High-molecular-weight comb-shaped polyethers, poly(ethylene oxide-co-2-(2-methoxyethoxy) ethyl glycidyl ether-co-allyl glycidyl ether) (P(EO/EM/AGE)) and poly(ethylene oxide-co-2-(2-methoxyethoxy)ethyI glycidyl ether) (P(EO/EM)), were synthesized and used for the preparation of the all solid polymer electrolyte and the composite polymer electrolyte combined with a plasticizer Star-EO-OMe, pentaerythritol tetrakis(2-methoxyethyl ether), which shows low vapor pressure, respectively. Some electrochemical properties of the polymer electrolytes and performances of the cell consisting of lithium/polymer electrolyte/LiCoO2 were studied. The addition of Star-EO-OMe to polymer electrolyte brought about a large increase in ionic conductivity. The composite electrolyte containing 50 wt.% of Star-EO-OMe complexed with LiTFSI, lithium bis(trifluoromethylsulfonyl)imide, exhibited high ionic conductivity in the order of 10(-4) S cm(-1) at 10degreesC and approximately 10(-1) S cm(-1) at -20degreesC. The cell performance was also improved by the addition of Star-EO-OMe. (C) 2004 Elsevier B.V. All rights reserved.