The voids are not randomly dispersed through the particles, but can be highly clustered, such as in the middle of third particle in Figure (red outline), where they are preferentially found in the middle of the crystallite. While the mechanism of void formation in NMC has been studied, the origin of void clustering remains unclear, and to the best of our knowledge has not been previously reported. One possible explanation is the formation of hollow structures during the growth process through the Kirkendall effect, and subsequent aggregation of these voids during annealing. The transition metals quickly migrate outward to form the Li-rich active material, accompanied by slow diffusion of oxygen atoms inward, thus creating cavities inside of the particles. Substantial quantities of voids certainly reduces the theoretical volumetric energy density of the material, while remaining invisible on the surface. The larger clusters of voids may be associated with the microstructure seen in both lattice parameter and orientation maps. The individual voids are too small, and too numerous to be directly linked to the mosaicity detected with SXDM, emphasizing the complementarity of the techniques for characterizing this pristine material.