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ID 48988
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Author
Ishikawa, Toru
Shimadzu, Saori
Yabuuchi, Naoaki
Komaba, Shinichi
Takeda, Kazuyuki
Goto, Atsushi
Deguchi, Kenzo
Ohki, Shinobu
Hashi, Kenjiro
Shimizu, Tadashi
Abstract
The state of sodium inserted in the hard carbon electrode of a sodium ion battery having practical cyclability was investigated using solid state 23Na NMR. The spectra of carbon samples charged (reduced) above 50 mAh g−1 showed clear three components. Two peaks at 9.9 ppm and 5.2 ppm were ascribed to reversible sodium stored between disordered graphene sheets in hard carbon because the shift of the peaks was invariable with changing strength of external magnetic field. One broad signal at about −9 to −16 ppm was assigned to sodium in heterogeneously distributed closed nanopores in hard carbon. Low temperature 23Na static and magic angle spinning NMR spectra didn't split or shift whereas the spectral pattern of 7Li NMR for lithium-inserted hard carbon changes depending on the temperature. This strongly suggests that the exchange of sodium atoms between different sites in hard carbon is slow. These studies show that sodium doesn't form quasi-metallic clusters in closed nanopores of hard carbon although sodium assembles at nanopores while the cell is electrochemically charged.
Keywords
Sodium ion battery
Anode
Hard carbon
23Na
Solid state NMR
Published Date
2013-03
Publication Title
Journal of Power Sources
Volume
volume225
Start Page
137
End Page
140
ISSN
0378-7753
Content Type
Journal Article
Official Url
http://dx.doi.org/10.1016/j.jpowsour.2012.10.025
language
英語
Copyright Holders
Copyright © 2012 Elsevier B.V. All rights reserved.
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author
Refereed
True
DOI