Two-Fold Anisotropy Governs Morphological Evolution and Stress Generation in Sodiated Black Phosphorus for Sodium Ion Batteries.
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.
Department of Engineering Science and Mechanics, and Materials Research Institute, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
Tianwu
0000-0002-3183-1507
T
Chen
Department of Engineering Science and Mechanics, and Materials Research Institute, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
Peng
P
Zhao
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.
Xu
X
Guo
Department of Engineering Science and Mechanics, and Materials Research Institute, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
Sulin
S
Zhang
Sodium ion batteries; anisotropic swelling; black phosphorus; chemo-mechanical modeling; stress generation