Development of magnesium-ion-conducting solid electrolytes from plant gum for magnesium-ion batteries

Naturally abundant magnesium-based metal batteries hold significant promise for addressing future energy demands. In the pursuit of sustainable electrochemical device development, biomaterial-based polymer electrolytes have garnered increasing attention. Plant exudates have emerged as a promising source for solid polymer electrolytes in various battery applications over the past decade. The gum of Moringa oleifera (MG) contains several polar groups within its polysaccharide structure, including D-glucuronic acid, L-mannose, and L-rhamnose. This study investigates the development of magnesium-ion-conducting biomaterial electrolytes by incorporating magnesium perchlorate Mg(ClO₄)₂ at varying weight percentages into Moringa oleifera gum using a solution casting method. The resulting membranes were characterized using X-ray diffraction (XRD), differential scanning calorimetry (DSC), AC impedance spectroscopy, linear sweep voltammetry (LSV), and cyclic voltammetry (CV). XRD analysis revealed that the membrane composed of 1 g MG + 0.70 wt% Mg(ClO₄)₂ (designated MGMC-4) exhibited a high degree of amorphous character. DSC analysis of MGMC-4 showed a low glass transition temperature of 133.22 °C. AC impedance spectroscopy demonstrated an increase in Mg²⁺ ionic conductivity with increasing Mg(ClO₄)₂ concentration, reaching a maximum conductivity of (1.26 ± 0.04) × 10⁻² S cm⁻¹ for MGMC-4. The MGMC-4 membrane exhibited an electrochemical stability window of 2.91 V and demonstrated good cycling stability within a potential range of − 2.5 to + 2.5 V for 64 cycles. A primary magnesium-ion battery was assembled using MGMC-4 as the electrolyte in the configuration Mg|MGMC-4|MnO₂-graphite. This battery exhibited a promising open-circuit potential of up to 1.91 V and reliable load discharge performance across a wide resistance range (100 kΩ to 15 Ω). Furthermore, the battery successfully powered a red LED for 480 continuous hours.