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Charge compensation and oxidation in NaxCoO2−δ and LixCoO2−δ studied by XANES |
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| Authors: | M Valkeapää Y Katsumata T Motohashi RS Liu H Yamauchi |
| Institution: | a Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama 226-8503, Japan b Department of Chemistry and Center for Nano Storage Research, National Taiwan University, Taipei 10617, Taiwan, Republic of China c National Synchrotron Radiation Research Center (NSRRC), Hsinchu 30076, Taiwan, Republic of China d Laboratory of Inorganic and Analytical Chemistry, Helsinki University of Technology, FIN-02015 Espoo, Finland |
| Abstract: | A comparative study on the oxidation and charge compensation in the AxCoO2−δ systems, A=Na (x=0.75, 0.47, 0.36, 0.12) and Li (x=1, 0.49, 0.05), using X-ray absorption spectroscopy at O 1s and Co 2p edges is reported. Both the O 1s and Co 2p XANES results show that upon removal of alkali metal from AxCoO2−δ the valence of cobalt increases more in LixCoO2−δ than in NaxCoO2−δ. In addition, the data of O 1s XANES indicate that charge compensation by oxygen is more pronounced in NaxCoO2−δ than in LixCoO2−δ. |
| Keywords: | Sodium cobaltates Lithium cobaltates NaxCoO2 LixCoO2 Cobalt oxidation Charge compensation Cobalt valence XAS XANES Deintercalation Chemical extraction |
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