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Structural and electrochemical studies of novel Na7V3Al(P2O7)4(PO4) and Na7V2Al2(P2O7)4(PO4) high-voltage cathode materials for Na-ion batteries

Abstract

A series of Na7V3+4–xAlx(P2O7)4(PO4) (x = 0, 1, 2, and 4) materials were synthesized by flux crystal growth. Novel Na7V4–xAlx(P2O7)4(PO4) (x = 1, 2) compositions were structurally characterized by single crystal and powder X-ray diffraction analyses using laboratory and high-resolution synchrotron X-ray sources. The investigation of the electrochemical behavior of two new mixed V/Al phases as positive electrodes in Na-based batteries was performed using charge – discharge galvanostatic tests and operando X-ray diffraction experiments. It is demonstrated that the substitution of a part of vanadium by aluminum in Na7V4(P2O7)4(PO4) significantly increases the gravimetric capacity of these materials: from 70.9 mAh/g to 113.1 mAh/g and from 48.1 mAh/g to 92.7 mAh/g in Na7V3Al(P2O7)4(PO4) and Na7V2A2l(P2O7)4(PO4), respectively thanks to the activation of the V4+/V5+ redox couple. Different degrees of reversibility of the electrochemical reactions operating on the V3+/V4+ and V4+/V5+ redox couples in Na7V3Al(P2O7)4(PO4) are discussed from the analysis of operando X-ray diffraction.

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Publication details

The article was received on 28 Apr 2017, accepted on 07 Jun 2017 and first published on 09 Jun 2017


Article type: Paper
DOI: 10.1039/C7TA03687F
Citation: J. Mater. Chem. A, 2017, Accepted Manuscript
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    Structural and electrochemical studies of novel Na7V3Al(P2O7)4(PO4) and Na7V2Al2(P2O7)4(PO4) high-voltage cathode materials for Na-ion batteries

    V. Kovrugin, J. Chotard, F. Fauth, A. Jamali, R. David and C. Masquelier, J. Mater. Chem. A, 2017, Accepted Manuscript , DOI: 10.1039/C7TA03687F

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