Poly[3,4-(ethylenedithio)thiophene] (PEDTT) has been synthesized by oxidative-coupling polymerization of 3,4-(ethylenedithio)thiophene (EDTT) in the absence of solvent at ambient conditions. The resulting polymer has been characterized by FT-IR, XRD, TGA, UV–vis and solution NMR analyses. In addition, PEDTT has been evaluated as the cathode active material for rechargeable lithium batteries. The charge–discharge tests are carried out at room temperature. PEDTT shows discharge specific capacity above 425mAhg−1. It is tentatively proposed that electrode reaction involves the formation of thioether cation, which imparts multi-electron redox reaction, high discharge specific capacity, high charge voltage and low discharge voltage.