High Active Magnesium Trifluoromethanesulfonate-Based Electrolytes for Magnesium–Sulfur Batteries

The shortage of high-performance and easily prepared electrolyte has hindered the progress of rechargeable magnesium–sulfur (Mg–S) batteries. In this paper, we develop a new electrolyte based on Mg­(CF3SO3)2–AlCl3 dissolved in tetrahydrofuran and tetraglyme mixed solvents. Mg­(SO3CF3)2 as an Mg2+ source is nonnucleophilic, easy to handle, and much cheaper than Mg­(TFSI)2 (TFSI = bis­(trifluoromethanesulfonyl)­imide). After modification with anthracene (π stabilizing agent) as a coordinating ligand to stabilize the Mg2+ ions and MgCl2 to improve the interface properties by accelerating the reaction of Mg­(CF3SO3)2 with AlCl3, the electrolyte exhibits a low overpotential for overall Mg deposition and dissolution, moderate anodic stability (3.25 V on Pt, 2.5 V on SS, 2.0 V on Cu, and 1.85 V on Al, respectively), and a suitable ionic conductivity (1.88 mS cm–1). More importantly, this electrolyte modulated by Li-salt additives exhibits good compatibility with S cathode and can be applicable for Mg–S batteries. The rational formulation of the new electrolyte could provide a new avenue for simply prepared Mg electrolytes of Mg–S and rechargeable magnesium batteries