MoO2 nanoparticles embedded in N-doped hydrangea-like carbon as a sulfur host for high-performance lithium–sulfur batteries

Abstract

Lithium–sulfur batteries are considered to be promising energy storage devices owing to their high energy density, relatively low price and abundant resources. However, the low utilization of insulated active materials and shuttle effect have severely hindered the further development of lithium–sulfur batteries. Herein, MoO₂ nanoparticles embedded in N-doped hydrangea-like carbon have been synthesized by liquid-phase reaction followed by an annealing process and used as a sulfur host. The nitrogen-doped carbon matrix improves electrical conductivity and provides pathways for smooth electron and Li ion transfer to uniformly dispersed sulfur. Meanwhile, MoO₂ nanoparticles can absorb polysulfide ions by forming strong chemical bonds, which can effectively alleviate the polysulfide shuttling effect. These results showed a good rate performance: 1361, 1071, 925, 815 and 782 mA h g⁻¹ at the current densities of 0.1, 0.2, 0.5, 1 and 2 A g⁻¹, and capacity retention of 85% after 300 cycles at 1 A g⁻¹. The excellent performance was due to the synergistic effects of the polar MoO₂ and nitrogen-doped carbon matrix, which can effectively restrain and reutilize active materials by absorbing polysulfides and catalyzing the transformation of polysulfides.