Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, New Mexico 87185, United States.
Nano Lett. 2011 Aug 10;11(8):3312-8. doi: 10.1021/nl201684d. Epub 2011 Jul 1.
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 LiCoO(2) 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.
我们报告了在与锂对电极的固体电解质或与 LiCoO(2)对电极的液体电解质进行锂化时，硅纳米线出人意料的各向异性肿胀的直接观察。这种各向异性膨胀归因于在锂化反应前沿处适应大体积应变的界面过程，该过程对晶体取向非常敏感。这种各向异性肿胀导致了具有显著哑铃形横截面的锂化硅纳米线，这是由于在锂化壳中拉伸环向应力的积累引起的塑性流动和随后的颈缩不稳定性而导致的。由塑性驱动的形态不稳定性通常会导致锂化纳米线断裂，现在可以在视频中捕捉到。这些结果为电池降解机制提供了重要的见解。
