Poly(3,4-ethylenedioxythiophene) (PEDOT) was chemically synthesized and characterized by FT-IR, XRD, XPS, TGA and organic elemental analysis (EA). The polymer was tested as cathode active material for rechargeable lithium batteries. The cyclic voltammetry (CV) and charge–discharge tests of PEDOT as the cathode active material was investigated in an electrolyte system of LiN(CF3SO2)2/1,2-dimethoxyethane/1,3-dioxopentane (1:2 by weight). The peak discharge capacity of up to 691mAh/g was obtained during the 1st cycle, and remained above 330mAh/g after 44 cycles. These results indicate that PEDOT can afford a high specific capacity as a cathode active material. A redox mechanism is tentatively proposed.