The cycling performances of the cell with poly(ethylene oxide) (PEO)-based composite polymer electrolyte using BaTiO3, TiO2, and Al2O3 as filler, lithium metal anode, and LiNi0.8Co0.2O2 cathode at 80°C have been examined. The cycling performance depended on the filler in PEO-Li(CF3SO2)2N electrolyte. The best result was obtained in the electrolyte with the BaTiO3filler. The good cycling performance in the cell of Li/PEO19Li(CF3SO2)2N-BaTiO3/LiNi0.8Co0.2O2 was explained by the improved interfacial stability between the electrolyte and the electrode. The cycling performance of PEO-based polymer electrolyte cell was influenced by the charge and discharge cut-off voltage. The electrochemical window of PEO19Li(CF3SO2)2N-BaTiO3 composite electrolyte was estimated to be <4.0V.