Metallic and polar Co₉S₈ inlaid carbon hollow nanopolyhedra as efficient polysulfide mediator for lithium−sulfur batteries

Lithium−sulfur (Li−S) batteries are promising to replace current commercial Li−ion batteries due to the high energy density. Despite this, the poor cyclic stability induced by the shuttle effect of electrolyte-soluble intermediate polysulfides is one of the great obstacles for the application of Li−S batteries. To overcome this issue, here we report a self-template synthesis of metallic and polar Co₉S₈ nanocrystals inlaid carbon (Co₉S₈/C) hollow nanopolyhedra as an efficient sulfur host material. The Co₉S₈/C hollow nanopolyhedra with large inner space can ensure the loading mass of sulfur and buffer the volume expansion of Li₂S_x species during cycling; while the metallic and polar Co₉S₈/C shell offers synergetic spatial confinement and chemical binding to immobilize polysulfides and prevent the shutting effect. The Co₉S₈/C-S composite cathode exhibits high capacity and long cycle life with a low capacity decay of 0.041% per cycle over 1000 cycles at 2.0 C. When the areal sulfur content is as high as 3.0 mg cm^–2, the Co₉S₈/C-S cathode still maintains high cycling stability.