Microstructure and battery performance of Mg-Zn-Sn alloys as anodes for magnesium-air battery

Four Mg-xZn-ySn (x = 2, 4 and y = 1, 3 wt.%) alloys are investigated as anode materials for magnesium-air (Mg-air) battery. The self-corrosion and battery discharge behavior of these four Mg-Zn-Sn alloys are analyzed by electrochemical measurements and Mg-air battery tests. The results show that addition of Sn stimulates the electrochemical activity and significantly improves the anodic efficiency and specific capacity of Mg-Zn alloy anodes. Among the four alloy anodes, Mg-2Zn-3Sn (ZT23) shows the best battery discharge performance at low current densities (≤ 5 mA cm−2), achieving high energy density of 1367 mWh g−1 at 2 mA cm−2. After battery discharging, the surface morphology and electrochemical measurement results illustrate that a ZnO and SnO/SnO2 mixed film on alloy anode surface decreases self-corrosion and improves anodic efficiency during discharging. The excessive intermetallic phases lead to the failure of passivation films, acting as micro-cathodes to accelerate self-corrosion.