title: Leapfrog cracking and nanoamorphization of ZnO nanowires during in situ electrochemical lithiation.
abstract: The lithiation reaction of single ZnO nanowire (NW) electrode in a Li-ion nanobattery configuration was observed by in situ transmission electron microscopy. Upon first charge, the single-crystalline NW was transformed into a nanoglass with multiple glassy nanodomains (Gleiter, H. MRS Bulletin2009, 34, 456) by an intriguing reaction mechanism. First, partial lithiation of crystalline NW induced multiple nanocracks ∼70 nm ahead of the main lithiation front, which traversed the NW cross-section and divided the NW into multiple segments. This was followed by rapid surface diffusion of Li(+) and solid-state amorphization along the open crack surfaces. Finally the crack surfaces merged, leaving behind a glass-glass interface (GGI). Such reaction front instability also repeated in the interior of each divided segment, further subdividing the NW into different nanoglass domains (nanoamorphization). Instead of the profuse dislocation plasticity seen in SnO(2) NWs (Science2010, 330, 1515), no dislocation was seen and the aforementioned nanocracking was the main precursor to the electrochemically driven solid-state amorphization in ZnO. Ab initio tensile decohesion calculations verified dramatic lithium embrittlement effect in ZnO, but not in SnO(2). This is attributed to the aliovalency of Sn cation (Sn(IV), Sn(II)) in contrast to the electronically more rigid Zn(II) cation.
authors.affiliation: Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Kushima
authors.forename: Xiao Hua
authors.initials: XH
authors.lastname: Liu
authors.forename: Guang
authors.initials: G
authors.lastname: Zhu
authors.forename: Zhong Lin
authors.initials: ZL
authors.lastname: Wang
authors.forename: Jian Yu
authors.initials: JY
authors.lastname: Huang
authors.forename: Ju
authors.initials: J
authors.lastname: Li
mesh_terms: D011211:Electric Power Supplies; D004559:Electric Wiring; D004563:Electrochemistry / Q000379:methods*; D008094:Lithium / Q000737:chemistry*; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D043942:Nanotubes / Q000737:chemistry*; D010316:Particle Size; D013499:Surface Properties; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D008094:Lithium; D015034:Zinc Oxide