@article{oai:tsukuba.repo.nii.ac.jp:00047931,
 author = {丹羽, 秀治 and 東山, 和幸 and 小林, 航 and 守友, 浩 and Niwa, Hideharu and Higashiyama, Kazuyuki and Amaha, Kaoru and Kobayashi, Wataru and Moritomo, Yutaka},
 journal = {Journal of power sources},
 month = {Apr},
 note = {Layered cobalt oxides are promising cathode materials for sodium ion secondary batteries (SIBs). By combined study of the X-ray absorption spectroscopy (XAS) around the O K-edge and ab initio calculation, we investigated the electronic state of the NaxCoO2 with different oxidization state, i.e, in O3-Na0.91CoO2 (CoO2−0.91) and P2-Na0.66CoO2 (CoO2−0.66). The O K-edge spectra in the pre-edge (529–536 eV) region shows significant change with oxidization of NaxCoO2. In O3-Na0.91CoO2, the spectra shows an intense band (B band) at 531 eV. In P2-Na0.66CoO2, the spectral weight of the B band increases and a new band (A band) appears at 530 eV. These spectral changes are qualitatively reproduced by the calculated partial density of states (pDOSs) of O3-NaCoO2 and P2-Na1/2CoO2. These results indicate that the electrons are partially removed from the O 2p state with oxidization of NaxCoO2.},
 pages = {156--159},
 title = {Electronic states in oxidized Na x CoO 2 as revealed by X-ray absorption spectroscopy coupled with ab initio calculation},
 volume = {384},
 year = {2018}
}