In this work, PMMA layer was immobilized onto PE separator skeleton via surface-initiated ATRP based on dopamine pretreatment. The incorporated "active" layer made separator matrix could be swollen by electrolyte solution to some extent and show some properties of gel polymer electrolyte. Resulted separators were characterized by ATR-FTIR, SEM, contact angle and electrochemical methods. The prepared separators showed improved thermal stability. The electrolyte uptake and ionic conductivity were also elevated due to the improved affinity between separator and liquid electrolyte. The room temperature ion conductivity reached up to 1.19 x 10(-3) S cm(-1). The stability of liquid electrolyte trapped in the separator was enhanced obviously. Cells assembled with such "active separators" showed better cycle performances. These results primarily showed that it was a promising way to prepare high performance PE based separators for lithium ion batteries. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.