Sensors and Electron Devices Directorate, Energy and Power Division, U.S. Army Research Laboratory , ATTN: RDRL-SED-C, Adelphi, Maryland 20783, United States.
ACS Nano. 2013 Oct 22;7(10):9173-82. doi: 10.1021/nn4037909. Epub 2013 Sep 10.
Using electron beam lithography, amorphous Si (a-Si) nanopillars were fabricated with a height of 100 nm and diameters of 100, 200, 300, 500, and 1000 nm. The nanopillars were electrochemically cycled in a 1 M lithium trifluoromethanesulfonate in propylene carbonate electrolyte. In situ atomic force microscopy (AFM) was used to qualitatively and quantitatively examine the morphology evolution of the nanopillars including volume and height changes versus voltage in real-time. In the first cycle, an obvious hysteresis of volume change versus voltage during lithiation and delithiation was measured. The pillars did not crack in the first cycle, but a permanent volume expansion was observed. During subsequent cycles the a-Si roughened and deformed from the initial geometry, and eventually pillars with diameters >200 nm fractured. Furthermore, a degradation of mechanical properties is suggested as the 100 and 200 nm pillars were mechanically eroded by the small contact forces under the AFM probe. Ex situ scanning electron microscopy (SEM) images, combined with analysis of the damage caused by in situ AFM imaging, demonstrate that during cycling, the silicon became porous and structurally unstable compared to as-fabricated pillars. This research highlights that even nanoscale a-Si suffers irreversible mechanical damage during cycling in organic electrolytes.
使用电子束光刻技术，制备了高度为 100nm、直径分别为 100nm、200nm、300nm、500nm 和 1000nm 的非晶硅（a-Si）纳米柱。将纳米柱在 1M 三氟甲烷磺酰锂的碳酸丙烯酯电解质中进行电化学循环。原位原子力显微镜（AFM）用于实时定性和定量研究纳米柱的形貌演变，包括体积和高度随电压的变化。在第一个循环中，测量到锂化和脱锂过程中体积变化与电压之间的明显滞后。在第一个循环中，纳米柱没有断裂，但观察到了永久的体积膨胀。在随后的循环中，a-Si 从初始几何形状粗糙化和变形，最终直径>200nm 的纳米柱断裂。此外，由于在 AFM 探针下的小接触力，100nm 和 200nm 的纳米柱被机械侵蚀，表明机械性能退化。原位 AFM 成像分析与非原位扫描电子显微镜（SEM）图像相结合，表明在循环过程中，与制备好的纳米柱相比，硅变得多孔且结构不稳定。这项研究强调了即使是纳米级的 a-Si 在有机电解质中循环时也会遭受不可逆的机械损伤。
