Superior specific capacity and energy density simultaneously achieved by Sr/In co-deposition behavior of Mg-Sr-In ternary alloys as anodes for Mg-Air cells

In this work, the combined addition of strontium/indium (Sr/In) to the magnesium anode for Mg-Air Cells is investigated to improve discharge performance by modifying the anode/electrolyte interface. Indium exists as solid solution atoms in the α-Mg matrix without its second-phase generation, and at the same time facilitates grain refinement, dendritic segregation and Mg₁₇Sr₂-phases precipitation. During discharge operation, Sr modifies the film composition via its compounds and promoted the redeposition of In at the substrate/film interface; their co-deposition behavior on the anodic reaction surface enhances anode reaction kinetics, suppresses the negative difference effect (NDE) and mitigates the “chunk effect” (CE), which is contributed to uniform dissolution and low self-corrosion hydrogen evolution rate (HER). Therefore, Mg-Sr-xIn alloy anodes show excellent discharge performance, e.g., 0.5Sr-1.0In shows an average discharge voltage of 1.4234 V and a specific energy density of 1990.71 Wh kg⁻¹ at 10 mA cm⁻². Furthermore, the decisive factor (CE and self-discharge HE) for anodic efficiency are quantitively analyzed, the self-discharge is the main factor of cell efficiency loss. Surprisingly, all Mg-Sr-xIn anodes show anodic efficiency greater than 60% at high current density (≥10 mA cm⁻²), making them excellent candidate anodes for Mg-Air cells at high-power output.