Methoxy poly(ethyleneglycol) monomethacrylate (PEGMA) graft-copolymerized poly(vinylidenefluoride) (PVDF), or the P(PEGMA)-g-PVDF copolymer, was synthesized. The PVDF homopolymer in N-methyl-2-pyrrolidone (NMP) solution was pretreated with ozone. The peroxides content of the ozone-treated PVDF was determined by assay with 2,2-diphenyl-1-picrylhydrazyl (DPPH). The activated PVDF was then subjected to thermal graft copolymerization with the PEGMA macromonomer in NMP. The microstructures and compositions of the P(PEGMA)-g-PVDF copolymers were characterized by contact angle measurements, FT-IR spectroscopy, X-ray photoelectron spectroscopy and elemental analyses. Nanoporous membranes were prepared from the P(PEGMA)-g-PVDF copolymer by the phase inversion technique. The morphology of the membranes was studied by scanning electron microscope. The potential applications of the P(PEGMA)-g-PVDF copolymer as the polymer electrolytic membranes for lithium-ion batteries were explored. Measurements of ionic conductivity, Li+ transference number, and electrochemical stability of the membranes were undertaken.