Mathematical modeling of salicylate effects on high-purity Mg anode for aqueous primary Mg-Air batteries

• Comprehensively study SAL effects on HP Mg anode electrochemistry via experiments. • Adding SAL boosts discharge voltage and stability at initial polarization phase. • Developed a FEM model to explain SAL impact on discharge potential and resistances. • Introduce a SAL-Mg complexation factor to quantify the mechanism of SAL's effects. • Validate the model via local tests to monitor interfacial pH and surface coverage. This study investigates the effectiveness of salicylate (SAL) as an electrolyte additive on the discharge behavior of high-purity (HP) Mg anode in an aqueous half-cell system, using an integrated approach of mathematical modeling and experimental analysis. A finite element-based model is developed to elucidate the key mechanisms by which SAL influences the voltage profile and pH. Systematic electrochemical measurements, especially intermittent discharge tests combined with electrochemical impedance spectroscopy (EIS), demonstrate that SAL can enhance initial voltage stability of HP Mg anode. Moreover, the model incorporates the SAL-Mg complexation factor to describe the role of SAL in modifying the deposit film on HP Mg surface. The agreement between model predictions and experimental observations suggests that SAL facilitates the formation of compact Mg(OH) 2 deposits and sustains a favorable pH environment within the half-cell compartment. This integrated approach provides new insights into understanding and optimizing additive effects for Mg-air batteries.