Effect of SiO2 Content on Performance of Polypropylene Separator for Lithium-Ion Batteries

Composite separators are prepared by introducing SiO2 nanoparticles on both sides of polypropylene separator with various SiO2 contents through a dip-coating process, where polyvinylidene fluoride-hexafluoropropylene is used as binder. Coated layers have highly porous structure, which is quantitatively analyzed by air permeability. Compared to pristine separator, composite separators show significant lower Gurley value, reduced thermal shrinkage, higher liquid electrolyte uptake, better mechanical properties, and better cell performance such as discharge C-rate capability and cycle performance. The influence of SiO2 content on these properties is also studied, and the best SiO2 content is given. (C) 2014 Wiley Periodicals, Inc.