Harper Angela F, Evans Matthew L, Morris Andrew J
Theory of Condensed Matter, Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, U.K.
School of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K.
Chem Mater. 2020 Aug 11;32(15):6629-6639. doi: 10.1021/acs.chemmater.0c02054. Epub 2020 Jun 25.
Using first-principles structure searching with density-functional theory (DFT), we identify a novel 3̅ phase of CuP and two low-lying metastable structures, an 4̅3-CuP phase and a -CuP phase. The computed pair distribution function of the novel -CuP phase shows its structural similarity to the experimentally identified -CuP phase. The relative stability of all Cu-P phases at finite temperatures is determined by calculating the Gibbs free energy using vibrational effects from phonon modes at 0 K. From this, a finite-temperature convex hull is created, on which 3̅-CuP is dynamically stable and the Cu P ( < 1) defect phase 2-CuP remains metastable (within 20 meV/atom of the convex hull) across a temperature range from 0 to 600 K. Both CuP and CuP exhibit theoretical gravimetric capacities higher than contemporary graphite anodes for Li-ion batteries; the predicted CuP phase has a theoretical gravimetric capacity of 508 mAh/g as a Li-ion battery electrode, greater than both CuP (363 mAh/g) and graphite (372 mAh/g). CuP is also predicted to be both nonmagnetic and metallic, which should promote efficient electron transfer in the anode. CuP's favorable properties as a metallic, high-capacity material suggest its use as a future conversion anode for Li-ion batteries; with a volume expansion of 99% during complete cycling, CuP anodes could be more durable than other conversion anodes in the Cu-P system, with volume expansions greater than 150%. The structures and figures presented in this paper, and the code used to generate them, can be interactively explored online using Binder.
利用基于密度泛函理论（DFT）的第一性原理结构搜索，我们识别出一种新型的CuP的3̅相以及两个低能亚稳结构，即4̅3 - CuP相和 - CuP相。计算得到的新型 - CuP相的对分布函数表明其结构与实验确定的 - CuP相相似。通过使用0 K时声子模式的振动效应计算吉布斯自由能，确定了所有Cu - P相在有限温度下的相对稳定性。据此创建了一个有限温度凸包，在该凸包上3̅ - CuP是动态稳定的，并且CuP（< 1）缺陷相2 - CuP在0至600 K的温度范围内保持亚稳（在凸包的20 meV/原子范围内）。CuP和CuP的理论重量容量均高于当代锂离子电池的石墨负极；预测的CuP相作为锂离子电池电极的理论重量容量为508 mAh/g，大于CuP（363 mAh/g）和石墨（372 mAh/g）。CuP还被预测为非磁性和金属性的，这应有助于阳极中的有效电子转移。CuP作为金属高容量材料的良好性能表明其可作为未来锂离子电池的转换阳极；在完全循环过程中体积膨胀99%，CuP阳极可能比Cu - P系统中体积膨胀大于150%的其他转换阳极更耐用。本文中呈现的结构和图表以及用于生成它们的代码，可以使用Binder在线进行交互式探索。
