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

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 g_c⁻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 g_c⁻¹ at 100 mA g_c⁻¹) and steady cycling for 270 cycles at 1000 mAh g_c⁻¹ under 2000 mA g_c⁻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.