Tracking Sodium-Antimonide Phase Transformations in Sodium-Ion Anodes [electronic resource] : Insights from Operando Pair Distribution Function Analysis and Solid-State NMR Spectroscopy
- Washington, D.C. : United States. Dept. of Energy. Office of Science, 2016. and Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy
- Physical Description:
- pages 2,352-2,365 : digital, PDF file
- Additional Creators:
- Argonne National Laboratory, United States. Department of Energy. Office of Science, Belgium. Office of the European Research Council Executive Agency (ERCEA), and United States. Department of Energy. Office of Scientific and Technical Information
- Restrictions on Access:
- Free-to-read Unrestricted online access
- We use operando pair distribution function (PDF) analysis and ex situ <sup>23</sup>Na magic-angle spinning solid-state nuclear magnetic resonance (MAS ssNMR) spectroscopy to gain insight into the alloying mechanism of high-capacity antimony anodes for sodium-ion batteries. Subtraction of the PDF of crystalline Na<sub>x</sub>Sb phases from the total PDF, an approach constrained by chemical phase information gained from <sup>23</sup>Na ssNMR in reference to relevant model compounds, identifies two previously uncharacterized intermediate species formed electrochemically; a-Na<sub>3–x</sub>Sb (x ≈ 0.4–0.5), a structure locally similar to crystalline Na<sub>3</sub>Sb (c-Na<sub>3</sub>Sb) 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-Na<sub>3–x</sub>Sb and, finally, crystalline Na<sub>3</sub>Sb. 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<sub>1.7</sub>Sb, then a-Na<sub>3–x</sub>Sb, whereas lower potentials are required for the sodiation of crystalline antimony, which reacts to form a-Na<sub>3–x</sub>Sb without the formation of a-Na<sub>1.7</sub>Sb. a-Na<sub>3–x</sub>Sb is converted to crystalline Na<sub>3</sub>Sb at the end of the second discharge. In the end, we find no evidence of formation of NaSb. Variable temperature <sup>23</sup>Na NMR experiments reveal significant sodium mobility within c-Na<sub>3</sub>Sb; this is a possible contributing factor to the excellent rate performance of Sb anodes.
- Published through SciTech Connect., 01/29/2016., Journal of the American Chemical Society 138 7 ISSN 0002-7863 AM, and Phoebe K. Allan; John M. Griffin; Ali Darwiche; Olaf J. Borkiewicz; Kamila M. Wiaderek; Karena W. Chapman; Andrew J. Morris; Peter J. Chupas; Laure Monconduit; Clare P. Grey.
- Funding Information:
- EP/K002252/1 and AC02-06CH11357
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