Optimization of salt concentration and explanation of two peak percolation in blend solid polymer nanocomposite films

The present paper is focused toward the preparation of the flexible and free-standing blend solid polymer electrolyte films based on PEO-PVP complexed with NaPF6 by the solution cast technique. The structural/morphological features of the synthesized polymer nanocomposite films have been investigated in detail using X-ray diffraction, Fourier transform infra-red spectroscopy, Field emission scanning electron microscope, and Atomic force microscopy techniques. The film PEO-PVP + NaPF6 (8) exhibits highest ionic conductivity similar to 5.92 x 10(-6) S cm(-1) at 40 A degrees C and similar to 2.46 x 10(-4) S cm(-1) at 100 A degrees C. The temperature-dependent conductivity shows an Arrhenius type behavior and activation energy decreases with the addition of salt. The high temperature (100 A degrees C) conductivity monitoring is done for the optimized PEO-PVP + NaPF6 (8) highly conductive system and the conductivity is still maintained stable up to 160 h (approx. 7 days). The thermal transitions parameters were measured by the differential scanning calorimetry (DSC) measurements. The prepared polymer electrolyte film displays the smoother surface on addition of salt and a thermal stability up to 300 A degrees C. The ion transference number (t (ion)) for the highest conducting sample is found to be 0.997 and evidence that the present system is ion dominating with negligible electron contribution. Both linear sweep voltammetry and cyclic voltammetry supports the use of prepared polymer electrolyte with long-term cycle stability and thermal stability for the solid-state sodium ion batteries. Finally, a two peak percolation mechanism has been proposed on the basis of experimental findings.