Sulfone-Based Electrolytes for Magnesium Rechargeable Batteries
After the breakthrough by Aurbach described above, various approaches have been tried for further improvements. Kim et al. enhanced the electrochemical performance of hexamethyldisilazide magnesium chloride (HMDSMgCl) in THF through the addition of aluminum chloride (AlCl3) together with the crystallization of electrochemical active species [Mg2(μ-Cl)3·6THF]+. Mohtadi et al. reported the reversible Mg electrolytes of magnesium borohydride Mg(BH4)2 in both THF and dimethoxyethane (DME). And recently, Abe et al. have found that magnesium deposition and dissolution can take place in some electrolyte solutions, such as magnesium bromide together with magnesium ethoxide in 2-methyltetrahydrofuran( (Mg(OEt)2 + MgBr2)/2-MeTHF), and MgBr2 in n-butyl methyl ether (MgBr2/n-BME). The same group has also found that Glymes and magnesium chloride (MgCl2) with AlCl3enabled the magnesium deposition and dissolution on platinum electrode with high coulombic efficiency.
Despite the improvements in the electrochemical properties, at least two more breakthroughs are required for the commercialization regarding Mg electrolytes; one is the reduction of chemical reactivity, and the other one is suppression of solvent evaporation. Here we report the development of a novel Mg electrolyte using sulfone as solvents. Although it does not include highly reactive materials such as organic magnesium compounds as well as Lewis acids, the electrolyte shows reversible Mg deposition and dissolution at room temperature. The electrochemical window is larger than 3.0V vs Mg without any corrosion on stainless steel electrodes. As the boiling point of the sulfone is high, we don’t need to care about the solvent evaporation at the operating condition. In addition to the details of our Mg electrolyte, the performance of Mg rechargeable battery whose energy density would be higher than the present Li-ion batteries, will be presented at the conference.