Effects of second phases in anode materials on discharge performance of Mg-air batteries

As-cast Mg-6Al and as-cast and hot-rolled Mg-6Al-1Ce alloys were used as anode materials in Mg-air batteries. Effects of second phases of anode materials on electrochemical properties and discharge behavior were investigated by backscattered electron (BSE), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), and electrochemical test. Many beta-(Mg17Al12) particles were found in as-cast Mg-6Al alloy. Deep corrosion pits were formed near these particles, which is not beneficial to improve discharge performance. The as-cast Mg-6Al-1Ce alloy forms larger gamma-(Al4Ce) grains, which retard the shedding of corrosion products. The contact between electrolyte and metal anode is hindered, and corrosion product accumulation leads to a slowly decreasing voltage. With hot rolling, the gamma phase breaks up into many fine and evenly distributed particles. In this way, corrosion products can easily peel off from the anode surface, leading to an improvement of anode discharge activity.