Enhanced ionic conductivity of intrinsic solid polymer electrolytes using multi-armed oligo(ethylene oxide) plasticizers

In this work, we report on star-shaped plasticizers with the various chain lengths of multi-armed oligo(ethylene oxide) in order to prevent the plasticizers from crystallizing and eventually to enhance the ionic conductivity at low temperature. The multi-armed plasticizers are compared with the linear ones in terms of the ionic conductivity of the polymer electrolytes using them. The ionic conductivity of the polymer electrolytes using the linear plasticizer abruptly decreases below 0 °C, while the temperature dependence of the ionic conductivity of the polymer electrolytes based on the multi-armed plasticizers shows a typical Vogel–Tamman–Fülcher (VTF) relationship in the temperature range from −30 to 100 °C. Such enhanced ionic conductivity at low temperature is because the multi-armed plasticizers are not crystallizing due to the branches or the multi-arms structure. The multi-armed plasticizers are found to be electrochemically stable up to 5.2 V by cyclic voltammetry analysis, which means that they are electrochemically stable enough for the application in the lithium ion batteries.