Impedance spectroscopy, ionic conductivity and dielectric studies of new Li^sup +^ ion conducting polymer blend electrolytes based on biodegradable polymers for solid state battery applications

Abstract

New solid polymer blend electrolyte films based on biodegradable polymer blend comprising of polyvinyl alcohol (PVA) and poly (N-vinyl pyrrolidone) (PVP) doped with different wt% of lithium carbonate (Li₂CO3) salt have been prepared by solution casting method. The resulting PVA/PVP/Li₂CO3 polymer blend electrolyte films have been characterized by various analytical techniques such as FTIR, UV-vis, XRD, TGA, polarized optical microscopy and scanning electron microscopy. The FTIR and XRD analysis confirmed the complex formation between PVA/PVP blend and Li₂CO3 salt. The ionic conductivity and the dielectric properties of PVA/PVP/Li₂CO3 polymer blend electrolyte films were investigated using an impedance spectroscopy. It was observed that the ionic conductivity of PVA/PVP/Li₂CO3 electrolyte system increases as a function of Li₂CO3 concentration. The highest ionic conductivity was found to be 1.15 × 10^-5 S cm^-1 for polymer blend electrolyte with 20 wt% Li₂CO3 content. On the other hand, the dielectric results revealed the non-Debye type of behaviour. The dielectric constant values indicate a strong dielectric dispersion in the studied frequency range which increases as the Li₂CO3 content increases. The dielectric constant as high as 1200 ([straight epsilon] = 1201.57, 50 Hz, 150 °C) and the dielectric loss well below 4 (tan δ = 3.94, 50 Hz, 150 °C) were obtained for polymer blend electrolytes with 25 wt% Li₂CO3 salt. Thus, the results obtained in the present study suggest that the PVA/PVP/Li₂CO3 polymer blend electrolyte system seems to be a promising candidate for solid state battery applications.