GOALI: Stress Evolution and Related Phenomena in Composite Electrodes for Li Ion Batteries

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The central goal of this research is to advance the understanding of Li insertion in battery electrode materials, with respect to mechanical limitations (i.e., stress and strain). The volume expansion of the candidate electrode materials are very large, and their basic deformation properties are not well characterized. For these reasons, we will begin with detailed studies of thin film configurations, with measurements of in-plane stresses (based on wafer curvature), out-of-plane expansions and lateral inhomogeneities (based on interferometry), and deformation properties (based on nano-indentation). By performing these experiments in situ during Li insertion and removal, we will be able to obtain detailed understanding of the materials behavior which are not currently available. These experiments will be closely coupled with model development at several different length scales. Continuum modeling is necessary for analysis of the experiments, and ultimately for developing improved design methodologies for battery electrodes. Atomistic modeling will provide detailed insight into the fundamental properties of the basic materials and the relevant interfaces. The integrated approach used in these efforts will be applicable to a wide range of battery electrodes, but in this program we will specifically focus on carbon and silicon materials in negative electrodes.Improved Li ion battery performance is a critical need for the near-term development of hybrid and electric vehicles. The planned research, both the methodology and the actual results, are designed to make significant contributions to new battery technology by providing important fundamental information about materials performance. The direct involvement of General Motors scientists provides an important avenue for disseminating this knowledge. The graduate student and post-doctoral associate who are supported with the requested funds will develop interdisciplinary expertise with a variety of methods. Working directly with the industrial participants will provide an important added dimension to their education, and both of these individuals will be well positioned for future work in battery-related fields. We also plan to involve at least six undergraduate researchers and one or more high school students with different aspects of this work.