Enhancing Ion Transport: Function of Ionic Liquid Decorated MOFs in Polymer Electrolytes for All-Solid-State Lithium Batteries

Poly(ethylene oxide) (PEO)-based polymer electrolytes have shown extraordinary promise for all-solid-state lithium batteries; however, the practical application was severely restricted by their low ionic conductivity. In this work, the robust pores of HKUST-1(Cu) were first filled by a lithium-containing ionic liquid (Li-IL) to form ion-conductive Li-IL@HKUST-1. Subsequently, flexible composite polymer electrolytes (CPEs) were constructed via a solution-casting approach upon the incorporation of Li-IL@HKUST-1 with PEO. The as-synthesized CPE membrane showed a high ionic conductivity of 1.20 × 10–4 S cm–1 at 30 °C compared to 9.76 × 10–6 S cm–1 for the PEO-only electrolyte. Furthermore, the assembled LiFePO4/Li solid-state batteries delivered a stable reversible capacity of 136.2 mAh g–1 with a capacity retention of 92% after 100 cycles at a high current density of 1 C (60 °C). The excellent electrochemical performance was mainly attributed to the combination of Li-IL@HKUST-1 and the PEO matrix, which effectively reinforced the polymer matrix and facilitated the fast transport of lithium ions. The present research provides an effective strategy for building high-performance all-solid-state lithium batteries.