In this work the preparation and the thermal and electrochemical characteristics of a polymer electrolyte cross-linked in presence of propylenecarbonate as plasticizer and based on polyester of 3,3’-thiodipropionic acid and tri-ethylene glycol with LiClO4 are reported. The lithium deposition-stripping process was tested by cyclic voltammetry and the Li/polymer electrolyte interface stability was investigated over time by impedance spectroscopy, and the results are reported and discussed. Cyclability data of a lithium battery operating at 25-degrees-C are also reported.