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Pseudocapacitors from metal oxides and activated carbon composites

Grant number: 18/20756-6
Support type:Scholarships in Brazil - Doctorate
Effective date (Start): May 01, 2019
Effective date (End): April 30, 2022
Field of knowledge:Engineering - Electrical Engineering
Principal Investigator:Hudson Giovani Zanin
Grantee:Willian Gonçalves Nunes
Home Institution: Faculdade de Engenharia Elétrica e de Computação (FEEC). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
Associated research grant:14/02163-7 - Development of supercapacitors devices from graphene, carbon nanotubes and diamonds, AP.JP

Abstract

The manufacture of supercapacitors (SC) or electrochemical capacitors (CE), which store large amounts of energy in a reversible way and allow their rapid release to electrical systems, is of paramount importance in the avant-garde research, since these devices are essential auxiliary elements for use in modern electric vehicles. The SC / CE can be classified according to the type of process responsible for energy storage: (i) electric double layer electrochemical capacitors (EDLCs) based on the charge / discharge of the electric double layer formed at the electrode / electrolyte interface (non-faradáico process) and (ii) electrochemical pseudocapacitors (EPCs), based on the pseudocapacitance derived from solid state redox reactions (faradáico process). Normally, it is noted that the EPCs, although costingmore expensive, they exhibit a higher specific capacitance (F g-1) when compared to EDLCs. In this context, the use of nanostructured composites composed of mixed oxides containing Ni and Co supported on highly rugged / porous carbon substrates (eg, carbon felt, carbon nanotubes, etc.) may result in high performance electrode materials for process of energy storage. In the present study, the electrodes will be obtained by electrodeposition of the Ni and Co metals in an aqueous medium, in different proportions (Ni: Co ratio), on different carbon substrates, followed or not by the heat treatment process. This synthesis process aims to obtain nanometric structures, such as NiCo2O4 spinel with different nanoarchitectures, which provide a high electrochemically active area for the energy storage process. The 'specific capacitance' values, the symmetry of the charge / discharge curves as well as the longevity during the cycling process (charge / discharge cycles) will be valued on alkaline electrolytes as well as on a 'solid polymer electrolyte' (Nafion membrane of DuPont), in order to elucidate the fundamental aspects responsible for the load storage process, that is, the behavior of the double electric layer in the presence of the pseudocapacitance phenomenon.The properties of the composite materials containing carbon and Ni and Co oxides will be investigated and compared using different in situ (electrochemical) and 'ex situ' (spectroscopic) characterization techniques, with special emphasis on the use of cyclic voltammetry ) to determine the Morphology Factor (j) and Electrochemical Porosity (f). Electrochemical Impedance Spectroscopy (EIS) will be used as a complementary technique to investigate the resistive and capacitive behaviors inherent to SC / CE.