Tailoring the discharge performance of extruded Mg-Sm-Al anode for Mg-air battery applications via control of Al content

We investigated the discharge performance and electrochemical properties of an as-extruded Mg-5Sm-xAl (x=0,1,3) anode for Mg-air batteries. Adding Al modified the phase composition and grain size of the anode. The addition of 1 wt% Al (Mg-5Sm-1Al) induced a high discharge voltage and power density due to the stimulation of the evenly distributed, fine Al11Sm3 particles. However, these particles increased the parasitical anodic hydrogen reaction rate, resulting in a decrease in anodic efficiency. These properties make the anode suitable for high-power density applications. The addition of 3 wt. % Al (Mg-5Sm-3Al) promoted the formation of an aluminium oxide film on the anode surface, which suppressed the anodic hydrogen reaction to improve the anodic efficiency. This film increased the battery's internal resistance resulting in low voltage. This anode is a good candidate for heavy-duty battery applications, where a steady voltage output and long service life are desired. By controlling the Al content, the tailoring of discharge performance of the Mg-Sm-Al anode is feasible to satisfy different battery load requirements.