Journal
ACS ENERGY LETTERS
Volume 3, Issue 7, Pages 1670-1676Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsenergylett.8b00762
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Funding
- Future Energy Systems of the University of Alberta [T12-P04]
- Natural Sciences and Engineering Research Council (NSERC) [RGPIN-2014-05195]
- Alberta Innovates Technology Futures [AITF iCORE IC50-T1 G2013000198]
- AITF graduate fellowship
- Canada Research Chairs program [CRC 207142]
- U.S. DOE's National Nuclear Security Administration [DE-NA-0003525]
- U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering [DE-SC0018074]
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beta-SnSb is known to be a highly stable anode for sodium ion batteries during cycling, but its sodiation-desodiation alloying reactions are poorly understood. Combining in situ TEM with electroanalytical methods, we demonstrate that beta-SnSb forms Na3Sb and Na15Sn4 in sequence upon sodiation and re-forms as beta-SnSb upon desodiation. The negative enthalpy of mixing for Sn and Sb is sufficient to cause sequentially deposited bilayers of Sn/Sb to transform into beta-SnSb, resulting in comparable cycling stability. The good cycling stability of beta-SnSb results from the complex two-phase amorphous-nanocrystalline microstructure in the partially charged discharged states, as well as the intrinsic mechanical toughness of the beta phase. Per the in situ TEM results, the sequential phase transformation shows minimal fracturing of the beta-SnSb, indicating facile buffering of stresses. Extensively cycled specimens eventually show crystalline Sn phase segregation, which may be the source of the ultimate capacity fade in the alloy and bilayers.
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