Development of magnesium ion conducting biomaterial electrolyte based on Centella asiatica for electrochemical devices

Solid biomaterial electrolytes have been prepared by using Centella asiatica (CA) as biomaterial with various compositions of magnesium nitrate hexahydrate (Mg(NO3)2·6H2O) salt by solution casting technique using double-distilled water as solvent. Surface morphological studies for pure and highest conducting membranes have been obtained by SEM analysis. The amorphous nature and crystalline percentage of the biomaterial electrolyte have been studied by X-ray diffraction analysis. The glass transition temperature of the pure and the prepared biomaterial electrolyte membranes have been determined by differential scanning calorimetric analysis. Thermal stability of pure and highest conducting membranes is studied by TGA analysis. Electrical conductivity of the biomaterial electrolyte is measured by AC impedance analysis, and the dielectric behavior of the biomaterial electrolyte is also analyzed. The maximum magnesium ionic conductivity of biomaterial membrane is [1.14 ± (0.07)] × 10−2 S/cm for 1 g CA + 0.5 M wt% Mg(NO3)2·6H2O at room temperature. Transference number measurements are calculated from Wagner’s and Evan’s DC polarization techniques. The electrochemical stability window for biomaterial membrane with maximum magnesium ionic conductivity is 3.26 V, obtained by linear sweep voltammetry technique. The electrochemical reversibility is studied by cyclic voltammetry technique for 101 cycles. The primary Mg-ion battery is constructed with maximum magnesium ionic conductivity membrane as electrolyte, magnesium metal of diameter 12 mm and thickness 1 mm as anode and MoS2 as cathode. Open-circuit voltage (OCV) of the constructed Mg-ion primary battery is 1.92 V. The performance of the primary Mg-ion battery is evaluated with different loads.