Dual-Confinement Effect of Nanocages@Nanotubes Suppresses Polysulfide Shuttle Effect for High-Performance Lithium-Sulfur Batteries.

The shuttle effect of lithium polysulfides (LiPSs) severely hinders the development and commercialization of lithium-sulfur batteries, and the design of high-conductive carbon fiber-host material has become a key solution to suppress the shuttle effect. In this work, a unique Co/CoN-carbon nanocages@TiO 2 -carbon nanotubes structure (NC@TiO 2 -CNTs) is constructed using an electrospinning and nitriding process. Lithium-sulfur batteries using NC@TiO 2 -CNTs as cathode host materials exhibit high sulfur utilization (1527 mAh g -1 at 0.2 C) and can still maintain a discharge capacity of 663 mAh g -1 at a high current density of 5 C, and the capacity loss is only 0.056% per cycle during 500 cycles at 1 C. It is worth noting that even under extreme conditions (sulfur-loading = 90%, surface-loading = 5.0 mg cm -2 (S) , and E/S = 6.63 µL mg -1 ), the lithium-sulfur batteries can still provide a reversible capacity of 4 mAh cm -2 . Throughdensity functional theory calculations, it has been found that the Co/CoN heterostructures can adsorb and catalyze LiPSs conversion effectively. Simultaneously, the TiO 2 can adsorb LiPSs and transfer Li + selectively, achieving dual confinement for the shuttle effect of LiPSs (nanocages and nanotubes). The new findings provide a new performance enhancement strategy for the commercialization of lithium-sulfur batteries.