ZIF-67 derived material encapsulated V2O3 hollow sphere structure of Co-NC@V2O3-sp used as a positive electrode material for lithium-sulfur batteries

Abstract

Lithium-sulfur (Li-S) batteries receive considerable attention for their high energy density, but their slow reaction kinetics and poor shuttle effects raise concerns. Here, synthesized V2O3 spheres were used as substrate templates, and ZIF-67 particles were grown on the surface of V2O3 by in-situ growth method. ZIF-67 was calcined at high temperature to form N-doped porous carbon attached to the surface of V2O3 spheres (Co-NC@V2O3-sp). The hollow structure of V2O3 spheres provided abundant buffer space for sulfur volume expansion and enhanced the stability of the battery cycle. In addition, the great pore volume and specific surface area resulted in abundant active physical and chemical sites, the strong chemical adsorption of V4+ effectively trapped polysulfides, and the cobalt nanoparticles on the surface effectively consolidated the active sites. The rapid transformation between shuttle effect and polysulfides were limited by physical coordination and chemisorption, respectively. Owing to this double synergistic effect, the prepared composites had an initial discharge capacity of 1483 mAh g−1 (0.1 C). The initial specific capacity reached 1002 mAh g−1 (0.5 C), and it achieved 645 mAh g−1 after 500 cycles. These results showed that Co-NC@V2O3-sp has high electrochemical function in Li-S batteries.