New ionic liquid-polymer gel electrolytes (IPGEs) are prepared from N-ethyl-N-methylmorpholinium bis(trifluoromethanesulfonyl)imide (Mor(1,2)TFSI) and poly(vinylidene fluoride)-hexafluoropropylene copolymer (PVdF(HFP)). To investigate the effect of propylene carbonate (PC) on the ionic conductivity of the IPGEs, the preparation methods are roughly divided into two groups according to the presence or absence of PC. The ionic conductivity for each IPGE is measured with increasing temperature and changing weight ratio of Mor(1,2)TFSI. The results show that the ionic conductivity increases as the temperature and weight ratio of the Mor(1,2)TFSI increase, and that the added PC improves the ionic conductivity of the IPGEs. In addition, thermogravimetric analysis and the data from infrared spectroscopy demonstrate the thermal stability of each IPGE and the presence of PC in the polymer network. Although the IPGEs that contain PC display high conductivity (similar to 1.1 X 10(-2) S cm(-1)) at 60 degrees C, they are thermally unstable. (c) 2005 Elsevier B.V. All rights reserved.