Advanced protective layer design on the surface of Mg-based metal and application in batteries: Challenges and progress

Mg metal draws wide attention in the field of electrochemical energy storage (batteries, supercapacitor) because of its high volume energy density and environmental compatibility as well as abundant reserves in the earth's crust. However, when it comes to electrode materials, a severe self-corrosive behavior occurs on the surface of metallic Mg inevitably due to its high chemical and electrochemical reactivity, which lowers the utilization rate of Mg electrode and limits reversible Mg plating/stripping process. In this review, we focus on summarizing the latest research progress in various coating layer on Mg/Mg alloys over the last decade from a traditional corrosion science perspective and highlighting the development tendency of protective layer design from engineering/industry field to electrode materials and energy storage areas. We aim to provide a comprehensive understanding and serve as a strategic guidance for designing and fabricating advanced passivation for Mg-based batteries, and to explore the possibility of these designs in practical application. We critically evaluate the existing technology and future opportunities. It is hoped that such an elaborately organized review can give assistance to the readers interested or ready to engage in Mg-based batteries and create more possibilities in this hot point and forward position field.