Boosting discharge performance of primary Mg-air batteries via adopting sodium citrate as electrolyte to suppress self-corrosion of Mg anode during discharge

Abstract

Primary magnesium (Mg)-air battery recently has attracted increasing interest as electrochemical energy storage system. However, the discharge performance of Mg anodes is critically limited by the severe self-corrosion of the anode and the accumulation of insoluble discharge products on the anode surface during discharge, inducing energy loss and surface blockage. In this work, sodium citrate (NaCA) solution as potential electrolyte, due to its high affinity to Mg²⁺, was explored for high-performance Mg-air batteries in comparison to the commonly used sodium chloride (NaCl) electrolyte. The utilization efficiency and specific capacity of Mg0.5Zn0.2Ge anode reached the highest compared to the previous reports, achieving 91.4 % and 2007 mAh g⁻¹ at 5 mA cm⁻² respectively, enhanced by 54 % compared to the counterparts in NaCl electrolyte. It is mainly attributed to the alleviated self-corrosion and the uniform dissolution of Mg0.5Zn0.2Ge anode during discharge in NaCA electrolyte. Mg-air battery tests with high-purity Mg and AZ31 alloy as comparisons as well further confirm the universal effectiveness of NaCA electrolyte and demonstrate that NaCA can sufficiently suppress the accumulation of discharge products by chelating with Mg²⁺ and induce pretty uniform dissolution of the anode materials during discharge, conferring boosted specific energy on the Mg-based anodes at low current density. The current work provides a strategic feasibility by adopting chloride-free electrolyte to develop advanced Mg-air batteries based on the intrinsic properties of Mg.