Composites of a lithium ion conducting ceramic with a lithium salt based polymer electrolyte matrix are described. Conductivity measurements as a function of the lithium ion conducting ceramic phase content in the composite show that there is a significant increase in conductivity at approximately 40 vol% of the ceramic. The room temperature conductivity above this ceramic content is enhanced by at least 100% over that of the polymer electrolyte phase alone. It is believed that this additional contribution is substantially lithium ion conduction. The major barrier to ion-motion in these materials appears to be the interface between the polymer and ceramic. This interfacial resistance is strongly moisture-sensitive.