Alternatively, full-field transmission X-ray microscopy (TXM) is a non-destructive technique that can resolve the entire 3D volume via tomography by collecting and reconstructing X-ray projection images across 180°. With synchrotron light sources, the energy of the incident X-rays can be tuned over a wide range. For different elements, the absorption coefficient undergoes step changes at their characteristic absorption edges, compared to smooth changes at all other energies. The sample absorption intensity is proportional to concentration. Relative elemental specificity can be obtained through the difference between the edge-jumps from above and below the K-edge. Here, dual-energy TXM was collected to map Ni, Mn, and Co in secondary particles of the three compositional gradient architectures synthesized by Shin et al., outlined in Figure . A high statistical significance of the radial concentration profiles in secondary particles was attained for the first time, indicating that diffusion significantly evens out, but does not completely eliminate, the initial compositional gradients towards the average composition of the material. Reduced heterogeneity of elemental content was observed to a greater extent for Ni and Co compared to Mn and in cathode particles with more compositional layers synthesized in the precursor. This method can easily be scaled for the automatic measurement of more particles to acquire further insight into the consistency of interparticle gradients. The methodology provides a feedback loop to build comprehensive theories of cation interdiffusion in heterostructures, informing the design of tailored heterostructured cathodes for Li-ion batteries with high energy density and durability.