Study on the preparation of Mg–Li–Mn alloys by electrochemical codeposition from LiCl–KCl–MgCl₂–MnCl₂ molten salt

Abstract

This study presents a novel electrochemical study on the codeposition of Mg, Li, and Mn on a molybdenum electrode in LiCl–KCl–MgCl₂–MnCl₂ melts at 893 K to form different phases Mg–Li–Mn alloys. Transient electrochemical techniques such as cyclic voltammetry, chronopotentiometry, and chronoamperometry have been used in order to investigate the codeposition behavior of Mg, Li, and Mn ions. The results obtained show that the potential of Li metal deposition, after the addition of MgCl₂ and MnCl₂, is more positive than the one of Li metal deposition before the addition. The codeposition of Mg, Li, and Mn occurs at current densities lower than −1.43 A cm⁻² in LiCl–KCl–MgCl₂ (8 wt%) melts containing 2 wt% MnCl₂. The onset potential for the codeposition of Mg, Li, and Mn is −2.100 V. α, α + β, and β phases Mg–Li–Mn alloys with different lithium and manganese contents were obtained via galvanostatic electrolysis from LiCl–KCl melts with different concentrations of MgCl₂ and MnCl₂. The microstructures of typical α and β phases of Mg–Li–Mn alloys were characterized by X-ray diffraction (XRD), optical microscopy (OM), and scanning electron microscopy (SEM). The analysis of energy dispersive spectrometry (EDS) and EPMA area analysis showed that the elements of Mg and Mn distribute homogeneously in the Mg–Li–Mn alloys. The results of inductively coupled plasma analysis determined that the chemical compositions of Mg–Li–Mn alloys correspond with the phase structures of XRD patterns, and lithium and manganese contents of Mg–Li–Mn alloys depend on the concentrations of MgCl₂ and MnCl₂.