International Research Fellowship Program: Solid-State Electrochemistry: Interfacial Storage and Confined Size Effects in Lithium Ion Batteries

0701145Mebane国际研究奖学金计划使美国科学家和工程师能够在国外进行9到24个月的研究。该计划的奖项提供了联合研究的机会，以及使用独特或互补的设施，专业知识和国外的实验条件。Mebane将与德国斯图加特马克斯普朗克研究所的Joachim Maier博士合作。该项目的重点是开发一个唯象模型来解释锂离子电池负极纳米材料中的存储现象。特别是，这项工作的重点是在过渡金属氧化物，如RuO2和CoO的存储能力。在与Li+循环时，这些材料形成由Li2O和纳米尺寸的金属颗粒组成的复合材料。这项工作扩展了Jamnik和Maier提出的理论，即这些纳米复合材料中的存储主要是一种空间电荷现象，将其构建成一个适合与实验进行比较的连续框架。在连续体框架中使用的现象学不仅解决了电荷分离的影响，但表面张力和化学相互作用对相关的电化学电位。这样的处理的电化学电位的变化相对于散装导致的能量缺陷的形成，运输和反应在有限的空间。这项工作成功的关键是建立理论工作和实验之间的联系。与Maier小组的实验人员合作，设计了独特的测试单元，并将实验结果与连续模型的预测进行了比较。此外，在适用的情况下，与理论家在第一原理模拟，如量子化学和分子动力学建模工作的连接，以减少未知常数的连续框架中的数量，并在更基本的水平上理解现象。

0701145MebaneThe International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a twenty-four-month research fellowship by Dr. David S. Mebane to work with Dr. Joachim Maier at Max Planck Institute in Stuttgart, Germany. The focus of the project is developing a phenomenological model to explain storage phenomena seen in nano-sized materials for negative electrodes in lithium ion batteries. In particular, the work focuses on the storage capabilities seen in transition metal oxides such as RuO2 and CoO. Upon cycling with Li+, these materials form composites comprised of Li2O and nanosized metallic particles. The work expands upon the theory, put forward by Jamnik and Maier, that storage in these nanocomposites is primarily a space-charge phenomenon, building it into a continuum framework suitable for comparison with experiment. The phenomenology used in the continuum framework addresses not only the effect of charge separation, but that of surface tension and chemical interaction on the relevant electrochemical potentials. Such a treatment of the change in electrochemical potentials with respect to the bulk leads to the energetics of defect formation, transport and reactivity in confined spaces. Key to the success of this effort is establishing connections between theoretical work and experiment. Collaborating with experimentalists in the Maier group, unique test cells are designed, and the experimental results compared with predictions of the continuum model. In addition, where applicable, connections with theorists working in first principles simulation, such as quantum chemical and molecular dynamics modeling, are made in order to reduce the number of unknown constants in the continuum framework and to understand the phenomenology on a more fundamental level.