In-Situ Assembled VS4 as a Polysulfide Mediator for High-Loading Lithium–Sulfur Batteries

A unique three-dimensional (3D) hybrid architecture configured with vanadium tetrasulfide (VS4) nanomediators uniformly anchored in a reduced graphene oxide scaffold (VS4@RGO) is fabricated as a sulfur host via a facile in-situ assembly route. In the hybrid structure, the conductive, porous RGO skeleton functions as 3D electron channels and polysulfide reservoirs, effectively localizing the diffusing polysulfides. Meanwhile, the sulfiphilic VS4 nanoparticles grown in situ in the 3D matrix act as a polysulfide mediator to offer sufficient polysulfide-anchoring and catalytic sites. The polysulfide adsorptivity and redox-conversion reversibility are substantially improved, as validated by first-principles calculations and in-situ XRD analysis. As a result, the Li–S cells achieve a low capacity-fading rate of 0.07% per cycle after 500 cycles. Furthermore, the assembled Li–S pouch cells with 200 mg of sulfur mass also deliver a high reversible discharge capacity of 730 mA h g–1 (146 mA h) after 50 cycles.