Ion Mobility of l-Ethyl-3-methylimidazolium Tetrafluoroborate and l-Ethyl-3-methylimidazolium Bis(trifluorosulfonyl)amide Ionic Liquids

摘要

Ionic liquids (ILs) have several excellent advantages, e.g., low-volatility and low-flammability, in comparison to conventional organic liquid solvents. Due to this, the ILs hold the promise as the electrolyte media for high-safety electrochemical devices, e.g., lithium ion secondary batteries, fuel cells, and double-layer capacitors (1). The diffusion coefficient under no electric field and the mobility under an electric field are mass transport parameters to understand the ion migration mechanism in pure ILs and their electrolyte solutions at the molecular level. Many research groups have so far reported the diffusion coefficients for the systems of the neat ILs and their electrolyte solutions (2). We also determined the diffusion coefficient of the neat ILs composed of various perfluorosulfonylamide anions by the pulsed-field gradient NMR technique and demonstrated the possible of the existence of the dynamic heterogeneity in the neat ILs (3). The mobility is the same important quantity as the diffusion coefficient; however, as far as we know, the information on the mobility of the neat IL and their electrolyte solution under electric field condition is unavailable in literature.