1、 1 1500 单词， 7500 英文字符， 2400 汉字 毕业设计（论文）外文译文 学生姓名： 学号： 专业名称： 新能源材料 与器件 译文标题（中英文）： Adsorption and Diffusion of Lithium on Layered Silicon for Li-Ion Storage（存储锂离子的层状硅中锂的吸收和扩散） 译文出处： School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States Internatio
2、nal Center for Quantum Materials, Peking University, No. 5 Yiheyuan Road, Haidian District, Beijing 100871, China Department of Physics, Harvard University, Cambridge, Massachusetts 02138, United States Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China 指导教师审阅 签名 ： 外文译文正文： 摘要 ：
3、 锂离子电池的能量密度主要取决于构成电极的特定的电荷容量。硅烯，石墨烯的 硅类 似 物 ，以原子层的厚度存在，作为锂离子二次电池高容量宿主。在这项工作中，我们使用第一原理计算来研究 在 无 依附 的单层和双层硅烯模型电极中 硅和锂 的相互作用。更具体地说，我们找到 锂的 强结合位置，计算力伴随 锂 扩散的能垒， 提出我们的研究结果，在 先前 的理论工作的背景下关于锂离子存储芯片的其他硅结构形式： 大块 和纳米线。锂的结合能是 2.2 eV 每个锂原子，考虑到锂的容量和硅烯的厚度（一层或两层）则 显示出微 小的变化 ，当然锂的扩散壁垒是相当低的，通常小于 0.6 eV。 我 们用我们的理论研究结
4、果来评估以 硅烯 层 存储锂离子 这种 形式的二维的硅的适用性 。 关键词 ：锂离子电池，储能，二维硅，原子吸附，表面扩散，初始计算 锂离子二次电池构成一个有前途的适合于便携式和网格应用的能量储存技术。其能量密度极大程度上取决于构成电极的具体充电容量。因为高的理论比容量 ，对 硅 基 阳极进行了研究，以代替现有的石墨阳极（ 4200 毫安每克），虽然硅的伴随电池操作和随后降低的充电速率的降解限制了这种电池技术的商业化。在与流行 的 单层和少数层二维层状材料 的制备中，被称为“硅烯”的硅的石墨烯状结构最近普遍有报道。硅烯合成的控制随着迄今 对 各种金属基材样品的制备得到持续不断地改进，例如，银，
5、铱，和 ZrB2。此外，还有一个正在进行的尝试，以便通过理论和模拟的属性更好地了解低维硅。 由于其比表面积大，硅烯可以作为锂离子二次电池的高容量宿主。在这个大背景下，锂 和 单层及多层硅烯的相互作用在很大程度上仍然未涉及。 为了评估作为用于锂的主体材料的硅烯的适用 性 ，我们在这项工作中使用基于密度泛函理论的第一原理计算，在模型中研究锂和 硅 的局部相互 作用 ，以及无 依附 的单层和双层硅烯结构 的相互作用。理论计算可以提供原子级的观察大量锂的扩散运动和硅二维结构，这是难以通过实验手段来获得的。具体来说，我们确定锂的结合位点，我们计算出扩散能垒。我们发现，作为锂容量和硅层的数量（一个或两个）
6、的函数，结合能（ 2.2 eV /每个锂原子）表示微小的变化，并且锂的扩散能垒相比较于在体积 硅 中 的扩散 和薄的硅纳米线往往 更小 （ 0.50 时 ，锂 的束缚力显著地减弱。例如，在 x = 0.67Li 含量时，其中硅烯层的两个表面都覆盖了 锂 ，随着一个锂吸附原子吸附在每个硅原子上面以及一个锂吸附原子吸附在每个硅原子下面，吸附能为 1.75 eV，这显示了在 锂原子和 锂 吸附层间 增加的斥力。因此，我们使用 SL-Li0.50Si0.50 代表充分 加氢氧化锂的单层硅烯结构 。我们进一步优化 SL-Li0.50Si0.50晶胞，我们发现了优化结构的晶格常数为 3.72埃（ Si-S
7、i键的长度为 2.39埃），即， 比原始的硅烯层小 了 4%。这种最优化减少 0.10eV 的 总能量 （ Eb = 2.38 eV） 。 3 ABSTRACT: The energy density of Li-ion batteries depends critically on the specific charge capacity of the constituent electrodes. Silicene, the silicon analogue to graphene, being of atomic thickness could serve as high-capacit
8、y host of Li in Li-ion secondary batteries. In this work, we employ first-principles calculations to investigate the interaction of Li with Si in model electrodes of free-standing single-layer and double-layer silicene. More specifically, we identify strong binding sites for Li, calculate the energy
9、 barriers accompanying Li diffusion, and present our findings in the context of previous theoretical work related to Li-ion storage in other structural forms of silicon: the bulk and nanowires. The binding energy of Li is 2.2 eV per Li atom and shows small variation with respect to Li content and si
10、licene thickness (one or two layers) while the barriers for Li diffusion are relatively low, typically less than 0.6 eV. We use our theoretical findings to assess the suitability of two-dimensional silicon in the form of silicene layers for Li-ion storage. KEYWORDS: Lithium-ion battery, energy stora
11、ge, two-dimensional silicon, adatom adsorption, surface diffusion, ab initio calculations Li-ion secondary batteries constitute a promising energy storage technology suitable for portable and grid applications. Their energy density depends critically on the specific charge capacity of the constituen
12、t electrodes.1,2 Sibased anodes are investigated as an alternative to the conventional graphite anode because of their high theoretical specific capacity (4200 mAh g1),25 although the degradation of silicon that accompanies battery operation and the subsequent reduction in charge rate have limited t
13、he commercialization of this battery technology.610 In line with the prevalent interest in two-dimensional layered materials1113 the preparation of single-layer and few-layer, graphene-like structures of silicon referred to as “silicene” has been recently reported.1416 Control of silicene synthesis
14、is continuously improving with samples having been prepared thus far on various metal substrates, for instance, Ag, Ir, and ZrB2.15,1720 There is also an ongoing effort to better understand the properties of low-dimensional silicon through theory and simulation.17,2130 Owing to its large surface are
15、a, silicene could serve as high-capacity host of Li in Li-ion secondary batteries. Within this broad context, the interaction of Li with single-layer and few-layer silicene remains largely unexplored.31,32 To assess the suitability of silicene as a host material for Li, we use first-principles calcu
16、lations based on density functional theory in this work to study the local interaction of Li with Si in model, free-standing single-layer and double-layer structures of silicene. Theoretical calculations can provide atomic-level insight into the kinetics of the diffusion of Li in bulk and two-dimens
17、ional structures of silicon, which is difficult to obtain solely by experimental means.7,10,3335 Specifically, we identify the binding sites for Li and we calculate the energy barriers for Li diffusion. We find that the binding energy (2.2 eV/Li atom) shows small variation as a function of Li conten
18、t and the number of Si layers (one or two), and energy barriers for Li diffusion that are typically smaller than those for diffusion in bulk silicon and thin silicon nanowires (0.6 eV). We modeled a free-standing single-layer structure of silicone using a two-atom unit cell with lattice constant asl
19、 = 3.88 , where the Si atoms are in a puckered honeycomb lattice arrangement and the bond length is 2.28 . The distance between two nearest neighbor Si atoms projected on the axis perpendicular to the plane is 0.44 . The optimized atomic configuration is in agreement with previous theoretical work.2
20、6,36,37 We also optimized the geometry of structures that consist of two silicene layers stacked together in either AA or AB arrangement. The lowest-energy structure corresponds to the AA arrangement with lattice constant adl = 4.13 (the bond length within each layer is 2.39 ), no puckering (in cont
21、rast to the case of the single-layer structure of silicene) and a distance between the atomic layers of 2.41 . We used this configuration to study the interaction of Li atoms with the double-layer silicene. For the calculation of adsorption energies, we used 2 2 supercells (Figure 1), and a void region of 15 separating the layers was included in the direction perpendicular to the silicene plane to ensure that the wave functions vanish smoothly at the
