Ab initio study of EMIM-BF(4) molecule adsorption on Li surfaces as a model for ionic liquid/Li interfaces in Li-ion batteries

作者：Valencia Hubert^*; Kohyama Masanori; Tanaka Shingo; Matsumoto Hajime

来源：Physical Review B, 2008, 78(20): 205402.

DOI：10.1103/PhysRevB.78.205402

The adsorption of 1-ethyl-3-methyl imidazolium tetrafluoroborate (EMIM-BF(4)) molecules onto Li (100), (110), and (111) surfaces is investigated by means of periodic density-functional theory calculations as a model for room-temperature ionic liquid/Li-metal anode interfaces in a Li-ion battery. We examined the atomic and electronic structures of isolated EMIM(+) and BF(4)(-) molecules, a pair of [EMIM](+)[BF(4)](-), and Li bulk and surfaces, which are in good agreement with previous theoretical and experimental results. We observed that the EMIM-BF(4) adsorption generally induces significant changes on the Li surfaces. One or two Li-surface atoms are greatly attracted to the BF(4) anion, resulting in electronic density depletion at the attracted Li atoms while the electrons are attracted toward the EMIM cation, regardless of the coordination mode of adsorption or the kinds of Li surfaces. These features represent the tendency of easy ionization of Li and Li(x)-BF(4)-cluster formation, coupled with reduction in EMIM(+), which is in contrast to the EMIM-BF(4) adsorption on a Au (100) surface without any displacements of Au atoms or any specific electronic behavior to reduce EMIM(+).

• 出版日期2008-11