Brookhaven National Laboratory, Upton, New York 11973, USA.
Nat Commun. 2012;3:1201. doi: 10.1038/ncomms2185.
Expectations for the next generation of lithium batteries include greater energy and power densities along with a substantial increase in both calendar and cycle life. Developing new materials to meet these goals requires a better understanding of how electrodes function by tracking physical and chemical changes of active components in a working electrode. Here we develop a new, simple in-situ electrochemical cell for the transmission electron microscope and use it to track lithium transport and conversion in FeF(2) nanoparticles by nanoscale imaging, diffraction and spectroscopy. In this system, lithium conversion is initiated at the surface, sweeping rapidly across the FeF(2) particles, followed by a gradual phase transformation in the bulk, resulting in 1-3 nm iron crystallites mixed with amorphous LiF. The real-time imaging reveals a surprisingly fast conversion process in individual particles (complete in a few minutes), with a morphological evolution resembling spinodal decomposition. This work provides new insights into the inter- and intra-particle lithium transport and kinetics of lithium conversion reactions, and may help to pave the way to develop high-energy conversion electrodes for lithium-ion batteries.
下一代锂电池的预期目标包括更高的能量和功率密度，以及日历寿命和循环寿命的大幅提高。为了满足这些目标，开发新材料需要更好地了解电极的工作原理，通过跟踪工作电极中活性成分的物理和化学变化来实现。在这里，我们开发了一种新的、简单的透射电子显微镜原位电化学池，并利用它通过纳米尺度成像、衍射和光谱学来跟踪 FeF(2)纳米颗粒中的锂传输和转化。在该系统中，锂的转化是在表面开始的，迅速扫过 FeF(2)颗粒，随后在体相发生逐渐的相变，导致 1-3nm 的铁纳米晶与非晶 LiF 混合。实时成像揭示了单个颗粒中令人惊讶的快速转化过程（在几分钟内完全完成），其形态演变类似于旋节分解。这项工作为锂离子电池的颗粒间和颗粒内锂传输以及锂转化反应动力学提供了新的见解，并可能有助于为高能转化电极的开发铺平道路。
