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    Improved accessibility of porous carbon electrodes with surfactant ionic liquids for supercapacitors

    Year: 2019

    Journal: J. Appl. Electrochem., Volume 49, FEB, page 151–162

    Authors: Xu, Ningjin; Klein, Jeffrey M.; Huang, Phoebe; Alwusaydi, Huda A.; Mann, Elizabeth K.; Gurkan, Burcu E.

    Keywords: Anionic surfactant ionic liquid; Ion accessibility; Electrode wettability; Capacitance; Impedance

    Ionic liquids (ILs) are promising electrolytes for supercapacitors due to their wide electrochemical window. However, most ILs are viscous in nature and require diffusional and rotational transformations to access the pore space of common supercapacitor electrodes. In this study, novel anionic surfactant ILs (ASILs) are synthesized to lubricate the electrode surface to improve pore accessibility by IL ions. ASIL composition (0-10wt%) and temperature (22-150 degrees C)-dependent capacitances, as a measure of pore accessibility and wettability, are determined by cyclic voltammetry. 10wt% 1-butyl-1-methylpyrrolidinium docusate, [PYR14][AOT], in the base IL 1-propyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [PYR13][TFSI], exhibits the highest specific capacitance (202Fg(-1) at 150 degrees C and 10mVs(-1)), compared to [PYR13][TFSI] (160Fg(-1)). Electrochemical impedance spectroscopy measurements indicate resistive charging for ASIL/IL electrolyte compared to the base IL at 22 degrees C due to reduced conductivitya consequence of larger non-polar domains. However, at elevated temperatures (>100 degrees C), electrolyte resistance is circumvented as the viscosity is reduced. The wide voltage window of ILs and improved wettability by ASILs can be coupled to maximize energy storage capability of supercapacitors for high-temperature power applications. [GRAPHICS] .
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