Ethoxy/Amide‐Functionalized UiO‐66‐(OH) ₂ MOF Composite Separators Enabling Water/HF scavenging and Li ⁺ Regulation for Stable Lithium Metal Batteries

ABSTRACT To overcome the disadvantages of commercial polyolefin‐based separators, such as inadequate electrochemical properties and dendrite growth, in lithium metal batteries, nanofiber separators coated with MOF are prepared using the electrospinning technique and a vacuum surface coating method. The Zr‐based MOF (UiO‐66‐(OH) ₂ ) materials that scavenge H ₂ O/HF in the electrolyte are synthesized via hydrothermal synthesis, and ethoxy/amide groups are introduced onto the MOF surface through a reaction between hydroxyl groups on UiO‐66‐(OH) ₂ surface and ICPTES (silane coupling agents). The fabricated MF‐U66I separator exhibits excellent performance, including high porosity (68.2 %), substantial electrolyte absorption capacity (750 %), outstanding mechanical strength (27.5 N mm ² ), dimensional stability (<5% shrinkage at 200 °C), and significantly high electrochemical properties (σ = 2.85 mS cm ⁻¹ , = 0.77). Moreover, Li metal‐based cells using the MF‐U66I separator show much greater capacity retention and cycle life than the other cells with PE and pristine MF separators. The NCM∥Gr full cell equipped with the MF‐U66I separator also maintains more than 93.5 % of its initial discharge capacity after 500 cycles at 55 °C. These results demonstrate that the MF‐U66I separator surpasses conventional PE and pristine MF separators and offers strong potential for practical application as a stable separator for lithium metal batteries.