Ionic conductive properties of solid polymer electrolyte based on poly(oxetane) with branched side chains of terminal nitrile groups

Solid polymer electrolyte films with high ionic conductivity are key materials for thinner and lighter practical batteries. A novel oxetane monomer (COA) with three cyanoethoxymethyl units in its each side chain is designed and prepared by coupling 3-ethyl-3-carboxyloxetane and tris(cyanoethoxymethyl)aminomethane. Ring opening cationic polymerization of the COA monomer provides sticky polymer, PCOA. The solid polymer electrolyte film prepared from PCOA, poly(vinylidene fluoride-co-hexafluoropropylene), and LiBF4 shows high ionic conduction, 0.2 mS cm− 1 at 293 K. High conductivity over 0.1 mS cm− 1 in the PCOA-based electrolyte films is offered from enhanced dissolution of lithium salts through solvation of lithium ions with the cyanoethoxymethyl groups in each side chain.