Structural evolution of mixed valent (V3+/V4+) and V4+ sodium vanadium fluorophosphates as cathodes in sodium-ion batteries: comparisons, overcharging and mid-term cycling

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dc.contributor.authorPalomares, Ven_AU
dc.contributor.authorSerras, Pen_AU
dc.contributor.authorBrand, HEAen_AU
dc.contributor.authorRojo, Ten_AU
dc.contributor.authorSharma, Nen_AU
dc.date.accessioned2021-12-07T22:24:09Zen_AU
dc.date.available2021-12-07T22:24:09Zen_AU
dc.date.issued2015-09-28en_AU
dc.date.statistics2021-11-12en_AU
dc.descriptionThis article is licensed under a Creative Commons Attribution-Non Commercial 3.0 Unported licence.en_AU
dc.description.abstractSodium vanadium fluorophosphates belonging to the Na3V2O2x(PO4)2F3−2x family of compounds have recently shown very good electrochemical performance versus Na/Na+ providing high working voltages (3.6 and 4.1 V) and good specific capacity values. In this work the electrochemical behaviour and structural evolution of two compositions, Na3V2O1.6(PO4)2F1.4 (V3.8+) and Na3V2O2(PO4)2F (V4+), are detailed using time-resolved in situ synchrotron X-ray powder diffraction. For the first time in sodium-ion batteries the effects of overcharging and mid-term cycling are analyzed using this technique. Differences in the composition of both materials lead to different combinations of biphasic and single-phase reaction mechanisms while charging up to 4.3 V and overcharging up to 4.8 V. Moreover, the analysis of particle size broadening of both samples reveals the higher stress suffered by the V4+ compared to the more disordered V3.8+ sample. The more “flexible” structure of the V3.8+ sample allows for maximum sodium extraction when overcharging up to 4.8 V while in the case of the V4+ sample no evidence is shown of more sodium extraction between 4.3 V and 4.8 V. Furthermore, the analysis of both materials after 10 cycles shows the appearance of secondary phases due to the degradation of the material or the battery itself (e.g. electrolyte degradation). This study shows examples of the possible degradation mechanisms (and phases) while overcharging and mid-term cycling which is in turn crucial to making better electrodes, either based on these materials or generally in cathodes for sodium-ion batteries. © The Royal Society of Chemistry 2015. This article is Open Access.en_AU
dc.description.sponsorshipThis work was financially supported by the Ministerio de Economía y Competitividad (MAT2013-41128-R) and the Gobierno Vasco/Eusko Jaurlaritza (IT570-13). Dr Sharma would like to thank AINSE Ltd for providing support through the research fellowship scheme. This research was undertaken on the Powder Diffraction beamline at the Australian Synchrotron, Victoria, Australia. The University of Basque Country is acknowledged for funding under project UFI11/53.en_AU
dc.identifier.citationPalomares, V., Serras, P., Brand, H. E. A., Rojo, T., & Sharma, N. (2015). Structural evolution of mixed valent (V 3+/V 4+) and V 4+ sodium vanadium fluorophosphates as cathodes in sodium-ion batteries: comparisons, overcharging and mid-term cycling. Journal of Materials Chemistry A, 3(45), 23017-23027. doi:10.1039/C5TA03780Hen_AU
dc.identifier.issn2050-7488en_AU
dc.identifier.issue45en_AU
dc.identifier.journaltitleJournal of Materials Chemistry Aen_AU
dc.identifier.pagination23017-23027en_AU
dc.identifier.urihttps://doi.org/10.1039/C5TA03780Hen_AU
dc.identifier.urihttps://apo.ansto.gov.au/dspace/handle/10238/12385en_AU
dc.identifier.volume3en_AU
dc.language.isoenen_AU
dc.publisherRoyal Society of Chemistryen_AU
dc.subjectValenceen_AU
dc.subjectCathodesen_AU
dc.subjectSodium ionsen_AU
dc.subjectElectric batteriesen_AU
dc.subjectElectrolytesen_AU
dc.subjectCapacitanceen_AU
dc.subjectEnergy lossesen_AU
dc.titleStructural evolution of mixed valent (V3+/V4+) and V4+ sodium vanadium fluorophosphates as cathodes in sodium-ion batteries: comparisons, overcharging and mid-term cyclingen_AU
dc.typeJournal Articleen_AU
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