Abstract
Magnesium (Mg) is a promising conversion-type anode material for next-generation energy storage systems due to its high theoretical volumetric capacity, excellent electrochemical activity, natural abundance, low cost, environmental friendliness, and relatively low susceptibility to dendritic growth. The anode-free battery configuration further enhances the specific capacity and energy density of the system. However, in anode-free designs, the microstructure of electrodeposited Mg on the current collector during the initial charge cycle plays a critical role in the subsequent battery performance. Therefore, this study investigates the microstructure of electrodeposited Mg in phenyl- and phenolate-based electrolytes on different current collectors with various characterization techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), atom probe tomography (APT), cross-sectional transmission electron microscopy (TEM), and electron back-scattered diffraction (EBSD).Comparative analysis was performed on electrodeposited Mg prepared in a phenolate-based magnesium complex (PMC) electrolyte and all phenyl complex (APC) electrolytes with and without lithium chloride (LiCl) addition. For all electrolytes, increasing the electrodeposition current density resulted in smaller grain sizes and reduced (002) texture, attributed to faster nucleation and deposition rates. Mg deposited from the APC electrolytes exhibited predominantly granular morphologies, whereas deposits from the PMC electrolyte were more tabular, particularly at high current densities. The addition of LiCl to the APC electrolyte enhanced the electrolyte conductivity and Mg species mobility, resulting in deposits with larger grain sizes and enhanced (102) and (103) texture. The dependence of Mg microstructure on the electrodeposition conditions and implications for subsequent stripping/plating behaviors will be discussed.