Electropolymerizations (EPs) of thiophene (Th), 3,4-ethylenedioxythiophene (EDOT) and the mixed monomers of Th and MOT in 0.05 M Et4NClO4/propylene carbonate (PC) solution were performed to prepare polymer films as potential cathode materials in lithium ion battery. The incorporation of MOT units into pure polythiophene (PTh) chain leads to large alternations on the experimental conditions of EPs and the properties of the resulting polymer films. Onset potential of the EPs was reduced with the participation of MOT component. The resulting polymers, PTh, poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(thiophene-co-3,4-ethylenedioxythiophene) (PTh-EDOT) were then served as cathode materials to test their capabilities to transport lithium ion in 1.0 M LiPF6/ethylene carbonate/dimethyl carbonate solution. With the inherent MOT unit, PEDOT and PTh-EDOT have better charge capacity, stability and response rate than pure PTh. Among the copolymers, PTh-EDOT (1/1) even shows better stability than pure PEDOT homopolymer, advantage of using MOT as copolymer component is thus evaluated. (c) 2005 Elsevier Ltd. All rights reserved.