High‐entropy Electrolyte Enables High Reversibility and Long Lifespan for Magnesium Metal Anodes

Abstract The stable cycling of Mg‐metal anodes is limited by several problems, including sluggish electrochemical kinetics and passivation at the Mg surface. In this study, we present a high‐entropy electrolyte composed of lithium triflate (LiOTf) and trimethyl phosphate (TMP) co‐added to magnesium bis(trifluoromethane sulfonyl)imide (Mg(TFSI) 2 /1,2‐dimethoxyethane (DME) to significantly improve the electrochemical performance of Mg‐metal anodes. The as‐formed high‐entropy Mg 2+ ‐2DME‐OTf − ‐Li + ‐DME‐TMP solvation structure effectively reduced the Mg 2+ ‐DME interaction in comparison with that observed in traditional Mg(TFSI) 2 /DME electrolytes, thereby preventing the formation of insulating components on the Mg‐metal anode and promoting its electrochemical kinetics and cycling stability. Comprehensive characterization revealed that the high‐entropy solvation structure brought OTf − and TMP to the surface of the Mg‐metal anode and promoted the formation of a Mg 3 (PO 4 ) 2 ‐rich interfacial layer, which is beneficial for enhancing Mg 2+ conductivity. Consequently, the Mg‐metal anode achieved excellent reversibility with a high Coulombic efficiency of 98 % and low voltage hysteresis. This study provides new insights into the design of electrolytes for Mg‐metal batteries.