Effect of Structural Features on Ionic Conductivity and Dielectric Response of PVA Proton Conductor-Based Solid Polymer
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https://doi.org/10.1007/s11664-020-08577-x Ó 2020 The Minerals, Metals & Materials Society
ORIGINAL RESEARCH ARTICLE
Effect of Structural Features on Ionic Conductivity and Dielectric Response of PVA Proton Conductor-Based Solid Polymer Electrolytes MARYAM A.M. SAEED1 and OMED GH. ABDULLAH
2,3
1.—Department of Physics, College of Science, University of Mosul, Mosul 41002, Iraq. 2.—Advanced Materials Research Laboratory, Department of Physics, College of Science, University of Sulaimani, Kurdistan Region 46001, Iraq. 3.—e-mail: [email protected]
In this study, the effect of structure on the ionic conductivity and dielectric response of polyvinyl alcohol solid polymer electrolyte films doped with ammonium nitrate (NH4NO3) was investigated. Structural studies show that the solid polymer electrolytes in a suitable salt ratio enhance the amorphous fraction of the host matrix and facilitate the fast movement of H-ions, resulting in the enhancement of electrical conductivity. The highest ionic conductivity at room temperature (5.17 9 105 S/cm) was achieved by incorporating 30 wt.% of NH4NO3, which shows the maximum ion dissociation in the host matrix due to ion–polymer interaction. The reduction in the ionic conductivity at higher salt concentrations (above 30 wt.%) is the consequence of a decrease in the carrier concentration and its movement, respectively, due to the formation of ion pairs and a reduction in the amorphous fraction of the system. A broad asymmetric peak of the imaginary part of the electrical modulus suggests a temperature-dependent non-Debye relaxation process for the present system. Key words: Solid polymer electrolytes, proton conductor, ionic conductivity, electrical modulus
INTRODUCTION Solid polymer electrolyte (SPE) materials have garnered considerable attention for potential use in various electrochemical energy storage devices. The primary advantages of SPEs include low cost, light weight, exceptional safety, high flexibility, stability, dimensionality, durability, and easy preparation methods.1–3 However, the main limitation of SPE is associated with its low ionic conductivity, especially at ambient temperature. Intensive research efforts have been devoted by numerous research groups to improve the ionic conductivity of different SPEs at room temperature by enhancing the amorphous fraction of the host polymer matrix.4–10 Most of the preceding studies have used lithium salts
(Received May 10, 2020; accepted October 20, 2020)
with a different polar polymer matrix to achieve SPEs with maximum ionic conductivity.11 However, the lower lattice energy of SPEs containing ammonium salts, compared to electrolytes in the presence of alkali metal salts, motivates us and many other researchers to study the SPE system based on different ammonium salts.12 Polyvinyl alcohol (PVA) is a hydrophilic synthetic polymer with a carbon chain backbone attached to many hydroxyl (OH) groups. The SPE based on PVA incorporated with ammonium nitrate (NH4NO3) salt leads to the formation of ion–polymer com
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