Dual confinement of sulphur with rGO-wrapped microporous carbon from β-cyclodextrin nanosponges as a cathode material for Li–S batteries

A novel approach is developed to synthesize microporous carbon spheres with pore size ranges from 5 to 11 Å from hyper-cross-linked polymer β-cyclodextrin. Sulphur is incorporated in the micropores by solution impregnation followed by melt infusion. The resultant carbon sulphur (C/S) composite is wrapped in reduced graphene oxide (rGO) to provide conductive pathways to access the sulphur in micropores and to protect the surface-adhered sulphur. The cathode material obtained from rGO wrapping delivers initial discharge capacity of 1103 mA h g−1 at 0.1 C, maintaining a capacity of 626 mA h g−1 at 0.2 C with capacity loss of 0.2% per cycle for more than 100 cycles. In another cell configuration using carbon paper as an interlayer, discharge capacity has raised to 850 mA h g−1 at 0.2 C and maintained 86% of its capacity for 100 cycles with excellent rate capability and high Coulombic efficiency. The good performance may be referred to excellent conductive networks, porous architecture of carbon spheres and adsorption of catholyte by fibrous interlayer that can effectively reduce the polysulfide shuttling.