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 PEO-based composite electrolytes. In this report as the addition of a small volume fraction (<1.5%) of moderately high surface area (∼60 m2 g−1) carbons results in composite lithium polymer electrolytes with excellent performance in terms of conductivity and interfacial stability is shown.