Facile synthesis of high-content nitrogen-doped hierarchical porous carbon spheres for high-capacity lithium-sulfur batteries

Here, nitrogen-doped hierarchical porous carbon spheres (NHPCS) with ultrahigh nitrogen content of 25.57 at% and high specific surface area (SSA) of 303.4 m2 g−1 are explored as a competitive sulfur host for high-performance lithium–sulfur (Li–S) batteries. The fabrication strategy, spray drying followed by annealing treatment, is simple and economical. Applied as sulfur host, high-content nitrogen doping endows NHPCS with efficient immobilization for lithium polysulfides(LiPSs), which significantly relieves the shuttle effect. Additionally, porous structure with high SSA and large pore volume provides enough space for accommodating sulfur and buffering volume expansion on the one hand and boosts the exposure of LiPSs anchoring sites on the other hand. Finally, NHPCS/S cathode delivers an impressive specific capacity of 1588.6 mAh g−1 at C-rate of 0.2 C, corresponding to ultrahigh sulfur utilization of 94.6%. And at 0.5 C, NHPCS/S cathode still reveals highly initial capacity of 1244.2 mAh g−1 and maintains high capacity of 605.7 mAh g−1 after 500 cycles. This work proposes a facile and low-lost strategy to achieve ultrahigh nitrogen content in nitrogen-doped carbon and provides a promising sulfur host to achieve high-performance Li–S batteries.