SynergisticSulfur Immobilization and BidirectionalCatalysis Enabled by VS₂‑VO_x/V₂C Heterostructure for Robust Lithium–SulfurBatteries

Abstract

Vanadium-based catalysts are considered an effective strategy to resolve the shuttle effect and sluggish solid–liquid–solid reaction kinetics in lithium–sulfur (Li–S) batteries, thanks to their strong adsorption and catalytic conversion capabilities toward polysulfides. Herein, a self-oxidation-driven solvothermal strategy was employed to construct a defect-rich homologous heterostructure of nanoflower-like VS₂-VO_x on a two-dimensional conductive V₂C network (denoted as VSOC). The experimental results demonstrate that VSOC effectively enhances the multiphase redox reaction kinetics of sulfur species through the strong adsorption and spontaneous transformation of long-chain polysulfides by the highly conductive V₂C and the accelerated catalytic reduction of insoluble short-chain Li₂S by the V–S–O heterostructure. Consequently, the Li–S cells assembled with VSOC-modified separator and normal loaded 1.0 mg cm^–2 KB/S cathode deliver a high first discharge capacity of 1340 mAh g^–1 at 0.2 C with a low-capacity decay rate of 0.03% per cycle during long-term cycling at 1 C. It still achieves a capacity contribution of 501.3 mAh g^–1 even at 5 C. Moreover, under challenging conditions such as high sulfur loading (4.2 mg cm^–2) and low temperature (0 °C), the VSOC-modified separator maintains 89% and 85% capacity retention and stable Coulombic efficiency. This study proposes a novel heterostructure design strategy for optimizing the performance of Li–S batteries.