Premium
Structural, thermal, and dielectric properties of porous PVDF / Li 4 Ti 5 O 12 nanocomposite membranes for high‐power lithium‐polymer batteries
Author(s) -
Nasrallah Doaa A.,
ElMetwally Essam G.,
Ismail Ahmed M.
Publication year - 2021
Publication title -
polymers for advanced technologies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.61
H-Index - 90
eISSN - 1099-1581
pISSN - 1042-7147
DOI - 10.1002/pat.5171
Subject(s) - materials science , nanocomposite , dielectric , polymer , polymer nanocomposite , lithium (medication) , ionic conductivity , composite material , polyvinylidene fluoride , thermal stability , analytical chemistry (journal) , chemical engineering , electrode , organic chemistry , chemistry , medicine , optoelectronics , engineering , electrolyte , endocrinology
Polymer nanocomposites consisting of materials such as ionic polymers and nano‐ceramic fillers are widely used in high‐power lithium‐polymer batteries because of their high ionic conductivity, good mechanical strength, electrothermal stability, and better compatibility with electrodes. Nanocomposite films of polyvinylidene fluoride (PVDF)/lithium titanium oxide Li 4 Ti 5 O 12 (LTO) with different volume fractions of LTO nanoparticles (NPs) are prepared via casting method. The DSC thermograms revealed a slight decrease in the melting temperature T m and a noticeable reduction in the degree of crystallinity with increasing the volume fraction of LTO. This decrease is confirmed by the increment in the relative fraction of β‐phase in the PVDF matrix calculated from both XRD and FTIR. SEM images indicated the growth of porous globular structures in the presence of LTO NPs. Besides, the hydrophilicity of PVDF is improved by incorporating LTO NPs. The dielectric constant ε ′( ω ) , loss ε ″( ω ) , ac conductivity σ ac ( ω ) , complex impedance Z * ( ω ) , and Nyquist plots of PVDF/LTO nanocomposites are investigated in the temperature range from 303 to 413 K and frequency range from 100 Hz to 1 MHz. The σ ac ( ω ) and frequency exponent s are found to obey the correlated barrier hopping model. Values of the frequency exponent s and the charge carriers binding energy W m for the studied nanocomposite films decrease with rising temperature and LTO addition. Furthermore, dielectric constant ε ′( ω ) , loss ε ″( ω ) , and ac electrical conductivity σ ac ( ω ) of films are found to be strongly frequency and temperature dependent. The localized states density N ( E F ) at the Fermi level increase with increasing temperature and LTO NPs volume fraction, resulting in the W m decrease and the enhancement of the ac electrical conductivity σ ac ( ω ) . The impedance spectrum and Nyquist plots provide an insight into the influence of LTO vol% in the resistive and capacitive characteristics of PVDF/LTO films. These results recommend the choice of LTO NPs as dopants to enhance the electrical properties of the PVDF matrix to be used in high‐power lithium‐ion batteries and electronic devices.