Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS) , Daejeon 305-701, Korea.
ACS Nano. 2014 Jul 22;8(7):7478-85. doi: 10.1021/nn502779n. Epub 2014 Jul 7.
Recent real-time analyses have provided invaluable information on the volume expansion of silicon (Si) nanomaterials during their electrochemical reactions with lithium ions and have thus served as useful bases for robust design of high capacity Si anodes in lithium ion batteries (LIBs). In an effort to deepen the understanding on the critical first lithiation of Si, especially in realistic liquid environments, herein, we have engaged in situ graphene liquid cell transmission electron microscopy (GLC-TEM). In this technique, chemical lithiation is stimulated by electron-beam irradiation, while the lithiation process is being monitored by TEM in real time. The real-time analyses informing of the changes in the dimensions and diffraction intensity indicate that the very first lithiation of Si nanoparticle shows anisotropic volume expansion favoring the ⟨110⟩ directions due to the smaller Li diffusion energy barrier at the Si-electrolyte interface along such directions. Once passing this initial volume expansion stage, however, Li diffusion rate becomes isotropic in the inner region of the Si nanoparticle. The current study suggests that the in situ GLC-TEM technique can be a useful tool in understanding battery reactions of various active materials, particularly those whose initial lithiation plays a pivotal role in overall electrochemical performance and structural stability of the active materials.
最近的实时分析为研究硅（Si）纳米材料与锂离子电化学反应过程中的体积膨胀提供了宝贵的信息，为在锂离子电池（LIBs）中设计高容量 Si 阳极提供了有力的依据。为了更深入地了解 Si 的首次嵌锂过程，特别是在实际的液体环境中，我们采用了原位石墨烯液体电池透射电子显微镜（GLC-TEM）技术。在该技术中，通过电子束辐照来刺激化学嵌锂，同时通过 TEM 实时监测嵌锂过程。实时分析表明，Si 纳米颗粒的首次嵌锂表现出各向异性的体积膨胀，这是由于在沿这些方向的 Si-电解质界面处，Li 扩散能垒较小。然而，一旦通过这个初始的体积膨胀阶段，Si 纳米颗粒内部区域的 Li 扩散速率变得各向同性。本研究表明，原位 GLC-TEM 技术可以成为理解各种活性材料电池反应的有用工具，特别是对于那些首次嵌锂在活性材料的整体电化学性能和结构稳定性中起着关键作用的材料。
