The Study of the Degree of Crystallinity, Electrical Equivalent Circuit, and Dielectric Properties of Polyvinyl Alcohol (PVA)-Based Biopolymer Electrolytes.

Shujahadeen B Aziz,Ayub S Marf,Elham M A Dannoun,Mohamad A Brza,Ranjdar M Abdullah

doi:10.3390/polym12102184

Shujahadeen B Aziz, Ayub S Marf + Show 3 more

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https://doi.org/10.3390/polym12102184

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This report presents a facile and efficient methodology for the fabrication of plasticized polyvinyl alcohol (PVA):chitosan (CS) polymer electrolytes using a solution cast technique. Regarding characterizations of electrical properties and structural behavior, the electrochemical impedance spectroscopy (EIS) and X-ray diffraction (XRD) are used, respectively. Crystalline peaks appear in the XRD pattern of the PVA:CS:NH4I while no peaks can be seen in the XRD pattern of plasticized systems. The degree of crystallinity is calculated for all the samples from the deconvoluted area of crystalline and amorphous phases. Considering the EIS measurements, the most conductive plasticized system shows a relatively high conductivity of (1.37 × 10−4) S/cm, which is eligible for applications in energy storage devices. The analysis of the EIS spectra reveals a decrease in bulk resistance which indicates an increase in free ion carriers. The electrical equivalent circuit (EEC) model is used in the analysis of EIS plots. Dielectric properties are modified with the addition of glycerol as a plasticizer. It is proved that the addition of glycerol as a plasticizer lowers ion association. It also shows, at the low-frequency region, a large value of a dielectric constant which is correlated with electrode polarization (EP). The distribution of relaxation times is associated with conducting ions.

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Solid polymer-based electrolytes as promising electrolytes have increased the awareness of numerous research groups due to the extensive utilization of these advanced materials in electrochemical energy devices; for example, in supercapacitors, dye-sensitized solar cells, fuel cells, and high energy solid-state batteries [1,2]
This study showed, as the 50 wt.% of polyvinyl alcohol (PVA) was blended with 50 wt.% of CS, the intensity of the diffraction peaks decreased and broadened
PVA-CS-NH4 I glycerol-based plasticized electrolytes were successfully fabricated via the solution cast technique

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Introduction

Solid polymer-based electrolytes as promising electrolytes have increased the awareness of numerous research groups due to the extensive utilization of these advanced materials in electrochemical energy devices; for example, in supercapacitors, dye-sensitized solar cells, fuel cells, and high energy solid-state batteries [1,2]. Polymers 2020, 12, 2184 that makes SPEs hard to utilize on a large scale is the relatively low ionic conductivity at ambient temperatures [6,7]. Polymer electrolytes are hosts for ion carriers while conductive polymers such as polyaniline (PANI) are hosts for electron carriers [12]. Polymer electrolyte ions are responsible for conduction [9,10,11], while in PANI electrons are sources for conduction [12]. The synthetic or man-made polymers can be synthesized from relatively low molecular weight compounds such as monomers, for example, polystyrene and polyethylene. The natural polymers can be obtained from natural resources just by modifications, for instance, rubber (Hevea), which is known as a polyisoprene in its synthetic form [13]

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