Encapsulating sulfur into mesoporous TiO2 host as a high performance cathode for lithium–sulfur battery

The commercialization of lithium–sulfur (Li–S) battery has so far hindered by the low electrochemical utilization and rapid capacity fading of sulfur cathode, which is induced by low electric/ionic conductivity, high dissolution of intermediate polysulfides and the volume expansion of sulfur. Herein, we describe an on-site adsorption strategy toward superior stability of sulfur electrode by encapsulating elemental sulfur into mesoporous TiO2 host. Brunauer–Emmett–Teller (BET), transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) measurements obviously indicate that elemental sulfur (S) occupy the mesopores of the TiO2 host, forming a core–shell liked nanostructure. The TiO2/S composite exhibits a superior cycling stability and high Coulombic efficiency during the charge/discharge process. Even at a high current rate of 1C, the TiO2/S composite shows an initial specific capacity of 650mAhg−1 and a specific retention of 89% after 100 cycles. The excellent electrochemical performances are critical related to the significant roles TiO2 host played during the electrochemical reaction. Firstly, the nano-sized TiO2 (∼5nm) traps the polysulfides via chemical bonding interaction to prevent their dissolution and minimize the “shuttle effect”. More importantly, the in situ formed LixTiO2, acting as a mixed electric/ionic conductor, facilitates easier Li+/e− transport. The unique functions of the TiO2 plus its easy availability make the current study conceptually provides new opportunities to reach long-term cycling stability of sulfur cathode using carbon-free hosts.