In situ covalent crosslinking strategy to construct highly stable composite separators for lithium-ion batteries

The separator is a crucial component in lithium-ion batteries, significantly impacting their performance, cycle life, and safety. This study presents a novel approach for constructing high-performance ceramic composite separators for lithium-ion batteries using a covalent coupling strategy. Employing glycidoxypropyltrimethoxysilane (GPTMS) as the coupling agent, the synthesized binder, poly(acrylic acid)–co-poly(tetrahydrofurfuryl acrylate) (P(AA-THFA)), is covalently linked to ceramic particles Boehmite (AlOOH). The silane establishes covalent bonds with Boehmite through siloxane linkages, while the epoxy groups of the silane react with the carboxyl groups of the binder, resulting in the formation of a covalently linked novel composite separator, PE@P(AA-THFA)/GPTMS/AlOOH. The composite separator demonstrates enhanced microstructural stability, showcasing significant improvements in thermal stability, peel strength and battery cycling performance. Thermal stability tests confirm its resistance to shrinkage even at 180 °C, underscoring the critical role of covalent coupling in separator stability. Peel strength tests indicate increased adhesion of the coating slurry, contributing to structural integrity. Moreover, the composite separator exhibits excellent wetting behavior with the electrolyte, leading to heightened ion conductivity. Measurements of lithium ion transference numbers highlight improved lithium ion movement within the composite separators. Battery performance tests, encompassing cyclic stability and rate capability, underscore the superiority of covalently coupled composite separators, especially under high-current–density conditions. This approach presents a promising method for fabricating lithium-ion battery separators with enhanced reliability and safety.