A new redox polymer consisting of benzene and thiuret, poly(p-phenylene thiuret) (PPT), is presented as a cathode material for lithium secondary batteries. The high capacity and cycleability are achieved by introduction of an S-S bond as a side group to a polymer. To prepare PPT, we synthesized a precursor polymer by a condensation of S-benzylthiourea with isothiocyanate and modified this polymer to PPT by an electrochemical reaction.