Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA.
Nano Lett. 2012 May 9;12(5):2429-35. doi: 10.1021/nl3004286. Epub 2012 Apr 11.
Material design in terms of their morphologies other than solid nanoparticles can lead to more advanced properties. At the example of iron oxide, we explored the electrochemical properties of hollow nanoparticles with an application as a cathode and anode. Such nanoparticles contain very high concentration of cation vacancies that can be efficiently utilized for reversible Li ion intercalation without structural change. Cycling in high voltage range results in high capacity (∼132 mAh/g at 2.5 V), 99.7% Coulombic efficiency, superior rate performance (133 mAh/g at 3000 mA/g) and excellent stability (no fading at fast rate during more than 500 cycles). Cation vacancies in hollow iron oxide nanoparticles are also found to be responsible for the enhanced capacity in the conversion reactions. We monitored in situ structural transformation of hollow iron oxide nanoparticles by synchrotron X-ray absorption and diffraction techniques that provided us clear understanding of the lithium intercalation processes during electrochemical cycling.
在形态上，除了固体纳米粒子以外，采用材料设计可以获得更先进的性能。以氧化铁为例，我们研究了空心纳米粒子作为阴极和阳极的电化学性能。这些纳米粒子含有非常高浓度的阳离子空位，可用于高效可逆的锂离子嵌入，而不会发生结构变化。在高电压范围内循环会导致高容量（在 2.5V 时约为 132mAh/g）、99.7%的库仑效率、优异的倍率性能（在 3000mA/g 时为 133mAh/g）和出色的稳定性（在 500 次循环以上的快速速率下没有衰减）。空心氧化铁纳米粒子中的阳离子空位也被发现对转化反应中的增强容量负责。我们通过同步加速器 X 射线吸收和衍射技术原位监测空心氧化铁纳米粒子的结构转变，这为我们提供了对电化学循环过程中锂离子嵌入过程的清晰理解。
