Enhancement of the discharge performance of Al-0.5Mg-0.1Sn-0.05Ga (wt.%) anode for Al-air battery by directional solidification technique and subsequent rolling process

Abstract The corrosion behavior and discharge characteristics of Al-0.5Mg-0.1Sn-0.05Ga (wt.%) alloys with different grain sizes in 4 M NaOH solution were investigated by collecting hydrogen, electrochemical measurement, discharge test, and microstructure analysis. The results reveal that the coarse-grained microstructure has a lower corrosion rate than the fine-grained one. As the annealing temperature increases, the grain size becomes larger, and more Sn-rich phases are solid-dissolved into the matrix, which results in less hydrogen evolution corrosion. The coarse-grained sample (6532 μm) produced by the directional solidification technique in combination with the rolling process and subsequent annealing at 600 °C has outstanding discharge performance. Its peak energy density reaches approximately 3743.9 Wh·kg−1 (at 40 mA cm−2), which exceeds the reported Al–Mg–Sn–In/Bi, Al–Mg-Ga-Sn-In, Al–Zn–In, Al–Bi–Pb-Ga, and Al–Sn/In/Ga anodes. Also, the anode efficiency and peak energy density of the sample at 40 mA cm−2 is 23.4% and 33.2% higher than that of the as-cast ones, respectively.