Department of Engineering Science and Mechanics, and Materials Research Institute, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, International Research Center for Computational Mechanics, Dalian University of Technology , Dalian 116023, People's Republic of China.
Nano Lett. 2017 Apr 12;17(4):2299-2306. doi: 10.1021/acs.nanolett.6b05033. Epub 2017 Mar 1.
Phosphorus represents a promising anode material for sodium ion batteries owing to its extremely high theoretical capacity. Recent in situ transmission electron microscopy studies evidenced anisotropic swelling in sodiated black phosphorus, which may find an origin from the two intrinsic anisotropic properties inherent to the layered structure of black phosphorus: sodium diffusional directionality and insertion strain anisotropy. To understand the morphological evolution and stress generation in sodiated black phosphorus, we develop a chemo-mechanical model by incorporating the intrinsic anisotropic properties into the large elasto-plastic deformation. Our modeling results reveal that the apparent morphological evolution in sodiated black phosphorus is critically controlled by the coupled effect of the two intrinsic anisotropic properties. In particular, sodium diffusional directionality generates sharp interphases along the [010] and [001] directions, which constrain anisotropic development of the insertion strain. The coupled effect renders distinctive stress-generation and fracture mechanisms when sodiation starts from different crystal facets. In addition to providing a powerful modeling framework for sodiation and lithiation of layered structures, our findings shed significant light on the sodiation-induced chemo-mechanical degradation of black phosphorus as a promising anode for the next-generation sodium ion batteries.
磷因其极高的理论容量而成为钠离子电池有前途的阳极材料。最近的原位透射电子显微镜研究证明了钠离子嵌入黑磷中的各向异性膨胀，这可能源于黑磷层状结构固有的两种内在各向异性性质：钠离子扩散的方向性和嵌入应变各向异性。为了理解钠离子嵌入黑磷中的形态演变和应力产生，我们通过将内在各向异性性质纳入到大弹塑性变形中，开发了一个化学力学模型。我们的建模结果表明，钠离子嵌入黑磷的明显形态演变主要受这两种内在各向异性性质的耦合效应控制。具体来说，钠离子扩散的方向性在[010]和[001]方向上产生了尖锐的相间层，从而限制了嵌入应变的各向异性发展。当从不同的晶面开始嵌入时，这种耦合效应产生了独特的应力产生和断裂机制。除了为层状结构的嵌入和脱嵌提供了强大的建模框架外，我们的研究结果还揭示了黑磷在钠离子电池中的化学机械降解机制，这为下一代钠离子电池提供了一种有前途的阳极材料。
