Despite the excellent linear correlation between PfEFIS estimate and NEB barrier, there are several outliers with deviations of up to 0.24 eV. Differing degrees of electronic and ionic relaxation upon ion insertion are two likely error sources to our PfEFIS estimation scheme. However, this could also be utilized in a physically meaningful way because it allows us to quantitatively assess different contributions to an NEB barrier: (1) electrostatics, (2) electronic relaxation (via "Selective dynamics" in VASP, for example), and (3) ionic relaxation. The different barrier contributions could be harnessed in the future as descriptors in machine learning approaches that aim at improving our understanding of intercalant diffusion.