signifies to a full discharge to the practical capacity within 1/n hours). Operando opti-1 cal microscopy observations also confirm the persistent presence of Li heterogeneities 2 within the cathode particle across a wide range of discharge rates . ity result in substantial differences in dislocation activity and accumulation between primary particles. This indicates that even primary particles of identical size and orientation will exhibit a degree of dislocation activity that highly depends on their location within the agglomerate. Additionally, the sharp drop in Li diffusivity towards higher Li content conditions leads to a pronounced concentration gradient across the secondary particle. This Li heterogeneity can generate a significant difference in lattice dimensions and distortions between the Li-rich and Li-poor domains. Therefore, as shown in Fig. , basal dislocations accumulate prominently near the exterior of the secondary particle, under both discharge and charge conditions. The formation of crystal defects, such as dislocations, will result in high stress build-up and very large local lattice strains. This effect, in turn, modifies the local bonding environment for oxygen, ultimately promoting oxygen deficiency . The accumulation of these basal dislocations thus facilitates the structural degradation from the layered structure to the spinel-like phase within the agglomerate's periphery . This structural degradation carries consequences beyond mere active material loss; it hinders the efficient Li transport into or out of the agglomerate's core. Consequently, this exacerbates the kinetically-induced capacity loss, compounding the adverse effects on the composite cathode's performance. Fig. show that anisotropic elastic stiffness and lattice dimension changes of NMC play a pivotal role in contact mechanics at the cathode/solid-electrolyte interface and grain boundaries among primary particles. Fig. shows the statistical variability in the maximum principle stress distribution on the cathode/solid-electrolyte interface (driving force for contact loss), before and after considering the effect of crystalline anisotropy. Fig. , f, j suggest that while the cathode particle exhibits volume expansion under discharge, most regions within the cathode/solid-electrolyte interface experience substantial tensile stress due to the anisotropic chemical expansion of primary particles, for both single crystal and polycrystal cathodes. Under the charge condition, Fig. , j show that the anisotropic deformation of primary particles results in high stresses both at the cathode/solid-electrolyte interface and grain boundaries within the polycrystal cathode particle. This observation indicates that the potential mechanical failure of the cathode/solid-electrolyte interface and primary-particle fragmentation at grain boundaries is driven by the combination of anisotropic lattice dimension changes upon (de)lithiation and microstructure heterogeneity.