Hollow Carbon Nanoballs Coupled with Ultrafine TiO2 Nanoparticles as Efficient Sulfur Hosts for Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries as among the most promising energy storage devices possess high theoretical capacity and energy density but suffer from the polysulfide dissolution, which hinders their practical application. Herein, we present a facile synthesis of hollow carbon nanoballs (HCNBs) anchored with ultrafine TiO2 nanoparticles (TiO2@HCNBs) in which the HCNBs with hollow interiors and graphitic crystallization accommodate the volume expansion of sulfur upon lithiation and improve the cathode conductivity, while the TiO2 nanoparticles effectively trap the polysulfides through strong chemical bonding. Notably, the S@TiO2@HCNBs with a high sulfur loading of ∼73 wt % demonstrate superior cycle performance at 0.5 C over 600 cycles with a slow capacity decay and deliver high specific capacities of 1217, 1013, 893, and 773 mA h/g at 0.1, 0.2, 0.5, and 1 C, respectively. The adsorption test clearly reveals the efficient suppression of the polysulfide shuttling owing to the spatial and chemical confinement of the TiO2@HCNBs host.