Ternary graphene/sulfur/SiO2 composite as stable cathode for high performance lithium/sulfur battery

Ternary graphene/sulfur/SiO2 (graphene/S/SiO2) composite has been successfully synthesized by compositing sulfur with graphene and then wrapping with SiO2. The graphene/S/SiO2 composite exhibits superior specific capacity and improved cycling stability owing to the combined contributions from both graphene and SiO2 when used as cathode materials for lithium/sulfur batteries. The graphene/S/SiO2 demonstrates a specific capacity of 696 mAh g−1 after activated, which is considerably higher than the graphene/S and pure sulfur samples. In addition, the graphene/S/SiO2 and graphene/S composites demonstrate improved cycling stability and much higher coulombic efficiency than the pure sulfur sample owing to the successful prevention of polysulfides diffusion. Furthermore, both graphene/S/SiO2 and graphene/S composites show an activation step in first 30 cycles, which can be attributed to the gradually increased capacity from reduction of high-order polysulfides to low-order polysulfides.