Ultrasmall CoFe Bimetallic Alloy Anchored on Fluoride-Free MXene by One-Pot Etching Strategy for the Barrier-Adsorption-Catalyst Functions of Polysulfides in Lithium-Sulfur Batteries

The rational construction of electrocatalysts has sparked a growing interest in accelerating redox kinetics of polysulfide and effectively restricting the "shuttle effect" in Li-S batteries. In this work, a novel MXene-supported ultrasmall Co3Fe7 bimetallic alloy hybrids are fabricated via a one-pot molten salt etching strategy. The Ti3AlC2 precursor can be directly converted to Co3Fe7-MXene using this environmentally friendly approach, eliminating the need for acid/alkaline treatments and complex procedures. Meanwhile, the ultrasmall Co3Fe7 alloy particles are in situ formed and tightly anchored on the MXene substrate. By simple coating, Co3Fe7-MXene modified separator functions as a barrier to effectively inhibit the shuttle effect. Furthermore, electrochemical tests and theoretical calculations demonstrate that Co3Fe7-MXene exhibits exceptional adsorption capacity and remarkable catalytic ability toward polysulfides, owing to the synergistic effect of bimetallic alloy. Consequently, Li-S cells assembled with Co3Fe7-MXene modified separator achieve a high capacity, excellent rate performance, and superior cycle stability. This study provides a comprehensive insight into the design of MXene with bimetallic alloys as efficient electrocatalysts for LiPSs in high-performance and long-life Li-S batteries. A novel MXene-supported ultrasmall Co3Fe7 bimetallic alloy hybrids are prepared via a one-pot molten salt etching strategy. Electrochemical tests and theoretical calculations demonstrate that Co3Fe7-MXene exhibits remarkable adsorption capacity and exceptional catalytic ability toward polysulfides. The electrochemical property of Li-S cells can be significantly improved because of the physical barrier and synergistic effect of bimetallic alloy. image