A Study on Structural Changes and Thermal Stability of Charged Ni-based Cathode for Li-Ion Batteries Using HR-TEM

Abstract

In this study, the morphological and structural changes of the charged Li1-xNi0.8Co0.15Al0.05O2 (0.5≤x≤0.9) cathode material during heating have been evaluated in real time over the temperature range of room temperature to approximately 400oC, using a Gatan 652 double-tilt heating holder attached to high resolution environmental TEM (FEI Titan 80/300 ETEM). This instrument is well suited to investigate the effects of both temperature and environment on the reaction and degradation mechanisms of cathode materials at different charge depth. Our preliminary TEM results for the overcharged Li0.1Ni0.8Co0.15Al0.05O2 cathode material clearly showed the structural differences between surface and bulk, as well as morphological changes during heating. For the overcharged Li0.1Ni0.8Co0.15Al0.05O2, a porous-like structure was observed during heating near 200℃ and sustained up to 400℃. In addition, in the thin surface and edge areas, the spinel (space group of Fd3m) and rock-salt (space group of Fm3m) high temperature phases coexisted with the R3-m layered structure near room temperature. All the details will be available at the meeting.