Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, New Mexico 87185, United States.
Nano Lett. 2011 Jun 8;11(6):2251-8. doi: 10.1021/nl200412p. Epub 2011 May 12.
Using advanced in situ transmission electron microscopy, we show that the addition of a carbon coating combined with heavy doping leads to record-high charging rates in silicon nanowires. The carbon coating and phosphorus doping each resulted in a 2 to 3 orders of magnitude increase in electrical conductivity of the nanowires that, in turn, resulted in a 1 order of magnitude increase in charging rate. In addition, electrochemical solid-state amorphization (ESA) and inverse ESA were directly observed and characterized during a two-step phase transformation process during lithiation: crystalline silicon (Si) transforming to amorphous lithium-silicon (Li(x)Si) which transforms to crystalline Li(15)Si(4) (capacity 3579 mAh·g(-1)). The ultrafast charging rate is attributed to the nanoscale diffusion length and the improved electron and ion transport. These results provide important insight in how to use Si as a high energy density and high power density anode in lithium ion batteries for electrical vehicle and other electronic power source applications.
利用先进的原位透射电子显微镜，我们发现，碳涂层的添加与重掺杂相结合，使得硅纳米线的充电速率达到了创纪录的水平。碳涂层和磷掺杂都使纳米线的电导率提高了 2 到 3 个数量级，进而使充电速率提高了 1 个数量级。此外，在锂化过程中的两步相变过程中，直接观察到并描述了电化学固态非晶化（ESA）和逆 ESA：晶体硅（Si）转变为非晶态锂硅（Li(x)Si），然后再转变为晶体 Li(15)Si(4)（容量为 3579 mAh·g(-1)）。超快的充电速率归因于纳米级的扩散长度以及电子和离子传输的改善。这些结果为如何将硅用作锂离子电池中的高能量密度和高功率密度阳极提供了重要的见解，适用于电动汽车和其他电子电源应用。
