Transition Metals Ion Behavior of Cathode Materials for Li Ion Battery By Electron Beam Irradiation in Scanning Transmission Electron Microscopy

Abstract

Investigating the structural properties of Li-ion batteries (LIBs) and, if possible, determining the overall structure is important in understanding the physical and chemical properties. Understanding the structural properties and the electrochemical properties of the arranged atoms of cathode materials is therefore essential for new battery material design and system optimization. Particularly, cathode materials such as LiNixMnyCo1-x-yO2 (NMC), lithium-rich Li(LiyNix-yMnxCo1-2x)O2, lithium-rich / manganese-rich xLi2MnO3 (1-x)LiMO2 are analyzed by the scanning transmission electron microscopy (STEM) techniques to identify structural characteristics, leading to the conversion of the layer structure to the spinel and/or salt structure, leading to increased impedance, voltage reduction and capacity of the LIBs. The atomic behavior of Li ion in the cathode materials that determines LiBs performance is hardly characterized by transmission electron microscopy (TEM) owing to its weak electron-scattering power. In this sense, annular bright-field (ABF) STEM, in which the contrast has a low scaling rate with the atomic number, has been proven to be a robust technique for simultaneous imaging of light and heavy elements. However, it is very important to understand the damage mechanism of cathode materials by electron-beam irradiation in STEM and to develop this technique. In this study, we investigated the effect of electron-beam irradiation damage on the surface reaction layer and LiNi0.6Co0.2Mn0.2O2 material during STEM data acquisition. This electron-beam irradiation damage process is similar to the lattice reconstruction and chemical evolution caused by the charge-discharge cycle. Furthermore, based on the phase transition phenomenon by the electron-beam irradiation, it is examined whether the electron beam irradiation damage in the lattice structure substituted by Al and Ti affects the phase transition phenomenon.