Layered Cu7.2S4@N-Doped Carbon Hybrid as a Synergistic Trap Catalyst for Polysulfide Conversion in Lithium–Sulfur Batteries

Abstract Lithium–sulfur batteries (LSBs) are a leading next-generation energy storage technology, owing to their high theoretical capacity and energy density. However, the lithium polysulfide (LiPS) shuttle effect and slow redox kinetics limit the cycling stability and rate capability of LSBs. To address this challenge, a layered Cu7.2S4 uniformly embedded within a nitrogen-doped carbon (NC) matrix (Cu7.2S4@NC) is synthesized and employed as a functional coating on the separator. The NC framework establishes a conductive network that enhances the confinement of LiPSs. Meanwhile, Cu7.2S4 serves as catalytic centers that significantly accelerate the redox kinetics of LiPSs, thereby boosting the overall electrocatalytic activity. Electrochemical evaluations reveal that the cell with the Cu7.2S4@NC separator exhibits outstanding cycling performance, maintaining 771 mAh g–1 after 500 cycles at 0.5 C. With a sulfur loading of 5.3 mg cm–2, the cell achieves an areal capacity of 5.5 mAh cm–1. The cells exhibit stable cycling performance across a broad temperature range (0–60 °C). Furthermore, combined density functional theory calculations and in situ Raman spectroscopy confirm that Cu7.2S4 exhibits strong binding affinity toward LiPSs, thereby enabling efficient sequestration of these species. This work demonstrates that Cu7.2S4@NC serves as a functional catalyst capable of enabling high-performance LSBs with broad temperature adaptability.