Microstructure design of advanced magnesium-air battery anodes

Metal-air battery is an environmental friendly energy storage system with unique open structure. Magnesium (Mg) and its alloys have been extensively attempted as anodes for air batteries due to high theoretical energy density, low cost, and recyclability. However, the study on Mg-air battery (MAB) is still at the laboratory level currently, mainly owing to the low anodic efficiency caused by the poor corrosion resistance. In order to reduce corrosion losses and achieve optimal utilization efficiency of Mg anode, the design strategies are reviewed from microstructure perspectives. Firstly, the corrosion behaviors have been discussed, especially the negative difference effect derived by hydrogen evolution. Special attention is given to the effect of anode micro-structures on the MAB, which includes grain size, grain orientation, second phases, crystal structure, twins, and dislocations. For further improvement, the discharge performance, long period stacking ordered phase and its enhancing effect are considered. Meanwhile, given the current debates over Mg dendrites, the potential risk, the impact on discharge, and the elimination strategies are discussed. Microstructure control and single crystal would be promising ways for MAB anode.