Constructing Efficient Mg(CF₃SO₃)₂ Electrolyte via Tailoring Solvation and Interface Chemistry for High‐Performance Rechargeable Magnesium Batteries

Abstract

Abstract Non‐passivating and chlorine‐free electrolytes are crucial for making rechargeable magnesium batteries practically feasible. Rational design of a brand‐new electrolyte should balance both Mg salt and solvent considering that the interfacial reactions occurring at electrolyte/electrode interface involve with ion solvation structure. Herein, nitrogenous 2‐methoxyethylamine (MOEA) is employed as co‐solvent to regulate the coordination behavior of cations/anions in Mg(CF 3 SO 3 ) 2 ‐G2 electrolyte after a series of screenings, which enables significantly ameliorated physiochemical properties. In‐depth insight on the mechanism of MOEA participating in the solvation structure formation and interfacial reactions is deduced via density functional theory calculations and molecular dynamics simulations. The decompositions of MOEA‐tailored cationic/anionic complexes shield Mg anode and Mo 6 S 8 cathode with Mg 3 N 2 and C x N y ‐rich layers, respectively, which enable to suppress side reaction and accelerate Mg 2+ transportation with competing desolvation at the interfacial layer. All the merits endow remarkable performances of symmetric/asymmetric cells with ultralong‐cycle lives over 5000 h and a remarkable average Coulombic efficiency of 98.3% after 8200 cycles (≈11 months), respectively. Additionally, a cheerful discharge capacity of ≈59.3 mAh g −1 is obtained over 1000 cycles at 0.5 C in Mo 6 S 8 ||Mg full cell.