Coupling bimetallic selenides with homogeneous mediators synergistically accelerating overall sulfur redox kinetics for high-performances lithium–sulfur batteries.

Bimetallic selenide ZnSe-CoSe 2 as a heterogeneous mediator, which is further combined with CoCp 2 homogeneous mediator, to establish a multifunctional catalytic system. The synergistic effect between ZnSe-CoSe 2 and CoCp 2 accelerates the conversion of LiPSs and the nucleation/decomposition of Li 2 S, expediting the overall sulfur redox kinetics. [Display omitted] • The bimetallic ZnSe-CoSe 2 is prepared via one-step carbonization–selenylation reaction. • The ZnSe-CoSe 2 heterostructure shows superior capability to chemically anchor both soluble LiPSs and CoCp 2 molecules. • The ZnSe-CoSe 2 /CoCp 2 synergistic system enhances the LiPSs conversion and Li 2 S nucleation/decomposition kinetics. • The cell employing the ZnSe-CoSe 2 /CoCp 2 system exhibits superior long-term cycling stability. The practical applications of lithium-sulfur batteries (LSBs) are hampered by poor electrical conductivity, severe shuttling of intermediate lithium polysulfides (LiPSs) and sluggish redox kinetics. Herein, we introduce a multifunctional catalytic system by integrating bimetallic ZnSe-CoSe 2 with CoCp 2 mediators, aimed at serving as redox kinetic accelerators in LSBs. In this design, the ZnSe-CoSe 2 heterostructure with hierarchical pores and large surface area, is capable of immobilizing both soluble LiPSs and CoCp 2 mediators, but also provides abundant active sites for catalyzing LiPSs conversions. Concurrently, the soluble CoCp 2 mediators contribute to promoting the high-dimensional growth of Li 2 S and reducing the interface polarization. Electrochemical experiments and theoretical analyses reveal that the ZnSe-CoSe 2 /CoCp 2 system synergistically accelerates overall sulfur redox kinetics. Consequently, the cell with the ZnSe-CoSe 2 /CoCp 2 system under a sulfur loading of 2.3 mg cm−2 exhibits superior long-term cycling stability at 1.0C. Additionally, it achieves a remarkable areal capacity of 6.5 mAh cm−2 under a high sulfur loading of 8.0 mg cm−2 and a low electrolyte-to-sulfur ratio of 5.0 µL mg−1. [ABSTRACT FROM AUTHOR]