Energy-storage covalent organic frameworks: improving performance via engineering polysulfide chains on walls

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Covalent organic frameworks (COFs) offer potential for energy storage due to their ordered channels.
• The shuttle effect of lithium-sulfide intermediates limits the performance of lithium-sulfur (Li-S) batteries.
• Physical confinement of sulfur within COF channels alone is insufficient to prevent this shuttle effect.

Purpose of the Study:

• To develop a strategy to suppress the shuttle effect in Li-S batteries by covalently engineering polysulfide chains on the pore walls of imine-linked frameworks.
• To investigate the impact of immobilized polysulfide chains on the electrochemical performance of Li-S cells.

Main Methods:

• Synthesis of imine-linked frameworks.
• Covalent engineering of polysulfide chains onto the pore walls of the frameworks.
• Electrochemical characterization of Li-S batteries utilizing the engineered frameworks.

Main Results:

• Imine linkages successfully triggered sulfur polymerization and anchored polysulfide chains on the channel walls.
• The immobilized polysulfide chains effectively suppressed the shuttle effect.
• The engineered frameworks demonstrated improved capacity, enhanced sulfur accessibility, better rate capability, and superior cycle stability in Li-S batteries.

Conclusions:

• Pore wall engineering of COFs by covalently immobilizing polysulfide chains is an effective strategy to tackle key issues in Li-S energy storage.
• This approach significantly improves the overall performance of Li-S batteries by mitigating the shuttle effect and enhancing redox activity.