Synergetic enhancement of polysulfide chemisorption and electrocatalysis over bicontinuous MoN@N-rich carbon porous nano-octahedra for Li–S batteries

Abstract

The real-world application of Li–S batteries is challenged with the problems of the shuttle effect of lithium polysulfides (LiPSs) and sluggish reaction kinetics. Herein, a porous MoN@nitrogen-doped carbon (MoN-NC) nano-octahedron with a bicontinuous intertwined MoN and NC porous structure was designed as a novel S host material for Li–S batteries. With hierarchical pore structures, the NC immobilized the LiPSs by physical-chemical confinement. Moreover, the continuous MoN framework demonstrated excellent chemisorption with LiPSs as well as the electrocatalysis of the LiPS redox reactions, which was confirmed by our experimental and theoretical results. Due to the synergetic effect of the NC and MoN, the S/MoN-NC cathode with a high S content up to 77% exhibited greatly enhanced electrochemical performances. At 0.5C, the S/MoN-NC cathode delivered a long life of 895 mA h g⁻¹ after 350 cycles, which was much higher than that of its S/MoN and S/NC counterparts (71% and 49% after 100 cycles, respectively). At a high current density of 2C, the specific capacity of S/MoN-NC was 3.2 and 1.3 times higher than that of its S/MoN and S/NC counterparts, respectively. Remarkably, with the increase in the S loading up to 6.5 mg cm⁻², the high capacity retention was still maintained (0.059% capacity decay over 200 cycles). This study gives useful guidance to enable high-energy and high-power Li–S batteries for practical applications.