Heterostructures composed of oxides and sulfides (nitrides or carbides) show great potential as sulfur host additives because of the strong adoptability of oxides and catalytic capability of sulfides towards the notorious lithium polysulfides (LiPSs). However, the migration and conversion pathway of LiPSs is seriously confined at a localized interface with inadequate active sites. In this work, the introduction of selenium vacancies into VSe_2−x has been demonstrated to successfully synergize the adsorbability and catalytic reactions of LiPSs at an integrated functional surface. The N-doped carbon nanosheets-assembled flower architectures embedded with selenium vacancy-rich VSe_2−x and partial vanadium oxides have been controllably synthesized and employed as the cathode additives for lithium-sulfur (Li-S) batteries. Both the experiments and first-principle calculations reveal their strong adsorption to LiPSs and their bidirectional catalytic functionality towards the conversion between S₈ and Li₂S. As expected, the charge and discharge kinetics of VSe_2−x containing sulfur cathodes is fundamentally improved (an outstanding rate capabilitiy with 693.7 mAh·g⁻¹ at 2 C, a remarkable long-term cyclability within 1,000 cycles at 2 C with S loading 2.27 mg·cm⁻², and an excellent areal capacity with 3.44 mAh·cm⁻² within 100 cycles at 0.5 C). This work presents an effective resolution to couple the adsorbability and catalytic reactions of LiPSs at the material design perspective, and the insights on bidirectional catalytic functionality are of vital to develop functional materials for advanced Li-S batteries.

High energy density and low-cost lithium-sulfur batteries have been considered as one of the most promising candidates for next-generation energy storage systems. However, the intrinsic problems of the sulfur cathode severely restrict their further practical application. Here, a unique double-shell architecture composed of hollow carbon spheres@interlayer-expanded and sulfur-enriched MoS_2+x nanocoating composite has been developed as an efficient sulfur host. A uniform precursor coating derived from heteropolyanions-induced polymerization of pyrrole leads to space confinement effect during the in-situ sulfurization process, which generates the interlayer-expanded and sulfur-enriched MoS_2+x nanosheets on amorphous carbon hollow spheres. This new sulfur host possesses multifarious merits including sufficient voids for loading sulfur active materials, high electronic conductivity, and fast lithium-ion diffusive pathways. In addition, additional active edge sites of MoS_2+x accompanied by the nitrogen-doped carbon species endow the sulfur host with immobilizing and catalyzing effects on the soluble polysulfide species, dramatically accelerating their conversion kinetics and re-utilization. The detailed defect-induced interface catalytic reaction mechanism is firstly proposed. As expected, the delicately-designed sulfur host exhibits an outstanding initial discharge capacity of 1, 249 mAh·g^-1 at 0.2 C and a desirable rate performance (593 mAh·g^-1 at 5.0 C), implying its great prospects in achieving superior electrochemical performances for advanced lithium sulfur batteries.