Magnetic Ionic Liquids

　Ionic liquids consist of only ionic components, having high ionic conductivity suitable for a liquid electrolyte. An electrolyte for a secondary battery requires not only high ionic conductivity but also non-volatility, heat-resistivity, non-inflammability, and non-corrosiveness. Ionic liquids cover these conditions. The cationic component of ionic liquid involves alkyl-substituted imidazolium, pyrrolidinium, piperidinium, ammonium, phosphonium, sulfonium and the anionic component involves halide, BF₄, PF₆, thiocyanate, and di(sulfonyl)imide. Chemical modifications of the cation and anion control melting point, viscosity and ionic conductivity. Hamaguchi et al. observed magnetic ionic liquids by introducing FeCl₄ to the anion part to form 1-butyl-3-methylimidazolium tetrachloroferrate, (Bmim)FeCl₄.^1,2) A magnetic fluid is a liquid with magnetic properties. However, a conventional magnetic fluid contains volatile solvents. It causes a change of viscosity and phase separation by cohesion/precipitation. On the other hand, the magnetic ionic liquid is a highly stable and non-volatile liquid. Moreover, this magnetic ionic liquid responds to a magnetic field by a permanent magnet, because it shows large magnetic susceptibility at room temperature.