Effect of trace Ca and Y on the corrosion behavior and discharge performance of Mg-In anodes for Mg-air battery

Four Mg-In series alloys including Mg-2.0In, Mg-2.0In-0.5Ca, Mg-2.0In-0.5Y, and Mg-2.0In-0.5Ca-0.5Y are investigated as anode materials for magnesium-air (Mg-air) batteries. The microstructure morphologies, corrosion behavior and discharge behavior of four alloys are studied. The results indicate that the addition of trace Ca provides many Mg2Ca phases with semi-continuous network structure for Mg-2.0In-0.5Ca and Mg-2.0In-0.5Ca0.5Y, while second phase Mg24Y5 phases in Mg-2.0In-0.5Y and Mg-2.0In-0.5Ca-0.5Y are rare which of structure presents particles. In the electrochemical corrosion process, Mg2Ca phase acts as anode in micro-galvanic corrosion, while Mg24Y5 phase acts as micro-cathode due to the difference of potential between second phase and alpha-Mg phase. Moreover, the dense corrosion products layer could increase the corrosion resistance of Mg2.0In-0.5Ca alloy. The corrosion current density of Mg-2.0In-0.5Ca alloy is 1.2 x 10-2 mA center dot cm- 2 which is more than three other alloys. For discharge performance, after adding trace Ca and Y, the discharge activity of Mg-2.0In-0.5Ca-0.5Y increases and discharge products fall off the surface more easily. Thus, Mg-2.0In-0.5Ca0.5Y anode exhibits high discharge voltage (1.346 V) at 10 mA center dot cm- 2.