Hierarchical Co/CoSe@MoSe2 heterostructures enable efficient polysulfides trapping and conversion for highly stable lithium-sulfur batteries

Abstract

Lithium-sulfur batteries (LSBs) are now facing great challenges in the sluggish reaction kinetics and the severe shuttle effect of polysulfides. To address these issues, it is of crucial importance to design efficient sulfur cathode with strong adsorption, high catalytic activity and high electrical conductivity. Herein, Co/CoSe@MoSe₂ hierarchically heterostructured catalyst is synthesized via a facile pyrolysis and hydrothermal method, in which MoSe₂ nanosheets are coated on Co/CoSe hollow microspheres. As-prepared structure serves as a sulfur host for lithium-sulfur batteries (LSBs). Metal–organic framework (MOF)-derived Co/CoSe metallic junction facilitates rapid catalytic conversion of lithium polysulfide (LiPSs), while two-dimensional MoSe₂ nanosheets possessing a strong polarity and high specific surface area effectively trap LiPSs and suppress the shuttle effect. Last but not least, porous carbon networks derived by MOFs accelerate the charge transfer within the catalyst. With these synergistic advantages from their heterogeneous components, the assembled LSBs based on Co/CoSe@MoSe₂ sulfur cathode delivers a high discharge capacity of 1313.9 mA h g⁻¹ at 0.1C with a sulfur loading of 1.5 mg cm⁻². Even at a high sulfur loading of 3.0 mg cm⁻², it still demonstrates a stable cycling with a low capacity decay of 0.042 % per cycle after 200 cycles at 0.2C. This work provides new insights into understanding of heterostructured catalyst systems with balancing adsorption and catalysis for high-performance LSBs.