Fig. 1: Redox behaviour and structural design of Li1+X(r)M1−X(r)O2 particles with a continuous gradient from the Li-rich bulk to the Li-poor surface.
From: Gradient Li-rich oxide cathode particles immunized against oxygen release by a molten salt treatment
a, Redox behaviours of transition metal cations and oxygen anions of the Li-poor surface and the Li-rich bulk. b, Schematic of the cross-section of a Li1+X(r)M1−X(r)O2 particle. The zoomed-in sector is a two-dimensional cross-section from the particle bulk to the surface. The deeper colour indicates more M and less Li. c, STEM-HAADF lattice image from the core to the surface in a lattice-coherent particle. Rectangle A is from the Li-poor surface, and rectangle B is from the Li-rich bulk. The circle with the cross inside denotes the direction travelling into the page. d, Schematic of the layered structure of the Li-gradient region in a lattice-coherent particle from the Li-rich (Li substitution in M layer) bulk to the Li-poor (M substitution in Li layer) surface. e, STEM-HAADF images from rectangle A and rectangle B in c with higher magnification, where MLiL pillars can clearly be seen in the Li layers (due to higher average atomic number, Z, of the atomic column) in rectangle A but not in B.
