Improving the Performance of Lithium Sulfur Batteries Employing First Principles Guided Approaches

锂电池被广泛使用。它们通常由锂石墨阳极和氧化物阴极组成。锂硫电池代表了电池发展的新概念。优点是极高的能量密度。缺点是充电和放电循环次数有限。在本计画中，我们希望利用从头算分子动力学，研究导致硫化锂及其副产物逐步形成的基本化学反应。从头算分子动力学使用电子云的量子力学描述和原子核的经典描述，它允许描述任何物理基础上的化学反应。这种方法受到有限CPU时间的限制。由于在电化学应用中，我们可以通过电荷转移来触发反应，因此可以在中等CPU时间内观察化学反应。结果可以以电影的形式呈现，这允许传输大量信息。特别是，通过电影，我们可以演示在化学反应中每个原子是如何从A移动到B的。因此，从头算分子动力学允许在原则上理解任意化学反应的机制。在这个项目的过程中，我们希望从相当简单的模型结构开始，然后一步一步地进行到由1000多个原子组成的更现实的异质结构。

Lithium batteries are widely used. They consist typically in a lithium-graphite anode and an oxide cathode. Lithium sulfur batteries represent a new concept in the development of batteries. An advantage is the extremely high energy density. A disadvantage is the limited number of charge and discharge cycles. In the present project, using ab-initio molecular dynamics, we want to investigate the basic chemical reactions which lead step-wise to the formation of lithium sulfide and byproducts. Ab-initio molecular dynamics uses a quantum mechanical description of the electronic cloud and a classical description of the nuclei, which allows to describe any chemical reactions on physical grounds. This approach is limited by limited CPU time. Since, in electrochemical applications, we can trigger the reactions by charge transfer, it is possible to observe chemical reactions with moderate CPU time. The result can be presented in the form of movies, which allows to transport a lot of information. In particular, using movies, we can demonstrate how every single atom moves from A to B during a chemical reaction. Hence, ab-initio molecular dynamics allows to understand in principle the mechanisms of arbitrary chemical reactions. In the course of the project we want to start with rather simple model structures and then proceed step-by-step to more realistic hetero structures consisting of more than 1000 atoms.