The cycling performances of the cell with poly(ethylene oxide) (PEO)-based composite polymer electrolyte using BaTiO 3, TiO 2, and Al 2O 3 as filler, lithium metal anode, and LiNi 0.8Co 0.2O 2 cathode at 80°C have been examined. The cycling performance depended on the filler in PEO-Li(CF 3SO 2) 2N electrolyte. The best result was obtained in the electrolyte with the BaTiO 3filler. The good cycling performance in the cell of Li/PEO 19Li(CF 3SO 2) 2N-BaTiO 3/LiNi 0.8Co 0.2O 2 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 PEO 19Li(CF 3SO 2) 2N-BaTiO 3 composite electrolyte was estimated to be <4.0 V.