Secondary Battery Performance of Solid Polymer Electrolyte Membranes Based on Lithium Ion Conductive Polyimide Nanofibers

Poly(ethylene oxide) (PEO)-based solid polymer electrolytes have been investigated for the applications to all-solid-state lithium ion batteries. However, the lithium ion conductivities of the present electrolyte membranes are insufficient for practical applications. In our previous study, composite membranes composed of PEO-grafted polyimide (PI-g-PEO) nanofibers showed good electrolyte characteristics. In this study, a series of PI-g-PEO with various PEO lengths and grafting ratios were synthesized and converted to nanofibers. The nanofiber frameworks (NfFs) with high PEO weight fractions showed much higher ion conductivity than the corresponding membranes. The NfF composite membrane was fabricated by composing the best NfF and the PEO/Li matrix electrolyte. The NfF composite membrane showed high ion conductivity at low temperatures and good secondary battery performances.