Synergy Strategy between Fluorine Functionalization and Defect Engineering Enables the High-Performance MOF-Based...

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-F₄, where HP_X represents the defect degree of UiO-66-F₄, 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-F₄ 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-F₄ 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-F₄ |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.