A Multifunctional Catalytic Interlayer for Propelling Solid–Solid Conversion Kinetics of Li ₂ S ₂ to Li ₂ S in Lithium–Sulfur Batteries

Abstract The theoretically high‐energy‐density lithium–sulfur batteries (LSBs) are seriously limited by the disadvantages including the shuttle effect of soluble lithium polysulfides (LiPSs) and the sluggish sulfur redox kinetics, especially for the most difficult solid–solid conversion of Li 2 S 2 to Li 2 S. Herein, a multifunctional catalytic interlayer to improve the performance of LSBs is tried to introduce, in which Fe 1– x S/Fe 3 C nanoparticles are embedded in the N/S dual‐doped carbon network (NSC) composed by nanosheets and nanotubes (the final product is named as FeSC@NSC). The well‐designed 3D NSC network endows the interlayer with a satisfactory LiPSs capture‐catalytic ability, thus ensuring fast redox reaction kinetics and suppressing LiPSs shuttling. The density functional theory calculations disclose the catalytic mechanisms that FeSC@NSC greatly improves the liquid–solid (LiPSs to Li 2 S 2 ) conversion and unexpectedly the solid–solid (Li 2 S 2 to Li 2 S) one. As a result, the LSBs based on the FeSC@NSC interlayer can achieve a high specific capacity of 1118 mAh g −1 at a current density of 0.2 C, and a relatively stable capacity of 415 mAh g −1 at a large current density of 2.0 C after 700 cycles as well as superior rate performance.