A Hybrid Solid Electrolyte Enabled by Dual MOFs and Ionic Liquids for Stable Solid-State Lithium Batteries

Substituting traditional liquid electrolytes with solid-state electrolytes has become a key strategy for enhancing the safety and energy density of energy storage devices. Owing to advantages such as low cost, ease of processing, and favorable interfacial compatibility, poly(ethylene oxide) (PEO)-based solid polymer electrolytes have become a research focus. However, their key properties, including ionic conductivity and electrochemical window, remain relatively modest. In this work, we synthesized two zirconium-based metal−organic frameworks (MOFs), namely, MOF-801 and MOF-808, and successfully combined them to form a composite MOF-801@808 filler. Lithium salt-loaded ionic liquids (Li-ILs) were subsequently incorporated into both the MOF-801@808 filler and the PEO matrix, resulting in a composite polymer electrolyte (CPE) containing both MOF fillers and ILs. This unique structure provides abundant ion dispersion sites for efficient ion transport pathways. Consequently, the resulting CPE achieves a room-temperature ionic conductivity of approximately 1.67 × 10 −4 S·cm −1, an expanded electrochemical stability window of ∼5.22 V, and an enhanced Li + transference number of ∼0.31. Furthermore, this composite material exhibits significantly improved cycling performance in Li||CPE||Li symmetric cells, maintaining stable operation for over 600 h. In Li||CPE-4||LFP full cells, an initial discharge specific capacity of 143 mAh g −1 was achieved at 0.2C, retaining over 130 mAh g −1 after 40 cycles, while the Coulombic efficiency remained consistently above 98%, demonstrating excellent cycling stability. Therefore, this work reveals a promising approach for achieving high ionic conductivity and superior cycling stability in CPEs, highlighting its significant research potential and attractive commercial prospects.