show that the formation of Li ₃ Fe ₂ S ₄ modulates the electronic structure of the Fe d‐band center, which not only effectively promotes the d‐p orbital hybridization, but also synergistically catalyzes the conversion of lithium polysulfides. As a result, the as‐designed Fe ₂ O ₃ /NCS@S electrode achieves a high initial discharge capacity of 1387.1 mAh g⁻¹ at 0.5 C. Li‐S pouch cell can exhibit a high areal capacity of 7.6 mAh cm ⁻² even under a sulfur loading of 8.4 mg cm ⁻² . The discovery of Fe ₂ O ₃ /Li ₃ Fe ₂ S ₄ intermediate‐phase catalysts offers novel insights into engineering the structure and functionality of transition metal catalysts, while paving the way for high‐specific‐energy LSBs development.