Engineering multi-chambered carbon nanospheres@carbon as efficient sulfur hosts for lithium–sulfur batteries

Abstract

Despite their advantages of high theoretical capacity and energy density, lithium–sulfur (Li–S) batteries still suffer from poor electrochemical performance resulting from the accelerated shuttle effect of polysulfides and the intrinsically low electroactivity of elemental sulfur. Herein, we report an ideal core–shell sulfur host material based on core–shell carbon encapsulated multi-chambered carbon nanospheres (MCCN@C) for Li–S batteries. The hierarchical and micro–mesoporous core in MCCN@C can allow a high sulfur loading (83.1 wt%) and serve as the physical barrier to block the polysulfide dissolution, and the carbon shell can provide additional physical confinements for improving the retention of soluble polysulfides. Moreover, the well-designed conductive networks of the MCCN@C material interconnected by carbon chambers can promote fast electron transfer and electrolyte penetration. In Li–S batteries, MCCN-S@C composite cathodes deliver significantly enhanced electrochemical performance with a high reversible capacity of 1163 mA h g⁻¹ at 0.2C after 100 cycles, remarkable rate capability (626 mA h g⁻¹ at 5.0C) and ultrahigh long-term cycle stability at high rates (651 mA h g⁻¹ after 1000 cycles at 2.0C with 0.032% capacity decay per cycle). More importantly, the MCCN@C–S composite cathode with 3.6 mg cm⁻² sulfur also delivers a high and stable electrochemical performance over 200 cycles.