Identification and quantification of the distributed capacitance and ionic resistance in carbon-based supercapacitors using electrochemical techniques and the analysis of the charge-storage dynamics

[Display omitted] •A theoretical analysis was presented to understand the distributed capacitance and resistance in supercapacitors in the time domain.•The porous electrode behavior was characterized by two different time constants.•The dynamics of the charge-storage process were verified to occur in different ways at low and long polarization times.•It was verified a connection between the outer and inner surface areas and the charge-storage mechanism in supercapacitors. This study reports the in-situ characterization of nanosized carbon-based electrodes to identify and quantify the distributed capacitance and resistances verified in the time domain during the charge-storage process in aqueous-based symmetric coin cells. A theoretical model was proposed to represent the electrochemical response considering the presence of the so-called ‘inner’/internal and ‘outer’/external surface regions. The derivative analysis of the galvanostatic findings revealed the presence of two distinct voltage plateaux that were ascribed to the progressive assessment of the ‘outer’ and ‘inner’ surface regions by the ionic species. For the first time, it was demonstrated a connection between the heterogeneous surface nature of carbon electrodes and the charge-storage process in supercapacitors where different charge-storage dynamics regarding the migration of the ionic species can be identified due to the progressive transfer of ions from the ‘outer’ to the ‘inner’ surface regions as a function of the polarization time. The synthesized carbon materials were ex-situ characterized by scanning electron microscopy, Raman, and X-ray photoelectron spectroscopies. Specifically, the surface-modified MWCNTs allowed us to focus on a fundamental approach for studying the overall capacitance characteristics of nanostructured carbon-based electrodes. Thus, the charge-storage mechanism in the time domain and the individual contribution of the pseudocapacitance in the frequency domain were studied to clarify the real electrochemical behavior exhibited by porous carbon-based electrode materials.