Lithium-ion transfer at the interface between the lithium-ion-conductive ceramic of La0.55Li0.35TiO3 (LLT) and the polymer electrolyte of polyethylene oxide (PEO) complexed with LiCF3SO3 (PEO-LiCF3SO3) was studied by ac impedance spectroscopy for the system of Li/PEO-LiCF3SO3/LLT/PEO-LiCF3SO3/Li. The impedance ascribed to ion transfer through the interface was observed. The resistance due to the lithium-ion transfer at the interface was larger than those through phases of LLT and PEO-LiCF3SO3, and the temperature dependence of the interfacial resistances showed Arrhenius-type behavior. The activation energy of the interfacial resistances was larger than those for lithium-ion conduction in LLT and PEO-LiCF3SO3. The design of the ion-conductive ceramic and the polymer composite electrolytes is discussed based on the results. (C) 2004 The Electrochemical Society.