Lithium has been intercalated chemically and electrochemically in LnNb3O9 (Ln = La, Nd) perovskite-type phases and LiW3O9F which can be considered as a hexagonal tungsten bronze derivative.
The crystallographic formula of the LnNb3O9 starting material is □3/2 (Ln□1/2 )Nb3O9. In both systems, solid solutions are observed in the fir part of the intercalation reaction. While almost all perovskite cavities are filled in the neodymium phases, the higher ionic character of the La-O bonds prevents practically the Li intercalation in the □' sites.
In the LiW3O9F phase two lithium atoms can be electrochemically intercalated via a single phase mechanism. The reaction is completely reversible. For higher amounts of intercalation (x > 3), irreversible structural modifications occur.
In both systems the unit cell parameter variation is negligible during intercalation. This behavior results from the blocking up of the framework by Ln3+ ions in LnNb3O9 phases or by the stacking of the three octahedra triangular arrangement in the hexagonal tungsten bronze structure.