Mesoporous TiO2 Nanocrystals/Graphene as an Efficient Sulfur Host Material for High-Performance Lithium–Sulfur Batteries

Rechargeable lithium–sulfur (Li–S) batteries are promising in high-energy storage due to the large specific energy density of about 2600 W h kg–1. However, the low conductivity of sulfur and discharge products as well as polysulfide-shuttle effect between the cathode and anode hamper applications of Li–S batteries. Herein, we describe a novel and efficient S host material consisting of mesoporous TiO2 nanocrystals (NCs) fabricated in situ on reduced graphene oxide (rGO) for Li–S batteries. The TiO2@rGO hybrid can be loaded with 72 wt % sulfur. The strong chemisorption ability of the TiO2 NCs toward polysulfide combined with high electrical conductivity of rGO effectively localize the soluble polysulfide species within the cathode and facilitate electron and Li ions transport to/from the cathode materials. The sulfur-incorporated TiO2@rGO hybrid (S/TiO2@rGO) shows large capacities of 1116 and 917 mA h g–1 at the current densities of 0.2 and 1 C (1 C = 1675 mA g–1) after 100 cycles, respectively. When the current density is increased 20 times from 0.2 to 4 C, 60% capacity is retained, thereby demonstrating good cycling stability and rate capability. The synergistic effects of TiO2 NCs toward effective chemisorption of polysulfides and conductive rGO with high electron mobility make a promising application of S/TiO2@rGO hybrid in high-performance Li–S batteries.