The molecular dynamics computer simulation technique was used to study electrolyte/cathode interfaces formed in Li-based thin film oxide solid state ionic devices at the atomistic level. The solid electrolytes were lithium silicate glasses while the cathodes were V2O5 or WO3 crystals. The work presented will focus on the behavior at the glass/V2O5 interface. The molecular dynamics simulation technique was successfully used to simulate a variety of silicate glasses and glass surfaces, with results consistent with a variety of experimental data. The simulations of the vanadia crystal reproduced the experimental crystal structures, vibrational frequency, and the appropriate phase transition of V2O5 as Li ions enter the crystal. The simulations had also shown that Li transport into the crystal was affected by the orientation of the crystal at the interface as well as by surface roughness. While the crystal oriented with the (001) planes parallel to the crystal/glass interface showed the appropriate phase transition to the δ-LiV2O5 phase as Li ions enter the crystal, the work presented here showed that the crystal oriented with the (100) planes parallel to the interface did not transform. The difference was attributed to the effect of interface bonding between the ions in the first crystal layer and those in the glass surface. The simulations exhibited a relaxation occurring in a lithium metasilicate glass electrolyte but not in a lithium disilicate electrolyte. In addition, relaxation at the interface between a roughened glass surface and the crystal creates a distortion in the crystal planes in immediate contact with the glass that creates an induced strain in the crystal.

Molecular Dynamics Simulations of Cathode/Glass Interface Behavior: Effect of Orientation on Phase Transformation, Li Migration, and Interface Relaxation. Garofalini, S.H., Shadwell, P.: Journal of Power Sources, 2000, 89[2], 190-200