Regulation of waste-derived hierarchically porous carbon for optimizing the sulfur cathode host of LiS batteries

Porous carbon matrixes have been widely recognized as the simple and effective host materials for encapsulating sulfur and enhancing electronic conductivity in lithium sulfur batteries . Herein, a waste honeycomb is used to prepare in-situ N-doping hierarchically porous carbon materials by systematically regulating the simultaneous activation/carbonation temperature. The high-temperature is conducive to promoting the porous structural formation and high graphitization of carbon materials. As the increased carbonation temperature, the N-heteroatom doping content decreases and the graphitization degree increases gradually. The carbon material prepared at 900 °C shows the abundant hierarchically porous structure with high specific surface area of 1932.9 m 2  g −1 and large pore volume of 1.292 cm 3  g −1 , hence can well accommodate the sulfur and capture the soluble polysulfides by the porous adsorption and bonding effect of in-situ doped nitrogen atoms . Besides, the improved graphitization endows the carbon material with a high electronic conductivity , boosting the fast electron transport. Due to these structural merits, the optimized porous carbon/sulfur composite cathode shows a high initial discharge capacity of 969.3 mAh g −1 at 0.2C. Even at high current rate of 1.0C, the relatively high discharge reversible capacity of 492.2 mAh g −1 is still maintained after 500 cycles.