SPECIAL SEMINAR: Understanding structural ambiguities and degradation mechanisms in lithium ion battery materials using multi-length scale, electron microscopy-based techniques

Macroscopic degradation of cathode materials in  lithium-ion batteries often begin with microscopic changes and it is important to study pristine and cycled cathode materials at the atomic level.  Electron microscopy is widely used to characterize battery materials owing to the high spatial resolution it provides using a variety of imaging, diffraction and spectroscopy techniques. However, researchers are often faced  with ambiguities in structural determination of these materials due to similarities between various phases present in battery materials and oversimplifications in interpreting the data. In this talk, I will discuss three examples. For lithium- and manganese-rich lithium transition metal oxides, I will demonstrate how atomic resolution, HAADF STEM imaging using multiple zone axes was critical in solving the structure while diffraction provided ambiguous results. For electrochemically cycled nickel-rich lithium transition metal oxides, I will show how electron diffraction, including 4DSTEM nanodiffraction mapping helped in correctly identifying the transformed phase as compared to atomic resolution imaging that exhibited higher amount of ambiguity.  Finally, I will show how a correlative, multi-length scale approach was used to understand degradation mechanisms in solid-state batteries by complementing electron microscopy with focused ion beam-assisted tomography, in situ X-ray diffraction, X-ray absorption spectroscopy and transmission X-ray microscopy.