Electrochemical and spectroscopic analyses of lithium ion conductive polymers prepared by the copolymerization of ionic liquid monomer with lithium salt monomer

Abstract

Lithium ion conductive polymer electrolytes have been prepared by copolymerization of an imidazolium salt type ionic liquid monomer; 1-(1-acryloyloxyhexyl)-3-ethylimidazolium bis(trifluoromethanesulfonyl)imide with polyether-containing salt monomer with low glass transition temperature; methacryloyloxy octa(ethylene oxide)-2-sulfobenzoate lithium salt. The ampholytic copolymers were obtained as flexible and transparent films. Their ionic conductivity and glass transition temperature depended on monomer mixing ratio. Some copolymers containing higher lithium salt monomer fraction than that of ionic liquid monomer had lithium ion transference number exceeding 0.5. Against these, high ionic conductivity was found in the copolymers with high ionic liquid monomer fraction. Copolymerization of monomers containing either ionic liquid unit or lithium salt unit provided ion conductive polymers with a wide variety of conductive characteristics.