Orbital Coupling of PbO7 Node in Single-Crystal Metal-Organic Framework Enhances Li-O2 Battery Electrocatalysis

摘要

Optimizing the local coordination environment of metal centers in metal-organic frameworks (MOFs) is crucial yet challenging for regulating the overpotential of lithium-oxygen (Li-O-2) batteries. Herein, we report the synthesis of a class of PbO7 nodes in a single crystal MOF (naphthalene-lead-MOF, known as Na-Pb-MOF) to significantly enhance the kinetics of both discharge and charge processes. Compared to the PbO6 node in the single-crystal tetramethoxy-lead-MOF (4OMe-Pb-MOF), the bond length between Pb and O in the PbO7 node of Na-Pb-MOF increases, resulting in weaker Pb 5d-O 2p orbital coupling, which optimizes the adsorption interaction toward intermediates, and thereby promotes the rate-determining steps of both the reduction of LiO2 to Li2O2 and the oxidation of LiO2 to O-2 for reducing the activation energy of the overall reaction. Consequently, Li-O-2 batteries based on Na-Pb-MOF electrocatalysts exhibit a low total charge-discharge overpotential of 0.52 V and an excellent cycle life of 140 cycles.

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