MOF-derived nanoporous multifunctional fillers enhancing the performances of polymer electrolytes for solid-state lithium batteries

Polymer electrolytes usually suffer from low ionic conductivity and poor stability against the lithium electrode. Taking advantage of nanostructured metal–organic frameworks (MOFs), novel nanoporous fillers, i.e., UIO/Li-IL, are developed for polymer electrolytes; in UIO/Li-IL, a Li-containing ionic liquid (Li-IL) is absorbed in UIO-66 MOFs. These fillers are multifunctional: high ionic conductivity and capability to suppress the crystallinity and to improve the stability of polyethylene oxide (PEO) against the lithium electrode. PEO-n-UIO composite polymer electrolytes are formed by dispersing the multifunctional fillers in PEO; the conductivity of the PEO-n-UIO solid electrolytes is increased by a factor of ∼37 to 1.3 × 10−4 S cm−1 at 30 °C with 40% UIO/Li-IL, and the current density for stable Li plating/stripping in PEO-n-UIO solid electrolytes is enhanced to 500 μA cm−2 at 60 °C. Solid-state lithium batteries based on the PEO-n-UIO solid electrolyte show an initial discharge capacity of ∼151 mA h g−1 with a capacity retention of 95% after 100 cycles at 0.5C and 60 °C. Our work pioneers novel multifunctional fillers to boost the performances of composite polymer electrolytes for high energy density, safe and long lifetime energy storage systems.