Fabrication and characterization of SiO₂/PVDF composite nanofiber-coated PP nonwoven separators for lithium-ion batteries

SiO₂/polyvinylidene fluoride (PVDF) composite nanofiber-coated polypropylene (PP) nonwoven membranes were prepared by electrospinning of SiO₂/PVDF dispersions onto both sides of PP nonwovens. The goal of this study was to combine the good mechanical strength of PP nonwoven with the excellent electrochemical properties of SiO₂/PVDF composite nanofibers to obtain a new high-performance separator. It was found that the addition of SiO₂ nanoparticles played an important role in improving the overall performance of these nanofiber-coated nonwoven membranes. Among the membranes with various SiO₂ contents, 15% SiO₂/PVDF composite nanofiber-coated PP nonwoven membranes provided the highest ionic conductivity of 2.6 × 10^-3 S cm^-1 after being immersed in a liquid electrolyte, 1 mol L^-1 lithium hexafluorophosphate in ethylene carbonate, dimethyl carbonate and diethyl carbonate. Compared with pure PVDF nanofiber-coated PP nonwoven membranes, SiO₂/PVDF composite fiber-coated PP nonwoven membranes had greater liquid electrolyte uptake, higher electrochemical oxidation limit, and lower interfacial resistance with lithium. SiO₂/PVDF composite fiber-coated PP nonwoven membrane separators were assembled into lithium/lithium iron phosphate cells and demonstrated high cell capacities and good cycling performance at room temperature.