Electropolymerized Porous Conjugated Polymer Film as an Electrode for a Stable, High Energy Density Thin Film Asymmetric Supercapacitor

A novel π-conjugated monomer tert-butyl 3,8-di([2,2′-bithiophen]-5-yl)-6- oxophenanthridine-5(6H)-carboxylate (PNBTH-Boc) with a labile side chain was synthesized. The monomer was electropolymerized to form redox-active polymer (Poly-PNBTH-Boc) on the current collector. The labile side chains on the polymer were then removed by thermal annealing, resulting in the porous electroactive film (Poly-PNBTH). The annealed polymer exhibited a stable oxidation process and high specific areal capacitance. Asymmetric supercapacitors were fabricated with the polymer as the positive electrode and vertically aligned carbon nanotubes as the negative electrode. The supercapacitor exhibited outstanding cyclability with 85% capacitance retention after 10 000 cycles. The thin film supercapacitor device demonstrated an energy density of 23.5 μWh/cm2 and a power density of 14 mW/cm2.