Researchers have honed the ability to fine-tune these materials comprising different compositional layers during precursor synthesis with high accuracy and precision. To bring the synthesis of such refined cathodes to manufacturing scales, Shin et al. recently developed a "digital-gradient" process for precursors where a continuous-flow method through cascading continuous stirred tank reactors (CSTR) enabled increasingly complex compositional changes as additional layers on a baseline material. The structures of representative multi-shell architectures made by this method are outlined in Figure . Starting from an initial baseline material, Ni0.9Co0.05Mn0.05(OH)2, the process was extended to grow a series of additional layers of hydroxide where the Ni:Co:Mn ratios of the synthesis feeds successively changed to 8:1:1, 6:2:2 and 1:1:1, targeting materials with increasing average Mn/Ni ratios and compositional differences between interior and surface. After these architectures are formed, the precursor is mixed with a lithium salt and sintered at high temperatures (>700C) to produce the oxide cathode. The elevated temperature causes significant morphological changes, like decreased particle size from dehydration and increased porosity from gas release. More importantly, in the context of the design of heterostructures, it also causes cation interdiffusion of transition metals within secondary particles when compositional gradients exist, changing the elemental profile (Figure ) and challenging the control of the final architecture. A study was conducted using SEM-EDS measuring linear diffusion coefficients of Ni 3+ , Mn 3+ , and Co 3+ for increasing temperatures performed on laminar pressed pellets, due to the difficulty of measuring concentration profiles in the radial direction, which found that Co 3+ exhibited a 10x higher diffusion rate than Mn 3+ when diffusing opposite Ni 3+ . Insufficient quantification of the actual gradients in their final form, and their homogeneity across the particle morphology, introduces the risk of misinformed assignment of performance gains and misdirection of future synthesis.