A critical review on lithium–air battery electrolytes

Metal-air batteries, utilizing the reduction of ambient oxygen, have the highest energy density because most of the cell volume is occupied by the anode while the cathode active material is not stored in the battery. Lithium metal is a tempting anode material for any battery because of its outstanding specific capacity (3842 mA h g(-1) for Li vs. 815 mA h g(-1) for Zn). Combining the high energy density of Li with ambient oxygen seems to be a promising option. Specifically, in all classes of electrolytes, the transformation from Li-O2 to Li-air is still a major challenge as the presence of moisture and CO2 reduces significantly the cell performance due to their strong reaction with Li metal. Thus, the quest for electrolyte systems capable of providing a solution to the imposed challenges due to the use of metallic Li, exposure to the environment and handling the formation of reactive discharged product is still on. This extended Review provides an expanded insight into electrolytes being suggested and researched and also a future vision on challenges and their possible solutions.