Effects of the combinative Ca, Sm and La additions on the electrochemical behaviors and discharge performance of the as-extruded AZ91 anodes for Mg-air batteries

Abstract

Abstracts The effects of combinative Ca and rare earth (Samarium, Sm and Lanthanum, La) additions on the microstructures, electrochemical properties and discharge performance of the as-extruded Mg 9%Al 1%Zn (wt.%) anodes for magnesium-air batteries are systematically investigated. The combinative addition of Ca, Sm and La can bring additional Al2Ca and Al2(Sm,La,Ca) compound phase and reduce the grain size from 17.2 ± 1.9 μm to 11.7 ± 0.9 μm. The β-Mg17Al12 phase gets refined and dispersed with the Al2Ca phase in the matrx. The modified Mg 9%Al 1%Zn anodes have more positive corrosion potential and better corrosion resistance than the original. The addition of Sm and La strongly increases the desorption resistance of surface product. Mg 9%Al 1%Zn with Ca, Sm and La anode exhibits stable discharge voltage and good discharge performance. It has high discharge capacity and anodic efficiency of 1381 mA h·g−1 and 61.9%, respectively, at 40 mA·cm−2. The prior corrosion of grain boundaries makes bulk of α-Mg grains peel away along the grain boundaries, significantly reducing the anodic efficiency. The disperse particle phase around grain boundaries can serve as strong barriers so as to achieve uniform dissolution.