Molecular dynamics simulations of the interface between amorphous and crystalline solids

Oxide glasses in contact with crystalline ceramics exist in a number of important materials. While bulk properties of each component may be well understood for specific applications, the interfaces present in glass/crystal systems may modify overall material properties and understanding such interfaces is known to be important. Understanding the atomistic behavior of these interfaces is especially relevant, but is also experimentally difficult to achieve. We have been using the molecular dynamics (MD) computer simulation technique, combined with experimental studies, to address the atomistic behavior at the interface between glasses and crystals, especially as related to solid state oxide thin film batteries. Previous simulations in our lab showed that the orientation of the crystalline planes of a layered oxide cathode, V ₂O ₅, in contact with the solid electrolyte significantly affects Li ion transport into the cathode. Activation energies for this layered oxide are anisotropic, with a high activation barrier for Li intercalation into the cathode in the orientation that is observed experimentally. In the current simulations, results show the effect of an amorphous intergranular film present between the crystals in a polycrystalline vanadia on Li ion transport in the cathode. A model lithium silicate glass is used as the solid electrolyte while the cathode is a nanocrystalline vanadia (c-V ₂O ₅) with an amorphous V ₂O ₅ (a-V ₂O ₅) intergranular film (IGF) separating the crystals. The presence of the a-V ₂O ₅ IGF allows for rapid transport of Li ions into the cathode as well as intercalation into the vanadia crystals via the IGF.