1、 1 1500 汉字， 860 单词， 4600 英文字符 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）： Ti3C2 MXene 作为金属（ Li、 Na、 K、 Ca）离子电池的高容量电极 Ti3C2 MXene as a High Capacity Electrode Material for Metal (Li, Na, K, Ca) Ion Batteries 译文出处： ACS(美国化学学会 )期刊数据库 指导教师审阅 签名 ： 外文译文正文： 能量储存系统曾 促进了世界科技 的发展。他们的应用变得多样化，从便携式电子设备和电动车辆
2、到 调控间歇性可再生能源供应的大规模功率输电网。在不同的能量存储系统中，电池存在几个优点，例如它们的小体积和它们的高效率。更特别的是锂离子电池（ LIBs）拥有高能量密度及宽泛的电压窗口，所以 在 1991年通过索尼公司最先实现商业化也因此吸引了更多的注意。然 而，锂离子电池的发展受限于安全和造价争议并且当前应用的材料与其 理论最高能量转化率 密切相关 。因此，电池有必要利用其它金属离子。另外，由于锂离子电池的电流增长率应用于电动车辆和输电网储存系统，锂 缺乏将可能成为未来的难题。由于钠比锂存储量更多 且 造价更便宜，钠离子电池（ NIBs）将来可能成为替代锂离子电池的一个 很好的选择 。除了
3、钠离子电池，其他碱性离子例如钾也被发现存在这种希望。如果每个离子能有两到三个电子转移，那么多价态离子，例如铝、镁和钙可能比单价态的锂 提供更高的能量密度。然而，基于大多数非常规金属离子电池的表现 ，对它们来说仍需要更多的提高来达到现实的应用需求。大多数 面临挑战的问题涉及优化每个系统的电解液及寻找作为电极的主要材料。 对于锂离子电池来说 石墨是一个很棒 的阳极，但它不能用于钠离子电池，因为 Na C 相互作用太弱以至于不能提供 必要的库伦作用力。 二维材料作为金属离子电池的主要材料具有特殊性，归因于它们独特的形态学特点，表面完整的暴露可以加快离子扩散和提供更多的离子插入通道。最近，二维早期过度
4、金属碳化物和碳氮化物的一个族系通过 MAX 相的原子在室温下使用氢氟酸（ HF）选择性刻蚀的方法被合成，称为“ MXenes”。 MAX 相是三元金属碳化物的一个很大的族系（超过 60 个相），成分为 Mn+1AXn,其中 M 是一个早期过度金属， A 是 A 组基础元素之一， X 是指碳或者氮， n 可以是 1 或 2 或 3。目前，下列 MXenes 已用试 验方法合成： Ti3C2， Ti2C，（ Ti0.5Nb0.5）2C， Ta4C3,(V0.5Cr0.5)3C2， Ti3CN,V2C 和 Nb2C。由于这些 发现， MXenes 赢得了很大的关注 并且呈现出有趣的性能。例如，多层
5、MXenes 的导电性 可与多层石墨烯相比拟。在 MXenes 系统的实验发现之后不久关于不同性能的理论研究也开始了。 Shein 和 Ivanovskii 曾研究其结构特点和 MXene Tin+1Cn与 Tin+1Nn(n=1,2,3)之间的稳定性关系。密度泛函理论（ DFT）的计算显示 MXenes 在可调带隙作用下能够 成为半导体，可调带隙可以通过改变表面终端来控制，但是没有终端的 MXenes 是金属的并且有希望拥有最高的导电性。 Ivanovskii et al.利用密度泛函理论估计出 MXenes 的内面弹性常数，超过了 500GPa，这意味着 MXenes 有希望拥有比结 2
6、构钢（ 400GPa）更高的刚性。 MXenes 有希望成为锂离子电池和锂离子电容器的电极材料。尽管 MXenes 对于 Li 的容量与商业的石墨电极锂离子电池（ 372,mAh/g）相近， MXenes 表现出杰出的 处理高循环率的能力。例如，对于无添加剂终止的 Ti3C2，在 36 的循环效率下，可获得 110mAh/g 的可逆容。 注意，石墨不能处理这样的高循环速率。这是因为 Ti3C2对锂原子较小的扩散势垒区。利用密度泛函理论计算， Shen et al发现锂原子在 Ti3C2（ 0.07eV）上的扩散势垒区比锐钛矿 TiO2(0.35 0.65eV)和石墨的小。然而，电子性能的研究和
7、 MXenes 的应用需要利用 其它金属离子 电池 。目前还没有使用 MXenes 电极的钠离子电池或其它金属离子电池的数据被报道。在这篇文章中，我们选择 Ti3C2作为例子和最佳研究 MXene 并且利用第一性原理密度泛函理论计算，就 它作为不同金属（ Li、 Na、 K 和 Ca）离子电池的电极材料表现的性能作报告。 我们所有计算的执行运用了维也纳从头计算模拟包（ VASP），利用了投影机增强波（ PAW）的电势来确定电子核心以及采用 了 广义梯度近似（ GGA）的 PBE 方式。 用 650eV 的截止能量来 阐述价电子波函数的水平波。为了模拟单个 Li， Na， K 和 Ca 原子的化
8、学吸附，我们使用了一个 3x3x1 的超晶胞，相应的在 Ti3C2MX中吸附原子满足 x=1/9。继续研究 吸附原子直到满足 x=2.0。为了避免模拟二维 Ti3C2单层薄片与周期图像的相互作用，我们使用了一 个大于 10 的真空空间。所有的结构不被约束同时所有原子允许移动直到每个原子上的压力小于 0.05eV/。 外文原文： MXenes as High Capacity Electrode Materials for Metal (Li, Na, K, Ca)-ion batteries D Er， J Li， M Naguib， M Barsoum， Y Gogotsi. Energy
9、storage systems have powered the world of technology. Their applications vary from portable electronic devices and electric vehicles, to large scale power grid systems that are needed to manage intermittent renewable energy supplies. Among different energy storage systems, batteries have several adv
10、antages such as their compact size and their high efficiency. More specifically, lithium-ion batteries (LIBs) have attracted most attention since their first commercialization by Sony in 1991, because of their high energy density and wide voltage window. However, the development of LIBs has been hin
11、dered by safety and cost issues, and the currently used materials operate close to their theoretical limit. Therefore, batteries utilizing other metal ions are needed. In addition, with the current growth rate of LIB use in electric vehicles and grid-level storage systems, Li scarcity can be a futur
12、e problem. Since sodium is more abundant and cheaper than lithium, Na-ion batteries (NIBs) can be a good candidate to replace LIBs in the future. In addition to NIBs, other alkali ions such as potassium have been found promising. Multivalent ions, such as aluminum, magnesium, and calcium may offer h
13、igher energy density than monovalent Li, if two or three electrons can transfer per ion. However, in most of the nonconventional metal ion batteries described above, more improvements are still needed in order for them to get to real world applications. Most of the challenging questions involve the
14、optimum electrolyte for each system and finding host materials to work as electrodes. Graphite, which is a successful anode for LIBs, cannot be used in NIBs, because the NaC interaction is found to be too weak to contribute to the necessary Coulomb interactions. 3 Two-dimensional (2-D) materials are
15、 of special interest as host materials for metal ion batteries, due to their unique morphology, which enables fast ion diffusion and offers more ion insertion channels with the whole surface exposed . Recently, a new family of 2-D early transition metal carbides and carbonitrides, so-called “MXenes”
16、, was synthesized by selective etching of A atoms from MAX phase s with hydrofluoricacid (HF) at room temperature. The MAX phase is a large family (+60 phases) of ternary metal carbides with composition of Mn+1AXn, where M is an early transition metal, A is one of the group A elements, X is carbon a
17、nd/or nitrogen, and n can be 1, 2, or 3. To date, the following MXenes have been synthesized experimentally: Ti3C2,Ti2C,(Ti0.5Nb0.5)2C, Ta4C3,(V 0.5Cr0. 5)3C2,Ti3CN,V2C, andNb2C. Since their discovery, MXenes have attracted great attention and have displayed interesting properties. For example, the
18、conductivity of multilayered MXenes was found comparable to that of multilayered graphene. Theoretical studies regarding different properties also began soon after the experimental discovery of MXene systems. Shein and Ivanovskii have studied the structural features and relative stabilities of the M
19、Xene Tin+1Cn and Tin+1Nn( n = 1,2,3). Density functional theory (DFT) calculations showed that MXenes can be semiconductors with tunable band gap that can be controlled by changing the surface termination, but nonterminated MXenes are metallic and are expected to have the highest conductivity. Kurto
20、glu et al. have estimated the in-plane elastic constants of MXenes, using DFT, to be more than 500 GPa, which means that MXenes are expected to have higher stiffness than structural steel (400 GPa). MXenes have been found to be promising electrode materials for LIBs and lithium ion capacitors. Altho
21、ugh the capacity of MXenes for Li is close to that of commercial graphite electrodes in LIBs (372 mAh/g), MXenes have shown an excellent capability to handle high cycling rates. For example, at a cycling rate of 36 C, a reversible capacity of 110 mAh/g was obtained for additive-free terminated Ti3C2
22、. Note that graphite cannot handle such high cycling rates. This may be attributed to the smaller diffusion barrier for Li atoms on Ti3C2. Using DFT calculations, Shen et al. found that the diffusion barrier of Li atoms on Ti3C2(0.07 eV) is smaller than that inanatase TiO2(0.35 0.65 eV) and graphite
23、. However, studies of electronic properties and applications of MXenes are needed to utilize other metal ions in batteries. No experimental data for NIBs or other metal ion batteries with MXene electrode have been reported to date. In this work, we choose Ti3C2 as the representative and best studied
24、 MXene and report on its performance as an electrode material for different metals (Li, Na, K, and Ca) ion batteries using first-principles DFT calculations. All our calculations were performed using the Vienna ab initio simulation package (VASP) with the projector augmented wave (PAW) potentials fo
25、r core electrons and the Perdew BurkeErnzerhof (PBE) form of the generalized gradient approximation (GGA). An energy cutoff of 650 eV was used for the plane wave expansion of valence electron wave functions. To simulate the adsorption of single Li, Na, K, and Ca, we used a 3x3 x 1 supercell, corresp
26、onding to the adatom content x =1/9inTi3C2Mx. Higher adatom contents up to x = 2.0 were also investigated. To avoid interactions between simulated two-dimensional Ti3C2 monolayer sheet and the periodic images, a vacuum space larger than 10 was used. All structures were relaxed with all atoms allowed to move until the force on each atom was less than 0.05 eV/. （正文页面 不够可加页，并在正文后附外文原文 ，统一用 A4 纸 张 打印 或手工誊写 ）
