Oxygen – a fatal impurity for reversible magnesium deposition/dissolution

Rechargeable magnesium batteries (RMBs) are promising large-scale stationary energy storage devices. A manufacturing system similar to that used for lithium-ion batteries should be adoptable to the fabrication of RMBs. However, the compatibility of RMB components with atmospheric components other than moisture has not been studied yet. In this study, we investigated the effects of atmospheric conditions on the electrochemical dissolution–deposition behavior of magnesium in non-aqueous electrolytes and revealed for the first time that even a miniscule amount of O2 in the electrolyte solution is a fatal impurity for reversible magnesium electrochemistry. The carbonate-based interface on magnesium metal negative electrodes induced by a contact with O2-bearing electrolytes impedes interfacial electrochemical reactions, which can be overcome by surface functionalization by appropriate elements. A diethylzinc-derived interface leads to remarkably stable magnesium dissolution–deposition.