A copolymer of poly(acrylonitrile-co-styrene) (SAN) was synthesized via an emulsion polymerization method.Novel polymer electrolyte membranes cast from the blends of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), SAN and fumed silica (SiO2) are microporous and can be used in polymer lithium-ion batteries. The membrane shows excellent characteristics such as high ionic conductivity and good mechanical strength when the mass ratio between SAN and PVDF-HFP and SiO2 is 3.5/31.5/5. The ionic conductivity of the membrane soaked in a liquid electrolyte of 1 mol/L LiPF6/EC/DMC/DEC is 4.9 × 10-3 Scm-1 at 25℃. The membrane is electrochemical stable up to 5.5 V versus Li+/Li in the liquid electrolyte. The influences of SiO2 content on the porosity and mechanical strength of the membranes were studied.Polymer lithium-ion batteries based on the membranes were assembled and their performances were also studied.