Tamarind gum based magnesium ion conducting polymer membrane for energy storage applications

Abstract

A solid bio polymer electrolyte (SPE) based on tamarind gum (TG) and magnesium nitrate was synthesized by a solution casting technique. The amorphous behavior is observed by X-ray diffraction (XRD) analysis, and the degree of crystallinity is calculated from the XRD deconvolution spectra. The interaction between the polymer and the salt was confirmed by Fourier transform infrared (FTIR) analysis. Using FTIR deconvolution spectra, the percentage of free ions can be calculated. The glass transition temperature (T_g) was determined via differential scanning calorimetry (DSC). A higher ionic conductivity (σ) of 1.97 × 10⁻⁴ S/cm is observed for the sample with 1 g of tamarind gum and 0.5 g of magnesium nitrate (4 TMN). The conduction mechanism shows that sample 4 TMN obeys the quantum mechanical tunneling model (QMT) at low frequency. The prepared SPEs follow the Arrhenius behavior, and the minimum activation energy (E_a) of 0.207 eV is observed for sample 4 TMN. The lowest relaxation time (τ) was 3.46 × 10⁻⁷ s for 4-TMN according to the tangent spectra. The transference number of ions (t_ion) is calculated by Wagner’s polarization method. The electrochemical stability window observed by linear sweep voltammetry (LSV) is 2.25 V. The primary battery is fabricated by using sample 4TMN, and an open circuit voltage (OCV) of 2.01 V is observed.