Interface phenomena in ionic systems: a surface science approach

具有离子电极的电化学装置对我们未来的能源经济至关重要。这种电化学装置中的界面对其性能起着关键作用，但在基本水平上没有被理解。在这个项目中，我们的目标是提高实际接口的基本理解。为此，我们研究了锂离子电池中的界面，更具体地说，本提案旨在研究锂离子电池复合阴极内部异质界面的结构和反应性及其对锂离子和电子传输的影响。通过结合实验和计算研究，我们的目标是更好地了解电池的性能以及故障模式，并随后阐述了合理的接口设计。因此，我们的建议解决了先进的电池设备的未来设计的关键问题，以及一般的电化学设备。我们的方法是表征良好定义的异质界面的表面科学方法和联合收割机的结果与理论计算。通过从气相冷凝一步一步地制备界面，并在每一步之后通过光电发射进行分析。这种方法已被证明产生独特的见解界面的形成和性能，如能级对齐，偶极和空间电荷层的存在，以及离子和电子转移。工作的重点是电极/电解质界面。对于实验部分的工作，我们应用我们的特高压集群系统在达姆施塔特，致力于电池的研究，和我们的特高压为基础的固液分析系统在Bessy II在柏林。我们通过沉积异质膜序列，使用物理气相沉积方法，或通过吸附挥发性电解质物种来制备特定的界面。光电发射分析得到了其他表面科学技术的支持，如HREELS和HRTEM，以及标准的电化学和电学测量。由于该建议的基本性质，工作是在众所周知的材料上进行的。阴极材料与电解质（液体以及固体）和集流体材料的界面都得到了解决。具体来说，我们将制备LixCoO 2薄膜，并研究作为锂含量的函数的界面形成。固体电解质是氮取代的磷酸盐玻璃（LiPON），标准液体电解质物质是溶剂碳酸二乙酯（DEC）。

Electrochemical devices with ionic electrodes are of central importance to our future energy economy. Interfaces in such electrochemical devices play a key role for their performance, but are not understood on a fundamental level. In this project, we aim to improve the fundamental understanding of practical interfaces. To this end, we investigate interfaces in Li-ion batteries.More specifically, this proposal aims to investigate the structure and reactivity of heterogeneous interfaces inside Li-ion battery composite cathodes and their influence on lithium ion and electron transport. By combining experimental and computational studies our goal is to better understand battery performance as well as failure modes and subsequently elaborate a rational design of the interfaces. Our proposal therefore addresses key issues for the future design of advanced battery devices, as well as electrochemical devices in general.Our approach is to characterize well defined hetero-interfaces by surface science methods and combine the results with theoretical calculations. Interfaces are prepared step-by-step by condensation from the gas phase, and analyzed by photoemission after each step. This methodology has been shown to yield unique insights about interface formation and properties, such as energy level alignment, presence of dipole- and space charge layers as well as ion- and electron transfer. The focus of the work is on electrode/electrolyte interfaces.For the experimental part of the work, we apply our UHV-cluster system at Darmstadt, dedicated to battery research, and our UHV-based solid-liquid analysis system at Bessy II in Berlin. We prepare specific interfaces by deposition of hetero film sequences, using physical vapor deposition methods, or by adsorption of volatile electrolyte species. Analysis by photoemission is supported by other surface science techniques, such as HREELS and HRTEM, as well as standard electrochemical and electrical measurements.Due to the fundamental nature of the proposal, work is conducted on well known materials. Interfaces of cathode material both with electrolyte (liquid as well as solid) and current collector materials are addressed. Specifically, we will prepare LixCoO2 thin films and investigate the interface formation as function of lithium content. The solid electrolyte is nitrogen-substituted phosphate glass (LiPON), the standard liquid electrolyte species the solvent diethyl carbonate (DEC).