Rapid construction of highly-dispersed cobalt nanoclusters embedded in hollow cubic carbon walls as an effective polysulfide promoter in high-energy lithium-sulfur batteries

The ultrahigh specific energy density and low cost of lithium-sulfur batteries are suitable for the next generation of energy storage. However, the shuttle issue and sluggish conversion kinetics of polysulfides remain unsolved. Confining metal nanoclusters with strong polarity in conductive porous carbon is an effective strategy for tackling such knotty issues. Herein, we design and synthesize hollow cubic carbon embedded with highly dispersed cobalt nanoclusters as an effective sulfur reservoir for lithium sulfur batteries. The large cavity structure and well-dispersed cobalt nanoclusters, with uniform sizes near 11 nm, enable the hosting structure to hold the high sulfur loading, 70% capacity retention after 500 cycles at 2 C with a high sulfur loading of 6.5 mg·cm−2, effective stress release, accelerated polysulfide conversion, superior rate performance, strong physical confinement and chemical absorption capability. Further density functional theoretical calculations demonstrate that the well-dispersed cobalt nanoclusters in the hosting structure play a critical electrocatalytic role in boosting the capability of absorbing and converting polysulfides.