Unravelling the Complex LiOH-Based Cathode Chemistry in Lithium-Oxygen Batteries.

The LiOH-based cathode chemistry has demonstrated potential for high-energy Li-O 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 O acts as intermediate in low water-content electrolyte but LiHO 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.