The present invention relates to a process for preparing metal chloride Mx+Clx -, in which metal carbonate (1) in solid form is reacted with a chlorinating agent (2) selected from chlorine and oxalyl chloride to give metal chloride Mx+Clx - (1'), where the metal M is selected from the group of the alkali metals, alkaline earth metals, Al and Zn, preferably Li and Mg, more preferably Li, and x corresponds to the valency of the metal cation, wherein metal M (3) is additionally added as reactant. The present invention likewise relates to an apparatus (R) for conducting the process.