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Sodium Ion Diffusion in Al2O3: A Distinct Perspective Compared with Lithium Ion Diffusion

Cited 56 time in Web of Science Cited 57 time in Scopus
Authors
Jung, Sung Chul; Kim, Hyung-Jin; Choi, Jang Wook; Han, Young-Kyu
Issue Date
2014-11
Citation
Nano Letters, Vol.14 No.11, pp.6559-6563
Keywords
Na ion batteriesAl2O3ion conductivitymolecular dynamicsdensity functional calculations
Abstract
Surface coating of active materials has been one of the most effective strategies to mitigate undesirable side reactions and thereby improve the overall battery performance. In this direction, aluminum oxide (Al2O3) is one of the most widely adopted coating materials due to its easy synthesis and low material cost. Nevertheless, the effect of Al2O3 coating on carrier ion diffusion has been investigated mainly for Li ion batteries, and the corresponding understanding for emerging Na ion batteries is currently missing. Using ab initio molecular dynamics calculations, herein, we first find that, unlike lithiation, sodiation of Al2O3 is thermodynamically unfavorable. Nonetheless, there can still exist a threshold in the Na ion content in Al2O3 before further diffusion into the adjacent active material, delivering a new insight that both thermodynamics and kinetics should be taken into account to describe ionic diffusion in any material media. Furthermore, Na ion diffusivity in NaxAl(2)O(3) turns out to be much higher than Li ion diffusivity in LixAl(2)O(3), a result opposite to the conventional stereotype based on the atomic radius consideration. While hopping between the O-rich trapping sites via an Na-O bond breaking/making process is identified as the main Na ion diffusion mechanism, the weaker Na-O bond strength than the Li-O counterpart turns out to be the origin of the superior diffusivity of Na ions.
ISSN
1530-6984
URI
http://hdl.handle.net/10371/164574
DOI
https://doi.org/10.1021/nl503169v
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College of Engineering/Engineering Practice School (공과대학/대학원)Dept. of Chemical and Biological Engineering (화학생물공학부)Journal Papers (저널논문_화학생물공학부)
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