Synthesis, characterization, and charge/discharge properties of polynorbornenes carrying 2,2,6,6-tetramethylpiperidine-1-oxy radicals at high density

TEMPO-containing norbornene monomers 1-8 (TEMPO = 2,2,6,6-tetramethylpiperidine-1-oxy) were synthesized and polymerized via ring-opening metathesis using a ruthenium-carbene catalyst. The TEMPO moiety did not inhibit the polymerization, and the monomers gave corresponding polymers in good to high yields. Poly(2) and poly(3) were soluble in common solvents and possessed high molecular weight, while other polymers were insoluble. The resulting polymers were thermally stable up to ca. 240 degrees C according to TGA measurements in air. In the case of poly(1)-poly(3), the charge/discharge capacities of the polymer-based cells were largely dependent on the spatial arrangement of the two TEMPO moieties on each repeating unit. Quite interestingly, the capacity of the poly(2)-based cell reached its theoretical value (109 A h/kg), and a large capacity (> 90 A h/kg) was retained even at high current densities up to 6 A/g, indicating the possibility of very fast charging (within 1 min). The cells utilizing the present polymers as cathode-active materials demonstrated excellent cycle life; e.g., the discharge capacities of poly(2) and poly(3) showed no more than 10% decrement even after 400 cycles.