The path toward practical Li-air batteries

Wide adaptation of intermittent renewable energies into the power grid and more affordable electric vehicles cannot be realized without low-cost, high-energy, and long-life energy storage systems. Using lithium, the lightest metal, and ubiquitous O2 in the air as active materials, lithium-air (Li-air) batteries promise up to 5-fold higher specific energy than current Li-ion batteries at a lower cost. However, the Li-air technology is still in its infancy, and its development has been challenged by severe instability originating from the high reactivities of various oxygenated species. Over the past decade, much effort has been devoted to fundamental mechanistic studies, leading to substantial improvement in the reversibility of Li-air batteries. Meanwhile, relatively less attention has been focused on demonstrating practical performance and realizing the promised high specific energy. In this perspective, we identify four critical ongoing challenges to achieving practical Li-air batteries: improving positive electrode reversibility with high precision quantification of side reactions, achieving high specific capacity and rate capability at pouch cell level or above, developing open systems in atmospheric air, and stabilizing the Li metal negative electrode. We discuss the state-of-the-art progress and highlight future developments needed for achieving practical Li-air batteries and their future commercialization.