A highly efficient double-hierarchical sulfur host for advanced lithium-sulfur batteries.

Li-S batteries have attracted enormous interest due to their potentially high energy density, non-toxicity and the low cost of sulfur. The main challenges of sulfur cathodes are the short cycling life and limited power density caused by the low conductivity of sulfur and dissolution of Li polysulfides. Here we design a new double-hierarchical sulfur host to address these problems. Hierarchical carbon spheres (HCSs), constructed from building blocks of hollow carbon nanobubbles for loading sulfur, are sealed within a thin, polar MoS coating composed of ultrathin nanosheets. Experimental and theoretical studies show a strong absorption of the MoS nanoshell to polysulfides, and the excellent stability of the MoS nanosheets after the adsorption of polysulfides. Moreover, MoS promotes the electrochemical redox kinetics in Li-S batteries. Benefiting from the unique hierarchical, hollow and compositional characteristics of the host, the S/MoS@HCS composite electrode shows a high capacity of 1048 mA h g at 0.2C, good rate capacity and long cycling life with a slow capacity decay of 0.06% per cycle.