Synthesis and characterization of sodium ion conducting solid polymer electrolytes based on poly (ethylene oxide)
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Date
2015
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Uva Wellassa University of Sri Lanka
Abstract
Developments of novel ion conducting materials for energy storage devices are presently
receiving much attention due to demand of energy. Among different strategies, polymer based
solid electrolytes have several advantages such as light weight, flexibility and absence of leakage
of electrolyte, compared to the conventional liquid electrolytes (Gray, F. M., 1991). In this work,
synthesis of poly (ethylene oxide) (PEO) based sodium ion conducting electrolytes and
characterization them using complex impedance spectroscopy, polarization microscopy, and FTIR
spectroscopy are discussed.
Methodology
The polymer electrolytes were synthesized using common solvent casting method. Prior to use,
PEO and salt (NaClO4) were vacuum dried at 50 °C and 120 °C respectively. Appropriate
quantities of PEO and NaClO4 were mixed keeping the oxygen to Na molar ratios as n:1, where
n=80, 60, 50, 40, 30, 20, and 15. Mixtures were dissolved in acetonitrile and stirred well for 24hrs
at room temperature and the slurry was cast on a Teflon support. Prior to take measurements, the
prepared electrolyte films were vacuum dried over 24 hrs. In order to study the temperature
dependence of ionic conductivity, the complex impedance measurements were carried out. The
surface morphology and polymer-salt interactions of some selected samples have been studied
using polarization microscopy and FTIR spectroscopy respectively.
Results and Discussion
The temperature dependence of ionic conductivity for the solid polymer electrolytes (PEO)n
NaClO4 (n=80, 60, 50, 40, 30, 20, and 15) is shown in Figure 01(A). It is clear from this figure
that the electrolyte (PEO)20NaClO4 shows the highest ionic conductivity at room
temperature(25 °C). The room temperature conductivity of the sample (PEO)20 NaClO4 is
S cm . The plots of the variation of conductivity versus Na /PEO molar ratios at
various temperatures (conductivity isotherms) is shown in Figure 01(B). These results also indicate
the highest ionic conductivity for the sample (PEO)20NaClO4 for different temperatures.
A closer inspection of the curves of Figure 01(A) reveals that the semi-crystalline to amorphous
phase transition occurs around 60 °C and that a much greater conductivity enhancement occurs in
the crystalline phase compared to that of amorphous phase. The crystalline to amorphous phase
transition of the samples (PEO)nNaClO4 (n=80, 60, 50, 40, and 30) is much more visible compared
to the samples of (PEO)15NaClO4 and (PEO)20NaClO4 and transition has almost disappeared
for those two samples. This is revealed that the ionic conductivity of electrolytes (PEO)15NaClO4
and (PEO)20NaClO4, does not follow the Arrhenius type but Vogel-Tamman- Fulcher (VTF)
behavior indicating their amorphous nature (Pitawala et al., 2007).
Description
Keywords
Science and Technology, Technology, Polymer Science, Power System, Electronic Engineering