Stable and Dendrite-Suppressed Li-Mg Alloy Anode for Lithium-Air Batteries

Abstract Lithium-air batteries (LABs) have an energy density of 500–1000 Wh kg ^-1 , which exceeds that of current lithium-ion batteries. However, their practical application is currently limited by poor cycle life and safety risks associated with unstable lithium metal anodes, such as sudden ignition caused by short circuits or contact with water. Alloying lithium with magnesium (Li-Mg) is a promising solution as it incorporates the Li source within the alloy lattice. This study evaluated Li-Mg alloys containing 10 wt% (Li-0.1Mg) and 20 wt% (Li-0.2Mg) magnesium as an alternative to pure lithium anodes. Lithium dissolution and plating in pure oxygen revealed that the alloy anodes exhibited enhanced cycling stability, with the Li-0.1Mg alloy demonstrating the lowest overpotential. LAB cells with carbon cathodes and Li-0.1Mg anodes exhibited performance comparable to that of cells with pure Li anodes. SEM analysis confirmed considerable dendrite suppression. Stack-type LAB cells with Li-0.1 Mg anodes achieved a capacity of 0.51 Ah and an energy density of 530 Wh kg ^-1 in dry air. The reduced reactivity of Li-Mg alloy anodes with water further enhances safety without compromising the cell’s light weight and capacity. These findings provide new guidelines for designing safe and durable metal anodes for practical LABs.