Hierarchical MoxC@NC hollow microsphere with incorporated Mo vacancies as multifunctional confined reactors for high-loading Li–S batteries

Abstract

The undesirable shuttling of lithium polysulfides (LiPSs) and sluggish redox kinetics lead to the serious reduction in cycle life and sulfur utilization. Herein, to tackle these problems simultaneously, a strategy is demonstrated for preparing defective Mo_xC@NC with rich incorporated Mo vacancies, additional active sites and nitrogen-doped carbon (NC) coating for boosting the performance of Li–S batteries. The hollow structure of Mo_xC@NC achieves the physical confinement of the active materials and facilitates the ion/electrolyte penetration. Relevant experiments confirmed that the meso-microporous thin outer shell and the uniformly distributed Mo_xC nanoparticles in the shell can significantly suppress the LiPSs shuttle effect by chemisorption. Furthermore, the defective Mo_xC can accelerate conversion of LiPSs by a catalytic effect, promoting the polysulfide redox kinetics of the sulfur species and prevent the dissolution of polysulfides. The resultant 77S-Mo_xC@NC electrode acquired 982 mA h g⁻¹ after 400 cycles with an ultralow capacity decay rate of 0.14% per cycle.