Atomic resolution enabled STEM imaging of nanocrystals at cryogenic temperature

Abstract

In this study, we address the problem of electron-beam induced damage on two energy-related materials: LiNi0.5Mn1.5O4 used as a cathode material for lithium-ion batteries and ZnCo1.8Ni0.2O4 used as a catalyst for oxygen evolution reaction. Both materials were found to transform from the spinel into the rocksalt phase while being imaged by high-resolution scanning transmission electron microscopy (HR-STEM) at room temperature. To mitigate the degradation, we found HR-STEM characterization at cryogenic temperature delays the critical electron dose for structural modification. We determined the native phase of materials to be spinel while the other phases observed by HR-STEM were induced by the electron-beam. From a careful analysis of the experimental data and a detailed understanding of the different degradation processes induced by an energetic electron beam, we conclude that radiolysis is the mechanism responsible for the degradation in LiNi0.5Mn1.5O4 and ZnCo1.8Ni0.2O4 nanoparticles.