Soft X-ray Absorption Spectroscopic and Raman Studies on Li1.2Ni0.2Mn0.6O2 for Lithium-Ion Batteries

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• 作者：Sunny Hy ; Wei-Nien Su ; Jing-Ming Chen ; Bing-Joe Hwang
• 刊名：The Journal of Physical Chemistry C
• 出版年：2012
• 出版时间：December 6, 2012
• 年：2012
• 卷：116
• 期：48
• 页码：25242-25247
• 全文大小：418K
• 年卷期：v.116,no.48(December 6, 2012)
• ISSN：1932-7455

文摘

Soft X-ray absorption spectroscopy and Raman spectroscopy studies were conducted on Li<sub>1.2sub>Ni<sub>0.2sub>Mn<sub>0.6sub>O<sub>2sub> in order to understand the electronic structures of metal and oxygen ions and the local structural changes that take place during electrochemical cycling. The O K-edge under fluorescent yield mode shows that the spectral ratio significantly drops during the oxygen plateau, while the Ni and Mn L<sub>IIsub>,<sub>IIIsub>-edges under total electron yield mode show a change in the electronic condition of the surface transition-metal ions during the oxygen plateau as evidenced by a sharp increase in the spectral features. This supports the transition-metal densification model where the surface transition-metal ions migrate to the bulk while oxygen leaves the lattice. Raman spectra show that Li migration is substantially suppressed during the plateau at 4.55 V due to shrinkage along the axial plane. Finally, both Raman spectroscopy and the Mn L<sub>IIsub>,<sub>IIIsub>-edges show the surface of the material changes from layered to spinel and grows continuously with subsequent cycles, while Mn is reduced from 4+ after the first cycle and is directly involved in the charge compensation mechanism.