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Spectroscopic Signature of Oxidized Oxygen States in Peroxides.

  • Author(s): Zhuo, Zengqing
  • Pemmaraju, Chaitanya Das
  • Vinson, John
  • Jia, Chunjing
  • Moritz, Brian
  • Lee, Ilkyu
  • Sallies, Shawn
  • Li, Qinghao
  • Wu, Jinpeng
  • Dai, Kehua
  • Chuang, Yi-de
  • Hussain, Zahid
  • Pan, Feng
  • Devereaux, Thomas P
  • Yang, Wanli
  • et al.
Abstract

Recent debates on the oxygen redox behaviors in battery electrodes have triggered a pressing demand for the reliable detection and understanding of nondivalent oxygen states beyond conventional absorption spectroscopy. Here, enabled by high-efficiency mapping of resonant inelastic X-ray scattering (mRIXS) coupled with first-principles calculations, we report distinct mRIXS features of the oxygen states in Li2O, Li2CO3, and especially, Li2O2, which are successfully reproduced and interpreted theoretically. mRIXS signals are dominated by valence-band decays in Li2O and Li2CO3. However, the oxidized oxygen in Li2O2 leads to partially unoccupied O-2p states that yield a specific intraband excitonic feature in mRIXS. Such a feature displays a specific emission energy in mRIXS, which disentangles the oxidized oxygen states from the dominating transition-metal/oxygen hybridization features in absorption spectroscopy, thus providing critical hints for both detecting and understanding the oxygen redox reactions in transition-metal oxide based battery materials.

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