Diethylene Glycol Diethyl Ether as Electrolyte Solvent for Reversible Electrochemical Magnesium Plating

Due to their high theoretical energy density and the abundance of magnesium, rechargeable Mg batteries are promising candidate systems for future energy storage. However, finding suitable electrolytes that are compatible with the metallic Mg electrode and enable highly reversible Mg plating is still challenging. Typical electrolytes for rechargeable magnesium batteries are based on ether solvents such as tetrahydrofuran (THF), dimethoxyethane (DME), or higher glymes. Drawbacks are the high volatilites and low flashpoints of THF and DME and their harmfulness, problematic factors for industrial applicability. One potential alternative is diethylene glycol diethyl ether (DEGDEE) which is also an ether, but has significantly higher boiling and flashpoints than THF and DME, and is from today's perspective less harmful than any of the previously mentioned solvents. To test the suitability and stability of this class of electrolytes, different Mg salts in combination with DEGDEE for their electrochemical Mg plating and stripping properties are studied. Although Mg deposition needs higher overpotentials than for their DME‐based counterparts, the investigated electrolytes enable reversible Mg plating with relatively high Coulombic efficiencies, making DEGDEE a promising alternative electrolyte solvent for rechargeable Mg batteries.