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

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至24个月的研究。该计划的奖项提供了联合研究的机会，并利用国外独特或互补的设施、专业知识和实验条件。该奖项将支持David S.Mebane博士与德国斯图加特Max Planck研究所的Joachim Maier博士合作的为期24个月的研究奖学金。该项目的重点是开发一个现象学模型，解释锂离子电池负极纳米材料中的存储现象。特别是，这项工作的重点是过渡金属氧化物，如RuO2和CoO中的存储能力。当与Li+循环时，这些材料形成由Li2O和纳米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，将其构建成适合与实验进行比较的连续统框架。在连续统框架中使用的唯象不仅涉及电荷分离的影响，而且还涉及表面张力和化学相互作用对相关电化学势的影响。这种对电化学势相对于块体的变化的处理导致了缺陷形成、传输和受限空间中的反应性的能量学。这一努力成功的关键是在理论工作和实验之间建立联系。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介质模型的预测进行了比较。此外，在适用的情况下，与从事第一性原理模拟的理论家建立联系，例如量子化学和分子动力学建模，以便减少连续统框架中未知常数的数量，并在更基本的水平上理解唯象。

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.