Sol–Gel Engineered MXene/Fe3O4 as an Efficient Mediator to Suppress Polysulfide Shuttling and Accelerate Redox Kinetics

Lithium-sulfur (Li-S) batteries are renowned for their high theoretical energy density and low cost, yet their practical implementation is hampered by the polysulfide shuttle effect and sluggish redox kinetics. Herein, a sol-gel strategy is proposed to engineer a multifunctional MXene/Fe₃O₄ composite as an efficient mediator for the cathode interlayer. The synthesized composite features Fe₃O₄ nanospheres uniformly anchored on the highly conductive Ti₃C₂T_x MXene lamellae, forming a unique 0D/2D conductive network. This structure not only provides abundant polar sites for strong chemical adsorption of polysulfides but also significantly enhances charge transfer, thereby accelerating the conversion kinetics. As a result, the Li-S battery based on the MXene/Fe₃O₄ interlayer delivers a high initial discharge capacity of 1367.1 mAh g^-1 at 0.2 C and maintains a stable capacity of 1103.4 mAh g^-1 after 100 cycles, demonstrating an exceptionally low capacity decay rate of only 0.19% per cycle. Even at a high rate of 1 C, a remarkable capacity of 1066.1 mAh g^-1 is retained. Electrochemical analyses confirm the dual role of the composite in effectively suppressing the shuttle effect and catalyzing the polysulfide conversion. This sol-gel engineering approach offers valuable insight into the design of high-performance mediators for advanced Li-S batteries.