Conformal Li${}_2$O${}_2$ growth and decomposition within 3D lithiophilic nanocages of metal-organic frameworks for high-performance Li-O${}_2$ batteries

Li-O${}_2$ batteries (LOBs) have the largest theoretical capacity among current batteries, but the irreversible growth and decomposition of Li${}_2$O${}_2$ 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 Li${}_2$O${}_2$ growth during discharging, while allowing Li${}_2$O${}_2$ decomposition at a low overpotential (0.487 V vs Li${}^{+}$/Li at 200 mA g${}_c$${}^{-1})$ during charging process, outperforming the Pt/C-based electrode (0.857 V). Moreover, 3D-tomography and density functional theory calculations consistently support the Li${}_2$O${}_2$ growth and decomposition mechanism inside bpyN-MOF/g. Furthermore, bpyN-MOF/g//Li LOBs achieve an exceptional discharge capacity (17 275 mAh g${}_c$${}^{-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. (© 2024 The Author(s). Advanced Energy Materials published by Wiley‐VCH GmbH)