Extended Data Fig. 3: Cross-sectional SEM and TEM images of transition-metal hydroxide mixture with lithium hydroxide heated ex situ at 500 °C.

(a) Cross-sectional SEM image. TEM images and SAED pattern of primary particles at the (b) core and (c) shell region, as marked in (a). The radial heterogeneity was alleviated to some extent, which agrees with the results of the negative intensity difference at higher temperature (> 340 °C) in Fig. 2f. The SAED patterns on the sample also indicate that both the core and surface regions of the particle evolved to the lithium-containing layered oxide. This result suggests that the continuous inward supply of lithium through the interface could induce the full lithiation within the secondary particle at this temperature, although the path toward the layered structure formation differs for the shell and core regions.