Nanostructured zeolitic imidazolate framework-67 reinforced poly(ethylene oxide) composite electrolytes for all solid state Lithium ion batteries

Composite polymer electrolyte is a promising solid electrolyte for all solid state lithium ion batteries (ASSLIBs) due to its reliable safety, high ionic conductivity and excellent flexibility. Here, the uniform rhomboid dodecahedron structured zeolitic imidazolate framework-67 (ZIF-67) with high specific surface area and abundant nano-pores have been prepared by adjusting the synthetic solvent, which are subsequently incorporated into poly(ethylene oxide) (PEO) matrixes to form solid composite electrolyte (SCE). ZIF-67 MOFs can reduce the crystallinity of PEO matrixes, coordinate with C-O-C bonds of PEO and improve the mechanical properties of solid electrolyte. Additionally, abundant pore structure of ZIF-67 can endow its ability to absorb anions. The optimized SCE shows high ionic conductivities of 1.51 × 10−5 S/cm at 25 °C, wide electrochemical stable window of around 5.2 V and good interfacial compatibility with lithium. Furthermore, LiFePO4/Li ASSLIB exhibits high electrochemical performances. At current rates of 0.2 C, 0.5 C, 1 C and 2 C, the battery has specific discharging capacities of 155.13, 153.77, 148.83 and 139.90 mAh·g−1, respectively, and it demonstrates high capacity retention of 90.17% after 100 cycles at 0.5 C. Therefore, it is concluded that ZIF-67/PEO SCE is a good solid electrolyte candidate for ASSLIB.