In Situ Polymer Electrolyte Coating for Lithium–Sulfur Batteries

Abstract

The transition from liquid electrolytes to solid-state electrolytes represents a key strategy for improving the safety and energy efficiency of lithium-sulfur (Li-S) batteries. However, poor interfacial contact and high resistance at the electrode-electrolyte interface remain critical barriers to commercialization. In this study, we report an in situ coating approach, where a crosslinkable polytetrahydrofuran-based solid polymer electrolyte (aPTHF-SPE) is directly formed on the surface of C@S cathodes via UV-curing. SEM and EDS analyses confirm the formation of a uniform polymer layer with a thickness of 35-46 μm, ensuring intimate interfacial contact and reduced void formation. Electrochemical tests demonstrate that the  coated cathodes deliver an initial discharge capacity of ~250 mA·h·g^-1, with subsequent cycles exhibiting improved stability due to enhanced ionic transport and electrode activation. Despite gradual fading after extended cycling, the strategy significantly improves the electrode-electrolyte interface compared to uncoated cathodes. These findings highlight in situ polymer electrolyte coating as a promising and scalable method for addressing interfacial challenges in solid-state Li-S batteries, paving the way toward safer and higher-performance energy storage systems.