Regulation of waste-derived hierarchically porous carbon for optimizing the sulfur cathode host of Li-S 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 degrees C shows the abundant hierarchically porous structure with high specific surface area of 1932.9 m2 g-1 and large pore volume of 1.292 cm3 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.