Ethoxy/Amide-Functionalized UiO-66-(OH)₂ MOF Composite Separators Enabling Water/HF scavenging and Li⁺ Regulation for...

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 H₂O/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 mm²), dimensional stability (<5% shrinkage at 200 °C), and significantly high electrochemical properties (σ = 2.85 mS cm^-1, $t_{L{i}^{+}}$ = 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.