Browsing by Author "Cisternas, Eduardo"

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    Determination of the Conformational Preference of para-Aminobenzoic Acid on Vanadium Pentoxide Surface: An XPS and DFT Study
    (2021) Dietrich, Fabian; Fernandez, Juan; Hevia, Samuel; Cisternas, Eduardo; Flores, Marcos
    Self-assembled monolayers are a promising opportunity to control the electrochemical reactions taking place on electrodes of lithium-ion batteries. Such control is relevant to diminish the aging process and to improve the performance of these energy storage devices. From this point of view, the adsorption of para-aminobenzoic acid on vanadium pentoxide, an attractive high-capacity cathode material, is investigated with the combination of experimental angle-resolved X-ray photoelectron spectroscopy as well as dispersion-corrected density functional calculations. Our results show that the molecules prefer a lyingdown or up-standing configuration depending on their concentration. The comparison between experiment and simulation indicates a high coverage of the surface and hence the formation of a self-assembled monolayer of up-standing molecules.
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    High performance of V2O5 thin film electrodes for lithium-ion intercalation
    (2022) Hevia, Samuel A.; Orive, Joseba; Guzman, Fernando; Cisternas, Eduardo; Dietrich, Fabian; Villarroel, Roberto; Lisoni, Judit
    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 degrees 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.