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/Fe3O4composite as an efficient mediator for the cathode interlayer. The synthesized composite features Fe3O4nanospheres uniformly anchored on the highly conductive Ti3C2TxMXene 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/Fe3O4interlayer delivers a high initial discharge capacity of 1367.1 mAh g−1at 0.2 C and maintains a stable capacity of 1103.4 mAh g−1after 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−1is 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.