Facilitating Li plus conduction channels and suppressing lithium dendrites by introducing Zn-based MOFs in composite electrolyte membrane with excellent thermal stability for solid-state lithium metal batteries

Solid-state lithium metal batteries have received a lot of attention in comparison to conventional liquid lithium batteries because of their greater energy density and safety. Nevertheless, the broad practical use of solid electrolyte membranes made of poly (ethylene oxide) (PEO) is constrained by their poor capacity to suppress lithium dendrite formation and low room temperature ionic conductivity. In this study, a fluorinated Polymphenyleneisophthalamide (PMIA) nanofiber membrane loaded with ZIF-8 nanoparticles was introduced into the PEO-LiTFSI to get a solid composite electrolyte membrane. The open metal sites in the ZIF-8 can couple with the anions in lithium salt, dissociating more free lithium ions. In addition, the PMIA molecular chain contained special meta-phenylene amide bonds, which can form hydrogen bonds among PMIA, PEO and LiTFSI. These hydrogen bonds can provide a novel pathway for fast migration of Li+. The polyvinylidene fluoride hexafluoropropene (PVDF-HFP) as fluorination source and salts in spinning solution also gave the fiber membrane a special 3D structure. The unique structure can provide excellent mechanical strength for the electrolyte membranes. Because of these benefits, the electrolyte membranes had an ion conductivity of 2.39 x 10-4 S cm- 1 (30 degrees C) In addition, the symmetric battery exhibited stable cycling performance at 0.4 mA h cm-2. The composite electrolyte membranes exhibited excellent compatibility with LiFePO4 and NCM811 cathodes.