title: Tuning the Outward to Inward Swelling in Lithiated Silicon Nanotubes via Surface Oxide Coating.
abstract: Electrochemically induced mechanical degradation hinders the application of Si anodes in advanced lithium-ion batteries. Hollow structures and surface coatings have been often used to mitigate the degradation of Si-based anodes. However, the structural change and degradation mechanism during lithiation/delithiation of hollow Si structures with coatings remain unclear. Here, we combine in situ TEM experiment and chemomechanical modeling to study the electrochemically induced swelling of amorphous-Si (a-Si) nanotubes with different thicknesses of surface SiOx layers. Surprisingly, we find that no inward expansion occurs at the inner surface during lithiation of a-Si nanotubes with native oxides. In contrast, inward expansion can be induced by increasing the thickness of SiOx on the outer surface, thus reducing the overall outward swelling of the lithiated nanotube. Moreover, both the sandwich lithiation mechanism and the two-stage lithiation process in a-Si nanotubes remain unchanged with the increasing thickness of surface coatings. Our chemomechanical modeling reveals the mechanical confinement effects in lithiated a-Si nanotubes with and without SiOx coatings. This work not only provides insights into the degradation of nanotube anodes with surface coatings but also sheds light onto the optimal design of hollow anodes for high-performance lithium-ion batteries.
authors.affiliation: Center of Electron Microscopy and State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University , Hangzhou 310027, China.|Department of Mechanical Engineering and Materials Science, University of Pittsburgh , Pittsburgh, Pennsylvania 15261, United States.
authors.forename: Jiangwei
authors.initials: J
authors.lastname: Wang
authors.affiliation: Woodruff School of Mechanical Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332, United States.
authors.forename: Hao
authors.initials: H
authors.lastname: Luo
authors.affiliation: Department of Materials Science and Engineering, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Mechanical Engineering and Materials Science, University of Pittsburgh , Pittsburgh, Pennsylvania 15261, United States.
authors.forename: Yang
authors.initials: Y
authors.lastname: He
authors.affiliation: Department of Mechanical Engineering, University of Nevada , Reno, Nevada 89557, United States.
authors.forename: Feifei
authors.initials: F
authors.lastname: Fan
authors.affiliation: Center of Electron Microscopy and State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University , Hangzhou 310027, China.
authors.forename: Ze
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Mechanical Engineering and Materials Science, University of Pittsburgh , Pittsburgh, Pennsylvania 15261, United States.
authors.forename: Scott X
authors.initials: SX
authors.lastname: Mao
authors.affiliation: Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory , Richland, Washington 99352, United States.
authors.forename: Chongmin
authors.initials: C
authors.lastname: Wang
authors.affiliation: Woodruff School of Mechanical Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332, United States.
authors.forename: Ting
authors.initials: T
authors.lastname: Zhu
keywords: Nanotube; in situ TEM electrochemical testing; lithium-ion batteries; mechanical confinement; surface coating; volume expansion