Hierarchical cathode from hollow CoP embedded in graphene nanosheets to synergistically confine SeS₂ for advanced Li/SeS₂ batteries

Selenium sulfide (SeS₂) has been considered as a potential cathode for batteries because it has superior conductivity to sulfur and higher theoretical capacity than selenium. Here, the composite of cobalt phosphide embedded in graphene nanosheets (CoP-NC@GN) is synthesized and used to encapsulate SeS₂. The fabricated CoP-NC@GN@SeS₂ composite is applied for Li/SeS₂ batteries. With selenium sulfide content at 52.7%, the CoP-NC@GN@SeS₂ composite, when cycled at 2 A g⁻¹, delivers the discharge capacity of 868.6 mAh g⁻¹ and 580.2 mAh g⁻¹ at the 1st and 200th cycle, respectively. The improved performance of CoP-NC@GN@SeS₂ is closely related to the elaborately designed structure. The graphene as a substrate ensures the formation of the ZIF-67 and subsequent CoP in nanosize, and allows the maximum exposure of CoP active sites to capture polysulfide/polyselenide intermediates chemically, which is a big plus over the physical adsorption by hollow CoP-NC. The close contact between MOF-derived CoP-NC and graphene nanosheets constructs an excellent consecutive conductive network to accelerate electron conduction and expedite the redox conversion. The synergistic effect enhances cyclic stability and rate performance. This work provides an approach to cathode fabrication for high performance Li/SeS₂ batteries.