A new gel polymer electrolyte (GPE), fumed silica-doped poly(butyl methacrylate-styrene) ( P(BMA-St))based gel polymer electrolyte, was developed for lithium ion battery. The copolymer P(BMA-St) was synthesized by emulsion polymerization, the copolymer membranes doped with and without fumed silica were prepared through phase inversion, and the GPEs were obtained by immersing the membranes in 1 M LiPF(6) solution. The structure and performances of the copolymer, the membranes and the GPEs were characterized by Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), scanning electron spectroscopy (SEM), thermogravimetric analysis (TGA), linear sweep voltammetry (LSV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). The copolymer P(BMA-St) is formed through the breaking of the double bond C=C in the monomers, butyl methacrylate and styrene. By doping 10 wt.% fumed silica in P( BMA-St) membrane, the properties of the membrane and the corresponding GPE were improved. The membrane doped with fumed silica is stable up to 355 degrees C and its pore size becomes more uniform and smaller; oxidative decomposition potential of the GPE doped with fumed silica is raised to 5.2 V (vs. Li/Li(+)) and its ionic conductivity is as high as 2.15 x 10(-3) S cm(-1) at ambient temperature. (C) 2010 Elsevier BM. All rights reserved.