N-doped mesoporous-carbon polyhedron as an effective sulfur host for lithium-sulfur batteries

An effective sulfur host material of N-doped mesoporous-carbon polyhedron (NMCP) was derived from zeolitic imidazolate framework-8. We prepared an NMCP/S composite by sublimating sulfur into NMCP. As a Li-S battery cathode, the NMCP/S composite delivers a high initial capacity of 1308mAhg(-1) at 50mAg(-1), a stable reversible capacity of 496.3mAhg(-1) after 150 cycles at 400mAg(-1), and an excellent rate capacity of 639mAhg(-1) at 800mAg(-1). The excellent electrochemical performance is ascribed to the unique 3D carbon matrix. The mesoporous-carbon polyhedron structure ensures fast electron/ion diffusion and provides large free space for volumetric expansion of sulfur during repeated charge/discharge. Furthermore, nitrogen doping enhances conductivity and interaction between carbon host and polysulfide guest via chemical binding, which can suppress the shuttle of polysulfides to a certain extent.