Stable Deep Doping of Vapor-Phase Polymerized Poly(3,4-ethylenedioxythiophene)/Ionic Liquid Supercapacitors

Liquid-solution polymerization and vapor-phase polymerization (VPP) have been used to manufacture a series of chloride- and tosylate-doped poly(3,4-ethylenedioxythiophene) (PEDOT) carbon paper electrodes. The electrochemistry, specific capacitance, and specific charge were determined for single electrodes in 1-ethyl-3-methylimidazolium dicyanamide (emim dca) ionic liquid electrolyte. VPP-PEDOT exhibits outstanding properties with a specific capacitance higher than 300Fg(-1), the highest value reported for a PEDOT-based conducting polymer, and doping levels as high as 0.7charges per monomer were achieved. Furthermore, symmetric PEDOT supercapacitor cells with the emim dca electrolyte exhibited a high specific capacitance (76.4Fg(-1)) and high specific energy (19.8Whkg(-1)). A Ragone plot shows that the VPP-PEDOT cells combine the high specific power of conventional (pure) capacitors with the high specific energy of batteries, a highly sought-after target for energy storage.