Polyethylene (PE) separator grafted with 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (siloxane) was newly prepared by electron beam irradiation. The degree of grafting and morphology of the grafted separators were characterized by FT-IR and scanning electron microscopy (SEM). The polymer electrolytes based on the grafted separators were prepared by immersing the separators in the electrolyte containing 1 M LiPF6 in EC/DMC (1:1 by volume). The ionic conductivity of the grafted separators was changed with the degree of grafting and showed the highest value of 7 x 10(-4) S cm(-1) at the degree of grafting of 6%. The electrochemical stability limit of the grafted separator with the degree of grafting of 6% was increased to 5.2 V. The Li ion cell using the grafted separator also showed an improved performance. suggesting that the grafted separator is a good candidate for the separator of lithium batteries at high voltage operation. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.