Impact of low viscosity ionic liquid on PMMA-PVC-LiTFSI polymer electrolytes based on AC -impedance, dielectric behavior

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urairaj Department of Mechanical and Material Engineering, Faculty of Engineering & Science, Universiti Tunku Abdul Rahman, Setapak, 53300 Kuala Lumpur, Malaysia (Received 31 July 2012; accepted 2 August 2012)

The preparation of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BmImTFSI)based poly(methyl methacrylate)–poly(vinyl chloride), PMMA–PVC, gel polymer electrolytes was done by solution casting technique. The ionic conductivity of gel polymer electrolytes was increased, up to a maximum value of (1.64 6 0.01)  104 S/cm by adding 60 wt% of BmImTFSI. Conductivity–frequency dependence, dielectric relaxation, and dielectric moduli formalism were also further analyzed. These studies assert the ionic transportation mechanisms in the polymer matrix. Occurrence of polarization electrode–electrolyte interface is also observed. This leads to the formation of electrical double layer and hence indicates the non-Debye characteristic of the polymer matrix in the dielectric studies. Based on the changes in shift, changes in intensity, changes in shape, and existence of new peaks, attenuated total reflectance–Fourier transform infrared divulged the complexation between PMMA, PVC, lithium bis(trifluoromethanesulfonyl)imide, and BmImTFSI, as shown in the infrared spectra.

I. INTRODUCTION

Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2012.343

Typically, RTIL consists of bulky, and asymmetric organic cations and highly delocalized–charge inorganic anions along with a low melting point (,100 °C). It is also known as room temperature molten salt and remains in liquid form at ambient temperature.2 Indeed, RTILs possess many inherent and attractive properties such as nonvolatility, nontoxicity, nonflammability, excellent chemical, thermal, mechanical, and electrochemical stabilities. Other intrinsic advantages are wide electrochemical window (up to 6 V), high ionic conductivity due to high ion content, and inter alia, as well as excellent safety performance.3–7 In addition, it has potential to replace those volatile organic solvents, as vapor pressure is negligible.8 RTIL is readily dissolved in a wide range of organic, inorganic, and organometallic compounds. Furthermore, it does not coordinate with metal complexes, enzymes, and different organic substrates.8 Cations and counteranions are the major aspects to concern in the development of ionic liquid, as the solubility of ionic liquids strongly depends on the nature of cations and counteranions.8 Among all the cations, 1,3-dialkylimidazolium (Im) is an appealing cation due to its favorable properties in applications.9 On the contrary, some common anions are used to form a neutral and stoichiometric ionic liquid.8 However, TFSI anion is chosen because of its bulky structure, which enhances the electrochemical stability.10 Apart from that, high charge delocalization across the SO2–N–SO2 segment is another reason

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Ó Materials Research Society 2012

Solid polymer electrolytes (SPEs) are promising candidate to replace the