Cost-effective and sustainable battery materials for large-scale batteries are the need of the hour to garner renewable energy with high-performance metal battery technologies. Here, we report the high-performance and long cycle life electrolyte prepared from low-cost triethylamine hydrochloride (Et3NHCl) and aluminum chloride (AlCl3) termed as (TA) with different concentrations of magnesium diethylphosphate (Mg(DEP)2) salt. The optimized ratio of the 0.1 M Mg(DEP)2 electrolyte has shown a high ionic conductivity of 4.5 × 10-3 S cm-1 at ambient temperature and good anodic stability of 2.41 V vs. Mg/Mg2+. The dissolution/deposition of magnesium (Mg) on a Pt working electrode was systematically analyzed in this electrolyte. Cyclic voltammetry (CV) of the Mg-graphite battery was used to probe the intercalation/de-intercalation of Mg-AlCl4- ions into/from the graphite layer structure. This was confirmed by various analytical techniques, such as energy dispersive X-ray spectroscopy, X-ray diffraction technique and X-ray photoemission spectroscopy. Notably, during the galvanostatic study analysis, the assembled Mg cell delivered a high discharge capacity of 115 mA h g-1 at a high C/10 rate, with more than 180 cycles at >80% coulombic efficiency. This electrolyte will be helpful in grid-scale power storage systems in future generations.