Synthesis and fundamental properties of carbon dioxide/alkylene oxide copolymers as ion-conductive polymers

Abstract

Solid polymer electrolytes (SPEs) have been proposed as solid-state alternatives to liquid electrolytes in electrochemical applications such as allpolymer Li batteries. However, these suffer from low ionic conductivity in the solid state compared with common liquid, gel and ceramic electrolytes. In this study, the preparation of SPEs using an alternative copolymer obtained from CO2 with an epoxide monomer instead of polyether was proposed synthesized and evaluated as a novel polymer candidate for SPEs. We used four types of polycarbonates (PCs) possessing different alkyl side groups; the SPE samples were prepared by the addition of 20-80 mol% LiTFSI. In all PC-based electrolytes, the glass transition temperature linearly decreased and the ionic conductivity increased with increasing LiTFSI concentration. Furthermore, longer alkyl side chains in PC decreased the conductivity, because the alkyl groups prevented LiTFSI dissociation. © 2013, The Society of Polymer Science, Japan.