Recent years have seen a surge in interest in biopolymers, a kind of natural biodegradable polymer. Researchers were compelled to engage in the biopolymer business due to rising environmental consciousness and the depletion of fossil fuel supplies. Cellulose, chitosan, pectin, agar-agar, and carrageenan are a few of the biopolymers utilised in the manufacture of rechargeable batteries. Given the hazardous nature of lithium-based materials, researchers are eager to find an alternative energy storage system that is similar to lithium-ion battery technology. In this study, a team has explored magnesium ion conducting polymers made from iota carrageenan and magnesium chloride salt for potential battery applications. To construct the solid polymer electrolyte, methyl cellulose (MC) and magnesium chloride (MgCl2.6H₂O) were combined using the solution solvent and casting methodologies. Structural analyses including X-ray diffraction (XRD) technology appear to its amorphous nature while Fourier transform infrared (FTIR) technique confirms its compatibility with both polymer components. To understand the glass transition temperature, differential scanning calorimetry (DSC) was employed. The electric and dielectric properties of the polymer electrolyte were studied using AC impedance spectroscopy. Evidently, when one-gram is I-carrageenan joins 0.4 weight percent of MgCl2, it produced a maximum ionic conductivity at 6.1 10-4 S/cm with a lowest activation energy value of 0.175 eV per gramme. An evaluation of a biopolymer membrane consisting of 40% CA to 60% MgCl2 revealed that it demonstrated maximum conductivity at room temperature of 4.05*10-4 S/cm. Through linear sweep voltammetry, this material was found to possess an electrochemical stability up to 3.58 Volts, with a total ionic transference number around 0.98. Subsequently, this high conducting polymer electrolyte was employed in constructing a primary magnesium ion battery.