Comprehensive study on corrosion and discharge performance of Mg–Ca alloy with high Ca content

The corrosion and discharge performance of as-cast and extruded Mg-8.5Ca alloys have been systematically investigated as the anodes for Mg-air batteries, using electrochemical techniques and Mg-air battery tests. The extrusion deformation greatly refines the grain size, decreases the content and size of the Mg 2 Ca phase, and promotes the uniform distribution of the Mg 2 Ca phase in the matrix. The results of the Scanning Kelvin Probe Force Microscope (SKPFM) reveal that the potential difference of as-cast Mg-8.5Ca and extruded Mg-8.5Ca is approximately 60 mV and 100 mV lower than that of the α-Mg matrix, respectively. The results reveal that the Mg 2 Ca and α-Mg matrix in Mg-8.5Ca alloys act as micro-anode and micro-cathode, respectively. The superior potential difference renders extruded Mg-8.5Ca to have strong micro-galvanic corrosion, which enhances the electrochemical and discharge performance. For extruded Mg-8.5Ca alloy, the corrosion performance of the alloy is effectively enhanced, and hydrogen evolution during discharge is largely inhibited. The extruded Mg-8.5Ca anode exhibits excellent comprehensive discharge performance, with the highest anode utilization and specific capacity of 44.6 %, and 914.1 mAh⋅g −1 at 10 mA cm −2 , respectively. The discharge voltage and anode utilization of the as-cast Mg-8.5Ca decrease severely, attributed to the excessive Mg 2 Ca phase and coarse and uneven grain size accelerating the self-corrosion and causing the severe chunk effect.