Banca de DEFESA: LARISSA APARECIDA TOLEDO COSTA MOUTINHO

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : LARISSA APARECIDA TOLEDO COSTA MOUTINHO
DATE: 19/08/2024
TIME: 13:30
LOCAL: https://meet.google.com/evo-truk-kyf
TITLE:

SYNTHESIS, CHARACTERIZATION AND ELECTROCHEMICAL STUDIES OF VO2 AND HYBRID COMPOUNDS CONTAINING VO2, CHITOSAN, POLYETHYLENE OXIDE AND POLYANILINE

KEY WORDS:

VO2, lithium ion batteries, intercalation, PEO, PANI, chitosan.

PAGES: 155
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Química Inorgânica
SUMMARY:

Due to the increase in electronic devices and forms clean energy alternatives, there has been an increase in demand for lithium-ion batteries. Thus, low-cost cathode materials and with high energy density have been investigated for such applications. Newer lithium-ion batteries use lithium-based cathodes transition metals as lithium ion insertion matrix. VO2 is considered a promising cathode material for ion batteries lithium, due to its high capacity and fast transfer rate ions. However, the development of VO2 is hampered by disadvantages of low electrical conductivity, low density of energy and low diffusion coefficient that make the search by new synthesis processes of this oxide is intermittent, as the insertion of conductive polymers. In this way, the present research aimed to obtain VO2 by hydrothermal synthesis at from V2O5 used as a precursor, and polymers, in different proportions of 1:1, 2.5:1 and 5:1 v/v, such as polyethylene oxide, polyaniline and chitosan. When evaluating the influence of interleaving conductive polymers in the VO2 matrix, hybrid compounds were synthesized and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, tests electrochemical cyclic voltammetry, charge variation and voltammetry square wave, spectroscopy tests in the visible region and bandgap studies. The XRD results demonstrate that a mixture of monoclinic VO2 (M) and (B) was obtained and the hybrid compounds showed variation in lamella displacement indicating a possible intercalation. The stretch and vibration bands indicate that the intercalation of polymers occurred in the matrix. The micrograph images show a difference between the microfilamentous VO2 and spongy surface of the VO2 interspersed with polymers in different v/v proportions. From cyclic voltammetry it was possible to observe both VO2 as VO2/polymers anodic and cathodic peaks linked to the redox process of the V(IV)/V(III) pair which, in turn, is derived from process of insertion/disinsertion of lithium ions in which each hybrid compound showed a different voltammetric profile. The total load curves as a function of cycles better demonstrate cycling stability and higher total load of hybrid compounds compared to VO2. Square wave voltammetry analyzes confirm the cyclic voltammetry results showing oxidation and reduction and charge transfer. The UV-Vis spectra show the absorptions that can be transitions of each material are assigned. Absorption in the region visible decreases for hybrid compounds in relation to VO2. The hybrid compounds presented lower bandgap values, compared to VO2 being more conductive. These results demonstrate that hybrid compounds have potential as cathode materials for lithium-ion batteries.

BANKING MEMBERS:
Interno - 1444161 - DANE TADEU CESTAROLLI
Presidente - 1742429 - ELIDIA MARIA GUERRA
Externo à Instituição - HERENILTON PAULINO OLIVEIRA - USP
Interna - 2434901 - HOSANE APARECIDA TAROCO
Externa à Instituição - VIVIENNE DENISE FALCAO - IFMG