Construction of amino functional metal-organic framework modified aramid composite separators with high Li⁺ transport channels for dendrite-free lithium-ion batteries

The formation and growth of lithium dendrites is an ever-present and urgent problem in lithium-ion batteries (LIBs). At the same time, the low melting point of commercial polyolefin separators may lead to safety issues during application. On this basis, in this work, poly (m-phenylene isophthalamide) (PMIA)/Zr-based metal-organic framework (NH₂-UiO-66) composite separator was prepared by non-solvent induced phase separation (NIPS). Firstly, the substantial quantity of Lewis acid sites and channels present in NH₂-UiO-66 plays a great role in obstructing anions in electrolytes while improving the transport of lithium-ion (Li⁺). Besides, simultaneously, because of the incorporation of -NH₂ within NH₂-UiO-66, electrolyte uptake and retention were further enhanced, while the resistance to Li⁺ migration is reduced, resulting in a lower interfacial impedance (the interface resistance is 2.3 Ω). And the ion conductivity of the PMIA/NH₂-UiO-66 composite separator is measured at 0.79 mS/cm, with a Li⁺ migration number also at 0.79, indicating superior performance. Furthermore, when MOF nanoparticles are incorporated into PMIA, the exposed Zr sites significantly increase the lithium affinity. It also regulates the Li⁺ transport path at the electrolyte-anode interface, resulting in a uniform and smooth Li metal surface topography after cycling, achieving excellent electrochemical performance, and ensuring long-term electrochemical stability over a wide range. The results show that the battery constructed using PMIA/NH₂-UiO-66 composite separator demonstrated outstanding rate performance and cycling stability. In a word, the designed PMIA/NH₂-UiO-66 composite separator provides an innovative way to develop high-performance separators in LIBs.