Hydrogel and sulfur co-coating on semispherical TiO2 as polysulfides-immobilized cathodes for high capacity and stable rate performance lithium-sulfur batteries

Li-S batteries are promising new energy-storage systems owing to their high theoretical energy density. However, the volume-change and poor conductivity of S, and shuttle effect severely restrict applications. Here, we present a novel semispherical composite consisting of sulfur and polyaniline (PANI) hydrogel coating on a bowl-shaped hollow TiO2. The TiO2@PANI@S composites show an excellent performance with a high capacity of 1058 mAh g(-1) after 200 cycles at 0.2 C, and a stable Columbic efficiency of 99.8%. The composites also possess a recoverable rate-performance under repeated tests. The Li+ ion diffusion co-efficiency is studied, which indicates that the semispherical composite enables a rapid Li+ ion transportation. In addition, the density functional theory calculations confirm a strong adsorption of TiO2 towards polysulfides including for Li2S4, Li2S6, and Li2S8, which efficiently suppress the shuttle effect.