Electrochemical and structural study on cycling performance of γ-LiV<inf>2</inf>O<inf>5</inf> cathode

Abstract

Electrochemical and structural properties of LiV2O5 cathode were investigated. Obtained by solid state reaction at high temperature the material crystallized as gamma polymorph phase, γ-LiV2O5. The gamma structure provides two crystallographic sites to accommodate lithium ions, Li1 and Li2 position. Lithium insertion at these two sites occurs at two respective voltages versus lithium metal: ~3.6 V (Li1) and ~2.4 V (Li2). Intercalation at Li1 position is reversible in both organic and aqueous electrolyte and provides stable cycling performance at the high voltage. On the contrary, sluggish insertion/removal of Li+ at Li2 sites causes unstable performance and significant storage capacity fade at lower voltages. Lithium diffusion 3d landscape was determined by bond valence calculations applied on the γ-LiV2O5 phase, as well as on the metastable phases of γ′-V2O5 and ζ-Li2V2O5 that exist at high and low voltages respectively. The model was proposed based on inactivity of Li2 position of the metastable ζ-Li2V2O5 phase which provides explanation for the observed storage capacity loss at low voltages.