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dc.contributor.authorAllan, Phoebe
dc.contributor.authorGriffin, John M
dc.contributor.authorDarwiche, Ali
dc.contributor.authorBorkiewicz, Olaf J
dc.contributor.authorWiaderek, Kamila M
dc.contributor.authorChapman, Karena W
dc.contributor.authorMorris, Andrew
dc.contributor.authorChupas, Peter J
dc.contributor.authorMonconduit, Laure
dc.contributor.authorGrey, Clare
dc.description.abstractOperando pair distribution function (PDF) analysis and ex situ (23)Na magic-angle spinning solid-state nuclear magnetic resonance (MAS ssNMR) spectroscopy are used to gain insight into the alloying mechanism of high-capacity antimony anodes for sodium-ion batteries. Subtraction of the PDF of crystalline NaxSb phases from the total PDF, an approach constrained by chemical phase information gained from (23)Na ssNMR in reference to relevant model compounds, identifies two previously uncharacterized intermediate species formed electrochemically; a-Na(3-x)Sb (x ≈ 0.4-0.5), a structure locally similar to crystalline Na3Sb (c-Na3Sb) but with significant numbers of sodium vacancies and a limited correlation length, and a-Na(1.7)Sb, a highly amorphous structure featuring some Sb-Sb bonding. The first sodiation breaks down the crystalline antimony to form first a-Na(3-x)Sb and, finally, crystalline Na3Sb. Desodiation results in the formation of an electrode formed of a composite of crystalline and amorphous antimony networks. We link the different reactivity of these networks to a series of sequential sodiation reactions manifesting as a cascade of processes observed in the electrochemical profile of subsequent cycles. The amorphous network reacts at higher voltages reforming a-Na(1.7)Sb, then a-Na(3-x)Sb, whereas lower potentials are required for the sodiation of crystalline antimony, which reacts to form a-Na(3-x)Sb without the formation of a-Na(1.7)Sb. a-Na(3-x)Sb is converted to crystalline Na3Sb at the end of the second discharge. We find no evidence of formation of NaSb. Variable temperature (23)Na NMR experiments reveal significant sodium mobility within c-Na3Sb; this is a possible contributing factor to the excellent rate performance of Sb anodes.
dc.description.sponsorshipThis research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. P.K.A, J.M.G and C.P.G acknowledge EPSRC (via the Supergen consortium, J.M.G.; EP/K002252/1, PKA) and the EU ERC (via an Advanced Fellowship to C.P.G.) for funding. P.K.A acknowledges a Junior Research Fellowship from Gonville and Caius College, an Oppenheimer Fellowship from the University of Cambridge and the EPSRC for funding. We thank Dr Karen Johnston, Mr Joshua Stratford and Dr Oliver Pecher for helpful discussions. The authors declare no competing financial interest.
dc.publisherAmerican Chemical Society (ACS)
dc.rightsAttribution 4.0 International
dc.rightsAttribution 4.0 International
dc.rightsAttribution 4.0 International
dc.titleTracking Sodium-Antimonide Phase Transformations in Sodium-Ion Anodes: Insights from Operando Pair Distribution Function Analysis and Solid-State NMR Spectroscopy.
dc.description.versionThis is the final version of the article. It first appeared from the American Chemical Society via
prism.publicationNameJ Am Chem Soc
dc.contributor.orcidMorris, Andrew [0000-0001-7453-5698]
dc.contributor.orcidGrey, Clare [0000-0001-5572-192X]
rioxxterms.typeJournal Article/Review
pubs.funder-project-idEngineering and Physical Sciences Research Council (EP/K002252/1)
pubs.funder-project-idEngineering and Physical Sciences Research Council (EP/L019469/1)
cam.orpheus.successThu Jan 30 10:20:17 GMT 2020 - The item has an open VoR version.

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Attribution 4.0 International
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