Preparation and characterization of magnesium ion conducting green solid polymer electrolyte using tamarind gum for electrochemical cell applications

Abstract

Solid polymer electrolytes (SPEs) based on tamarind gum (TG) and magnesium triflate (C₂F₆MgO₆S₂) have been prepared using a solution casting technique. The X-ray diffraction analysis confirms the amorphous nature of the electrolytes. Fourier transform infrared spectroscopy (FTIR) is used to study the complex formation between the polymer and salt. Deconvolution of the XRD and FTIR spectra provides insights into the degree of crystallinity and the percentage of free ions in the prepared electrolytes. Differential scanning calorimetry (DSC) is used to determine the glass transition temperature (T_g) of the electrolytes. The ionic conductivity calculated using AC impedance analysis is higher for the 5 MTF sample (1 g of TSP and 0.5 g of salt) as 1.02 × 10⁻⁴ S/cm at room temperature. Temperature-dependent conductivity analysis shows that all electrolytes follow Arrhenius behavior and the sample. 5 MTF has low activation energy as 0.14 eV. The conduction mechanism of 5 MTF is observed between 303 and 353 K, which aligns with the overlapping large polaron tunneling (OLPT) model. The relaxation time determined using tangent spectra is lower for 5 MTF as 1.14 × 10⁻⁶ s. Transference number analysis is carried out using the Wagner polarization method and the Evans polarization method. The DC Wagner polarization method confirms that conductivity is ion-driven. Using the Evans method, the value of cationic transference number is calculated. The potential stability of the electrolyte is assessed using linear sweep voltammetry (LSV). An electrochemical cell fabricated using 5 MTF sample exhibits an open circuit voltage (OCV) of 1.96 V, and its discharge characteristics are also observed.