Understanding the Role of Lithium Iodide in Lithium–Oxygen Batteries

Lithium-oxygen (Li-O₂ ) batteries possess a high theoretical energy density, which means they could become a potential alternative to lithium-ion batteries. Nevertheless, the charging process of Li-O₂ batteries requires much higher energy, due to the insulating nature of the discharge product. It has been revealed that the anion additive, lithium iodide (LiI), can tune the cell chemistry to form lithium hydroxide (LiOH) as the product and facilitate the kinetics during the charging process. Although numerous studies have been reported, the role of this additive is still under investigation. Herein, the recent advances focusing on the use of LiI in Li-O₂ batteries are reviewed, its catalytic behavior on discharge and charge is discussed, and its synergistic effect with water is understood. The ambiguity existing among the studies are also revealed, and solutions to the current issues are introduced.