Fluorinated Covalent Organic Framework-Based Nanofluidic Interface for Robust Lithium-Sulfur Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Practical application of lithium-sulfur (Li-S) batteries is hindered by uncontrolled lithium deposition and polysulfide shuttling.
• Existing permselective membranes struggle to balance fast ion transport with low polysulfide crossover.

Purpose of the Study:

• To design and synthesize a fluorinated covalent organic framework (4F-COF)-based membrane for Li-S batteries.
• To improve Li-ion migration, inhibit lithium deposition, and prevent polysulfide shuttling.
• To enhance battery lifespan and electrochemical performance.

Main Methods:

• Synthesis of a fluorinated covalent organic framework (4F-COF) membrane.
• Density functional theory (DFT) calculations and molecular dynamic (MD) simulations.
• In situ Raman analysis.
• Electrochemical testing of Li symmetrical cells and Li-S batteries.

Main Results:

• The 4F-COF membrane demonstrated high permselectivity, effectively eliminating polysulfide shuttling and dendritic lithium formation.
• Li symmetrical cells showed stable Li plating/stripping for 2000 hours at 1 mA cm⁻².
• Li-S batteries with the 4F-COF/PP separator achieved 82.3% capacity retention over 1000 cycles at 2 C and a rate performance of 568.0 mA h g⁻¹ at 10 C.

Conclusions:

• Functionalizing nanochannels in covalent organic frameworks (COFs) can impart permselectivity for energy storage.
• The 4F-COF membrane offers a promising solution for advancing Li-S battery technology.
• The developed membrane significantly increases battery lifespan and improves rate capability.