Structural optical and electrical conductivity properties of Li₂SO₄ doped polymer electrolytes

Abstract

Structural optical and electrical conductivity properties of Li₂SO₄ doped with Poly (ethylene oxide) (PEO) films have been studied. The films are characterized by using X-ray diffractometry (XRD) at room temperature. The peak observed at 2θ = 19.16° for pure PEO and shifted to 19.22° for doped films. Diffraction peaks are shifting towards higher angles, indicate crystal sizes are decreasing. The XRD results indicate the reducing crystallinity and increasing amorphous nature with Li₂SO₄. The optical absorption studies in 200–800 nm range confirmed, the increase in the absorbance with increasing dopant concentration and, shifting the absorbance maximum towards lower energy. This shift is caused by unsaturated center of the molecules, i.e. in compounds containing double or triple bonds of, C=O and/or C=C mainly in the polymer and the increase in the concentration of Li₂SO₄. The direct band gap decreased from 4.50 to 3.75 eV and indirect band gap decreased from 4.51 to 3.80 eV. The FTIR results noticed that there is a significant change in the intensities as well as frequencies of spectra and the appearance of new peaks confirm the better complexation of dopant with PEO. Conductivity plots of all polymer films showed increasing nature with temperature and concentration of Li₂SO₄.

Keywords:

• XRD
• optical properties
• FTIR: electrical conductivity

Acknowledgments

Authors thank Prof. B.R. Kerur in the Gulbarga University for providing XRD facility and USIC, Mangalore University for providing FTIR facility.