Sulfone-Based Electrolyte Solutions for Rechargeable Magnesium Batteries Using 2,5-Dimethoxy-1,4-benzoquinone Positive Electrode

We examined three sulfone-based electrolyte solutions for use in rechargeable magnesium batteries; i.e ., sulfolane (SL), ethyl- i -propyl sulfone (EiPS) and di- n -propyl sulfone (DnPS), in which was dissolved 0.5 mol L −1 magnesium bis(trifluoromethanesulfonyl)amide (Mg(TFSA) 2 ). The specific conductivities of these sulfone-based Mg-electrolyte solutions were 1–2 mS cm −1 at 30°C. These electrolyte solutions were thermally stable < 250°C, and electrochemically stable < 2 V vs. Mg reference electrode (Mg wire). In these electrolyte solutions, an organic positive electrode made of 2,5-dimethoxy-1,4-benzoquinone (DMBQ) underwent reversible charge-discharge reactions. The reduction-oxidation current of the metallic Mg negative electrode was observed. A two-electrode cell composed of Mg|Mg(TFSA) 2 /SL|DMBQ endured more than 50 charge-discharge cycles at 30°C.