A combined computational/experimental study of anode-concerned voltage drop in aqueous primary Mg-air batteries

The voltage drop appearing at Mg anode-electrolyte interface is a critical issue for the battery power and energy density of aqueous primary Mg-air batteries. The respective voltage loss is typically assigned to the deposits layer forming on the anode surface during discharge. In this work, we experimentally and computationally investigate the critical factors affecting the voltage drop at Mg anode towards a deeper understanding of the contribution of deposit and its growth. A two-dimensional (2D) mathematical model is proposed to compute the voltage drop of Mg-0.15Ca wt.% alloy (Mg-0.15Ca) by means of a semi-empirical formulas and experiments-based modification model, considering the effect of discharge current density, the negative difference effect (NDE) and surface deposits layer itself. This model is utilized to simulate the discharge potential of the anode at predefined experimental current densities. The computed voltage drop (half-cell voltage) is in good agreement with the experimental value. The applicability of the mathematical model is successfully validated on the second material (namely high-purity Mg).