Complex Structures and Electrochemical Properties of Magnesium Electrolytes

Magnesium organohaloaluminate in tetrahydrofuran [0.25 mol/L Mg(AlCl 2 EtBu) 2 /THF, Et:C 2 H 5 ,Bu:C 4 H 9 ] is an electrolyte solution that is able to deposit and dissolve magnesium electrochemically and reversibly at room temperature. It has been reported that the electrochemical window is ruled by Lewis acidity of the aluminum compounds involved, and some complex species formed in the electrolyte have been suggested based on the analysis of nuclear magnetic resonances and Raman spectroscopy. Because in these analytical methods there are not enough controls to identify all the included compounds, neither the complete complex structures nor the mechanism of the reversible reaction has been revealed yet. Here, we show the complete complex structures in this electrolyte directly observed by the X-ray absorption fine structure measurements, which reveal the reversible equilibrium reaction as well as the other electrochemical properties of this electrolyte.