Soft x-ray microscopy of lithium-rich layered-oxide cathode materials for high capacity lithium batteries

We have used for the first time soft X-ray transmission microscopy at the MISTRAL beamline to visualize chemical modifications during cycling of a lithium-rich, cobalt-poor lithium manganese, nickel, cobalt oxide cathode material used as active cathode material in high capacity lithium batteries. We observed Li1.2Mn0.56Ni0.16Co0.08O2 particles with and without VOx coating extracted from electrodes stopped at different state of charge. Even with these homogeneous and small-sized particles (typically 200 nm) it was possible to appreciate particles at different degree of intercalation in the same sample, with a variable distribution during different states of charge. Identification of conducting carbon and binder regions allowed attributing delay in deintercalation at least partially to binder accumulation. Other effects such as local oxygen loss within a particle have probably been also observed. Correction of absorbance saturation could lead to further and more comprehensive information on spatial heterogeneity in these samples.