Electrochemical and Chemical Na+/Li+ Ion Exchange in Na-Based Cathode Materials: Na1.56Fe1.22P2O7 and Na3V2(PO4)2F3

In this work, XRD, EDX, Mössbauer and NMR spectroscopy were used to study chemical and electrochemical Na+/Li+ ion exchange in the sodium iron pyrophosphate Na1.56Fe1.22P2O7 with a triclinic symmetry, S. G. P-1, and sodium vanadium fluorophosphate Na3V2(PO4)2F3 with a tetragonal symmetry, S. G. P42/...

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Bibliographic Details
Published in:Journal of the Electrochemical Society 2016-12, Vol.164 (1), p.A6192-A6200
Main Authors: Kosova, Nina V., Rezepova, Daria O., Petrov, Sergey A., Slobodyuk, Arseny B.
Format: Article
Language:English
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Summary:In this work, XRD, EDX, Mössbauer and NMR spectroscopy were used to study chemical and electrochemical Na+/Li+ ion exchange in the sodium iron pyrophosphate Na1.56Fe1.22P2O7 with a triclinic symmetry, S. G. P-1, and sodium vanadium fluorophosphate Na3V2(PO4)2F3 with a tetragonal symmetry, S. G. P42/mnm, cathode materials. Electrochemical Na+/Li+ ion exchange was performed in hybrid-ion cells with Li metal anode and LiPF6-based electrolyte, while chemical ion exchange was realized in the solution of LiBr in acetonitrile. A facile electrochemical and chemical Na+/Li+ ion exchange was observed for both cathode materials, resulting in the formation of the mixed Na-Li compositions: ∼Na1.2Li0.36Fe1.22P2O7 and ∼Na2.47Li0.53V2(PO4)2F3, respectively. Partial Na+/Li+ ion exchange did not cause noticeable structural changes to the pristine sodium-based materials. Both materials showed an excellent electrochemical performance in hybrid-ion cells. It was suggested that during cycling, a mixed Na+/Li+ cathode reactions occurred.
ISSN:1945-7111
DOI:10.1149/2.0301701jes