Graphene/sulfur/carbon nanocomposite for high performance lithium-sulfur batteries

Abstract

Here, we report a two-step synthesis of graphene/sulfur/carbon ternary composite with a multilayer structure. In this composite, ultrathin S layers are uniformly deposited on graphene nanosheets and covered by a thin layer of amorphous carbon derived from β-cyclodextrin on the surface. Such a unique microstructure, not only improves the electrical conductivity of sulfur, but also effectively inhibits the dissolution of polysulfides during charging/discharging processes. As a result, this ternary nanocomposite exhibits excellent electrochemical performance. It can deliver a high initial discharge and charge capacity of 1410 mAh·g -1 and 1370 mAh·g -1, respectively, and a capacity retention of 63.8% can be achieved after 100 cycles at 0.1 C (1 C = 1675 mA·g -1). A relatively high specific capacity of 450 mAh·g -1 can still be retained after 200 cycles at a high rate of 2 C. The synthesis process introduced here is simple and broadly applicable to the modification of sulfur cathode for better electrochemical performance.