Facet‐Regulated MOF Nanosheets Enable Ion‐Selective Separators for Stable Lithium Metal Batteries

Abstract

Lithium metal batteries are promising energy storage systems but suffer from dendrite growth and interfacial instability caused by uneven Li + flux and uncontrolled anion migration. Herein, we report a facet‐regulated strategy to construct ultrathin two‐dimensional metal‐organic framework (MOF) nanosheets for ion‐selective separator modification. Density functional theory reveals that gluconate anions preferentially adsorb on high‐energy facets, suppressing vertical crystal growth and enabling the formation of Zn(bim)(OAc) based nanosheets (ZBO‐NS). When coated onto a polypropylene (PP) separator, the resulting ZBO‐NS@PP forms a uniform lamellar architecture with abundant open metal sites and hydroxyl groups. This structure enables strong anion anchoring and promotes selective Li + transport, as evidenced by an increased Li + transference number (0.73) and homogenized ion distribution confirmed by theoretical simulations. As a result, ZBO‐NS@PP effectively suppresses concentration polarization and dendrite growth, delivering stable Li + plating/stripping for more than 1000 h at a current density of 0.5 mA/cm 2 and an areal capacity of 1 mA·h/cm 2 , while maintaining a low overpotential of approximately 28 mV. In Li | |LiFePO 4 full cells, it achieves a high capacity retention of 85% after 500 cycles at 1 C. This work provides a general strategy for constructing ion‐selective interfaces via facet engineering of MOFs toward high‐performance lithium metal batteries.