Electrochemical Preparation of Porous Poly(3,4-ethylenedioxythiophene) Electrodes from Room Temperature Ionic Liquids for Supercapacitors

Abstract

Poly(3,4-ethylenedioxythiophene) (PEDOT) electrodes were prepared using current pulse method from different room temperature ionic liquids electrolytes (1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMI][TFSI]), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMI][BF4]), 1-allyl-3-(2-methoxyethyl)-imidazolium bis(trifluoromethylsulfonyl)imide ([AMO][TFSI]), and organic solution (0.1 M LiClO4 in acetonitrile)). The SEM and XPS studies show that the PEDOT films electropolymerized in [BMI][BF4] are highly porous and have a higher anion doping level than those electropolymerized in [BMI][TFSI], [AMO][TFSI], and LiClO4/ACN electrolytes. The electrochemical performance of the symmetrical supercapacitor based on PEDOT electrodes were investigated in 0.1 M KClO4 aqueous electrolyte by cyclic voltammetry and galvanostatic charge-discharge test. The PEDOT electrodes prepared from ionic liquids exhibit higher capacitative performance than those prepared from conventional solvent (ACN). Especially, the PEDOT electrodes prepared from a [BMI][BF4] ionic liquid exhibited high specific capacitance (191 F/g) with an obvious improvement in energy density and power density as comparison to the PEDOT electrodes prepared from ACN solution (100 F/g) in aqueous electrolyte. The symmetrical supercapacitor based on PEDOT electrodes prepared from [BMI][BF4] ionic liquid shows maximum specific energy of 5.37 Wh/Kg and good cycle durability. This study shows using ionic liquids as electrolytes for preparing PEDOT electrodes is an efficient way to improve performance of supercapacitors.