An Investigation on the Properties of Palm-Based Polyurethane Solid Polymer Electrolyte

Palm-based polyurethane electrolyte was prepared via prepolymerization method between palm kernel oil polyol (PKO-p) and 2,4′-diphenylmethane diisocyanate (MDI) in acetone at room temperature with the presence of lithium trifluoromethanesulfonate (LiCF₃SO₃). The effect of varying the concentration of LiCF₃SO₃salt on the ionic conductivity, chemical interaction, and structural and morphological properties of the polyurethane solid polymer electrolyte was investigated. The produced film was analyzed using electrochemical impedance spectroscopy (EIS), attenuated total reflection Fourier transform infrared (ATR-FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The EIS result showed that the highest ionic conductivity was at 30 wt% LiCF₃SO₃with a value of 1.6 × 10⁻⁵ S·cm⁻¹. Infrared analysis showed the interaction between lithium ions and amine group (–N–H) at (3600–3100 cm⁻¹), carbonyl group (–C=O) at (1750–1650 cm⁻¹), and ether group (–C–O–C–) at (1150–1000 cm⁻¹) of the polyurethane forming polymer-salt complexes. The XRD result proved that LiCF₃SO₃salt completely dissociates within the polyurethane film as no crystalline peaks of LiCF₃SO₃were observed. The morphological study revealed that the films prepared have a good homogeneity and compatibility as no phase separation occurred.