Fig. 3: Multi-scale length structure and chemical evolution of the valence gradient NMC811 material (VG-NMC811) after 40 electrochemical cycling.
From: Hierarchical nickel valence gradient stabilizes high-nickel content layered cathode materials
a Schematics of where the pillar was cut from the cycled secondary particle. b Three-dimensional X-ray tomography of the central pillar of a cycled secondary particle as marked in (a), which shows the formation of micro-cracks. c Atomic-scale HAAD-STEM imaging of the surface of an internal primary particle showing surface rock-salt reconstruction. d Soft X-ray absorption spectroscopy (XAS) of Ni L-edge for materials in pristine, after 1st cycle and after 40th cycle collected in total electron yield (TEY) and total fluorescence yield (TFY) modes. e The electron energy loss spectra of Ni L2,3-edge from the surface to the center at charged state (4.4 V) and discharged state (2.7 V).
