Journal
JOURNAL OF ENERGY STORAGE
Volume 31, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.est.2020.101583
Keywords
Operando supercapacitor analysis; Raman; XRD synchrotron; Manganese oxide; Nickel hydroxide
Categories
Funding
- CNPq [301486/2016-6]
- FAPESP [2018/20756-6, 2016/25082-8, 2017/11958-1, 2014/02163-7]
- CAPES [1740195]
- Fundacao ao Amparo a Pesquisa do Estado de Minas Gerais - FAPEMIG [CEX-112-10]
- Secretaria de Estado de Ciencia, Tecnologia e Ensino Superior de Minas Gerais - SECTES/MG
- Conselho Nacional de Desenvolvimento Cientifico e Tecnologico - CNPq (PQ-2 grant)
- ANP (Brazil's National Oil, Natural Gas and Biofuels Agency)
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We report on the synthesis, characterization of nickel hydroxide and manganese oxide nanoparticles decorating multiwalled carbon nanotubes composite material, and electrochemical performance for energy storage pro-cesses in symmetric electrochemical capacitors. A large pseudocapacitive voltage range of 1.7 V is presented using a coin cell containing a 1.0 M Li2SO4 aqueous solution, resulting in a maximum specific capacitance of 420 F g(-1) verified at 1.67 A g(-1) during the discharge process. The symmetric coin cell was highly stable with a very high coulombic efficiency of 99% even after 70,000 cycles of charge-discharge. The high electrochemical stability of coin cell was attributed to a synergism between the nanostructured carbon support and metal (hydr) oxides nanoparticles, i.e., the transport of electrons and ions across the porous electrode structure enables with a high degree of reversibility for the solid-state redox transitions reactions, which is the main contribution to the whole electrode specific capacitance. Near-surface structural changes of the electrodes were monitored during dynamic polarization by Raman and XRD synchrotron measurements. The presence of the active Ni-O stretching mode was verified during the charge-discharge processes according to the reversible solid-state redox process. The Raman shifts were also correlated with the reversible intercalation-deintercalation processes of Li+-ions into the MnOx host material, as well as reversible adsorption of solvated ions on the surface defects of carbon nanostructures.
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