Functionalized Metal–Organic Framework Composite Electrolyte Membrane for High-Performance Solid Li Batteries

Metal-organic frameworks (MOFs)/polymer composite electrolytes have garnered worldwide attention because of their outstanding performance in energy-related applications. Here, a highly lithiated MOF (LZM) is designed as a filler into poly(ethylene oxide) (PEO). LZM is synthesized through a postsynthetic modified strategy to obtain preeminent single-ion conducting performance. The Lewis acidic sites in LZM interact with polymer segments and salt anions due to electrostatic interactions, which accelerate both the amorphization of PEO chains and Li⁺ transportation. Furthermore, the high content of Li⁺ and nanochannels in LZM frameworks facilitates the Li-ion transport in composite electrolytes, which is confirmed by the DFT result. The resulting composite electrolytes (P/LZM) achieve an ionic conductivity (6.86 × 10^-4 S cm^-1 at 60 °C) higher than the control PEO membrane. The electrochemical stability window of P/LZM is up to 5.07 V, which is wider than that of the blank PEO. The Li|Li cells operate stably without degradation for 1876 h under 0.1 mA cm^-2. The LiFePO₄ (LFP)|Li cell based on P/LZM electrolytes maintains a reversible discharge capacity of 126.4 mAh g^-1 and commendable capacity retention of 90.8% over 450 cycles under 2 C. Collectively, all of the results suggest the P/LZM membranes are potentially stable solid-state electrolytes for solid-state Li batteries.