Intercalation chemistry and chemical bonding

In contrast to amphoteric graphite, the layer-type oxides or chalcogenides generally play the role of acceptors in chemical or electrochemical intercalation reactions. Due to the more ionic character of the M---O bonds, the structural evolution of the oxides may usually be explained on hand of electrostatic considerations, or in terms of cation oxido-reduction. For the more covalent chalcogenides, the occupancy of higher energy levels in the band structure by the transferred electrons constitute mostly a prevailing factor, giving rise to structural changes but also to modifications of the physical properties. The ionic character of the M---O bonds accounts for the strong tendency of the oxides to undergo 2D→3D transformations as a result of intercalation processes.