NMR study for electrochemically inserted Na in hard carbon electrode of sodium ion battery

Kazuma Gotoh, Toru Ishikawa, Saori Shimadzu, Naoaki Yabuuchi, Shinichi Komaba, Kazuyuki Takeda, Atsushi Goto, Kenzo Deguchi, Shinobu Ohki, Kenjiro Hashi, Tadashi Shimizu, Hiroyuki Ishida

Research output: Contribution to journalArticlepeer-review

163 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)137-140
Number of pages4
JournalJournal of Power Sources
Publication statusPublished - Mar 1 2013
Externally publishedYes


  • Anode
  • Hard carbon
  • Na
  • Sodium ion battery
  • Solid state NMR

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Energy Engineering and Power Technology
  • Physical and Theoretical Chemistry
  • Electrical and Electronic Engineering


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