Polaronic Influences on the Charge Transport Properties of Battery Anodes

电池，尤其是那些基于锂离子转移的电池，在现代社会无处不在，随着电动汽车的出现，变得更加重要。考虑到这种普遍程度，在普通电池负极材料（如氧化钛锂（LTO））中发生的基本过程根本没有得到很好的理解，这是相当令人惊讶的。我们最近在还原LTO中发现了极化子，即通过周围材料的极化定位的电子，首次解释了氧空位的产生如何导致实验观察到的材料的电子导电性大大提高。在离子电导率方面也发现了类似的改进，这就提出了一个重要的问题，即极化子是否也起作用。因此，我们提出验证这样一个假设，即LTO和镧锂钛氧化物（另一种被提议的电池负极材料）的许多（也在操作中）实验观察到的性质可以考虑极化子的发生来解释。为此，我们将采用我们开发的高效固态嵌入技术和hubbard校正密度泛函理论来探索两种材料中极化子的不同局域模式及其对电子和离子电导率的影响。因此，我们将估计动力学扩散屏障，这将作为一个有待开发的动力学模型的基础。这将使我们能够检查在不同的材料锂化程度（即电池充电），不同的缺陷浓度和不同的缺陷分布下任何电荷载流子的可能相关运动。总而言之，除了对LTO和潜在的LLTO中的传输机制有详细的了解外，该项目还将为改进电池阳极的合理设计标准指明道路，例如以某些缺陷模式的形式。

Batteries, especially those based on the transfer of lithium ions, are ubiquitous in modern society and, with the advent of electro-mobility, are becomming even more important. Given this degree of pervasiveness, it is quite astonishing that elementary processes occurring in common battery anode materials such as lithium titanium oxide (LTO) are not at all well understood. Our recent discovery of polarons, electrons localized through the polarisation of the surrounding material, in reduced LTO for the first time explained how the generation of oxygen vacancies leads to an, experimentally observed, much improved electronic conductivity of the material. Similar improvements upon reduction have been found for the ionic conductivity, raising the important question if also there polarons play a role. Therefore, we propose to test the hypothesis that many of the (also in operando) experimentally observed properties of LTO and lanthanum lithium titanium oxide, another proposed battery anode material, can be explained considering the occurrence of polarons. To this end, we will employ an efficient solid state embedding technique developed by us together with Hubbard-corrected density functional theory to explore different localization patterns of polarons in both materials and their influence on electronic and ionic conductivity. Thereby, we will estimate kinetic diffusion barriers which will serve as the basis of a to be developed dynamical model. This will allow us to examine the possibly correlated motion of either charge carrier at different degrees of lithiation of the material (i.e. charging of the battery), different defect concentrations, and different defect distributions. All in all, besides yielding a detailed understanding of the transport mechanisms in LTO and, potentially, LLTO, this project will also point the way towards rational design criteria for improved battery anodes, e.g. in the form certain defect patterns.