Composite polymer electrolyte (PE) films comprising of thermoplastic polyurethane (TPU) and polyacrylonitrile (PAN) (denoted as TPU–PAN) have been prepared by two different processes. Scanning electron microscope (SEM) of the films reveal the differences in morphology between them. The electrochemical properties of composite electrolyte films incorporating LiClO4–propylene carbonate (PC) were studied. TPU–PAN based gel PE shows high ionic conductivity at room temperature. Thermogravimetric analysis informs that the composite electrolyte possesses good thermal stability with a decomposition temperature higher than 300°C. Electrochemical stability in the working voltage range from 2.5 to 4.5V was evident from cyclic voltammetry. Cycling performances of Li/PE/LiCoO2 cells were also performed to test the suitability of the composite electrolyte in batteries.