A highly porous polyacrylonitrile (PAN) membrane was prepared and characterized. Polymer electrolyte was prepared by soaking the porous PAN membrane in an electrolyte solution, and its electrochemical characteristics were investigated. Ionic conductivity exceeding 1 x 10(-3) S/cm at room temperature was obtained, and the use of this membrane assured an electrochemical stability of at least 4.5 V. A lithium-ion cell employing the porous PAN membrane was assembled, and its charge/discharge cycling performance was evaluated. (C) 2002 The Electrochemical Society.