A comprehensive study about the influence of pore structures of carbon-based electrode materials on the charge-storage processes of water-in-salt based supercapacitors

• Published in: Journal of energy storage 2023-06, Vol.62, p.106858, Article 106858
• Main Authors: Pinzón C., Manuel J., de Aquino, José M., Freitas, Renato G., Pereira, Gabriel A., Da Silva, Leonardo M., Zanin, Hudson
• Format: Article
• Language: English
• Subjects: Carbon materials; Distributed capacitances; Double-Channel transmission line model; Supercapacitors; Water-in-salt electrolytes
• ISSN: 2352-152X; 2352-1538
• DOI: 10.1016/j.est.2023.106858

This work presents a comprehensive study involving water-in-salt electrolytes (WiSE) and carbon-based electrodes to evaluate the influence of pore structures on the charge-storage process using different techniques. A possible explanation for the influence of WiSE concentration on the working voltage window was presented considering the influence of electrical double-layer structure on the kinetic parameters present in Butler-Volmer and Marcus' theories. Chronoamperometric analysis unambiguously permitted identifying two-time constants attributed to the inner and outer active surface areas. Impedance data confirmed the porous electrode behavior. The experimental findings were interpreted using a double-channel transmission line model incorporating the transport anomalies exhibited by the ionic and electronic conductors and the dispersive capacitance effects. In addition, the tortuosity factor was used to evaluate the charge-storage behavior as a function of the WiSE concentration. Derivative analysis of the galvanostatic findings yielded relevant information about the charge dynamics in different pores. The charge-storage dynamics strongly depend on the pore-size distribution and experimental polarization conditions, as in the scan potential/voltage rate, applied voltage step, and specific current used in the galvanostatic experiments. Internal consistency for the experimental findings was verified through an interpretation of the different electrochemical data. The use of complementary techniques to obtain a more consistent analysis of the electrochemical behavior exhibited by complex electrode materials used in different energy storage devices was particularly stressed. The interaction of WiSE electrolytes with different electrodes based on micro and mesoporous carbons allows an increase of stored energy due to the extension of the working voltage window, generated in turn by creating a solvent-blocking interface in highly concentrated electrolytes. [Display omitted] •In-depth electrochemical study of EDLC supercaps based on carbons with different porosities and electrolyte concentrations;•Rigorous evaluation of the working voltage window and the distributed capacitance;•Multiple techniques used for the evaluation of chemical, structural and textural properties of electrodes;•Raman and FTIR spectroscopies for structural characterization of electrolytes;•A clear relationship between electrolyte concentration, pore size distribution, and charge-storage dyn