An Interatomic Potential for LixSi Alloys and Its Applications to Lithiation Induced Deformation and Failure in Silicon

本项目的目标是(1)获得LixSi合金的原子间相互作用势，以及(2)利用这种原子间相互作用势来研究锂离子电池中锂离子引起的硅负极的变形和失效。让太阳能变得经济和通过聚变提供能源是美国国家工程院确定的两项重大挑战。这两个挑战的一个关键组成部分是能源储存。目前，最经济、最有效的太阳能储存方式是电池组。锂离子电池被认为是最有前途的高密度储能技术，而硅是容量最大的负极材料。尽管近年来硅基阳极发展迅速，取得了长足的进步，但其容量退化和使用寿命短的问题仍未得到解决。其中，对锂的插入/提取机理缺乏了解，以及缺乏有效的工具来设计硅基阳极是阻碍技术突破商业化的主要障碍。为了满足上述需求，本项目是(1)获得LixSi合金的原子间相互作用势，(2)利用这种原子间相互作用势来研究锂离子电池中硅负极的变形和失效。LixSi合金的这种原子间相互作用势将是一个强有力的工具。它使我们能够验证各种关于锂插入的连续介质模型。它可以用来估计一些很难通过实验获得的材料属性。这为我们研究断裂失效的微观组织机制提供了一种手段。除了对科学和工程做出贡献外，研究活动还将通过以下方式对学生产生更广泛的影响：(1)将研究成果整合到一门核心工程课程--“多尺度建模”中；(2)招收本科生进行研究，重点关注女性和少数族裔；(3)为研究生之间的跨部门互动提供平台；以及(4)招募当地高中教师和学生到PI的实验室进行暑期研究体验。

The goals of this project are (1) to obtain an interatomic potential for LixSi Alloys and (2) to use this interatomic potential to study the lithiation induced deformation and failure of silicon anode in lithium-ion batteries. Making solar energy economical and providing energy from fusion are two of the grand challenges identified by the National Academy of Engineering. A key component of both challenges is energy storage. At the moment, the most economical and efficient way of storing solar energy is electrical battery. Lithium-ion battery is considered the most promising technology for high density energy storage, and silicon is the highest capacity anode material. Despite the rapid development and significant progress made in recent years, capacity degradation and short lifetime have not been solved for silicon based anodes. Among other things, the lack of understanding of the mechanisms for lithium insertion/extraction, and the lack of efficient tools for designing Si-based anodes are the major roadblocks that prevent the technology breakthroughs for commercialization.To meet the above needs, this project is (1) to obtain an interatomic potential for LixSi Alloys and (2) to use this interatomic potential to study the deformation and failure of silicon anode in lithium ion batteries. Such an interatomic potential for LixSi alloys will be a powerful tool. It enables us to validate the various continuum models on lithium insertion. It can be used to estimate some of the material properties that are difficult to obtain experimentally. It gives us a mean to study the microstructural mechanisms of fracture and failure. Besides contributing to science and engineering, the research activities will also have a broader impact on educating students by (1) integrating the research results into a core engineering course, "Multi-scale Modeling", (2) recruiting undergraduates for research, focusing on women and minorities, (3) providing a platform for cross-department interactions among graduate students, and (4) recruiting local high school teachers and students for summer research experience in the PI's lab.