Ab initio study of EMIM-BF4 crystal interaction with a Li (100) surface as a model for ionic liquid/Li interfaces in Li-ion batteries.
Ab initio study of EMIM-BF4 crystal interaction with a Li (100) surface as a model for ionic liquid/Li interfaces in Li-ion batteries.
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DOI：
10.1063/1.3273087
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发表时间：
2009-12
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影响因子：
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通讯作者：
H. Valencia;M. Kohyama;Shingo Tanaka;H. Matsumoto
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文献类型：
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作者：
H. Valencia;M. Kohyama;Shingo Tanaka;H. Matsumoto
采用周期性密度泛函方法研究了1-乙基-3-甲基咪唑四氟硼酸盐（EMIM-BF（4））离子液晶与Li（100）表面界面的原子和电子结构，并以此作为锂离子电池电极上室温离子液体（RTIL）电解质/Li界面的模型.结果与我们以前对EMIM-BF（4）分子在Li表面吸附的理论研究[H.瓦伦西亚等人，Phys. Rev. B 78，205402（2008）]。对于EMIM-BF（4）晶体结构，本文的广义梯度近似投影缀加波方法能较准确地再现分子内结构和较满意的短程分子间距离，但由于缺乏对长程色散相互作用的正确描述，对长程分子间距离估计过高。我们构建了一个相干晶体/晶体界面模型，其中四个EMIM-BF（4）对堆叠在p（4 × 3）Li（100）表面单元上，以模拟Li表面上的RTIL层沉积。我们观察到表面Li离子对接触的BF（4）（-）阴离子的显著吸引力，通过界面附近向EMIM（+）阳离子的电子转移来抵消，揭示了Li和Li（x）-BF（4）团簇形成的容易电离的趋势，以及EMIM（+）的还原。这些特征与EMIM-BF（4）分子吸附中观察到的特征相似，而这些特征已被证明发生在晶层吸附中。我们研究了粘合剂的能量，润湿性，和详细的电子结构在晶体/晶体界面。
We examined the atomic and electronic structures of an interface between a 1-ethyl-3-methyl imidazolium tetrafluoroborate (EMIM-BF(4)) 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-BF(4) molecular adsorption on Li surfaces [H. Valencia et al., Phys. Rev. B 78, 205402 (2008)]. For the EMIM-BF(4) 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-BF(4) pairs are stacked on a p(4x3) 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 Li(x)-BF(4) cluster formation, coupled with the reduction of EMIM(+). These features are similar to those observed in the EMIM-BF(4) 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.