Porous high density polyethylene (HDPE) membrane is an important type of separator for lithium ion batteries (LIBs). To improve the electrochemical performances of HDPE-based separators, a copolymer of poly(ethylene-block-ethylene glycol) (PE-b-PEG) was blended into porous HDPE separators via TIPS process. By measuring the composition, morphology and crystallinity, etc., the phase behavior and surface enrichment behavior of the HDPE/PE-b-PEG/LP system were studied. Compared with pure HDPE separators, surface enrichment of PE-b-PEG chains enhanced the compatibility between separators and liquid electrolyte and electrodes. The ionic conductivity of liquid electrolyte soaked blend separator was up to 1.24 x 10(-3) S cm(-1) at 25 degrees C. Furthermore, the interface resistance between separator and electrode was effectively reduced by the surface enriched polyether chains. All the results indicated that PE-b-PEG could be a promising blend substance to improve the electrochemical performances of HDPE separators prepared via TIPS process. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.