Fig. 3: Evolution of the Li deficiency and disordered structure near the surface of NCM-300 cycles.
From: Evolution and expansion of Li concentration gradient during charge–discharge cycling
a APT depth profile at the top surface, showing a significant Li deficiency up to ~15 nm (region enclosed by dotted square). b, c STEM-HAADF image (b) and intensity profile (c) at the top surface. The rock-salt-like phase evolves because of TM migration (inset: magnified image). Red arrows indicate TM migration from 3b to 3a sites. d APT depth profile starting at ~30 nm from the top surface, showing the gradual increase in the Li concentration along the depth. e, f STEM-HAADF image (e) and intensity profile (f) starting at ~30 nm from the surface (inset: magnified image). The red arrows show that 30 nm below the surface, TMs migrate to a lesser extent than they do near the top surface in (c). Error bars show the standard deviation of each dataset.
