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

• In Li-S batteries, the Fe-MoSe 2 @rGO nanohybrid is presented as a novel improved separator. • Fe-doping exposes additional active selenium edge sites of MoSe 2 , bringing a new approach for LiPSs adsorption. • Designing a novel multi-layer cathode approach for Li-S cells with high sulfur loading and a low E/S ratio. • The Fe-MoSe 2 @rGO-PP exhibits excellent anti-self-discharge and cycling stability even under lean E/S ratios associated with high sulfur loading. The lithium polysulfide shuttle and sluggish sulfur reaction kinetics still pose significant challenges to lithium-sulfur (Li-S) batteries. The functional plane of Fe-MoSe 2 @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 1000 th at 0.5 C and 516 mAh g −1 after the 600 th 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 100 th cycle and 3.0 mAh cm −2 after the 120 th cycle, respectively. This research not only demonstrates that the Fe-MoSe 2 @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.