in contrast to amphoteric graphite, the layer-type oxides or chalcogenides generally play the role of accepters 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 oxide-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. Such features are determining for the choice of the electrode materials for lithium-ion batteries as far as users require high electrode capacity, stability, and cyclability.