Thin Fiber-Based Separators for High-Rate Sodium Ion Batteries

A thermally resistant, high-performance electrospun hybrid PVDF-HFP/SiO₂ fiber-based separator (EHS) has been successfully fabricated and its performance for sodium ion batteries explored. The EHS, containing 40% of its weight as SiO₂, is made of intermingled nonwoven hybrid organic (PVDF-HFP) inorganic (SiO₂) fibers (∼145 nm) to produce a highly porous network (∼85% in volume). This EHS separator shows an important electrolyte uptake with nearly no swelling, and an interface stability comparable to today’s commercialized Al₂O₃-coated PP and cellulose separators. Full NVPF//NaPF₆-EC:PC//hard carbon cells using EHS show low ionic resistance, excellent rate capability, cycling retention, and longer short-circuit time.