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Electrochemical and Diffusional Investigation of Na2FeIIPO4F Fluorophosphate Sodium Insertion Material Obtained from FeIII Precursor
journal contribution
posted on 2017-09-18, 00:00 authored by Lalit Sharma, Prasant Kumar Nayak, Ezequiel de la Llave, Haomin Chen, Stefan Adams, Doron Aurbach, Prabeer BarpandaSodium iron fluorophosphate
(Na2FeIIPO4F) was synthesized by
economic solvothermal combustion technique
using FeIII precursors, developing one-step carbon-coated
homogeneous product. Synchrotron diffraction and Mössbauer
spectroscopy revealed the formation of single-phase product assuming
an orthorhombic structure (s.g. Pbcn) with FeII species. This FeIII precursor derived Na2FeIIPO4F exhibited reversible Na+ (de)intercalation with discharge capacity of 100 mAh/g at
a rate of C/10 involving flat FeIII/FeII redox
plateaus located at 2.92 and 3.05 V (vs Na/Na+). It delivered
good cycling stability and rate kinetics at room temperature. The
stability of Na2FePO4F cathode was further verified
by electrochemical impedance spectroscopy at different stages of galvanostatic
analysis. Bond valence site energy (BVSE) calculations revealed the
existence of 2-dimensional Na+ percolation pathways in
the a–c plane with a moderate migration barrier
of 0.6 eV. Combustion synthesized Na2FeIIPO4F forms an economically viable sodium battery material. Although
the capacity of this cathode is relatively low, this study continues
systematic work, which attempts to broaden the scope of reversible
sodium insertion materials.
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Na 2 Fe II PO 4 FFe III precursorssolvothermal combustion technique3.05 Vsingle-phase productsodium battery materialSynchrotron diffractionelectrochemical impedance spectroscopybond valence site energyDiffusional InvestigationNa 2 Fe II PO 4 F formsFe II speciessodium insertion materialsmigration barrierrate kineticsFe III precursorcycling stabilitydischarge capacityNa 2 FePO 4 F cathodeFe III Precursor Sodium iron fluorophosphate0.6 eVgalvanostatic analysisNa 2 Fe II PO 4 F Fluorophosphate Sodium Insertion Material Obtainedpercolation pathwaysBVSEroom temperature
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