The Synergistic Catalytic Effect of 2D Ultrathin Fe₂O₃-Fe₃O₄ 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) Fe₂O₃-Fe₃O₄ heterointerface is rapidly synthesized. As an adsorption and catalytic medium for LiPSs, it exhibits a stronger LiPS affinity than the single-component Fe₃O₄ and Fe₂O₃. 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.