Tracking Sodium-Antimonide Phase Transformations in Sodium-Ion Anodes: Insights from Operando Pair Distribution Function Analysis and Solid-State NMR Spectroscopy

Journal Article · Mon Feb 15 00:00:00 EST 2016 · Journal of the American Chemical Society

DOI:https://doi.org/10.1021/jacs.5b13273· OSTI ID:1392929

Allan, Phoebe K. ^[1]; Griffin, John M. ^[2]; Darwiche, Ali ^[3]; Borkiewicz, Olaf J. ^[4]; Wiaderek, Kamila M. ^[4]; Chapman, Karena W. ^[4]; Morris, Andrew J. ^[5]; Chupas, Peter J. ^[4]; Monconduit, Laure ^[3]; Grey, Clare P. ^[2]

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1. University of Cambridge, University Chemical Laboratory, Lensfield Road, Cambridge, CB2 1EW, U.K.; Gonville and Caius College, Trinity Street, Cambridge, CB2 1TA, U.K.
2. University of Cambridge, University Chemical Laboratory, Lensfield Road, Cambridge, CB2 1EW, U.K.
3. Institut Charles Gerhardt Montpellier-UMR 5253 CNRS, ALISTORE European Research Institute (3104 CNRS), Université Montpellier 2, 34095, Montpellier, France; Réseau sur le Stockage Electrochimique de l’Energie (RS2E), FR CNRS 3459, 80039 Amiens Cedex, France
4. X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, United States
5. Theory of Condensed Matter Group, Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, U.K.

Operando pair distribution function (PDF) analysis and ex situ Na-23 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 Na-23 ssNMR in reference to relevant model compounds, identifies two previously uncharacterized intermediate species formed electro-chemically; a-Na3-xSb (x approximate to 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-Na1.7Sb, a highly amorphous structure featuring some Sb-Sb bonding. The first sodiation breaks down the crystalline antimony to form first a-Na3-xSb 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 amorphofis network reacts at higher voltages reforming a-Na1.7Sb, then a-Na3-xSb, whereas lower potentials are required for the sodiation of crystalline antimony, which reacts to form a-Na3-xSb without the formation of a-Na3-xSb. a-Na3-xSb is converted to crystalline Na3Sb at the end of the second discharge. We find no evidence of formation of NaSb. Variable temperature Na-23 NMR experiments reveal significant sodium mobility within c-Na3Sb; this is a possible contributing factor to the excellent rate performance of Sb anodes.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Science - Office of Basic Energy Sciences - Scientific User Facilities Division
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 1392929
• Journal Information: Journal of the American Chemical Society, Vol. 138, Issue 7; ISSN 0002-7863
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English