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

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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.