Ionic liquid impregnated lithium ion conductive solid electrolytes based on poly(acetyl ethylene glycol methacrylate-co-methyl acrylate)

Poly(ethylene glycol)methacrylate (PEGMA) was modified with acetyl chloride to afford acetyl-poly(ethylene glycol)methacrylate (AEGMA) containing PEG and carbonyl groups at the pendant position. AEGMA was further reacted with methyl acrylate (MAc) to synthesize poly(AEGMA-co-MAc) copolymer containing additional carbonyl groups. When lithium salts such as lithium perchlorate (LiCLO₄) and lithium bis(trifluoromethanesulfony)imides (LITFSI) were introduced into the poly(AEGMA-co-MAc) membrane, the ionic conductivity increased with increasing lithium salt concentration up to 15 wt%, followed by a decrease because when the lithium ion concentration was above its saturation level, the excess lithium salts aggregated together exerting a negative effect on ion transport. The maximum ionic conductivity of the copolymer system containing lithium salt was 1.1 × 10^-4 S cm^-1 at 15 wt% MAc and 15 wt% of LiTFSI concentration. When room temperature ionic liquid (RTIL), PYR14-TFSI in addition to LiTFSI salt was introduced to the poly(AEGMA-co-MAc)-LiTFSI, the ionic conductivity increased monotonically with increasing salt/RTIL concentration. The maximum ionic conductivity of 1.2 × 10^-3 S cm^-1 was obtained at 70 wt% 0.5 M LiTFSI/PYR14-TFSI concentration.