For all-solid-state lithium batteries (ASSLBs), polymer-blended solid composite electrolytes (SCEs) have drawn wide interest owing to their significance in improving the interfacial solid-solid contacts and inhibiting the growth of lithium dendrites. In this work, SCEs based on PVDF-HFP/PMMA matrix containing MOFs (NH₂-MIL-53(Al)) and LiTFSI were designed and synthesized employing an easy solution casting method. The synthesized samples were examined by XRD, SEM, EDS, and electrochemical tests. It was found that MPP-2 SCE not only has excellent ionic conductivity at 60 °C of 5.54 × 10⁻⁴ S cm⁻¹, but also exhibits superior interfacial compatibility in Li||Li symmetric batteries, which can constantly cycle for about 800 h at 0.1 mA cm⁻² with no short-circuiting. The assembled Li|MPP-2|LiFePO₄ cell exhibited a first discharge specific capacity of up to 157.1 mAh g⁻¹ at 60 °C and 0.2 C. This work may help to further advance the progress of ASSLBs in the future.