Hybrid MgCl2/AlCl3/Mg(TFSI)2 Electrolytes in DME Enabling High-Rate Rechargeable Mg Batteries

Rechargeable magnesium batteries (RMBs) are considered as one of the most promising next-generation secondary batteries due to their low cost, safety, dendrite-free nature, as well as high volumetric energy density. However, the lack of suitable cathode material and electrolyte is the greatest challenge facing practical RMBs. Herein, a hybrid electrolyte MgCl2/AlCl3/Mg­(TFSI)2 (MACT) in dimethyl ether (DME) is developed and exhibits excellent electrochemical performance. The high ionic conductivity (6.82 mS cm–1) and unique solvation structure of [Mg2(μ-Cl)2(DME)4]2+ promote the fast Mg kinetics and favorable thermodynamics in hybrid Mg salts and DME electrolyte, accelerating mass transport and the charge transfer process. Therefore, the great rate capability can be realized both in symmetric Mg/Mg cell and in CuS/Mg full cell.