Synergistic Effect between the Co Metal Center and Porphyrin Ring Ligand and Singlet Oxygen Elimination Boost Rechargeable LiOH-Based Li-O2 Batteries

For high-energy Li-O-2 batteries, LiOH chemistry-based batteries are considered to be promising candidates owing to their better chemical and electrochemical stability, compared to typical Li2O2 chemistry-based batteries. However, the mechanism of formation of LiOH remains undefined. Herein, we adjust the type of metal centers and ligands in 5,10,15,20-tetrakis(4-aminophenyl)-porphyrin-Co (Co-TAP) to successfully synthesize a series of organometallic complexes and utilize them as redox mediators (RMs) for Li-O-2 batteries. The synergistic effect between the ligands and metal centers of RMs can alter the types and morphologies of discharge products, thereby affecting the electrochemical performance of batteries. Only the interaction between the Co metal center and porphyrin ring ligand can promote LiOH formation. Li-O-2 batteries operated via LiOH chemistry can completely eliminate O-1(2) generation, suggested by ex situ EPR and operando fluorescence. This work provides a promising strategy to develop reversible and efficient LiOH-based Li-O-2 batteries.