Nanoscale Mapping of Spatial Fluctuations in Oxygen Redox Activity within a Single Particle of Li-rich Layered Oxide

Direct visualization of the spatial distribution of oxygen redox activity in single particles of Li-rich layered oxide (LLO) is essential for a deeper understanding of its reaction mechanism. In this study, we propose a real-space mapping approach for identifying oxygen redox-active domains using scanning transmission electron microscopy (STEM)-based electron energy-loss spectroscopy (EELS). Electron-released oxygen (oxidized oxygen) was clearly detected by EELS and soft X-ray absorption spectroscopy (S-XAS) in the charged state of Li1+x(Ni0.3Mn0.7)1-xO2 (0 < x < 1/3). STEM-EELS spectrum imaging clarified that the fluctuations in oxygen redox activity closely correlate with the Ni distribution within LLO particles. The heterogeneous distribution of transition metals leads to non-uniform activation of oxygen in the particles, with Ni-rich domains suppressing oxygen redox activity. This real-space mapping of oxygen activity domains at the LLO single-particle level contributes to understanding the material’s mechanism.