Lithium polymer electrolytes containing oligomeric imidazolium ionic liquids

摘要

New polymer electrolytes for lithium ion batteries with enhanced operational safety with the addition of room temperature imidazolium ionic liquids are reported. Imidazolium salts modified by us were applied as ionic liquids, which, for higher reduction potential stability, were substituted at position C2 with oligooxyethylene groups of various length ([BuMeImnEO]X-+(-), where n = 3.5, 7, 8.4 and X=CF3SO3, BF4, N(CF3SO2)(2)). Poly(ethylene oxide) (PEO), copolymers of vinylidene fluoride with hexafluoropropylene (p(VdF-co-HFP)) and of acrylonitrile with butyl acrylate (p(AN-co-BuA)) were utilized as polymer matrices. Thermal and electrochemical characterizations of the obtained electrolytes were carried out. On the basis of impedance measurements, the ionic conductivity and lithium transference numbers were determined. The best conducting properties were shown by systems with an ionic liquid [BuMeIm 3.5EO]+TFSI- and PEO or p(VdF-co-HFP) characterized by ambient temperature ionic conductivity of the order of 10(-5) Scm(-1). On the basis of polarization measurements by the variable-current method, the proportion of lithium cations in electric charge transfer was determined. The values obtained were low, as those typically obtained for ionic liquids (they do not exceed several percent), except for some cases, for which a value of 0.4 was reached. (c) 2016 Society of Chemical Industry