High performance of supercapacitors containing an ionic liquid electrolyte by means of electrochemical and computational studies

R Venancio and DAC da Silva and LO Borges and IA Silva and LM Da Silva and G Doubek and LJA Siqueira and H Zanin, ELECTROCHIMICA ACTA, 535, 146569 (2025).

DOI: 10.1016/j.electacta.2025.146569

This study characterizes the electrochemical behavior of symmetric coin cells with AC-based electrodes filled with the ammonium-based ionic liquid, a promising supercapacitor electrolyte due to its large voltage window and ambient temperature operation. We employed cyclic voltammetry, single-step chronoamperometry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge techniques to evaluate the electrochemical performance of the supercapacitors thoroughly. Our findings highlight the quasi-rectangular current-voltage profile up to 3.6 V, beyond which a faradaic current due to electrolyte degradation becomes significant. These results revealed a minor faradaic component, with impedance analysis showing typical behavior of well-formed electrical double layers (EDLs), influenced by the unique properties of ionic liquids. We observed that the ion dynamics and capacitance behavior align well with theoretical models, particularly the Goodwin- Kornishev mean-field theory. The study underscores the potential of ionic liquid-based supercapacitors to achieve high performance, with specific capacitance values reaching similar to 2000 F g(-1) and great energy and power output, comparable to lithium-ion batteries. Molecular dynamics simulations further elucidated the charging mechanisms, ion migration, and structural interactions within the EDLs. These comprehensive insights validate the suitability of butyltrimethylammonium bis(trifluoromethylsulfonyl)imide N-1114NTf2 for advanced supercapacitor applications, highlighting its ability to deliver exceptional electrochemical performance under optimized conditions.

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