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 Li2Sx 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.