Effect of Fabrication Parameter on Microstructure of Mg–5.3 mass%Al–3 mass%Ca for Development of Mg Rechargeable Batteries

Abstract

Various motor using transportation system in land-sea-air, high speed mobile terminal with 5G specification, and renewable energy storage equipment have required innovative metal rechargeable batteries compared with lithium ones. In particular, magnesium has huge potentialities as an anode material from the standpoint of its theoretical volumetric capacity superior to that of lithium. Secondly, magnesium has been one of the most abundant elements in the Earth’s crust. Moreover, the potential safety by short-circuiting evading with non-dendritic deposition of magnesium. In general, magnesium-based ribbon as an anode has been manufactured by cold rolling which requires multistage process including heat treatment. We have studied rapid liquid quenching process in order to develop low-cost manufacturing technique. On the other hand, we have focused Mg–6 mass%Al–3 mass%Ca alloy due to this unique microstructure which consist of primary crystals and intermetallic compounds along grain boundary. In addition, calcium has affected to prevent of molten magnesium burning in air atmosphere. The structural properties and surface morphology are investigated by XRD and Digital Microscope, respectively. Microstructure has been observed by FE-SEM and FE-TEM. Moreover, these electrochemical properties have been examined by constant current charge - discharge tests using 3 electrodes type cell. Mg–3 mass%Al–1 mass%Zn alloy cold rolled thin plate has been investigated as comparison. The ribbons that exhibited electrochemical properties had a fine microstructure. It is suggested that the grain refinement and dispersion of the second phase are important to improve the charge-discharge properties of Mg–Al–Ca based anode materials.