LiNi0.8Co0.15Al0.05O2 (NCA) is widely used as a commercial lithium-ion battery cathode material, despite operating well below its theoretical performance limits. A thorough understanding of the underlying degradation processes of this material is necessary in order to overcome these limitations and unlock the full cathode capacity. X-ray spectroscopy provides a means of investigating these processes by directly probing the electronic structure of the material. By coupling soft X-ray spectroscopy with several X-ray microscopy techniques spanning a range of spatial resolutions, we have uncovered chemical inhomogeneities that are not apparent by bulk measurement alone. The large number of independent, pixel-wise spectra acquired by chemical imaging enables advanced statistical analyses, revealing reduced nickel states resulting from degradation processes at the surface of particles. The relative abundances of the various states are then mapped within individual particles at several states of charge. Additionally, a novel X-ray enabled tunneling microscopy technique provides a spatially resolved chemical probe that is sensitive to the first few atomic layers of the particle. Comparing measurements from bulk to nanometer length-scales provides insights that are not accessible when considered separately.

Multi-scale chemical microscopy of reaction inhomogeneities in LiNi0.8Co0.15Al0.05O2 cathode primary particles

256th National Meeting (2018)

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