High performance of V₂O₅ thin film electrodes for lithium-ion intercalation

A reduced toxicity production route of vanadium pentoxide thin films together with the study of the fabrication parameters that allow optimizing the performance of this material as a cathode for lithium-ion batteries is presented. V₂O₅ films were fabricated on silicon and stainless-steel substrates by combining electron beam evaporation of metallic vanadium film followed by an oxidation process. A strong dependence on their performance as cathodes for LiBs to the film thickness and microstructure was found, the later depending mainly on the oxidation temperature. Particularly, V₂O₅ electrodes with 150 nm of thickness fabricated from 50 nm of metallic vanadium oxidized at 500 °C, exhibit excellent performance with a reversible and fast Li storage capability, a high average discharge capacity up to 271 mAh/g at 0.5C, very close to the theoretical capacity (294 mAh/g), with near to 100% of coulombic efficiency. First-principles calculations of Li⁺ diffusion in three main V₂O₅ crystallographic directions using density functional theory (DFT) were performed to explain how this remarkable performance is related to the film microstructure.