Evading efficiency-voltage trade-off in magnesium-air batteries through solute atoms and second phases synergy

The quest for high-energy-density magnesium-air batteries is hindered by the efficiency-voltage trade-off, ultimately leading to an unsatisfactory energy density. Here, we effectively mitigate the inherent efficiency-voltage trade-off by introducing a novel anode material, specifically, Mg-0.5Sn-0.5In-0.5Ga. This anode demonstrates exceptional anodic efficiency, achieving 60.5 ± 2.5% at 1 mA cm⁻², 65.3 ± 2.7% at 10 mA cm⁻², and 71.4 ± 1.2% at 20 mA cm⁻². Furthermore, the discharge voltage is significantly enhanced, reaching 1.76±0.01 V at 1 mA cm⁻², 1.44±0.02 V at 10 mA cm⁻², and 1.21±0.08 V at 20 mA cm⁻². Consequently, our newly developed anode exhibits a remarkable energy density of 2312±98 W h kg⁻¹, placing it among the top-performing magnesium anodes documented in the literature. Density functional theory calculations and experimental investigations have unveiled that the exceptional performance can be attributed to the inhibition of water reduction, facilitated by the hybridization between solute atoms and neighboring Mg atoms. Furthermore, the activation of the second phase, introducing additional galvanic couples, significantly contributes to this performance. This study presents valuable insights that can guide the design of novel anodes, contributing to the advancement of high-performance magnesium-air batteries.