Optimized sulfur-loading in nitrogen-doped porous carbon for high-capacity cathode of lithium–sulfur batteries

Among the candidates to the next-generation energy storage system (EES), lithium–sulfur (LiS) batteries represent an attractive option due to high theoretical specific energy. Intensively studied carbon/sulfur (C/S) composite cathodes are the key elements to determine the performance of LiS batteries. Herein, a novel in-situ nitrogen-doped porous carbon possessing ultrahigh surface area (2163.776 m2/ g) and total pore volume (1.048 cm3/ g) was obtained from hickory-shell via a transitional KOH activation process. Numerous pores in micro-scale offer substantial active sites for sulfur adsorption and accommodate the volume expansion during the charge/discharge cycles. Meanwhile, the nitrogen-doped carbon promotes polysulfides adsorption and improves the conductivity of the carbon framework. C/S composite cathodes of different sulfur loadings were investigated to exhibit that the composite with 55% sulfur delivers the highest initial discharge capacities of 1446.1 and 991.7 mAh g−1 at 0.1 and 1.0C rate, respectively, with a tiny capacity fading rate of 0.095% per cycle up to 1000 cycles at 1.0C. Considering the low cost, environmental friendliness and excellent electrochemical performances, this nitrogen-doped porous carbon exhibits great potential in applications of high performance LiS batteries.