Hierarchical porous carbon doped with high content of nitrogen as sulfur host for high performance lithium–sulfur batteries

Abstract

The applications of Li S batteries are restricted by the issues of the imperfect conductivity and severe volumetric change of active materials together with shuttle effect of lithium polysulfides, which requires a kind of material with appropriately multifunctional structure as sulfur host. Herein, an N–doped hierarchical porous carbon composite is synthesized via a high temperature carbonization method. The N–doped hierarchical porous carbon with a large number of micropores, mesopores and macropores provides the abundant interconnected network matrixes and high specific surface area, thus guaranteeing a high sulfur loading, and adapting the volumetric expansion during the lithium intercalation process. The macropore channels and conductive interconnected networks can accelerate the diffusion of electrons/ions among the cathode. Moreover, the mesopores and micropores besides the high amount N–doping accommodate high–level sulfur loading and immobilize lithium polysulfides via physical absorption and chemical confinement. The as–prepared N–doped hierarchical porous carbon compounded with sulfur as a cathode delivers a satisfactory initial capacity of 1285 mAh g −1 at 0.2 A g −1 and a reversible capacity of 517 mAh g −1 at 0.5 A g −1 over 1000 cycles, illustrating the improved electrochemical performances of the cathode. The high temperature carbonization method provides a new way to construct the hierarchical porous structured carbon with chemical doping. • N-doped hierarchical porous carbon was developed. • It has a large number of micropores, mesopores and macropores. • N-doped hierarchical porous carbon exhibit high capacity and rate performance. • High performance is ascribed to the porous hierarchical structure and N doping.