Molecular cleavage strategy enabling optimized local electron structure of Co-based metal-organic framework to accelerate the kinetics of oxygen electrode reactions in lithium-oxygen battery

Abstract

Metal-organic frameworks (MOFs) are considered as promising oxygen electrode materials for lithium-oxygen (Li-O2) batteries. However, their structure-activity relationship in catalyzing oxygen electrode reactions in Li-O2 battery is currently overlooked. Herein, molecular cleavage strategy is adopted to optimize local coordination structure of Co-MOF via introducing missing linkers. Theoretical calculation certifies that the introduction of monodentate ligand-benzoic acid (BA) as the missing linker causes the generation of defect state. Moreover, asymmetrically coordinated cobalt with surrounding oxygen caused by the introduction of BA optimizes electron coupling between Co 3d orbits and oxygen adsorbents, eventually promoting oxygen electrode reactions in Li-O2 batteries. However, excessive missing linkers can lead to the collapse of framework, covering active sites and thus deteriorating the catalytic activity of MOF. As a result, Li-O2 battery with Co-MOF containing 10 mol% BA (named as Co-MOF-BA0.1) delivers low overpotential of 0.86 V and large discharge capacity of 14011 mAh g−1.