Synthesis and characterization of electroactive PEDOT-TEMPO polymers as potential cathode materials in rechargeable batteries

Herein we report a novel series of conjugated polymers bearing stable nitroxide pendant groups for possible applications as cathode-active material in secondary batteries. The polymers comprise a 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) moiety immobilized on a poly(3,4-ethylenedioxythiophene) (PEDOT) backbone via ester groups (PEDOT-TEMPO P1 and PEDOT-diTEMPO P2). The multistep synthesis of the corresponding monomers and their chemical characterization are described. Furthermore, oxidative electrochemical and chemical polymerization were performed in order to synthesize polymers on gram-scale for battery tests and to investigate their electrochemical behaviour, respectively. In addition, the electrochemical properties of polymer P1 were studied by potentiodynamic and galvanostatic methods. The results demonstrate that the as-synthesized nitroxide radical polymers showed an electrochemically reversible redox reaction of the TEMPO radicals at 3.5 V vs Li/Li+. When used as cathode material in galvanostatic cycling tests, P1 exhibited a moderate initial specific capacity of 47 mA h g−1 (62% of the theoretical capacity) which slowly fades to 38 mA h g−1 within 50 cycles.