Sulfur composite was prepared by encapsulating sulfur into CMK-3 mesoporous carbon with different heating times and then used as the cathode material for lithium sulfur batteries. Thermal treatment at 300 degrees C plays an important role in the sulfur encapsulation process. With 20 h of heating time, a portion of sulfur remained on the surface of carbon, whereas with 60 h of heating time, sulfur is confined deeply in the small pores of carbon that cannot be fully exploited in the redox reaction, thus causing low capacity. The S/CMK-3 composite with thermal treatment for 40 h at 300 degrees C contained 51.3 wt.% sulfur and delivered a high initial capacity of 1375 mA h g(-1) at 0.1 C. Moreover, it showed good capacity retention of 704 mA h g(-1) at 0.1 C and 578 mA h g(-1) at 2 C even after 100 cycles, which proves its potential as a cathode material for high capability lithium sulfur batteries. (C) 2014 Elsevier Ltd. All rights reserved.