The effect of ceramic nanofillers on conductivity and ion-transport behavior in potato starch-based solid bio-polymer electrolyte for advanced energy storage devices

Abstract

The solution cast method was used to synthesize the nanocomposite solid polymer electrolytes, which were composed of potato starch (PS) as the host polymer, sodium iodide (NaI) as an ion source, and dispersed with Ce-substituted cobalt ferrite (CoFe_1.95Ce_0.05O₄). The nanocomposite solid polymer electrolyte was characterized using a variety of techniques, including electrical impedance spectroscopy (EIS), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy and its deconvolution, X-ray diffraction (XRD), linear sweep voltammetry (LSV), cyclic voltammetry (CV), and galvanostatic charge–discharge (GCD). The maximum conductivity of 9.06 × 10⁻³ S/cm is attained for a system of 1.0 wt.% of Ce-substituted cobalt ferrite nanofillers. Inside the polymer matrix, the ion motion is triggered by the ceramic nanofillers. Therefore, the conductivity of the electrolyte was increased. The FTIR verified complexation behavior in the material. The deconvolution of FTIR spectra in the desired region yielded ion transport parameters, such as diffusion coefficient (D), mobility (µ), and carrier density (n). DSC thermograms indicate an endothermic process, and a broad melting peak at 60 °C is in the electrolyte system consisting of 50 wt.% NaI in potato starch due to the gelatinization of the starch granules, which is followed by another broad peak observed at 137 °C due to the dissociation of the material. TGA thermograms show multistage decomposition mechanisms with three processes. LSV and CV analyses indicate that the material is purely capacitive in nature and contains a broad electrochemical stability window, making it suitable for device applications.