Synergistic Effect\nbetween the Co Metal Center and\nPorphyrin Ring Ligand and Singlet Oxygen Elimination Boost Rechargeable\nLiOH-Based Li–O<sub>2</sub> Batteries

For high-energy Li–O<sub>2</sub> batteries, LiOH\nchemistry-based\nbatteries are considered to be promising candidates owing to their\nbetter chemical and electrochemical stability, compared to typical\nLi<sub>2</sub>O<sub>2</sub> chemistry-based batteries. However, the\nmechanism of formation of LiOH remains undefined. Herein, we adjust\nthe type of metal centers and ligands in 5,10,15,20-tetrakis(4-aminophenyl)-porphyrin-Co\n(Co-TAP) to successfully synthesize a series of organometallic complexes\nand utilize them as redox mediators (RMs) for Li–O<sub>2</sub> batteries. The synergistic effect between the ligands and metal\ncenters of RMs can alter the types and morphologies of discharge products,\nthereby affecting the electrochemical performance of batteries. Only\nthe interaction between the Co metal center and porphyrin ring ligand\ncan promote LiOH formation. Li–O<sub>2</sub> batteries operated\nvia LiOH chemistry can completely eliminate <sup>1</sup>O<sub>2</sub> generation, suggested by ex situ EPR and operando fluorescence.\nThis work provides a promising strategy to develop reversible and\nefficient LiOH-based Li–O<sub>2</sub> batteries.