Ion and electron conducting hetero-aggregates for electrochemical applications

新一代锂电池，即所谓的全固态电池（ASSB），最近正在开发中，以固体电解质（SE）取代液体电解质，以潜在地提高能量密度和安全性。然而，阴极内部的亚微米结构，即活性物质的局部分布，固体电解质以及导电添加剂颗粒，很可能还有粘合剂，对于电子和离子的传输以及阴极可能的机械降解以及由此产生的电池性能是非常决定性的。我们从材料的角度假设，较小的粒径≤1µm的活性材料和固体电解质是有利的，一旦这些颗粒均匀混合并产生定制的颗粒结构。然而，亚微米结构对电池性能的确切影响尚不清楚。此外，生产这些固态阴极的工艺还没有得到很好的研究。此外，考虑到二氧化碳足迹和生产成本的最小化，即将问世的全固态电池的阴极应该通过干法生产，这需要一种高效且易于理解的混合工艺来混合不同的固体成分，从而开发出异质团块/聚集体（以下称为聚集体）的目标结构。我们将研究四种不同的过程，提供不同的模式，强度和频率的应力，并评估应力条件对骨料形态和结构特征的影响，其中包括通过FIB-SEM测量。应力条件将根据适当的dem模拟来确定。从这个角度出发，我们的假设是，如果作用在颗粒材料上的应力历史是已知的，那么异质聚集体的结构以及在此基础上它们的性能——特别是它们的电子和离子电导率——将是可预测的。为了深入了解异质聚集体结构对物理和电化学性能的影响，将利用SIMS和KPFM对聚集体中的异质界面进行研究，研究最终分解产物和这些界面上的电位下降。将进行三维断层扫描（HR-SEM和SIMS），并结合SEM中的原位三电极电化学分析，研究离子和电渗透作为聚集体结构的功能。所选骨料结构的力学和导电性也将使用DEM进行模拟，以便能够预测未来的性能。从分析的角度来看，我们的假设是，颗粒处理与nm和µm尺度上的系统分析表征之间的反馈回路将导致优化的颗粒聚集体和得到的阴极复合材料。

A new generation of Lithium-batteries, the so-called all solid state batteries (ASSB), with solid electrolytes (SE) replacing the liquid ones is recently under development to potentially increase energy density and safety. However, the submicron structure within the cathodes, i.e. local distributions of active material, solid electrolyte as well as conductive additive particles and most probably a binder, is very decisive for the electron and ion transport as well as for the possible mechanical degradation of the cathode and, thus, the resulting battery cell performance. Our hypothesis from the materials perspective is that smaller particle sizes ≤ 1 µm of active material and solid electrolyte of are advantageous, once these particles are homogeneously mixed and result in a tailored particulate structure. However, the exact effect of the submicron structure on the cell performance is hardly known. Moreover, processes to produce these solid state cathodes are not well investigated, yet. Additionally, with regard to the minimization of the CO2-footprint and production costs, the cathodes for the upcoming all solid state batteries should be produced by dry processes, which requires an efficient and well understood mixing process for the different solid components and, thus, the development of targeted structuring of hetero agglomerates/aggregates (in the following named as aggregates). We will investigate four different processes providing different modes, intensities and frequencies of stresses and evaluate the effect of the stress conditions on the aggregate morphology and structure characteristics, measured among others by FIB-SEM. The stress conditions will be determined based on appropriate DEM-simulations. Our hypothesis from this perspective is that if the stress history acting on the particulate materials is known, the structure of the hetero aggregates and on this basis their performance properties – especially their electronic and ionic conductivities – shall be predictable. In order to deeply understand the effect of the hetero aggregate structure on the physico- and electro-chemical properties, the hetero-interfaces in the aggregates will be probed by SIMS and KPFM with respect to eventual decomposition products and the potential drop across these interfaces. 3D tomography (HR-SEM and SIMS) will be carried out and in combination with in-situ 3-electrode electrochemical analysis in the SEM, ionic and electrical percolation will be studied as function of aggregate structure. The mechanical and conductivity properties of selected aggregate structures will also be simulated using DEM in order to be able to predict the properties in the future. Our hypothesis from the analytical perspective is that the feedback loop between particle processing and systematic analytical characterization on the nm and µm scale will lead to optimized particle aggregates and resulting cathode composites.