Conductive networked polymer gel electrolytes composed of poly(meth)acrylate, lithium salt, and ionic liquid

Self-standing films of (meth)acrylate-based polymer gel electrolytes with high ionic liquid content (80 wt %) were prepared by in situ thermally or photo induced radical copolymerization of mono-functional and di-functional (meth)acrylates in an ionic liquid in the presence/absence of a lithium salt. Their ionic conductivity, thermal property, mechanical property, and flammability were examined. 1-Ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMImTFSI) or 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMImFSI) was used as the ionic liquid, and lithium bis(trifluoromethanesulfonyl)imide LiTFSI was used as the lithium salt. The obtained films were semitransparent and flexible with good to moderate thermal stability and mechanical strength with high ionic conductivity. The EMImFSI-containing gel electrolytes showed higher ionic conductivity than the corresponding EMImTFSI-containing gel electrolytes. The ionic conductivity in the acrylate-based gel electrolytes was slightly increased by addition of lithium salt, while that in the corresponding methacrylate-based electrolytes was decreased significantly. The flame test showed the ionic liquid containing networked polymer gel electrolytes to have low if any flammability and was therefore confirmed to be highly safe. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012