Moisture-tolerant Mg-metal electrodes for practical fabrication of rechargeable Mg batteries.

Despite striking advantages in terms of cost and safety, penetration of rechargeable Mg batteries into the commercial market is still hampered by major technical challenges, including intrinsic hypersensitivity of Mg metal to moisture, which readily forms a compact ion-insulating film on the surface. To unlock this critical constraint, a moisture-tolerant Mg electrode is developed that is capable of efficient Mg plating-stripping even in the highly moist electrolytes. Here we show that short immersion of Mg metal in trimethyl phosphate creates a sacrificial protection layer containing dimethyl magnesium in magnesium dimethyl phosphate, which synergistically scavenges water molecules from the electrolytes instantly, enabling manufacturing of Mg-ion cells under moist and/or atmospheric conditions. This simple and scalable strategy provides a practical route to reducing the manufacturing costs of rechargeable Mg batteries, thereby expediting their early commercialization.