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Induced Rate Performance Enhancement in Off‐Stoichiometric Na 3+3 x V 2− x (PO 4 ) 3 with Potential Applicability as the Cathode for Sodium‐Ion Batteries
Author(s) -
Aragón María J.,
Lavela Pedro,
Ortiz Gregorio F.,
Alcántara Ricardo,
Tirado José L.
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201700716
Subject(s) - stoichiometry , x ray photoelectron spectroscopy , analytical chemistry (journal) , impurity , materials science , x ray crystallography , diffraction , crystallography , chemistry , nuclear magnetic resonance , physics , organic chemistry , chromatography , optics
Off‐stoichiometric Na 3+3 x V 2− x (PO 4 ) 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 Na 4 P 2 O 7 impurities. The synergic combination of the structural deviations and the presence of Na 4 P 2 O 7 impurities induce a significant improvement of the electrochemical performance and cycling stability at high rates, as compared to the stoichiometric Na 3 V 2 (PO 4 ) 3 sample. The fast kinetic response provided by the induced off‐stoichiometry involves a decrease of the cell resistance.