Li2O2 Formation Electrochemistry and Its Influence on Oxygen Reduction/Evolution Reaction Kinetics in Aprotic Li–O2 Batteries

Aprotic Li-O2 batteries are regarded as the most promising technology to resolve the energy crisis in the near future because of its high theoretical specific energy. The key electrochemistry of a nonaqueous Li-O2 battery highly relies on the formation of Li2 O2 during discharge and its reversible decomposition during charge. The properties of Li2 O2 and its formation mechanisms are of high significance in influencing the battery performance. This review article demonstrates the latest progress in understanding the Li2 O2 electrochemistry and the recent advances in regulating the Li2 O2 growth pathway. The first part of this review elaborates the Li2 O2 formation mechanism and its relationship with the oxygen reduction reaction/oxygen evolution reaction electrochemistry. The following part discusses how the cycling parameters, e.g., current density and discharge depth, influence the Li2 O2 morphology. A comprehensive summary of recent strategies in tailoring Li2 O2 formation including rational design of cathode structure, certain catalyst, and surface engineering is demonstrated. The influence resulted from the electrolyte, e.g., salt, solvent, and some additives on Li2 O2 growth pathway, is finally discussed. Further prospects of the ways in making advanced Li-O2 batteries by control of favorable Li2 O2 formation are highlighted, which are valuable for practical construction of aprotic lithium-oxygen batteries.