Room temperature ionic liquids are promising electrolytes for advanced batteries and ultracapacitors due to their unique physical and electrochemical properties.   These properties however are highly dependent on ionic liquid purity, with even trace amounts of impurities having a dramatic impact on performance.   This work reports on a spectroscopic study of ionic liquids and impurities from the ultraviolet through far infrared.  Optical absorption measurements were made using Fourier transform infrared (FTIR) and UV/VIS spectrometers covering optical wavelengths from 180 nm to 20 �m.  Quantitative measurements of absorption of neat samples of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [EMIM][TFSI] are reported in the infrared. Flow-cell measurements were also performed to quantitatively measure small concentrations of the process impurity 1-methylimidazole [MIM] in [EMIM][TFSI] by UV/VIS and infrared absorption techniques.   The reported measurements show promise for application of optical diagnostics for in-situ measurements of battery electrolytes.

Optical measurements of impurities in room-temperature ionic liquids

245th National Meeting (2013)

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