Direct impregnation of SeS₂ into a MOF-derived 3D nanoporous Co-N-C architecture towards superior rechargeable lithium batteries

Metal-organic framework (MOF) derived cobalt- and nitrogen-doped porous carbon (Co-N-C) polyhedra are employed, for the first time, as SeS₂ immobilizers (Co-N-C/SeS₂). As the cathode of lithium-sulfur (Li-S) batteries, the Co-N-C/SeS₂ composite with a high loading (66.5 wt%) of SeS₂ delivers a reversible capacity of 1165.1 mA h g^-1 and an over 84.1% capacity retention of the initial capacity (970.2 mA h g^-1) with a nearly 100% coulombic efficiency after 200 cycles. The Co-N-C/SeS₂ cathode shows excellent rate performances with capacities of 760 mA h g^-1, 604.1 mA h g^-1, and 439.7 mA h g^-1 at 1C, 2C, and 4C, respectively. The redox chemistry of SeS₂ is revealed by in situ Raman spectroscopic analysis and density functional theory (DFT) simulations. The superior electrochemical performance of the cathode is attributed to the unique Co-N-C structure with abundant micropores and uniformly-embedded ultrafine Co nanoparticles, which provide abundant SeS₂ absorption and catalytically active sites and efficiently prevent the dissolution of polysulfides and polyselenides. The conductive Co-N-C framework facilitates fast electron and ion transfer in electrochemical reactions. Our work facilitates the development of high-performance cathodes for Li-S batteries.