Facile In Situ Building of Sulfonated SiO₂ Coating on Porous Skeletons of Lithium-Ion Battery Separators

Polyolefin separators with worse porous structures and compatibilities mismatch the internal environment and deteriorate lithium-ion battery (LIB) combination properties. In this study, a sulfonated SiO₂ (SSD) composited polypropylene separator (PP@SSD) is prepared to homogenize pore sizes and in situ-built SSD coatings on porous skeletons. Imported SSD uniformizes pore sizes owing to centralized interface distributions within casting films. Meanwhile, abundant cavitations enable the in situ SSD coating to facilely fix onto porous skeleton surfaces during separator fabrications, which feature simple techniques, low cost, environmental friendliness, and the capability for continuous fabrications. A sturdy SSD coating on the porous skeleton confines thermal shrinkages and offers a superior safety guarantee for LIBs. The abundant sulfonic acid groups of SSD endow PP@SSD with excellent electrolyte affinity, which lowers Li⁺ transfer barriers and optimizes interfacial compatibility. Therefore, assembled LIBs give the optimal C-rate capacity and cycling stability, holding a capacity retention of 82.7% after the 400th cycle at 0.5 C.