Charge-storage mechanism of highly defective NiO nanostructures on carbon nanofibers in electrochemical supercapacitors

Author(s)

Nunes, Willian G. ^[1] ; Miranda, Andre N. ^[2] ; Freitas, Bruno ^[1] ; Vicentini, Rafael ^[1] ; Oliveira, Aline C. ^[3] ; Doubek, Gustavo ; Freitas, Renato G. ^[3] ; Da Silva, Leonardo M. ^[4] ; Zanin, Hudson ^[1]

Affiliation

^[1] Univ Estadual Campinas, Sch Elect & Comp Engn, Carbon Sci Tech Labs, Ctr Innovat New Energies, Adv Energy Storage Div, Av Albert Einstein 400, BR-13083852 Campinas, SP - Brazil

^[2] Univ Estadual Campinas, Sch Chem Engn, Lab Adv Batteries, Ctr Innovat New Energies, Adv Energy Storage Div, Av Albert Einstein 500, BR-13083852 Campinas, SP - Brazil

^[3] Univ Fed Mato Grosso, Lab Computat Mat, Dept Chem, ICET UFMT, BR-78060900 Cuiaba, MT - Brazil

^[4] Fed Univ Jequitinhonha Mucuris Valley, Lab Fundamental & Appl Electrochem, Dept Chem, Rodovia MGT 367, Km 583, 5000 Alto da Jacuba, BR-39100000 Diamantina, MG - Brazil

• Document type: Journal article
• Source: NANOSCALE; v. 13, n. 21, p. 9590-9605, JUN 7 2021.
• Web of Science Citations: 0

Abstract

An electrode composed of highly defective nickel oxide (NiO) nanostructures supported on carbon nanofibers (CNFs) and immersed in an Li+-based aqueous electrolyte is studied using Raman spectroscopy under dynamic polarization conditions to address the charge-storage phenomenon. By this operando technique, the formation of Li2SO4 center dot H2O during the discharge process is verified. At the same time, we observed the phase transformation of NiO to NiOOH. The Ni(OH)(2)/NiOOH redox couple is responsible for the pseudocapacitive behavior with intercalation of cationic species in the different Ni structures. A `substitutive solid-state redox reaction' is proposed to represent the amphoteric nature of the oxide, resulting in proton intercalation, while the insertion of Li+ occurs to a less extent. The electrode material exhibits outstanding stability with 98% coulombic efficiency after 10 000 charge-discharge cycles. The excellent electrode properties can be ascribed to a synergism between CNFs and NiO, where the carbon nanostructures ensured rapid electron transport from the hydrated nickel nanoparticles. The NiO@CNF composite material is a promising candidate for future applications in aqueous-based supercapacitors. DFT simulation elucidates that compressive stress and Ni-site displacement lead to a decrease up-to 3.5-fold on the electron density map located onto the Ni-atom, which promotes NiO/Ni(OH)(2)/NiOOH transition. (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