MOFs-derived porous Mo2C–C nano-octahedrons enable high-performance lithium–sulfur batteries

Abstract

The shuttle effect causing by the dissolution of lithium polysulfides (LiPSs) and sluggish redox reaction kinetics during the charge/discharge processes significantly reduce the cycle life and sulfur utilization in lithium-sulfur (Li–S) batteries. Herein, Mo2C–C nano-octahedrons (Mo2C–C NOs) with Mo2C nanoparticles embedded in a three-dimensional porous carbon matrix have been prepared via a metal-organic frameworks (MOFs) assisted strategy, and used as the sulfur host for Li–S batteries. The Mo2C–C NOs@S cathode demonstrates a high initial specific capacity of 1396 and 1050 mAh g−1 at 0.1 C and 1 C, respectively, with an ultra-low average specific capacity decay rate of 0.0457% per cycle within 600 cycles at 1 C. Moreover, Mo2C–C NOs@S cathode with high areal sulfur loading of 4.2 mgS cm−2 can deliver a high initial discharge specific capacity of 807 mAh g−1, and a capacity of 623 mAh g−1 after 100 cycles at 0.5 C. The existence of Mo2C nanoparticles can not only immobilize LiPSs via the formation of Mo–S bond, but also electrocatalytically accelerate the redox kinetics towards LiPSs conversion. Meanwhile, the interconnected porous carbon matrices contributes to effective sulfur/electrolyte infiltration, fast electron/Li+ ion transportation and sufficient buffer for volume change.