Defective VSe₂–Graphene Heterostructures Enabling In Situ Electrocatalyst Evolution for Lithium–Sulfur Batteries

Electrocatalysts remain vitally important for the rational management of intermediate polysulfides (LiPSs) in the realm of Li-S batteries. In terms of transition-metal-based candidates, in situ evolution of electrocatalysts in the course of an electrochemical process has been acknowledged; nevertheless, consensus has not yet been reached on their real functional states as well as catalytic mechanisms. Herein, we report an all-chemical vapor deposition design of the defective vanadium diselenide (VSe₂)-vertical graphene (VG) heterostructure on carbon cloth (CC) targeting a high-performance sulfur host. The electrochemistry induces the sulfurization of VSe₂ to VS₂ at Se vacancy sites, which propels the adsorption and conversion of LiPSs. Accordingly, the VSe₂-VG@CC/S electrode harvests an excellent cycling stability at 5.0 C with a capacity decay of only 0.039% per cycle over 800 cycles, accompanied by a high areal capacity of 4.9 mAh cm^-2 under an elevated sulfur loading of 9.6 mg cm^-2. Theoretical simulation combined with operando characterizations reveals the key role played by the Se vacancy with respect to the electrocatalyst evolution and LiPS regulation. This work offers insight into the rational design of heterostructure sulfur hosts throughout defect engineering.