Exploring the Effect of Strong Complexing Agents As Electrolyte Additives on Anode Performance in Mg-Air Primary Batteries

Abstract

Mg-air primary batteries have drawn increasing attention recently due to their low cost, safety, and high theoretical specific power density. However, high self-corrosion rate and anode fouling during discharge (mainly due to the formation of Mg(OH)2/MgO) lead to particularly lower delivered voltage and utilization efficiency. Modification of the battery electrolyte chemistry plays a crucial role in tackling these shortcomings and improving battery performance. Remarkable enhancements to the Mg anode’s performance by addition of group of organic complexing agents in the Mg-air battery electrolyte has recently been reported [1]. In this study, the effect of two strong organic complexing agents (i.e. disodium 4,5-dihydroxy-1,3-benzenedisulfonate(Tiron) and Nitrilotriacetic acid(NTA)) as additives to the Mg-air battery electrolyte was investigated. Commercially pure magnesium with relatively high Fe impurity level (i.e. 220ppm) has been chosen as the anode material in order to have a better understanding of the interaction of the complexing agents with pure Mg and the common Fe impurity. Half-cell measurements were conducted to evaluate the discharge performance of the anode in the presence of the complexing agents. The electrochemical and corrosion behavior were studied by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curve. The morphology of the anode surface after discharge was investigated by scanning electron microscope (SEM). The results indicate that strong complexing agents can remarkably improve the discharge potential by activating the Mg anode surface and mitigating the high cathodic activity stemmed from Fe impurities. A possible downside of adding strong complexing agents is the tendency to accelerate the corrosion rate of the Mg anode. However, tuning the complexing agent concentration in the electrolyte can significantly improve the utilization efficiency at the expense of a slight decrease in the battery delivered voltage. [1] D. Höche, S.V. Lamaka, B. Vaghefinazari, T. Braun, R.P. Petrauskas, M. Fichtner, M.L. Zheludkevich, Performance boost for primary magnesium cells using iron complexing agents as electrolyte additives, Scientific Reports, 8 (2018).