Coordination‐Gated MOF@COF Functional Separators for Regulating Ion Flux in Lithium Metal Batteries

Abstract

ABSTRACT Functional separators that regulate ion transport before lithium ions (Li + ) reach the lithium metal surface are critical for mitigating dendritic deposition and interfacial instability in lithium metal batteries. However, most separator designs mainly emphasize Li + affinity or electrolyte wettability, while the migration and decomposition behavior of anions remains insufficiently controlled. Herein, a coordination‐gated anion‐sieving separator is developed by constructing a UiO‐66@F‐COF@Ni core–shell interlayer on commercial polypropylene. In this architecture, the UiO‐66 core provides stable porous transport channels, and the fluorinated imine‐linked COF shell creates a polar ion‐regulating interface. The introduced Ni 2+ coordination centers interact with PF 6 − to modulate anion migration and interfacial decomposition. Benefiting from the coupled MOF@COF heterointerface and anion‐sieving effect, the separator exhibits high ionic conductivity, enhanced Li + transference, and reduced interfacial resistance. The regulated ion flux alleviates concentration polarization, guides uniform Li deposition, and promotes the formation of a compact inorganic‐rich SEI. Consequently, LFP||Li batteries retain 126.1 mAh g −1 after 1200 cycles at 2.0 C, and high‐voltage NCM811||Li batteries maintain 141.4 mAh g −1 after 600 cycles at 3.0 C. This coordination‐regulated MOF@COF separator provides a practical strategy for stable, high‐rate, and high‐voltage lithium metal batteries.