Conformal Li2O2 Growth and Decomposition Within 3D Lithiophilic Nanocages of Metal–Organic Frameworks for High-Performance Li─O2 Batteries

초록

Li─O2 batteries (LOBs) have the largest theoretical capacity among current batteries, but the irreversible growth and decomposition of Li2O2 products in positive electrodes cause dramatic degradation of their capacities over charging–discharging cycles. Herein, a metal–organic framework is reported with bipyridinic N linkers attached to graphene (bpyN-MOF/g) as a positive electrode material to overcome the challenge. The bpyN-MOF/g promotes conformal Li2O2 growth during discharging, while allowing Li2O2 decomposition at a low overpotential (0.487 V vs Li+/Li at 200 mA gc−1) during charging process, outperforming the Pt/C-based electrode (0.857 V). Moreover, 3D-tomography and density functional theory calculations consistently support the Li2O2 growth and decomposition mechanism inside bpyN-MOF/g. Furthermore, bpyN-MOF/g//Li LOBs achieve an exceptional discharge capacity (17 275 mAh gc−1 at 100 mA gc−1) and steady cycling for 270 cycles at 1000 mAh gc−1 under 2000 mA gc−1. Additionally, high gravimetric capacity at low mass loadings (0.27–0.44 mg cm−2) and stable cycle operation at a high areal current density (0.5 mA cm−2) open new opportunities for various practical applications. © 2024 The Author(s). Advanced Energy Materials published by Wiley-VCH GmbH.

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