Accelerated Polysulfide Conversion by Rationally Designed NiS2-CoS2 Heterostructure in Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries are considered as potential candidates for future-oriented energy storage systems. However, their practical deployment is hampered by the shuttle effect and the sluggish reaction kinetics of lithium polysulfides (LiPSs). A key strategy to mitigate these challenges is to develop efficient heterojunction catalysts to enhance reaction kinetics and suppress the shuttle effect. In this study, a NiS₂-CoS₂ heterojunction is introduced to address these challenges with density functional theory (DFT) calculations employed to determine the optimal combination from 5 × 5 crystal plane configurations. The identified NiS₂(210)-CoS₂(200) combination demonstrates excellent anchoring effects and catalytic properties for LiPSs, significantly enhancing rate performance (839.9 mAh g⁻¹ at 2 C and 730.8 mAh g⁻¹ at 3 C) and cycling stability. Furthermore, in situ Raman and X-ray diffraction (XRD) analyses reveal that the NiS₂-CoS₂ heterojunction rapidly catalyzes the conversion of LiPSs, reducing their migration toward the lithium anode and thereby suppressing the shuttle effect. The design strategy for transition metal sulfide heterojunctions offers an efficient approach to accelerating polysulfide conversion kinetics, effectively addressing the limitations of Li–S batteries.