Discharge performance and behavior of Mg-xSr binary alloys as novel anodes for primary Mg-Air cells

Novel as -cast magnesium -strontium (Mg-xSr, x = 0.2, 1.0 and 2.0 wt.%) anodes for Mg -Air cells are systematically investigated by microstructure characterization, self -discharge experiments, electrochemical techniques and discharge tests. With Sr added in magnesium alloy, granular and strip Mg17Sr2-phases precipitate at grain interior and boundaries, respectively. Mg17Sr2-phase acts as a weak anode with alpha-Mg in micro -galvanic couple, promoting the formation of initial discharge sites; meanwhile, Sr element modifies the composition and morphology of passivation film and discharge products. However, with Sr content increasing, continuously distributed coarse -second -phases produce stronger micro -galvanic corrosion effect and priority discharge at grain boundaries, enhancing the parasitical self -discharge hydrogen evolution rate (HER) and "Chunk effect" (CE). Mg0.2Sr exhibits the highest anodic efficiency of 60.18 % and specific capacity of 1342.28 mA h g-1 at 20 mA cm -2, which is attributed to the even distribution of fine Mg17Sr2 and the uniform dissolution of alpha-Mg matrix. Therefore, Sr is an optional micro -alloying element for improving discharge performance of Mg -anode for Mg -Air cells.