High performance lithium-sulfur batteries based on CoP nanoparticle-embedded nitrogen-doped carbon nanotube hollow polyhedra

Abstract

Lithium‑sulfur (Li-S) battery with high theoretical energy density is regard as one of the most appealing competitors for the promising next-generation energy storage systems. However, the severe polysulfide shuttling and the low electrical conductivity of sulfur cathode limit the practical application of Li-S batteries. Therefore, the designing of sulfur host materials with high electrochemical activity and high sulfur content have great significance for Li-S batteries. Here, we reported a novel hybrid nanostructure (a new sulfide matrix material) through the pyrolytic reduction phosphorization strategy form ZIF-67, in which CoP nanoparticles were embedded into nitrogen-doped carbon nanotubes hollow polyhedron (NCNHP). Due to the synergistic effect of highly active Co, CoP and nitrogen-doped carbon nanotubes (NCNTs), the Co/CoP-NCNHP hybrid improved the adsorption of polysulfides. Micropores in Co/CoP-NCNHP effectively impregnate sulfur and inhibit the diffusion of polysulfides through physical constraint. In addition, the Co/CoP-NCNHP conductive network of nitrogen doping carbon nanotubes (NCNTs) interconnection promoted electron transport and electrolyte infiltration. Therefore, the specific capacity, rate capability and cycling stability of Li-S batteries are significantly improved. In particular, we delivered the Co/CoP-NCNHP based cathode (loaded with 74.09 wt% sulfur), which could main the specific capacity of 885 mAh g−1 after 500 cycles of 0.5C current.