Mapping of Heterogeneous Chemical States of Lithium in a LiNiO[sub 2]-Based Active Material by Electron Energy-Loss Spectroscopy

It is difficult to analyze the local concentrations and chemical states of lithium in lithium-ion secondary battery electrodes by microanalysis techniques based on transmission electron microscopy because the core excitation spectra of transition metals invariably overlap with the absorption/emission spectra of Li–K. We propose a promising analysis method that enables the spatial distribution of lithium with different chemical states from the original phase in a -based positive electrode to be visualized. It employs a suite of spectrum imaging techniques including scanning transmission electron microscopy, electron energy-loss spectroscopy, and multivariate curve resolution. This method is successfully applied to a cross-sectioned positive electrode.