时 间：2018年9月28日15:00-16:30

地 点：喜达水业怎么样A101

报 告 人：Hyun-Wook Lee博士, 韩国蔚山国家科学技术学院（UNIST）助理教授

邀 请 人：孙永明 教授

报告题目（Title）：

原位透射电子显微镜技术可视化电池中的电化学反应

Direct visualization of electrochemical reactions in batteries by in-situ transmission electron microscopy

报告摘要 (Abstract)：

Extensive research for new energy storage materials has created a high demand for experimental techniques that can provide real-time, single-particle-level information on the dynamic electrochemical processes taking place at the electrode materials during battery charge/discharge cycles. In situ transmission electron microscopy (TEM) on lithium ion batteries has offered exceptional opportunities for monitoring the dynamic processes of electrode materials during electrochemical reaction at both spatial and temporal resolution.

In this talk, I will introduce in situ TEM studies on silicon anodes that suffer the anomalous volumetric changes and fracture during lithiation process. Previously, the lithiation behaviour of a single silicon particle system has been explained in detail by simulation data and experimental observation. However, in real batteries, since lithiation occurs simultaneously in clusters of silicon in a confined medium, understanding how the individual silicon structures interact during lithiation in a closed space is necessary. Ex situ SEM and in situ TEM studies reveal that compressive stresses change the reaction kinetics so that preferential lithiation occurs on free surfaces when the pillars are mechanically clamped. This experiment reveals the surprising effects of nanostructure shape, size, and void space for lithiation and the results will contribute to improved design of silicon structures at the electrode level for high-performance lithium-ion batteries.

储能材料的广泛研究进一步增强了人们对于先进检测技术的要求，尤其是在电池循环过程中对材料实时的单颗粒层面的监测。原位透射电子显微镜（TEM）技术的应用为锂离子电池研究提供了时间（实时监测）和空间（超高分辨率）两方面的极大帮助。

本报告将主要系统介绍原位透射电子显微镜技术在硅负极研究中的应用。硅负极在电池循环过程中主要面临着体积变化和破裂的风险。尽管在之前的研究中人们已经通过模拟或实验观察，对于单个硅颗粒的锂化行为作了详细解释；但是在实际的电池循环过程中，硅的锂化同时发生在多个硅颗粒中，因此有必要研究锂化过程中颗粒与颗粒之间相互作用及对电化学性能的影响。原位TEM的研究和SEM研究结果表明在硅负极材料锂化过程中颗粒之间产生的压力改变了反应动力学，发生了取向锂化反应。研究表明了纳米结构、尺寸和间隙结构对锂化行为的影响，对下一代高比能硅基锂电池的硅负极材料在电极尺度的结构设计提供了帮助，对其他新型高容量电极材料的研发具有指导意义。

报告人简介 (Biography)：

Hyun-Wook Lee is currently an assistant professor in the School of Energy and Chemical Engineering at Ulsan National Institute of Science and Technology (UNIST). He received his B.S. in Advanced Materials Engineering from Sejong University in 2007. After receiving his Bachelor of Engineering degree, he continued his graduate studies at Korea Advanced Institute of Science and Technology (KAIST) under the direction of Prof. Do Kyung Kim. He received his Masters of Science and Ph. D. in Materials Science and Engineering in 2009 and 2012. During his Masters and Ph. D. degree studies, his research focused on the synthesis of nanomaterials and Li-ion batteries. In 2012, he moved to a postdoctoral position at Stanford University under the supervision of Prof. Yi Cui. At that time, he carried out research on the Prussian Blue open framework structures as electrode materials for Na ion batteries and in situ/operando transmission electron microscopy (TEM) investigations of battery electrode materials under electrochemical reaction. His research interests include rechargeable batteries, synthesis of nanosized materials, and in situ/operando TEM studies. As the first author or co-author, he published 15 research papers in Nature Energy (4), Nature Nanotechnology (5), and Nature Communications (6).

Hyun-Wook Lee教授于2007年获世宗大学先进材料工程学士学位；2009年和2012年于韩国高等科学技术学院（KAIST）分别获科学硕士和材料科学与工程博士学位，导师Do Kyung Kim教授，研究方向为纳米材料和锂离子电池电极材料的合成；2012年至2015年在斯坦福大学从事博士后研究，合作导师崔屹教授，研究方向包括普鲁士蓝框架结构作为钠离子电池的电极材料和在透射电子显微镜（TEM）对多种电池材料进行了原位电化学表征和系统研究。Hyun-Wook Lee教授目前任蔚山国家科学技术学院（UNIST）能源与化学工程学院的助理教授。他的研究方向主要包括二次电池、纳米材料的合成以及原位TEM技术在电化学反应中的应用。作为第一作者或共同作者他在Nature子刊上发表研究论文15篇，包括Nature Energy (4), Nature Nanotechnology (5), Nature Communications (6)等。