The Mixed Contribution of Ionic and Electronic Carriers to Conductivity in Chitosan Based Solid Electrolytes Mediated by CuNt Salt

Abstract

This work shows the contribution of both ionic and electronic conductivities in chitosan (CS) based solid polymer electrolytes incorporated with various amounts of copper nitrate (CuNt). The samples were prepared using solution cast technique. The second semicircles at intermediate frequency in impedance plots were observed. Surface plasmonic resonance (SPR) was illustrated from the UV–Vis spectrophotometry, where broad peaks at 702 nm were obtained as an evidence for nanoparticles formation. The second semicircles in the impedance plots and the distinguished SPR peaks have revealed the contribution of electronic conductivity in CS:CuNt based polymer electrolytes. The same trend of UV–Vis spectra at different temperatures reveals that CS:CuNt polymer electrolyte is thermally stable. The presence of electronic conductivity is the main shortcoming of copper ion conducting solid polymer electrolytes. The role of lattice energy of the copper salts on electrical properties and morphological (SEM) appearance was discussed. The TEM image shows Cu nanopartciles with various sizes. A stable SPR peak and vanishing of second semicircle at high temperatures reveals the stability of copper ion conducting chitosan based polymer electrolytes. The pattern of DC conductivity and dielectric constant as a function of salt concentration are almost found to be similar. Both estimated DC conductivities from AC spectra and those calculated from impedance plots are shown to be comparable. Highest DC conductivity of 3.65 × 10⁻⁵ S/cm has been achieved for the sample incorporated with 21 wt% of CuNt. The high value of dielectric constant at low frequency can be ascribed to electrode polarization. Electric modulus parameters are studied to understand the relaxation process. Two semicircles in Argand plots were separated.