The rapid microwave-assisted hydrothermal synthesis of NASICON-structured Na3V2O2: X(PO4)2F3-2 x (0 < x ≤ 1) cathode materials for Na-ion batteries

Daria Burova, Iaroslava Shakhova, Polina Morozova, Anna Iarchuk, Oleg A. Drozhzhin, Marina G. Rozova, S. Praneetha, Vadivel Murugan, Jean Marie Tarascon, Artem M. Abakumov

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17 Citations (Scopus)

Abstract

NASICON-structured Na3V2O2x(PO4)2F3-2x (0 < x ≤ 1) solid solutions have been prepared using a microwave-assisted hydrothermal (MW-HT) technique. Well-crystallized phases were obtained for x = 1 and 0.4 by reacting V2O5, NH4H2PO4, and NaF precursors at temperatures as low as 180-200 °C for less than 15 min. Various available and inexpensive reducing agents were used to control the vanadium oxidation state and final product morphology. The vanadium oxidation state and O/F ratios were assessed using electron energy loss spectroscopy and infrared spectroscopy. According to electron diffraction and powder X-ray diffraction, the Na3V2O2x(PO4)2F3-2x solid solutions crystallized in a metastable disordered I4/mmm structure (a = 6.38643(4) Å, c = 10.62375(8) Å for Na3V2O2(PO4)2F and a = 6.39455(5) Å, c = 10.6988(2) Å for Na3V2O0.8(PO4)2F2.2). With respect to electrochemical Na+ (de)insertion as positive electrodes (cathodes) for Na-ion batteries, the as-synthesized materials displayed two sloping plateaus upon charge and discharge, centered near 3.5-3.6 V and 4.0-4.1 V vs. Na+/Na, respectively, with a reversible capacity of ∼110 mA h g-1. The application of a conducting carbon coating through the surface polymerization of dopamine with subsequent annealing at 500 °C improved both the rate capability (∼55 mA h g-1 at a discharge rate of 10C) and capacity retention (∼93% after 50 cycles at a discharge rate of C/2).

Original languageEnglish
Pages (from-to)19429-19440
Number of pages12
JournalRSC Advances
Volume9
Issue number34
DOIs
Publication statusPublished - 2019

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