A Single-Ion Conducting UiO-66 Metal–Organic Framework Electrolyte for All-Solid-State Lithium Batteries

A metal–organic framework (MOF) single lithium-ion conductor has been synthesized by covalently immobilizing anions to the skeleton of MOF structures. The functionalized UiO-66 MOF exhibits an electrochemical stability window of 5.2 V versus Li|Li⁺ and ionic conductivity of 6.0 × 10^–5, 7.9 × 10^–5, and 1.1 × 10^–4 S/cm at 25, 60, and 90 °C, respectively. It displays single-ion conducting behavior with a high Li-ion transference number of 0.90 at 25 °C in the absence of any plasticizer. After ethylene carbonate and propylene carbonate are incorporated into the MOF structure, its ionic conductivity reaches 7.8 × 10^–4 S/cm at room temperature. The MOF electrolyte has been evaluated with all-solid-state Li|MOF|LiFePO₄ batteries at room temperature, showing excellent rate capacity and cycling stability.