Optimization and Structural Analysis of a Gel Polymer Electrolyte Based on Polyacrylonitrile to be used for Na Batteries
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Date
2018
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Uva Wellassa University of Sri Lanka
Abstract
Today, an insurgence has arisen on non Li based batteries to meet the escalating
energy demand. Na, Mg, and Zn are some of the suggested alternatives.
Simultaneously, attention was focused on replacing liquid electrolytes due to their
inherent drawbacks such as leakage, evaporation and high reactivity. One solution is
employing quasi solid state gel polymer electrolytes (GPEs). Main objective of this
study is preparing, optimizing and structural analyzing of a GPE to be used for Na
batteries. GPE based on polyacrylonitrile (PAN) was prepared using the salt sodium
thiocyanate (NaSCN) and the solvents, ethylene carbonate (EC) and propylene
carbonate (PC). Materials were heated and the resultant was pressed between two
glass plates to obtain a thin film. This procedure was repeated varying the polymer
and the salt concentrations. The composition was fine tuned to obtain the highest
room temperature conductivity. The structure analysis was done using X Ray
Diffraction (XRD) technique. XRD measurements were carried out for two samples
— with and without salt. The highest conductivity observed was 1.92 x 10-3
S cm-1
from the sample 202.5 PAN: 500 EC: 500 PC: 35 NaSCN (weight basis). When the
polymer concentration was increased, conductivity increased first. However, further
increase of polymer reduced the conductivity. This may be a result of interplay
between dissociation of ion pairs and viscosity of the medium. Similarly, amount of
charge carriers and their mobility governs the conductivity and results an optimum
conductivity at a particular salt concentration. XRD results clearly suggest that
crystalline phase in the PAN: EC: PC structure diminishes upon addition of the salt.
It implies that the GPE is in amorphous phase and based on the conductivity value,
it is suitable to be employed for Na rechargeable batteries.
Keywords: Gel polymer electrolytes, X Ray Diffraction, Polyacrylonitrile, Sodium batteries
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Materials Sciences, Mineral Sciences