"Spectroscopic Signature of Oxidized Oxygen States in Peroxides"

Zengqing Zhuo: Chaitanya Das Pemmaraju, John Vinson, Chunjing Jia, Brian Moritz, Ilkyu Lee, Shawn Sallies, Qinghao Li, Jinpeng Wu, Kehua Dai, Yi-de Chuang, Zahid Hussain, Feng Pan, Thomas P. Devereaux, and Wanli Yang; The Journal of Physical Chemistry Letters, 10/16/18.

Additional Authors: Chaitanya Das Pemmaraju, John Vinson, Chunjing Jia, Brian Moritz, Ilkyu Lee, Shawn Sallies, Qinghao Li, Jinpeng Wu, Kehua Dai, Yi-de Chuang, Zahid Hussain, Feng Pan, Thomas P. Devereaux, and Wanli Yang

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 highefficiency mapping of resonant inelastic X-ray scattering (mRIXS) coupled with firstprinciples 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.