X-ray Photoemission Spectroscopy Study of Cationic and Anionic Redox Processes in High-Capacity Li-Ion Battery Layered-Oxide Electrodes

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• 作者：Dominique Foix ; Mariyappan Sathiya ; Eric McCalla ; Jean-Marie Tarascon ; Danielle Gonbeau
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：January 21, 2016
• 年：2016
• 卷：120
• 期：2
• 页码：862-874
• 全文大小：923K
• ISSN：1932-7455

文摘

Electrode materials based on Li-rich layered oxides are of growing interest for high-energy Li-ion battery applications because of their staggering capacities associated with the emergence of a novel, reversible anionic process. However, the fundamental science at work behind this new process needs to be well understood for further optimization. Here we report on the redox mechanisms in high-capacity Li-rich materials Li₂Ru_1–xM_xO₃ and Li₂Ir_1–xM_xO₃, by combining X-ray photoemission spectroscopy (XPS) core peaks and valence intensity analyses. We fully confirm that these materials electrochemically react with Li via cumulative reversible cationic/anionic redox processes, but more importantly we reveal that, depending on the nature of the metal (Ru or Ir), there is a delicate balance between metal and oxygen contributions. For instance, we show a greater implication of oxide ions for Ir-based electrodes, consistent with the higher covalent character of Ir–O bonds compared to Ru–O bonds. We equally provide evidence that the oxygen redox process is responsible for the high capacity displayed by the Li-rich NMC Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ electrodes that are serious contenders for the next generation of Li-ion batteries. These combined results highlight the benefit of collecting both XPS core and valence spectra for a better understanding of anionic redox mechanisms in Li-rich layered oxides.