DFT-Guided Rational Design of a UiO-66-NH2/MFC Composite Separator with Hierarchical Pores for Modulating Interfacial Lithium-ion Transport

To address microfibrillated cellulose (MFC) separator shortcomings in lithium-ion flux homogenization and dendrite growth due to uneven ion distribution, this study developed a UiO-66-MFC composite separator with 20-30% loading. The hierarchical pores (0.8-1.2 nm micropores and 2-50 nm mesopores) enable selective Li + screening and rapid transport, while MFC's hydroxyl groups form hydrogen bonds with amino groups of UiO-66-NH 2 , enhancing mechanical strength to 16 MPa at a 20% loading. Density functional theory (DFT) calculations further reveal a strong interaction between -NH 2 and PF 6 - , with a binding energy reaching -8.622 keV. This interaction effectively restricts the migration of PF 6 - , promotes the desolvation process of lithium salts, accelerates Li⁺ transport, and fosters more uniform lithium deposition behavior. The electrochemical test results indicate that the 20% UiO-66-NH 2 /MFC separator demonstrates the most favorable overall performance. After cycling for 1000 h at a current density of 1 mA cm -2 , the overpotential of the Li/Li symmetrical battery remains stable at ± 0.10 V, suggesting effective inhibition of lithium dendrite growth. When paired with the LiFePO 4 cathode, the battery exhibits a capacity retention rate exceeding 90% after 100 cycles, while the coulombic efficiency approaches 100%. This study significantly improves the ion conduction and interface stability of the separator by optimizing the MOF ratio, thereby offering a novel strategy for the material design of high-safety and long-life lithium-ion batteries. This MOF-incorporated MFC strategy significantly enhances separator ion conduction and stability, offering a novel approach for safe, long-life lithium-ion batteries.