Theory of anomalous voltage–discharge behavior for topotactic intercalation

Anomalous voltage–discharge behavior observed in topotactic intercalation materials is explained in terms of a lattice–gas model for interstitial sites with short-range nearest-neighbor repulsive interactions. For sufficiently strong interactions a second order phase transition results in the formation of fine structure of intercalated ions at certain critical concentrations. As a result a voltage–discharge curve shows a step-like behavior with nonanalytic features at the critical concentrations.