Anions for lithium battery electrolytes: A spectroscopic and theoretical study of the B(CN)(4)(-) anion of the ionic liquid C(2mim)[B(CN)(4)]

On the basis of computations, the B(CN)(4)(-) (bison) anion is shown to be of interest as a fluorine-free alternative in lithium-conducting electrolytes. Compared to PF(6)(-) the bison anion has an equally high stability toward oxidation, while at the same time offering a large reduction of the lithium-ion pair dissociation energy. The bison anion is readily available in a number of ambient-temperature ionic liquids (ILs). In this work, the Raman spectrum of the IL C(2mim)[B(CN)(4)] reveals an almost unperturbed bison anion and, consequently, the effects of the anion on the Raman shifts of C(2mim)(+) are also very small. (C) 2008 The Electrochemical Society.