Lithium electrolytes based on modified imidazolium ionic liquids

• Published in: International journal of hydrogen energy Vol. 39; no. 6; pp. 2943 - 2952
• Main Authors: Zygadło-Monikowska, E., Florjańczyk, Z., Kubisa, P., Biedroń, T., Sadurski, W., Puczyłowska, A., Langwald, N., Ostrowska, J.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Kidlington Elsevier Ltd 14-02-2014; Elsevier
• Subjects: Alternative fuels. Production and utilization; Applied sciences; Electrolytes; Energy; Exact sciences and technology; Fuels; Hydrogen; Hydrogen-based energy; Imidazolium salt; Ionic conductivity; Ionic liquids; Liquids; Lithium; Lithium batteries; Lithium electrolyte; Lithium transference number; Lithium-ion battery; Solvents; Lithium transference number; Ionic liquids; Imidazolium salt; Lithium-ion battery; Lithium electrolyte; Hydrogen; Battery; Lithium; Ionic liquid
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2013.06.003

In this study, new electrolytes for Li-ion batteries in the form of lithium salt solutions in room temperature imidazolium ionic liquids (RTIL) are reported. The ionic liquids applied, for higher reduction potential stability, were substituted at position C2 with oligooxyethylene groups of various length ([Im nEO]+X−; where: n = 0, 3, 7, 20 and X = Cl, BF4, N(CF3SO2)2). It was found that they are good solvents for lithium salts (LiBF4, LiN(CF3SO2)2, {[CH3(OCH2CH2)3O]3BC4H9}Li) forming liquid solutions of low glass transition temperature (Tg in the −70 to −40 °C range). Ionic conductivity depends on the length of oxyethylene substituent in Im nEO and on the concentration of the salt applied, for 10 mol%, σRT is of the order of 10−4 S cm−1. On the basis of polarization measurements by the variable-current method, the proportion of lithium cations in electric charge transfer (t+) has been determined. The values obtained (typical for ionic liquids) are low and depend on n and lithium salt concentration but do not exceed a dozen or so percent.
•The electrolytes based on imidazolium ionic liquids and lithium salts were obtained.•The examined imidazolium IL are substituted by oxyethylene groups at C2 position.•The viscosity and ionic conductivity of IL electrolytes were studied.•We report the electrochemical stability of substituted imidazolium ionic liquids.