Guangdong Provincial Key Laboratory of Micro/Nano Optomechatronics Engineering, College of Mechatronics and Control Engineering, Shenzhen University, Shenzhen 518060, China.
Nanoscale. 2017 Nov 16;9(44):17303-17311. doi: 10.1039/c7nr04289b.
Two-dimensional (2D) materials with tunable direct bandgaps are attractive for energy-related applications such as visible-light optical devices and cathode materials in metal-ion batteries. Here we perform first-principles calculations to investigate the structural, electrical, optical, and electrochemical properties of 2D tetragonal (t-) ZnX (X = S, Se) with layered structures and we also explore their applications in photocatalysts and Li-ion batteries. We find that t-ZnX layers prefer the AA stacking pattern when forming multi-layer (ML) structures. We also show that t-ZnX MLs and 3D bulks are all stable according to phonon calculations and ab initio molecular dynamics (MD) simulations. The band edge positions of these layered materials can be tuned by modifying the number of layers to transform them into being more suitable for photocatalysis. We further show that the t-ZnX layered structures, in particular t-ZnS single-layer (SL), are promising cathode materials for Li-ion batteries exhibiting a strong adsorption of Li atoms without reducing the Li mobility. Finally, we find that the most favorable adsorption configuration of Li atoms on t-ZnX SL strongly depends on the Li concentration. It is worth pointing out that the almost barrierless feature of Li diffusion on t-ZnS SLs makes t-ZnS SL a good candidate for a fast-charging device. Our work opens a promising avenue for the modulation of novel t-ZnX layered structures for a wealth of potential applications in energy conversion and storage.
二维（2D）材料具有可调谐的直接带隙，对于能源相关应用（如可见光光电器件和金属离子电池的阴极材料）具有吸引力。在这里，我们进行了第一性原理计算，以研究具有层状结构的二维四方（t-）ZnX（X=S，Se）的结构、电学、光学和电化学性质，并探索它们在光催化剂和锂离子电池中的应用。我们发现，当形成多层（ML）结构时，t-ZnX 层优先采用 AA 堆叠模式。我们还表明，根据声子计算和第一性原理分子动力学（MD）模拟，t-ZnX ML 和 3D 体相都是稳定的。通过改变层数可以调整这些层状材料的能带边缘位置，使其更适合光催化。我们进一步表明，t-ZnX 层状结构，特别是 t-ZnS 单层（SL），是一种很有前途的锂离子电池阴极材料，对 Li 原子具有很强的吸附作用，而不会降低 Li 的迁移率。最后，我们发现 Li 原子在 t-ZnX SL 上的最有利吸附构型强烈依赖于 Li 的浓度。值得指出的是，Li 在 t-ZnS SL 上扩散的几乎无势垒特征使得 t-ZnS SL 成为快充器件的良好候选材料。我们的工作为调制新型 t-ZnX 层状结构开辟了一条有前途的途径，有望在能量转换和存储领域得到广泛应用。
