Publication Details (including relevant citation information):
Hubert Valencia, Masanori Kohyama, Shingo Tanaka, and Hajime Matsumoto, J. Chem. Phys. 131(24), 244705 (2009).
We examined the atomic and electronic structures of an interface between a 1-ethyl-3-methyl imidazolium tetrafluoroborate (EMIM-BF4) ionic-liquid crystal and a Li(100) surface by periodic density-functional calculations, as a model for a room-temperature ionic-liquid (RTIL) electrolyte/Li interface at a Li-ion battery electrode. Results are compared with our previous theoretical study of the EMIM-BF4 molecular adsorption on Li surfaces [H. Valencia et al., Phys. Rev. B 78, 205402 (2008)]. For the EMIM-BF4 crystal structure, the present projector augmented wave scheme with the generalized gradient approximation can reproduce rather correct intramolecular structures as well as satisfactory short-ranged intermolecular distances, while long-range intermolecular distances are overestimated due to the lack of correct description of long-range dispersive interactions. We constructed a coherent crystal/crystal interface model where four EMIM-BF4 pairs are stacked on a p(4×3) Li (100) surface cell so as to simulate RTIL-layer deposition on a Li surface. We observed significant attraction of surface Li ions toward contacting BF−4 anions, counterbalanced by electron transfer toward EMIM+ cations near the interface, revealing the tendency of easy ionization of Li and Lix–BF4 cluster formation, coupled with the reduction of EMIM+. These features are similar to those observed in the EMIM-BF4 molecular adsorption, while these have been proved to occur in the crystal-layer adsorption. We examined the adhesive energy, wetability, and detailed electronic structure at the crystal/crystal interface.
Address (URL): http://dx.doi.org/10.1063/1.3273087