Induced Rate Performance Enhancement in Off-Stoichiometric Na3+3x V2-x (PO4 )3 with Potential Applicability as the Cathode for Sodium-Ion Batteries

María J Aragón; Pedro Lavela; Gregorio F Ortiz; Ricardo Alcántara; José L Tirado

doi:10.1002/chem.201700716

Induced Rate Performance Enhancement in Off-Stoichiometric Na_3+3x V_2-x (PO₄ )₃ with Potential Applicability as the Cathode for Sodium-Ion Batteries

Chemistry. 2017 May 29;23(30):7345-7352. doi: 10.1002/chem.201700716. Epub 2017 May 8.

Authors

María J Aragón¹, Pedro Lavela¹, Gregorio F Ortiz¹, Ricardo Alcántara¹, José L Tirado¹

Affiliation

¹ Departmento de Química Inorgánica e Ingeniería Química, Instituto Universitario de Química Fina y Nanoquímica, University of Córdoba, Marie Curie Building. Campus de Rabanales, 14071, Córdoba, Spain.

PMID: 28397973
DOI: 10.1002/chem.201700716

Abstract

Off-stoichiometric Na_3+3x V_2-x (PO₄ )₃ samples have been prepared by a sol-gel route. X-ray diffraction and XPS revealed the flexibility of the NASICON framework to accommodate these deviations of the stoichiometry; at least for low x values. X-ray photoelectron spectra evidenced the presence of Na₄ P₂ O₇ impurities. The synergic combination of the structural deviations and the presence of Na₄ P₂ O₇ impurities induce a significant improvement of the electrochemical performance and cycling stability at high rates, as compared to the stoichiometric Na₃ V₂ (PO₄ )₃ sample. The fast kinetic response provided by the induced off-stoichiometry involves a decrease of the cell resistance.

Keywords: battery; electrochemistry; intercalations; sodium; vanadates.