Labyrinth maze-like long travel-reduction of sulfur and polysulfides in micropores of a spherical honeycomb carbon to greatly confine shuttle effects in lithium-sulfur batteries

Abstract

Polysulfide absorption in a micropore-rich structure has been reported to be capable of efficiently confining the shuttle effect for high-performance lithium-sulfur (Li–S) batteries. Here, a labyrinth maze-like spherical honeycomb-like carbon with micropore-rich structure was synthesized, which is employed as a template host material of sulfur to study the shuttle effects. The results strongly confirm that a diffusion controlled process rather than an absorption resulted surface-controlled process occurs in an even micropore-rich cathode but still greatly inhibits the shuttle effect. Thus, the battery achieves a high initial discharge specific capacity of 1120 mAh g−1 at 0.25 C and super cycling stability for 1635 cycles with only 0.035% capacity decay per cycle with 100% Coulombic efficiency. We would like to propose a new mechanism for shuttle effect inhibition in micropores. In terms of the diffusion control process in microporous paths of a labyrinth maze structure, polysulfides experience a long travel to realize continuous reductions of sulfur and polysulfides until formation of the final solid product. This efficiently prevents the polysulfides escaping to electrolyte. The labyrinth maze-like honeycomb structure also offers fast electron transfer and enhanced mass transport as well as robust mechanical strength retaining intact structure for long cycle life. This work sheds lights on new fundamental insights behind the shuttle effects with universal significance while demonstrating prominent merits of a robust labyrinth maze-like structure in high performance cathode for high-performance Li–S batteries.

Keywords

• Lithium-sulfur batteries
• Labyrinth maze-like spherical honeycomb-like carbon
• Diffusion-controlled process
• Shuttle effects
• High performance