Chemical polymerization of pyrrole with disulfide structure and the application to lithium secondary batteries

An intramolecular cyclic disulfide-containing polypyrrole was prepared by the chemical-oxidative polymerization of 4,6-dihydro-1H-[1,2]dithiino[4,5-c]pyrrole (MPY), and the electrical properties were investigated as the cathode active material in lithium secondary batteries. Oxidizing agents and solvents for the chemical-oxidative polymerization were examined to prevent over-oxidation of the polypyrrole backbone. The conductivity of poly(MPY), the polymer prepared using FeCl3 in ethylene glycol, was around 10−4 S/cm. Poly(MPY) showed very little over-oxidation, good redox properties, and a high discharge capacity of 398 mAh/g based on the redox response of the disulfide.