Plasticization effect of ionic liquid on structural, thermal and ion transport properties of CS-PVA-NaI based bio-polymer electrolyte membranes

Plasticized bio-polymer blend electrolytes (BPBEs) based on CS-PVA-NaI-xwt% ionic liquid (IL), 1-ethyl-3-methylimidazolium methyl sulfate [EMIM][MS] were prepared using solution cast method. The prepared samples have been characterized using FTIR (in ATR mode), XRD, TGA, Impedance spectroscopy, ITN, LSV, and CV measurement. XRD result shows the semi-crystalline nature of BPEs films with characteristic peaks centered at 2 theta = 21 degrees. The % degree of crystallinity (X-c) for BPBE films were found to decrease up to 15 wt%IL. FTIR analysis shows the interaction of NaI/IL with the constituents of polymer CS/PVA. Thermo-gravimetric analysis (TGA) shows that the BPBE film has multistep decomposition. AC conductivity spectra follow the Joncher's power law (JPL) with the value of power law exponent >1. The transportation of charge carriers in the BPBE films follows the cage type correlate barrier hoping (CBH) mechanism. The sample, BPBE#15IL, was found to be optimum dc conductivity similar to 1.7x10(-4)S/cm at 30celcius. The electrode polarization and conductivity relaxation in terms of dielectric permittivity and electric modulus have been realized. Ionic transference number (ITN) measurement reveals that the sample BPBE#15IL has the ionic conductivity due to ions only (ITN similar to 0.99). LSV measurement shows that the value of electrochemical stability window (ESW) for sample BPBE#15IL similar to +/- 2.3 V. CV plot shows the appearance of symmetric oxidation-reduction peaks appeared at similar to +/- 1.5 V.