Proposal of a novel methodology for the electrochemical characterization of well-behaved redox-active materials used in supercapacitors

Author(s)

Da Silva, Leonardo M. ; De Sousa, Lindomar G. ; Vicentini, Rafael ; Aguiar, Joao Pedro ; Doubek, Gustavo ; Zanin, Hudson

• Document type: Journal article
• Source: Electrochimica Acta; v. 457, p. 15-pg., 2023-05-01.

Abstract

This work presents a new methodology to interpret the electrochemical behavior of pseudocapacitors (PCs) which is based on a new theoretical approach denoted as the generic electrochemical model (GE). Based on a single premise, the GE model is composed of two distinct time constants (tau = RC) used to represent the narrow-deep (n-d) and large-shallow (l-s) heterogeneous surface structures incorporating the different surface defects (e.g., cracks, fissures, pores, etc.), which incurs in the so-called distributed capacitance and resistance phenomena. Five different transition metal oxide (TMO) electrodes composed of Ni, Co, and Ru were used to verify the validity of the proposed model equations. The internal (inner) and external (outer) capacitances and resistances were accurately determined from the fitting analysis (e.g., r2 >= 0.998 and chi 2 < 10-5) involving the findings obtained using different techniques. Therefore, disagreements between the electrochemical techniques regarding the resistance and capacitance absolute values were ascribed to different average penetration depths intrinsic to each particular perturbation function, i.e., each electrochemical technique exhibits a particular sensitivity for detecting the capacitive and resistive phenomena in porous/defective electrodes. We verified for well-behaved PCs, where the so-called battery-like behavior is absent, that capacitive and pseudocapacitive phenomena are indistinguishable phenomena, as predicted by Save`ant and Conway. Therefore, the GE model can also be used for studying different carbon-based materials used in supercapacitors. Finally, the presence of different surface heterogeneous structures present in defective electrodes is the main cause of the distributed capacitance and resistance verified in both time and frequency domains. (AU)

• FAPESP's process: 17/11958-1 - CINE - Advanced Energy Storage Division
• Grantee: Rubens Maciel Filho
• Support Opportunities: Research Grants - Research Centers in Engineering Program
• FAPESP's process: 18/20756-6 - Pseudocapacitors from metal oxides and activated carbon composites
• Grantee: Willian Gonçalves Nunes
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 14/02163-7 - Development of supercapacitors devices from graphene, carbon nanotubes and diamonds
• Grantee: Hudson Giovani Zanin
• Support Opportunities: Research Grants - Young Investigators Grants