Banca de QUALIFICAÇÃO: LARISSA APARECIDA TOLEDO COSTA MOUTINHO

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : LARISSA APARECIDA TOLEDO COSTA MOUTINHO
DATE: 05/06/2023
TIME: 09:00
LOCAL: meet.google.com/adi-rtrz-xtt
TITLE:

VO2 SYNTHESIS AND INTERCALING REACTIONS FOR USE IN LITHIUM ION BATTERIES

KEY WORDS:

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

PAGES: 111
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Química Inorgânica
SUMMARY:

Due to the increase in electronic devices and alternative forms of clean energy, there has been an increase in demand for lithium-ion batteries. Thus, low-cost, high-energy-density cathode materials have been investigated for such applications. Newer lithium-ion batteries use transition metal-based cathodes as the lithium-ion insertion matrix. VO2 is considered a promising cathode material for LIBs due to its high capacity and fast ion transfer rate. However, the development of VO2 is hampered by the disadvantages of low electrical conductivity, low energy density and low diffusion coefficient, making the search for new synthesis processes for this oxide intermittent, such as the insertion of conductive polymers. Thus, the present research aimed to obtain VO2 by hydrothermal synthesis from V2O5 used as a precursor, and polymers, in different proportions of 1:1, 2.5:1 and 5:1 v/v, such as PEO, PANI and chitosan. By evaluating the influence of intercalation of conductive polymers on the VO2 matrix, the hybrid compounds were synthesized and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and electrochemical tests of cyclic voltammetry, variation of charge and square wave voltammetry. The XRD results demonstrate that the monoclinic VO2 was obtained and the hybrid compounds presented variation of lamella displacement indicating a possible intercalation. Stretching and vibration bands indicate that polymer intercalation has occurred in the matrix. The micrograph images show a difference of VO2 microfilament and spongy surface of VO2 interspersed with polymers in different v/v ratios. From cyclic voltammetry, it was possible to observe both anodic and cathodic peaks for both VO2 and VO2/polymers linked to the redox process of the VIV/VIII pair, which, in turn, is derived from the insertion/disinsertion process of lithium ions in which each hybrid composite showed a different voltammetric profile. The total load versus cycle curves demonstrates better cycling stability and higher total load of hybrid compounds compared to VO2. The square wave voltammetry analyzes confirm the results of cyclic voltammetry showing oxidation and reduction processes and charge transfer. These results demonstrate that hybrid compounds are candidates for cathode materials for lithium-ion batteries.

BANKING MEMBERS:
Externo à Instituição - HERENILTON PAULINO OLIVEIRA - USP
Presidente - 1444161 - DANE TADEU CESTAROLLI
Externa à Instituição - VIVIENNE DENISE FALCAO - IFMG