Ionic conduction and chemical diffusion in solid solutions of superionic conductors Cu2X-Me2X (Me = Ag,Li; X = S,Se)

Ionic conduction and chemical diffusion in silver-and lithium-substituted superionic copper selenides and sulfides are studied. Upon substitution of lithium for copper, a strong increase in the activation energy of ionic conduction in copper sulfide and selenide and the concomitant several-fold decrease in the ionic conductivity are observed. The reasons for the deterioration of ionic transport conditions are elucidated. In contrast to the substitution of lithium for copper, the substitution of silver leads to higher ionic conductivity and the appearance of superionic conduction by two types of cations. Structural aspects of diffusion are considered. Different consequences of substitution of atoms into the cationic sublattice are associated with different electronic sheaths of lithium (alkali metal), silver, and copper (noble metals), which give rise to different types and degrees of hybridization of valence electrons of atoms in the disordered sublattice and the anionic frame.