Unravelling the Complex LiOH‐Based Cathode Chemistry in Lithium–Oxygen Batteries

The LiOH‐based cathode chemistry has demonstrated potential for high‐energy Li−O(2) batteries. However, the understanding of such complex chemistry remains incomplete. Herein, we use the combined experimental methods with ab initio calculations to study LiOH chemistry. We provide a unified reaction mechanism for LiOH formation during discharge via net 4 e(−) oxygen reduction, in which Li(2)O(2) acts as intermediate in low water‐content electrolyte but LiHO(2) as intermediate in high water‐content electrolyte. Besides, LiOH decomposes via 1 e(−) oxidation during charge, generating surface‐reactive hydroxyl species that degrade organic electrolytes and generate protons. These protons lead to early removal of LiOH, followed by a new high‐potential charge plateau (1 e(−) water oxidation). At following cycles, these accumulated protons lead to a new high‐potential discharge plateau, corresponding to water formation. Our findings shed light on understanding of 4 e(−) cathode chemistries in metal–air batteries.