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Anisotropic Swelling and Fracture of Silicon Nanowires during Lithiation

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posted on 10.08.2011, 00:00 by Xiao Hua Liu, He Zheng, Li Zhong, Shan Huang, Khim Karki, Li Qiang Zhang, Yang Liu, Akihiro Kushima, Wen Tao Liang, Jiang Wei Wang, Jeong-Hyun Cho, Eric Epstein, Shadi A. Dayeh, S. Tom Picraux, Ting Zhu, Ju Li, John P. Sullivan, John Cumings, Chunsheng Wang, Scott X. Mao, Zhi Zhen Ye, Sulin Zhang, Jian Yu Huang
We report direct observation of an unexpected anisotropic swelling of Si nanowires during lithiation against either a solid electrolyte with a lithium counter-electrode or a liquid electrolyte with a LiCoO2 counter-electrode. Such anisotropic expansion is attributed to the interfacial processes of accommodating large volumetric strains at the lithiation reaction front that depend sensitively on the crystallographic orientation. This anisotropic swelling results in lithiated Si nanowires with a remarkable dumbbell-shaped cross section, which develops due to plastic flow and an ensuing necking instability that is induced by the tensile hoop stress buildup in the lithiated shell. The plasticity-driven morphological instabilities often lead to fracture in lithiated nanowires, now captured in video. These results provide important insight into the battery degradation mechanisms.