A series of compositions with the nominal formula Na1+xZnxAl1-xCl4 (NZAC) was synthesized by the mechanochemical method. Stoichiometric amounts of NaCl (Thermo Fisher, 99.5% purity, predried at 60 °C for 3 days under 50 mbar), AlCl3 (Sigma Aldrich, 99% purity), and ZnCl2 (Thermo Fisher, 99.995% purity) were ground with mortar and pestle by hand for 10 minutes to guarantee a homogeneous mixing process. The mixture of precursors was sealed in a zirconia jar (45 mL, Fritsch GmbH), and the mass ratio between milling media (ZrO2, 5 mm diameter) and precursors was 36:1. A Pulverisette 7 planetary ball milling machine (Fritsch GmbH) was set at 100 rpm for 10 min to pre-mix the precursors. Afterward, ball milling was carried out for 96 cycles at 600 rpm, each cycle including 5 minutes of ball milling and then a 10-minute break to avoid overheating.