Highly conductive, flexible polymer electrolyte membrane based on poly(ethylene glycol) diacrylate-co-thiosiloxane network

An amorphous co-network consisting of poly(ethylene glycol) diacrylate (PEGDA) and thiosiloxane was prepared by means of thiol-ene “click” reaction to impart high ion conduction via enhanced segmental mobility of the co-network. By varying PEGDA-thiosiloxane ratios, several polymer electrolyte membranes (PEM) have been fabricated to control the glass transition temperature (Tg), while keeping the equal molar ratio of succinonitrile (SCN) plasticizer and bis(trifluoromethane sulfonyl)imide (LiTFSI) salt for solid-state lithium ion batteries. It was found that the addition of thiosiloxane into the PEM network not only results in improved thermal stability and greater extensibility, but also reduces Tg leading to higher ionic conductivity that reaches the level of superionic conductor at room temperature, which further increases to 10−2 Scm−1 at high battery operating temperatures (60–70 °C). To evaluate their electrochemical performance, half-cells comprising of LiFePO4/PEM/Li foil were tested by means of cyclic voltammetry. An initial discharge capacity of 148 mAhg−1 was obtained at a current rate of 0.2 C with capacity retention of about 89%.