Structural and electrical properties of biopolymer blend electrolytes based on chitosan: dextran doped with lithium nitrate (LiNO3) salt

This study reports the preparation of solid polymer blend electrolytes (SPBEs) based on chitosan-dextran (CS: DX) blend impregnated with various amounts of lithium nitrate (LiNO₃) salt using solution casting procedure. The SPBE films have been analyzed by using X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) for their structural analysis. The XRD deconvolution approach was employed to estimate the degree of crystallinity of the electrolyte films. Crucial ion transport parameters (n, µ, D) were calculated from the deconvoluted absorption bands associated with the NO₃⁻ anion of the doped salt. The electrical and dielectric characteristics performed via electrical impedance spectroscopy (EIS) technique. EIS results revealed an increase in ionic conductivity with increasing LiNO₃ salt and the maximum ionic conductivity (σ_dc) attained was (1.4 × 10^-6 S.cm^-1) at 40 wt% of the added salt. The formation of ion aggregation at 50 wt% of the added salt was confirmed by both FTIR and XRD techniques. Dielectric studies revealed significant interfacial polarization between electrolytes and electrodes and relaxation phenomena, confirming improvements in both charge carrier density and charge mobility. Broad peaks of the loss tangent plot and the incomplete semicircular shape of Argand plots confirm non-Debye characteristics for the relaxation dynamics of ions. The AC conductivity pattern versus frequency illustrated three distinguished regions and fitted with Jonscher's power law. The results of this work establish that knowledge's about deconvolution of FTIR/XRD and fittings of impedance/AC conductivity are crucial to understand the structure-property relationships in polymer electrolytes.