Lithium-based oligomer ionic liquid for solvent-free conducting materials

Abstract

The synthesis of a new lithium conducting oligomer ionic liquid (IL), noted Jeffamine diLi, was obtained from a two-step grafting of bis(trifluoromethanesulfonyl) imide on the commercial diamine-telechelic poly (propylene oxide)-block-poly (ethylene oxide)-block- poly (propylene oxide) (PPO-PEO-PPO). This oligomer IL, with a conductivity of 4.8 × 10−3 S cm-1 at 100 °C, is liquid from −21 °C and stable up to 300 °C. An all-solid-electrochromic device using Jeffamine diLi as electrolyte was successfully fabricated. Then, two types of polymer network were selected to develop the lithium conducting materials. Jeffamine diLi was incorporated either in a poly (ethylene oxide) (PEO) or in a PPO-PEO-PPO network. The resulting semi-interpenetrating networks (semi-IPNs) are transparent, amorphous, self-standing and have ionic conductivity of 1.10−4 S cm−1 at 80 °C. The diffusion and relaxation NMR measurements paint a picture of the cations being much more strongly interacting with the anions of the IL in the PPO-PEO-PPO semi-IPN's than in the PEO semi-IPN's.