Regulating the Polysulfide Behavior by a Large-Scale Two-Dimensional Superlattice Interface in Li-S Chemistry.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Heterojunction engineering is crucial for developing efficient catalysts in lithium-sulfur (Li-S) batteries.
• Controlling electronic properties within the bulk phase of heterostructure catalysts remains a challenge for optimizing electrochemical performance.
• The shuttle effect of lithium polysulfides (LiPSs) significantly hinders the long-term stability and efficiency of Li-S batteries.

Purpose of the Study:

• To design and synthesize a multifunctional "tube-in-tube" catalyst for enhanced sulfur redox reactions (SRR) in Li-S batteries.
• To investigate the synergistic effects of a 2D Moiré superlattice interface in heterostructure catalysts for improved LiPSs adsorption and catalytic conversion.
• To demonstrate the efficacy of the engineered catalyst in improving the capacity, rate capability, and cycle life of Li-S batteries.

Main Methods:

• Fabrication of a novel "tube-in-tube" heterostructure catalyst (MoSe2/MoS2@CNTs) featuring a 2D superlattice interface.
• In situ studies and theoretical calculations to analyze the LiPSs adsorption and catalytic conversion mechanisms on the catalyst interface.
• Assembly of Li-S batteries using the catalyst-modified separator and evaluation of electrochemical performance, including discharge capacity, rate capability, and cycle stability.

Main Results:

• The MoSe2/MoS2@CNTs catalyst exhibited a significant synergistic effect, enhancing LiPSs adsorption and catalytic conversion during SRR.
• Li-S batteries with the modified separator achieved an outstanding initial discharge capacity of 1225 mAh g⁻¹ at 0.2 C and maintained 870 mAh g⁻¹ at 5 C.
• The engineered catalyst effectively suppressed the shuttle effect, resulting in a low capacity fading rate of 0.063% per cycle over 1000 cycles at 1 C, even with high sulfur loading.

Conclusions:

• The developed "tube-in-tube" multifunctional catalyst with a 2D Moiré superlattice interface provides effective electronic control for Li-S batteries.
• This heterostructure catalyst demonstrates superior performance in terms of capacity, rate capability, and long-term cycling stability by optimizing adsorption-catalysis synergy.
• The findings offer valuable insights for designing advanced catalysts for Li-S batteries and other catalytic energy storage systems.