Composite polymer electrolytes composed of poly(ethylene oxide) (PEO), BaTiO3 as a ceramic filler, LiN(CF3CF2SO2)(2) as a lithium salt, and hyperbranched polymer (HBP) (poly [bis(triethylene glycol)benzoatel capped with an acetyl group) as a platicizer were examined as the electrolyte for all solid-state lithium polymer batteries and the ionic conductivity was optimized. The optimized 90 wt.% [(80 wt.% PEO-20 wt.% HBP)(12)(LiN(CF3CF2SO2)(2))]-10 wt.% BaTiO3 electrolyte, where the PEO with M-n of 60 x 10(-4), HPB with M-n of 15,000, and BaTiO3 with a particle size of 0.5 mum were used, showed the ionic conductivity of 1.3 x 10(-4) S/cm at 30 degreesC and 1.6 x 10(-4) S/Cru at 80 degreesC, respectively. The optimized composite polymer electrolyte has an electrochemical stability window of 4.0 Vand also it was stable until 307 degreesC under air. Interfacial stability of the LiN(CF3CF2SO2)(2)-based composite polymer electrolyte for a lithium metal electrode was found to be better than that of LiN(CF3SO2)(2)-based one. (C) 2003 Elsevier Science B.V. All rights reserved.