The addition of fillers to lithium polymer electrolytes is a well established procedure to improve their mechanical stability as well as their interfacial stability with lithium anodes. As far only inert, non-conductive fillers have been used in the formulation of PEG-based composite electrolytes. In this report as the addition of a small volume fraction (< 1.5%) of moderately high surface area (similar to 60 m(2) g(-1)) carbons results in composite lithium polymer electrolytes with excellent performance in terms of conductivity and interfacial stability is shown. (C) 2000 Elsevier Science Ltd. All rights reserved.