One-Step Integration of Sulfonated Polymer Films with Separators for Shuttle Mitigation in Lithium-Sulfur Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Interfacial polymerization (IP) is a cost-effective method for thin polymer film fabrication.
• Lithium-sulfur batteries face challenges with polysulfide shuttling and limited ion transport.
• Separator coatings are crucial for improving battery performance and longevity.

Purpose of the Study:

• To develop a charge-selective sulfonated thin-film coating for commercial battery separators.
• To enhance selective transport and suppress polysulfide shuttling in lithium-sulfur batteries.
• To optimize the coating to balance capacity retention and rate performance.

Main Methods:

• A one-step interfacial polymerization reaction between triacyl chloride and sulfonated diamine monomers.
• Fabrication of a dense, charge-selective sulfonated thin-film coating on a commercial separator.
• Modification of monomer composition (fractional substitution) and addition of a nonsulfonated diamine to control film properties.

Main Results:

• The sulfonated coating effectively suppressed polysulfide shuttling, improving capacity retention.
• Initial dense films hindered lithium conduction, compromising rate performance.
• Optimized films with uniform coverage achieved by adding a small fraction of nonsulfonated diamine broke the rate-capacity trade-off.
• The optimized coating enabled a capacity of 711.6 mAh g-1 after 200 cycles at 0.5C and over 800 mAh g-1 at 2C.

Conclusions:

• A novel sulfonated thin-film coating via interfacial polymerization significantly improves lithium-sulfur battery performance.
• The optimized coating effectively addresses polysulfide shuttling and enhances both capacity retention and rate capability.
• This approach offers a promising strategy for advanced battery separator design.