A Polysulfides-Confined All-in-One Porous Microcapsule Lithium-Sulfur Battery Cathode

Developing emerging materials for high energy-density lithium-sulfur (Li-S) batteries is of great significance to suppress the shuttle effect of polysulfides and to accommodate the volumetric change of sulfur. Here, a novel porous microcapsule system containing a carbon nanotubes/tin dioxide quantum dots/S (CNTs/QDs/S) composite core and a porous shell prepared through a liquid-driven coaxial microfluidic method as Li-S battery cathode is developed. The encapsulated CNTs in the microcapsules provide pathways for electron transport; SnO2 QDs on CNTs immobilize the polysulfides by strong adsorption, which is verified by using density functional theory calculations on binding energies. The porous shell of the microcapsule is beneficial for ion diffusion and electrolyte penetration. The void inside the microcapsule accommodates the volumetric change of sulfur. The Li-S battery based on the porous CNTs/QDs/S microcapsules displays a high capacity of 1025 mAh g(-1) after 100 cycles at 0.1 C. When the sulfur loading is 2.03 mg cm(-2), the battery shows a stable cycling life of 700 cycles, a Coulombic efficiency exceeding 99.9%, a recoverable rate-performance during repeated tests, and a good temperature tolerance at both -5 and 45 degrees C, which indicates a potential for applications at different conditions.

Automated summary

Developing novel porous microcapsules containing a composite core of carbon nanotubes and tin dioxide quantum dots for high energy-density lithium-sulfur batteries is crucial to suppress polysulfide shuttling and accommodate sulfur volume changes. The microcapsules provide pathways for electron transport, immobilize polysulfides, allow for ion diffusion, and accommodate sulfur volumetric changes, resulting in a high capacity of 1025 mAh g(-1) after 100 cycles at 0.1 C.