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

This work presents a comprehensive study involving water-in-salt electrolytes (WiSE) and carbon-based elec-trodes 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.