Spectral Profile Unfolding and Chemical Mapping from Scanning Transmission Electron Microscopy–Spectral Imaging Datasets for All-Solid-State Lithium-Ion Battery Materials Analysis

Advancements of all-solid-state lithium-ion batteries (ASSLIBs) have led to a growing demand for the analysis of lithium and other light elements, which is one of the key issues to be resolved for providing guiding principles for the synthesis of better materials, and degradation analysis after repeated use of those materials. This chapter introduces a methodology to visualize the chemical states of constituent elements in a material from overlapping multiple spectral profiles at the nanometric scale, using a suite of scanning transmission electron microscopy, electron energy-loss spectroscopy, and spectral unfolding based on statistical approaches, referred to as spectral image analysis. The method was successfully applied in the chemical state analyses near the interfacial regions between an LiCoO2 cathode and LATP solid electrolyte of an ASSLIB composite fabricated by the aerosol deposition method, which clarified the microscopic origin of the interfacial resistance.