Encapsulating sulfur into highly graphitized hollow carbon spheres as high performance cathode for lithium-sulfur batteries

Encapsulating sulfur into a highly graphitized hollow carbon sphere (GHCS) is proposed as sulfur cathode for the first time. After annealing the amorphous hollow carbon sphere (HCS) at a high temperature of 2600 degrees C, the obtained GHCS shows polyhedral morphology and few layers graphene characteristic with extremely low oxygen content. When used as sulfur cathode, the S@GHCS composite delivers a high discharge capacity of similar to 800 mA h g(-1) at 4C rate and high capacity retention of 93.7% after 240 cycles at 1C rate, demonstrating much better rate capability and cycling performance compared to those of S@HCS composite.