Banca de DEFESA: JOSE LUIZ DE SOUZA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : JOSE LUIZ DE SOUZA
DATE: 14/04/2023
TIME: 08:30
LOCAL: https://meet.google.com/wgo-qnzc-pob
TITLE:

SYNTHESIS OF V2O5 THROUGH MICROWAVE RADIATION WITH POTENTIAL APPLICATION IN LITHIUM-ION BATTERIES

KEY WORDS:

Vanadium Oxide, Hydrotermal, Microwave, Synthesis

PAGES: 76
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Química Inorgânica
SUMMARY:

Due to the greater demand for lithium-ion batteries, low-cost cathode materials with high energy density have been extensively investigated. In this scenario, V2O5 deserves to be highlighted, as it has a theoretical specific energy of 294 mAhg-1, which is superior to some popularly used cathode materials. In this work, the purpose was to obtain structures of V2O5by different syntheses. In the first, vanadium oxidewas obtained by hydrothermalsynthesisusing ammoniummetavanadate, NH4VO3, asa precursor. Characterization studies indicated the formation of orthorhombic V2O5with a crystalline structure. Morphological characterizations showed a compact, heterogene ousand not very porous structure. This fact may help to explain the low electrochemical stability in the charging and discharging processes after successive cycles, as demonstrated by cyclic voltammetry analyses. In order to evaluate the influence of inserting conductive polymers in the V2O5 matrix on the electrochemical response, polyaniline and polyethylene oxide were intercalated in the oxide. Despite observing the presence of polymers in the inorganic matrix, there was no improvement in the electrochemical response of the hybrid materials compared to the matrix, even though the total charge was more stable. In the second synthesis, orthorhombic V2O5, evidenced by the XRD analysis, was obtained by heating assisted by domestic microwaver adiation, using V2O5 inpure powder, commercial, as precursor. For the oxide obtained via domestic microwave synthesis in an open system, the XRD analyzes showed data consistent with the layered structures of V2O5.nH2O. Absorption bands were observed at frequencies corresponding to the presence of water molecules in the vanadium pentoxide structure. The SEM images suggested a more compact and heterogeneous morphology, which helps to explain the weak structural stability of the product observed from the cyclic voltammetry tests,in which it was not possible to observe well-defined cathode and anode peaks.On the other hand, the SEM images of the material synthesized for 20 min under the action of domestic microwave radiation in a closed system, at a power of 20% of the equipment, showed a material with a homogeneous, por ousand uniform structure. From the cyclic voltammograms it was possible to observe good electrochemical stability and cyclability, in addition to a practically constant total charge during 100 charge and discharge cycles. These results indicate that the V2O5 obtained by microwave radiation in a closed system has a potential for applicability as a cathode in lithium ion batteries.

BANKING MEMBERS:
Interno - 1444161 - DANE TADEU CESTAROLLI
Presidente - 1742429 - ELIDIA MARIA GUERRA
Interna - 2434901 - HOSANE APARECIDA TAROCO
Externo à Instituição - LUCIANO NADREY MONTORO - UFMG
Externo à Instituição - TULIO MATENCIO - UFMG