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Functionalized Ionic Liquids Based on Trialkylimidazolium Cations with Alkoxymethyl Group at the N‑1 Position: Synthesis, Characterization, and Application as Electrolytes for a Lithium Ion Battery

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journal contribution
posted on 26.02.2014, 00:00 by Yide Jin, Shaohua Fang, Jianhao Zhang, Zhengxi Zhang, Kaiqiang Yu, Jianzhi Song, Li Yang, Shin-ichi Hirano
Twenty-four new functionalized ionic liquids (ILs) based on trialkylimidazolium cations with the alkoxymethyl group at the N-1 position were synthesized and characterized. Physicochemical properties of these ILs, such as melting point, thermal stability, density, viscosity, conductivity, and electrochemical stability, were studied systematically. Twenty-one ILs appeared in the liquid state at room temperature, and 14 ILs showed a melting point lower than −60 °C. Introduction of the alkoxymethyl group at the N-1 position of trialkylimidazolium cations could not be more beneficial than that of the alkoxyethyl group for reducing viscosity. Li/LiFePO4 cells employing three trialkylimidazolium ILs with methoxymethyl-group-based electrolytes showed good discharge capacity and cycle stability at a current rate of 0.1 C. This is the first report of ILs with the alkoxymethyl group used as electrolytes without an additive for a lithium ion battery.