FTIR, XRD, electrical and dielectric characteristics of solid polymer blend electrolytes based on chitosan: dextran inserted with NH 4 CF 3 SO 3 salt as proton provider

In the current study, solid polymer electrolytes (SPEs) based on chitosan and dextran biopolymers incorporated with various amounts of ammonium trifluoromethanesulfonate (NH4CF3SO3) were prepared employing a casting approach. NH4CF3SO3 is an ammonium-based salt that has been chosen in this study as a proton provider because it has low lattice energy (540.59 KJ/mol), delocalization, and low mobility of the anion part of the salt due to the large size of the triflate anion (-CF3SO3), which causes good ionic dissociation and provides more free ions by involving both NH+ and H+. Consequently, ionic conductivity will be improved. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) have been performed for structural analysis, ensuring the dissociation of dopant salt in a polymer blend and investigating the interaction and complexation between polymers and salt. The degree of crystallinity (Xc) of the prepared SPE samples was determined via deconvoluted XRD spectra. Electrochemical impedance spectroscopy (EIS) has been utilized to measure the ionic conductivity and to analyze electrical properties of SPE samples. The Nyquist plots were fitted with the proposed electric equivalent circuits (EECs); furthermore, the electrolyte sample with the highest DC conductivity has been selected, which is equal to 6.24 × 10−6 S/cm, which corresponds to the CDATF5 sample. Dielectric properties analysis, including dielectric constant (ε′) and loss (εʺ), electric modulus (M’ and M”), tanδ, and AC conductivity (𝜎AC) of the electrolyte films, has been studied. SPEs made of the CS:DX-ATF system demonstrate enhanced structural flexibility and electrochemical efficiency, positioning them as a viable alternative for sustainable applications of solid-state energy storage devices, e.g., rechargeable batteries, electrochemical double-layer capacitors (EDLCs), fuel cells, sensors, actuators, and dye-synthesized solar cells.