The Synergistic Catalytic Effect of 2D Ultrathin Fe ₂ O ₃ ‐Fe ₃ O ₄ Heterointerface on Lithium Polysulfides

The practical application of the sulfur cathode in lithium–sulfur (Li–S) batteries mainly depends on the suppression of lithium polysulfide (LiPSs) diffusion and the improvement of its kinetics. Efficient 2D adsorption‐catalytic media are an important direction for its future progress. Herein, the ultrathin (~2.2 nm) Fe 2 O 3 ‐Fe 3 O 4 heterointerface is rapidly synthesized. As an adsorption and catalytic medium for LiPSs, it exhibits a stronger LiPS affinity than the single‐component Fe 3 O 4 and Fe 2 O 3 . The built‐in electric field at the heterogeneous interface can significantly enhance the kinetics of charge transfer. It provides a positive regulatory effect on the smooth “adsorption‐migration‐conversion” process of active sulfur species. Both theoretical calculations and in situ Raman have verified its performance enhancement mechanism. As a result, the cell based on this heterointerface achieves reversible capacities of up to 737 mAh·g −1 at 4 C. A high capacity retention of 493 mAh·g −1 is maintained after 500 cycles at 2 C. Even under a high sulfur load of 4.2 mg·cm −2 , an area capacity of 6.1 mAh·cm −2 can still be obtained, with stable cycling maintained for dozens of cycles.