Process for the preparation of lithium rare-earth halides

A process for the preparation of a solid material according to general formula (I) as follows:

• Li6-3x-myRExTyX6 (I)
• wherein:
• X is a halogen;
• m is the valence of the element T
• 0<x+(m/3)y<2;
• 0≤y≤0.8;
• RE denotes one or more rare earth metals;
• the rare earth metals are different from each other;
• and
• T is selected from the group consisting of Zr, Hf, Al, Zn, Mg, Ca, Sr, Bi, Nb, Fe and Ta;
• said process comprising the step of:
• a) dissolving lithium halide, at least one hydrated rare-earth metal halide and optionally T halide in a solvent to obtain a solution