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 degreesC have been examined. The cycling performance depended on the filler in PEO-Li(CF(3)SG(2))(2)N electrolyte. The best result was obtained in the electrolyte with the BaTiO3 filler. The good cycling performance in the cell of Li/PEO19Li(CF3SO2)(2)N-BaTiO3/LiNi0.8Co0.2O2 was explained by the improved interfacial stability between the electrolyte and the electrode. The cycling performance of PEG-based polymer electrolyte cell was influenced by the charge and discharge cut-off voltage. The electrochemical window of PEO19Li(CF3SO2)(2)N-BaTiO3 composite electrolyte was estimated to be < 4.0 V.