Fig. 4: Formation of voids and large diamagnetic Li-rich regions over cycling.
From: Trapped O2 and the origin of voltage fade in layered Li-rich cathodes
a–c, ADF-STEM images showing single grains of the pristine (a), 2nd discharge (b) and 100th discharge (c) material showing the formation of voids about 4–12 nm in diameter over extended cycling. d, 129Xe NMR experiments. Samples were extracted from cells and infiltrated with Xe gas to probe the open porosity. e, 129Xe NMR of the pristine, 2nd discharge and 100th discharge materials. The orange region highlighted indicates the presence of open voids of 17 nm diameter and greater after 100 cycles. δiso, isotropic chemical shift. f,g, 6Li (f) and 17O (g) NMR isolating slow and fast relaxing environments. The sharp peaks at 0 ppm in the 6Li and slow relaxing 17O NMR spectra indicate the formation of large diamagnetic Li-rich regions on extended cycling.
