Analytical Transmission Electron Microscopy studies of LiNi0.33Mn0.33Co0.33O2, LiCoO2, and silicon electrode materials for lithium-ion batteries

Summary:

The modification of state-of-the-art electrode materials by nanostructured coatings is one approach to optimize crucial parameters for applications, such as the electronic conductivity or the mechanical stability of the electrode materials. In general, interfaces (e.g. active material/coating; electrode surface/electrolyte) determine the local Li ion transport kinetics and finally the electrochemical cell performance in terms of cycling stability or capacity retention. Therefore, it is necessary to study the structure and chemistry of electrodes and electrode/electrolyte interfaces. In this work, the structural and chemical evolution in the bulk and surface regions of LiNi0.33Mn0.33Co0.33O2 (NMC-111), LiCoO2 (LCO), and silicon electrode materials after electrochemical cycling are studied using transmission electron microscopy (TEM) imaging, nanobeam electron diffraction, and electron energy loss spectroscopy (EELS). In the case of NMC-111 and LCO electrodes, the effect of an Al doped ZnO – coated layer on the structural and chemical stability of the electrode surface upon electrochemical cycling at high charge voltages is studied. Moreover, in the case of a silicon electrode, the effect of a carbon coating layer on the mechanical integrity of Si active material and the stability of solid electrolyte interface (SEI) during cycling is studied.