Effects of polymer backbone connectivity on ion conduction in polymers bearing oligo(ethylene glycol) side chains

Abstract

Polymer electrolytes (PEs) based on graft polymers bearing oligo(ethylene glycol) side chains are promising materials for Li-ion batteries. While ion transport in poly(meth)acrylate-based systems has been extensively investigated, the use of poly(vinyl ester) backbones remains unexplored. Herein, we compare the ion-transport properties of poly[di(ethylene glycol)]vinyl ester (PDEGVE), acrylate (PDEGA), and methacrylate (PDEGMA) blended with LiTFSI. PDEGVE-based PE shows the highest conductivity, nearly twice that of PDEGA and one order of magnitude higher than that of PDEGMA. Structural, thermal and electrochemical characterizations reveal that the low conductivity of PDEGMA originates from its relatively low dielectric constant, which promotes Li-TFSI ion pairing, together with the reduced mobility of EO units. In contrast, the enhanced conductivity of PDEGVE arises from greater mobility of EO units and distinct polymer-ion interactions induced by the vinyl ester backbone connectivity. These findings elucidate the influence of backbone chemistry on the ion-transport ability of graft polymers and identify poly[oligo(ethylene glycol)]vinyl esters as a promising platform for optimizing the ionic conductivity of graft PEs.