Combined high catalytic activity and polysulfide confinement in hierarchical carbon-encapsulated CoSe hollow core-shell spheres for high-performance lithium-sulfur batteries

Hierarchical carbon-encapsulated CoSe (designated as C-CoSe) hollow core-shell sphere is designed and constructed to relieve shuttle effect of the LiPSs, thereby leading to the performance enhancement of the LSBs. The prepared C-CoSe spheres comprise of spherical nano-aggregates as hollow core and N-doped carbon shell. Kinetics experiments and theoretical calculation as well as in situ Raman spectra reveal that the C-CoSe hollow core-shell spheres can effectively immobilize the LiPSs intermediates by chemical adsorption and physical confinement, and meanwhile accelerate conversion kinetics of the LiPSs owing to strong catalytic effect and superior electron conductivity during electrochemical reaction, thereby the shuttle effect being effectively inhibited. In addition, as a sulfur host, sufficient sulfur storage space related to hierarchical porous structure enable effective accommodation of volume change and full efficacy with sulfur loading of 73%. Benefiting from above advantages, the C-CoSe sulfur cathode exhibits impressive rate performance and excellent cycle stability. Even at a sulfur loading of 3 mg cm-2, a capacity of 584 mAh g-1 at 0.5 C is achieved and the capacity is maintained 450 mAh g-1 after 200 cycles. Our results provide an effective strategy to design advanced sulfur hosts for the performance enhancement of the LSBs.

Automated summary

A hierarchical carbon-encapsulated CoSe hollow core-shell sphere is designed and constructed to alleviate the shuttle effect of LiPSs and enhance the performance of LSBs. The C-CoSe spheres effectively immobilize LiPSs intermediates through chemical adsorption and physical confinement, leading to inhibited shuttle effect and improved conversion kinetics. As a sulfur host, the C-CoSe cathode exhibits impressive rate performance and excellent cycle stability, even at high sulfur loading. This study provides an effective strategy for designing advanced sulfur hosts to enhance the performance of LSBs.