A rechargeable Mg|O2 battery.

Rechargeable Mg|O2 batteries (RMOBs) offer several advantages over alkali metal-based battery systems owing to Mg's ease of transport/storage in ambient environment, low cost originating from its high abundance, as well as the high theoretical specific energy of RMOBs. However, research on RMOBs has been stagnant for the past decade, largely owing to unacceptably poor electrochemical performance. Here, we present a RMOB that employs Mg anode, Mg((CF3SO2)2N)2-MgCl2 in diglyme (G2) electrolyte, and commercial Pt/C on carbon fiber paper (Pt/C@CFP) oxygen cathode. This battery demonstrates unparalleled improvement over existing RMOBs by rendering a discharge capacity over 1.6 mAh cm-2, achieving cycle lives up to 35 cycles with a cumulative energy density of ∼3.2 mWh cm-2 at room temperature. This RMOB system seeks to reignite the pursuit of novel electrochemical systems based on Mg-O2 chemistries.