Modulating of MoSe₂ functional plane via doping-defect engineering strategy for the development of conductive and electrocatalytic mediators in Li-S batteries

The lithium polysulfide shuttle and sluggish sulfur reaction kinetics still pose significant challenges to lithium-sulfur (Li-S) batteries. The functional plane of Fe-MoSe₂@rGO nanohybrid with abundant defects has been designed and applied in Li-S batteries to develop the functional separator and multi-layer sulfur cathode. The cell with a functional separator exhibits a retention capacity of 462 mAh g⁻¹ after the 1000th at 0.5 C and 516 mAh g⁻¹ after the 600th at 0.3 C. Even at low electrolyte conditions (7.0 µL mg_sulfur⁻¹ and 15 µL mg_sulfur⁻¹) under high sulfur loadings (3.46 mg cm⁻² and 3.73 mg cm⁻²), the cell still presents high reversible discharge capacities 679 and 762 mAh g⁻¹ after 70 cycles, respectively. Further, at sulfur loadings up to 8.26 and 5.2 mg cm⁻², the cells assembled with the bi-layers sulfur cathode and the tri-layers sulfur cathode give reversible capacities of 3.3 mAh cm⁻² after the 100th cycle and 3.0 mAh cm⁻² after the 120th cycle, respectively. This research not only demonstrates that the Fe-MoSe₂@rGO functional plane is successfully designed and applied in Li-S batteries with superior electrochemical performances but also paves the novel way for developing a unique multi-layer cathode technique to enhance and advance the electrochemical behavior of Li-S cells at a high-sulfur-loading cathode under lean electrolyte/sulfur (E/S) ratio.