Enhancing the Performances of Lithium Batteries through Functionalization of Porous Polyolefin Separators with Cross-Linked Single-Ion Polymer Electrolytes

Lithium-ion batteries (LiBs) require advanced separators to meet the growing demands of high energy density, safety, and durability. However, conventional polyolefin separators often suffer from poor electrolyte wettability and limited ionic conductivity, hindering the overall battery performance. This study presents a scalable approach for the surface functionalization of porous polyolefin separators using single-ion statistical copolymers bearing lithium sulfonate or lithium trifluoromethanesulfonamidosulfonyl groups. These copolymers are deposited via a wet coating process followed by UV cross-linking, achieving durable and uniform functionalization without compromising the separator's porous structure. The functionalized separators exhibit significantly enhanced wettability, electrolyte uptake, and effective ionic conductivity. Electrochemical performance tests of LiBs reveal stable interfacial resistance, improved cycle life, and better rate capabilities owing to the effectiveness of the covalently bonded ionic groups in promoting selective lithium-ion transport. This approach combines simplicity, scalability, and robust chemical stability, offering a promising solution for next-generation LiBs by addressing the key limitations of commercial separators.