Encapsulation of selenium sulfide in double-layered hollow carbon spheres as advanced electrode material for lithium storage

Selenium sulfide/double-layered hollow carbon sphere (SeS₂/DLHC) composites have been designed as high-performance cathode materials for novel Li–SeS₂ batteries. In the constructed composite, SeS₂ is predominantly encapsulated in the interlayer space of DLHCs with a high loading of 75% (weight percentage) and serves as the active component for lithium storage. The presence of Se in the composite and the carbon framework not only alleviate the shuttling of polysulfide, but also improve the conductivity of electrodes. Migration of active materials from the interlayer void to the hollow cavity of DLHCs after cycling, which further mitigates the loss of active materials and the shuttle effect, is observed. As a result, the SeS₂/DLHC composite delivers a high specific capacity (930 mA·h·g^-1 at 0.2 C) and outstanding rate capability (400 mA·h·g^-1 at 6 C), which is much better than those of SeS₂/single-layered hollow carbon sphere, Se/DLHC, and S/DLHC composites. Notably, the SeS₂/DLHC composite shows an ultralong cycle life with 89% capacity retention over 900 cycles at 1 C, or only 0.012% capacity decay per cycle. Our study reveals that both SeS₂ and the double-layered structures are responsible for the excellent electrochemical performance.