| Co-Investigator(Kenkyū-buntansha) |
MOMOTA Kunitaka Director and Chemical Division, Manager, 精密化学薬品事業部, 取締役事業部長
GOTO Takuya Kyoto Univ., Energy Science, Research Associate, エネルギー科学研究科, 助手 (60296754)
NOHIRA Tashiyuki Kyoto Univ., Energy Science, Research Associate, エネルギー科学研究科, 助手 (00303876)
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| Research Abstract |
Room temperature molten salts have received an attention for their excellent characteristics from the viewpoint of electrochemical and synthetic applications. In 1999, we developed a new ionic liquid, 1-ethyl-3-methylimidazolium fluorohydrogenate, EMIm(HF)_<2.3>F, having a high ionic conductivity (100 mScm^<-1>). In a series of studies supported by this grant, we have reported some studies on their physical and chemical properties, and practical applications for electrolytes of some electrochemical systems. EMIm(HF)_<2.3>F is prepared by metathesis of starting chloride and anhydrous hydrogen fluoride. EMImHF_2 prepared by thermal decomposition of EMIm(HF)_<2.3>F is a colorless crystalline solid at room temperature. The reaction of the salt with stoichiometric amount of aHF gives EMIm(HF)_nF (1<n<2.5) with negligibly small HF dissociation pressures at room temperature. A phase diagram of EMIm(HF)_nF has been constructed in this composition range. The melting points of lower than room te
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mperature are observed for the salts with n>1.2. A series of syntheses, physical and electrochemical characterization of 1,3-dialkylimidazolium fluorohydrogenates have been performed in order to develop ionic liquids with high conductivities and large breaking up voltages. As a result, 1,3-dimethylimidazolium fluorohydrogenate, DMIm(HF)_<2.3>F has been found to give a higher conductivity (110 mScm^<-1>) than that of EMIm(HF)_<2.3>F. Extension of the alkyl side chain on the cation increases the electrochemical window of these ionic liquids. The conductivities of these salts are higher than those found for the other ionic liquids by one order of magnitude. High energy X-ray diffraction studies of these ionic liquids show ordering of the planar molecular ions in liquid state, which is considered to be related to their low viscosity and high conductivity. Application of these room temperature molten salts has been investigated as the electrolytes of electrical double layer capacitors, exhibit excellent, charge-discharge 'performances in wide temperature ranges. Also, these fluorohydrogenates has been turned out to act as good fluorobases against some binary fluorides to give fluorometallate ionic liquids with high purities. Less
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