Li–O₂/Air Batteries Using Ionic Liquids – A Comprehensive Review

The remarkable surge in energy demand has compelled the quest for high-energy-density battery systems. The Li–O₂ battery (LOB) and Li–air battery (LAB), owing to their extremely high theoretical energy density, have attracted extensive research in the past two decades. The commercial development of LOB is hampered due to the numerous challenges its components present. Ionic liquids (ILs) are considered potential electrolyte solvents of LOBs and LABs due to their excellent electrochemical stability, thermal stability, non-flammability, low flammability, and O₂ solubility. In addition to electrolyte solvents, ILs also have other applications in LOB and LAB systems. This review reports the progress of IL-based LOBs and LABs over the years since treported for the first time in 2005. The impact of the physiochemical properties of ILs on the performance of LOB and LAB at various operating conditions is thoroughly discussed. The various methodologies are also summarized that are employed to tune ILs’ physiochemical properties to render them more favorable for rechargeable lithium batteries. Tunable properties of ILs create the possibility of designing cost-effective batteries with excellent safety, high energy density and high power density, and long-term stability.