Synergy Strategy between Fluorine Functionalization and Defect Engineering Enables the High-Performance MOF-Based Microporous Membrane Lithium-Ion Electrolytes

The low ionic conductivity and unstable interfacial contact of MOF-based microporous membrane electrolytes severely limit their practical applications. Herein, a series of fluorine-functionalized UiO-66 electrolytes (HP X -UiO-66-F 4, where HP X represents the defect degree of UiO-66-F 4, and X represents the proportion of mixed ligand with X = 1:9, 3:7, 5:5, 7:3) with defective structures have been successfully synthesized through the postmodification strategy of ligand exchange. Electrochemical performance investigations indicated that HP 5:5 -UiO-66-F 4 exhibits a significantly improved overall performance compared to UiO-66, with a higher ionic conductivity of 2.67 × 10 –3 S cm –1, larger lithium ion transference number ( t Li + ) of 0.88, and wider electrochemical window (EW) of 5.24 V at room temperature. Importantly, HP 5:5 -UiO-66-F 4 still can maintain high electrochemical performance at low temperatures (2.57 × 10 –4 S cm –1 at −40 °C, 0.6 and 5.10 V at −20 °C). Additionally, appropriate fluorination may facilitate the formation of LiF SEI and effectively inhibit the growth of lithium dendrites, enabling the Li| HP 5:5 -UiO-66-F 4 |Li battery to maintain a stable electroplating/discharging cycle of 760 h at 0.1 mA cm –2 . This strategy of synergistically modifying MOFs by introducing appropriate amounts of - F and defect structures provides a new approach to enhance the electrochemical performance of microporous membrane electrolytes.