Effects of potassium iodide (KI) on crystallinity, thermal stability, and electrical properties of polymer blend electrolytes (PVC/PEO:KI)

Potassium ion conducting solid polymer blend electrolytes based on PVC/PEO:KI of various compositions were prepared by solution-casting technique. The structural changes along with K+ ion-polymer blend electrolyte interactions and the thermal stability of the samples were studied by X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetty, scanning electron microscopy, and thermo-gravimetric analysis. Electrical properties were measured as a function of composition and temperature using complex impedance spectroscopy. The electrical conductivity exhibited Arrhenius type of behavior, with the activation energy decreasing with increasing KI concentration. The conductivity of the polymer blend (PVC/PEO) sample was obtained at ambient temperature (303 K) as 3.09 x 10(-6) S cm(-1), and for the PVC/PEO:KI (42.5:425:15) electrolyte as 3.66 x 10(-4) S cm(-1), the conductivities were greatly enhanced at 363 K to 8.23 x 10(-4) and 1.30 x 10(-2) S cm(-1), respectively. The ionic transference number of the PVC/PEO:KI (42.5:42.5:15) electrolyte was determined to be 0.98. The increase in amorphous phase and free K+ ion concentration was responsible for the conductivity improvement in the electrolyte system. (C) 2015 Elsevier B.V. All rights reserved.