A new method presented in this work mainly describes how to produce polymer electrolyte membranes by using water as plasticizer. Compared with the membranes made by traditional methods, the membranes made by the new method have the properties of easy handling and free-standing. The results of Ac impedance suggest that the polymer electrolyte membranes have high ionic conductivity. Moreover, the images of SEM show that the porous and alveolate structures are greatly improved. It is more important that using water as plasticizer can lower the cost of producing Li-ion batteries and eliminate the pollution produced in process of plasticizer extraction, in which some volatile solvents were used in traditional methods. (C) 2002 Elsevier Science B.V. All rights reserved.