Publication Details (including relevant citation information):
Hubert Valencia, Masanori Kohyama, Shingo Tanaka, and Hajime Matsumoto, Phys. Rev. B 78, 205402 (2008)
The adsorption of 1-ethyl-3-methyl imidazolium tetrafluoroborate (EMIM-BF4) 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]+[BF4]−, and Li bulk and surfaces, which are in good agreement with previous theoretical and experimental results. We observed that the EMIM-BF4 adsorption generally induces significant changes on the Li surfaces. One or two Li-surface atoms are greatly attracted to the BF4 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 Lix-BF4-cluster formation, coupled with reduction in EMIM+, which is in contrast to the EMIM-BF4 adsorption on a Au (100) surface without any displacements of Au atoms or any specific electronic behavior to reduce EMIM+.