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Title: Structure and electrochemistry of NaFePO{sub 4} and Na{sub 2}FePO{sub 4}F cathode materials prepared via mechanochemical route

Highlights: • Na{sub 2}FePO{sub 4}F is prepared by mechanochemically assisted solid state synthesis. • The crystal and local structure are studied by XRPD, FTIR, Mössbauer, and NMR. • Na{sup +}/Li{sup +} ion exchange is completed with the formation of NaLiFePO{sub 4}F. • The average D{sub Li} (10{sup −15} cm{sup 2} s{sup −1}) is determined from GITT measurements. - Abstract: Nanostructured NaFePO{sub 4} (space group Pmnb) and Na{sub 2}FePO{sub 4}F (space group Pbcn) were prepared by a quick and facile mechanochemically assisted solid state synthesis. Low-crystalline Na{sub 2}FePO{sub 4}F was formed as a result of direct mechanochemical reaction of NaFePO{sub 4} with NaF. It crystallizes upon subsequent heating to 600 °C and decomposes at higher temperatures. Crystal and local structure were analyzed by XRD using Rietveld refinement, FTIR, Mössbauer, and NMR spectroscopy. Electrochemical properties were studied by galvanostatic cycling in lithium cells and GITT. Although NaFePO{sub 4} showed some electrochemical activity, neither electrochemical nor chemical Na{sup +}/Li{sup +} exchange was observed by XRD. On contrary, electrochemical and chemical Na{sup +}/Li{sup +} ion exchange occurred in the case of Na{sub 2}FePO{sub 4}F and accomplished with the NaLiFePO{sub 4}F formation. Li{sup +} diffusion coefficient in NaLiFePO{sub 4}F at different delithiated/lithiated states was determinedmore » from GITT. Carbon-coated Na{sub 2}FePO{sub 4}F shows discharge capacity of 116 mA h g{sup −1} at 0.1 C rate within the 2.0–4.2 V voltage range and a good cyclability.« less
Authors:
 [1] ;  [2] ; ;  [1] ;  [3]
  1. Institute of Solid State Chemistry and Mechanochemistry SB RAS, 18 Kutateladze, 630128 Novosibirsk (Russian Federation)
  2. (Russian Federation)
  3. Institute of Chemistry FEB RAS, 159 Stoletiya Vladivostoka, 690022 Vladivostok (Russian Federation)
Publication Date:
OSTI Identifier:
22420723
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Research Bulletin; Journal Volume: 60; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CARBON; CLATHRATES; CRYSTALS; DIFFUSION; ELECTROCHEMISTRY; FOURIER TRANSFORMATION; INFRARED SPECTRA; ION EXCHANGE; IRON PHOSPHATES; LITHIUM; LITHIUM IONS; NANOSTRUCTURES; NUCLEAR MAGNETIC RESONANCE; SODIUM FLUORIDES; SODIUM IONS; SOLIDS; X-RAY DIFFRACTION