A polymer attached to the sodium terephthalate moiety as a side group is synthesized for the first time, and evaluate as a negative electrode active material. Both monomer and polymer are electrochemically characterized by cyclic voltammetry and battery performance. Compared to monomer, the polymer-based sodium terephthalates exhibit a lower oxidation peak. The electrochemical performance of polymer salt reveals the discharge potential (0.4 V vs. Na/Na+) along with discharge capacities up to 222 mAh g(-1) and a better cycling stability (130 cycles, 77%). The disodium terephthalate polymer is most suitable among the conjugated carbonyl organic compounds for use in the sodium ion battery. (c) 2018 The Electrochemical Society.