Molecular Dynamics Simulations of Li Insertion in a Nanocrystalline V 2 O 5 Thin Film Cathode

Abstract

The behavior of lithium ion diffusion from an electrolyte into a polycrystalline layered cathode has been studied using molecular dynamics computer simulations. Lithium silicate glass was the model solid electrolyte while the cathode was a nanocrystalline vanadia with amorphous intergranular films (IGF) between the crystals. Nanosized crystals were aligned with their (001) planes parallel to electrolyte/cathode interface, rotated 90° from each other around this interface’s normal in order to present two different orientations between the crystal planes for lithium intercalation via the amorphous vanadia IGF. A series of nanocrystalline vanadia cathodes with different IGF thicknesses was simulated to examine the effects of the IGF thickness on lithium transport into the cathodes. Results showed preferential diffusion of Li from the electrolyte into the amorphous vanadia IGF, with some of those Li diffusing into the crystalline from the IGF. Results also showed easier lithium diffusion from the IGF into the crystal along the 〈010〉 direction than along the 〈100〉 direction. Additionally, an optimum IGF thickness of 2.5-3.0 nm is suggested as being neither too thick to decrease the capacity of the cathode nor too thin to impede the transport of lithium from glassy electrolyte into the cathode. © 2005 The Electrochemical Society. All rights reserved.