Integrating complexing agents into organic anion electrolytes: A novel strategy for high-performance aqueous Mg-air batteries

Mg-air batteries represent highly promising primary power sources due to their high energy density, low cost, and environmental benignity. Nevertheless, their practical deployment is severely restricted by passivation and localized corrosion of the Mg anode. Herein, we propose a new strategy of integrating a complexing agent, ethylenediaminetetraacetic acid (EDTA), into an organic anion CH 3 COONa electrolyte to address these critical issues. The addition of EDTA significantly enhances the discharge performance. The optimal system, containing 0.03 M EDTA, delivers a remarkable energy density of 2611.51 ± 34.70 mWh·g −1 and an anode utilization efficiency of 70.12% ± 0.60% at 2.5 mA·cm −2 , with a stable discharge voltage of approximately 1.71 ± 0.01 V, far superior to that in the base electrolyte. A cooperative regulation mechanism is established between the chloride-free CH 3 COONa electrolyte matrix and the EDTA complexing additive: CH 3 COONa suppresses localized corrosion, while EDTA regulates the Mg/electrolyte interface by complexing Mg 2+ , limiting Mg(OH) 2 passivation, and forming an EDTA-derived adsorption layer. These coupled effects mitigate both localized corrosion and surface passivation, thereby promoting more uniform Mg dissolution and improving discharge stability and anode utilization. By combining Time-of-Flight Secondary Ion Mass Spectrometry with theoretical calculations including density functional theory and molecular dynamics simulations, it is confirmed that EDTA reduces the passive film thickness and modifies its composition by promoting the redeposition of alloying elements. This work establishes a mechanistic framework for cooperative interfacial regulation in aqueous Mg-air batteries, revealing how an organic anion electrolyte matrix and a complexing additive cooperatively govern Mg 2+ complexation, passive-film evolution, alloying-element redistribution, and Mg dissolution behavior. These findings provide theoretical guidance for designing high-performance electrolytes for advanced aqueous Mg-air batteries.