Oxygen vacancy-engineered Nb2O5-x quantum dots confined in mesoporous CMK-3 host-guest architecture for synergistic dual-regulation of polysulfide redox kinetics in lithium‑sulfur batteries

Defect engineering has emerged as a scalable strategy to address the lithium polysulfides (LiPSs) shuttling and sluggish reaction kinetics in lithium‑sulfur (LiS) batteries. However, the relationship among defect structure, material architecture, and polysulfide redox kinetics remains insufficiently explored. Herein, Oxygen vacancy-engineered Nb₂O_5-x quantum dots confined within an ordered mesoporous tubular carbon (CMK-3) host-guest architecture, designed as Nb₂O_5-x@CMK-3, was successfully developed as a functional separator for LiS batteries. The developed confinement strategy effectively suppresses the aggregation of Nb₂O_5-x quantum dots through spatial restriction within CMK-3 channels, and constructs a matrix integrating physical confinement with defect-mediated chemical interactions. This effectively regulates the deposition and conversion processes of sulfur, inhibits the shuttling of LiPSs, and promotes the kinetics of the sulfur electrode conversion reactions. Through the synergism of physical confinement, chemical adsorption, and catalytic conversion, the LiS batteries assembled with the Nb₂O_5-x@CMK-3 modified separators not only exhibit remarkable electrochemical performance but also achieve favorable stability under a high sulfur loading of 4.1 mg cm⁻². This work has great potential in the development of multi-functional intermediate layers for high-performance LiS batteries.