A defect cluster model for ion migration in solid electrolytes

A model that describes ion migration in crystalline solid electrolytes in terms of the movement of ion clusters is presented. It is based on investigation of the defect structures of a group of lithium ion conducting solids known as the ?-phases, and of which Li_2+2xZn_1-xGeO₄ (LISICON) and Li_3+xGe_xV_1-xO₄ are members. The mobile Li⁺ ions in these solid solutions order into defect clusters, which effectively migrate through the solid. Li_3+xGe_xV_1-xO₄ is one of the best Li⁺ ion conductors at room temperature and it is therefore particularly important to understand the mechanism of ion transport in this electrolyte. For both systems the variation of conductivity and defect structure with temperature is correlated, and the general applicability of the cluster model to other nonstoichiometric solid electrolytes, in which solid solution formation occurs entirely within the cation or anion sublattice, is discussed. © 1991.