Tailoring Ce-Centered Metal-Organic Frameworks for Fast Li⁺ Transport in Composite Polymer Electrolyte

Regulating metal nodes to innovate the metal-organic framework (MOF) structure is of great interest to boost the performance of MOFs-incorporated composite solid electrolytes. Herein, Ce⁴⁺ with a low-lying 4f orbital is selected as metal center to coordinate with organic ligand to prepare MOF of Ce-UiO-66. The unsaturated open metal sites and defected oxygen vacancies furnish Ce-UiO-66 with strengthened Lewis acidity, which promotes Ce-UiO-66 interacting effectively with both poly(ethylene oxide) (PEO) and Li salt anions. Accordingly, Ce-UiO-66 as additive fillers can be uniformly dispersed in PEO matrix to form an advanced composite solid-state electrolyte (Ce-UiO@PEO) with accelerated Li⁺ transport. The optimized Ce-UiO@PEO displays a boosted ionic conductivity of 4.20 × 10^-4 S cm^-1 and an improved Li⁺ transference number of 0.39 at 60 °C, which are highly comparable to those of other MOFs@PEO electrolytes. Combined with the mechanical and thermal stabilities, such a Ce-UiO@PEO electrolyte enables Li/Li symmetric and Li/LiFePO₄ full cells with superior cycling stability and rate performance. The Ce-UiO@PEO electrolytes are of great potential to be applied in high-performance lithium metal batteries.