Nanoscale Characterization of Composite Electrodes for All-Solid-State Batteries by means of Electrochemical AFM Methods

与现有技术的锂离子电池相比，块型全固态电池表现出潜在的增强的能量密度和增强的安全性，因此被认为是用于电动汽车领域中的未来应用的有前景的电化学能量存储装置。在Li全固态电池的情况下，复合电极由可逆地嵌入Li+离子的活性材料颗粒和固体电解质颗粒组成。两种类型的颗粒的平均尺寸在微米至亚微米范围内。为了更好地理解这种电极中的电化学过程，需要具有亚微米分辨率的空间分辨表征。基于AFM的电化学方法非常适合于此目的。在这个项目中，AFM为基础的方法，这是在以前的项目中开发的一部分，部分已知的文献，将用于复合电极的电化学表征。为此，将制备六种复合电极，其在活性材料颗粒和固体电解质颗粒之间的界面的热力学和动力学稳定性方面不同。在所有复合电极中，将使用离子电导率为约5 mS/cm的硫化物基固体电解质Li 5，3 PS 4，3ClBr 0，7（LPSClBr）。将施加以下活性材料颗粒：（i）未涂覆的LiCoO 2，（ii）具有LiNbO 3涂层的LiCoO 2，（iii）未涂覆的LiNi 0，6 Mn 0，2Co 0，2 O2;（iv）具有LiNbO 3涂层的LiNi 0，6 Mn 0，2Co 0，2 O2，（v）未涂覆的LiFePO 4和（vi）未涂覆的Li 4 Ti 5 O 12。为了制备ASSB，将相应的复合阴极与固体电解质隔膜和Li金属对电极组合。对于复合电极的表征，导电AFM，开尔文探针力显微镜和电化学应变显微镜将与FIB/SEM/EDX为基础的表面形貌和化学成分的分析相结合。这些结果将为复合电极中单个颗粒的局部电化学性质以及颗粒/颗粒界面的局部性质提供新的基本见解。（a）单个活性材料颗粒中Li+离子和电子的电荷态依赖的化学势;（B）单个活性材料颗粒中电荷态依赖的双极Li扩散系数;（c）单个活性材料颗粒中的Vegard应变;（d）在活性材料颗粒和固体电解质颗粒之间的界面处的空间电荷层和电阻界面。

Bulk-type all-solid-state batteries exhibit potentially enhanced energy density and enhanced safety as compared to start-of-the-art lithium-ion batteries and are thus considered as promising electrochemical energy storage devices for future applications in the field of electromobility. In the case of Li all-solid-state batteries, the composite electrodes consist of active material particles, which reversibly intercalate Li+ ions, and of solid electrolyte particles. The mean size of both types of particles is in the micro-m to sub-micro-m range. In order to achieve a better understanding of the electrochemical processes in such electrodes, a spatially resolved characterization with a resolution in the sub-micro-m is desirable. AFM-based electrochemical methods are well suited for this purpose. In this project, AFM-based methods, which were partly developed in a previous project and are partly known from the literature, will be used for the electrochemical characterization of composite electrodes. To this end, six composite electrodes will be prepared, which differ in the thermodynamic and kinetic stability of the interfaces between the active material particles and the solid electrolyte particles. In all composite electrodes, the sulfide-based solid electrolyte Li5,3PS4,3ClBr0,7 (LPSClBr) with an ionic conductivity of about 5 mS/cm will be used. The following active material particles will be applied: (i) LiCoO2 uncoated, (ii) LiCoO2 with LiNbO3 coating (iii) LiNi0,6Mn0,2Co0,2O2 uncoated; (iv) LiNi0,6Mn0,2Co0,2O2 with LiNbO3 coating (v) LiFePO4 uncoated and (vi) Li4Ti5O12 uncoated. For the preparation of an ASSB, the respective composite cathode will be combined with a solid-electrolyte separator and a Li metal counter electrode. For the characterization of the composite electrodes, conductive AFM, Kelvin probe force microscopy and electrochemical strain microsocopy will be combined with a FIB/SEM/EDX-based analysis of surface topography and chemical composition. The results will provide new fundamental insights into the local electrochemical properties of single particles in composite electrodes as well as into the local properties of particle/particle interfaces. The following aspects are in the focus of interest: (a) State-of-charge-dependent chemical potentials of Li+ ions and electrons in single active material particles; (b) State-of-charge-dependent ambipolar Li diffusion coefficients in single active material particles; (c) Vegard strains in single active material particles; (d) Space charge layers and resistive interphases at the interfaces between active material particles and solid electrolyte particles.