  Colossal Ion Conductivity (CIC) is the phenomenon in which large changes in
oxygen conductivity are observed when a solid state oxygen electrolyte is
placed in a heterolayer super lattice. Several hypotheses have been posed
concerning both structural changes of the ion conducting material and of the
ion conducting mechanism. The posed structural hypotheses are oxygen sub
lattice melting, phase change of the ion conducting material, and that the
heterolayer environment does not induce a phase change of the ion conducting
material. The posed mechanistic hypotheses are disorder, mechanics, and space
charge. Here, first principles molecular dynamics and statics of the ion
conducting interface are performed providing evidence that under CIC conditions
no sub lattice melting nor phase change has occurred and that the electrolyte
remains unchanged. A discussion of the posed mechanistic hypotheses is given
and cast as a series of mathematical statements. When these hypotheses are
compared with first principles calculations and literature results, they fail
to capture CIC; a new alternative dipole hypothesis is offered, which also
fails to capture CIC; further analysis of the literature points to CIC being an
interface mediated phenomenon, similar to grain boundary diffusion, where the
operando mechanism remain unclear.
