A mathematical model describing the surface evolution of Mg anode during discharge of aqueous Mg-air battery

Abstract

A numerical model is developed, aiming to understand and describe anode dissolution behavior and respective interface effects at an Mg-0.1Ca anode during discharge within an aqueous magnesium-air battery (MAB). In this model, the negative difference effect (NDE) that impairs the performance (e.g. utilization efficiency and capacity) of the anode is considered by adding a linear semi-empirical equation to calculate the total dissolution current density responsible for the dissolution of the Mg-0.1Ca anode. The proposed model is capable of predicting the effect of Mg(OH)2 deposit on the discharge process by consideration of surface coverage, layer thickness, and deposit porosity. In addition, the model can track the pH changes within electrolyte nearby the anode surface during discharge processes. The simulation results representing the development of local pH and the thickness of the deposited layer are validated by corresponding experimental measurements and are in good agreement with the experimental findings.