Influence of Lithium Salts on Optical Properties, FTIR Analysis, and AC Conductivity of PVP/PVA Blends for Solid Polymer Electrolyte Applications

Abstract

Blends of polyvinyl pyrrolidone (PVP) and polyvinyl alcohol (PVA) in equal weight ratios (50 wt.% PVP + 50 wt.% PVA) were doped with 15% of various lithium salts (Li₂CO₃, LiNO₃, Li₂SO₄H₂O, and LiCl) and prepared using the solution-casting method, with dimethylformamide (DMF) as the solvent. The impact of these salts on the blends was analyzed and the results showed that the energy gap was decreased by adding lithium salts Li₂CO₃, LiNO₃ and Li₂SO₄.H_₂O. The minimum energy gap value was 3.5 eV obtained from PVP/PVA:15% Li₂CO₃. The optical constants were determined in the range of 300-1100 nm. The results showed that all the optical constants for doped blends were grown with the addition of lithium salts. The FTIR study confirms the complex formation between the polymer and salt. The present study showed the highest ionic conductivity at room temperature was 2.17×10^-5 S/cm correspond to PVP/ PVA:15 % Li₂CO₃.