Electrospun zeolitic imidazolate framework-derived nitrogen-doped carbon nanofibers with high performance for lithium-sulfur batteries

Three-dimensional (3D) nitrogen-doped carbon nanofibers (N-CNFs) which were originating from nitrogen-containing zeolitic imidazolate framework-8 (ZIF-8) were obtained by a combined electrospinning/carbonization technique. The pores uniformly distributed in N-CNFs result in the improvement of electrical conductivity, increasing of BET surface area (142.82 m2 g−1), and high porosity. The as-synthesized 3D free-standing N-CNFs membrane was applied as the current collector and binder free containing Li2S6 catholyte for lithium-sulfur batteries. As a novel composite cathode, the free-standing N-CNFs/Li2S6 membrane shows more stable electrochemical behavior than the CNFs/Li2S6 membrane, exhibiting a high first-cycle discharge specific capacity of 1175 mAh g−1at 0.1 C and keeping discharge specific capacity of 702 mAh g−1 at higher rate. More importantly, as the sulfur mass in cathodes was increased at 7.11 mg, the N-CNFs/Li2S6 membrane delivered 467 mAh g−1after 150 cycles at 0.2 C. The excellent electrochemical properties of N-CNFs/Li2S6 membrane can be ascribed to synergistic effects of high porosity and nitrogen-doping in N-CNFs from carbonized ZIF-8, illustrating collective effects of physisorption and chemisorption for lithium polysulfides in discharge-charge processes.