Electrodeposition of magnesium from the eutectic LiCl-KCl melt

Electrodeposition of magnesium in the eutectic LiCl-KCl mixture (58-42 mol%) containing different MgCl2 concentrations was studied using tungsten as cathode material. The temperature was varied above and below the melting point of magnesium (983 K). Electrochemical techniques such as cyclic voltammetry, chronopotentiometry and chronoamperometry were employed in order to characterise the system and study nucleation and growth of the magnesium phase. With all the electrochemical techniques above mentioned, macroscopic growth of the solid magnesium deposit was observed. Liquid magnesium deposits were found to grow without giving rise to a significant increase in surface area. This may be related to lithium co-deposition and formation of Li-Mg liquid solution and the differences in interfacial properties of the cathodic deposits obtained in each case. The deposition of lithium on pre-deposited magnesium leads to the formation of Li-Mg solid alloys or to a liquid Li-Mg solution at temperatures below or above the melting point of magnesium, respectively. The diffusion coefficient of magnesium ions was determined by different electrochemical techniques. The values obtained showed the effect of macroscopic growth of the deposit in the case of solid magnesium deposits.