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<p>Anionic redox has reshaped the conventional way of exploring advanced cathode materials for Li-ion batteries. However, how anions participate in the redox process has been the subject of intensive debate, evolving from electron holes to O–O dimerization and currently to a focus on trapped molecular O<sub>2</sub> based on high-resolution resonant X-ray inelastic scattering research. Here we show that the resonant X-ray inelastic scattering signal of molecular O<sub>2</sub> is not exclusive to Li-rich oxide cathodes, but appears consistently in O-redox-inactive oxide materials even with a short beam exposure time as low as 1 min, indicating that molecular O<sub>2</sub> species are not directly related to voltage hysteresis and voltage decay. We further demonstrated that molecular O<sub>2</sub> is not a direct product of electrochemistry but more likely a consequence of the core excitation process in resonant X-ray inelastic scattering, for which the possible scenarios of the dissociation of ‘M-(O–O)’-like species on beam excitation must be considered. Collectively, our results reconcile the conflicting reported results on the (non-)observation of molecular O<sub>2</sub> signal collected from different beamlines and suggest that molecular O<sub>2</sub> is not the energetic engine of new battery oxide cathodes.</p>

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Clarifying the origin of molecular O2 in cathode oxides

  • 期刊论文

  • 发表日期：

    2025年3月10日

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  • Xu Gao,
  • Biao Li,
  • Kurt Kummer,
  • Andrey Geondzhian,
  • Dmitry A. Aksyonov,
  • Rémi Dedryvère,
  • Dominique Foix,
  • Gwenaëlle Rousse,
  • Mouna Ben Yahia,
  • Marie-Liesse Doublet,
  • Artem M. Abakumov,
  • Jean-Marie Tarascon

摘要

Anionic redox has reshaped the conventional way of exploring advanced cathode materials for Li-ion batteries. However, how anions participate in the redox process has been the subject of intensive debate, evolving from electron holes to O–O dimerization and currently to a focus on trapped molecular O2 based on high-resolution resonant X-ray inelastic scattering research. Here we show that the resonant X-ray inelastic scattering signal of molecular O2 is not exclusive to Li-rich oxide cathodes, but appears consistently in O-redox-inactive oxide materials even with a short beam exposure time as low as 1 min, indicating that molecular O2 species are not directly related to voltage hysteresis and voltage decay. We further demonstrated that molecular O2 is not a direct product of electrochemistry but more likely a consequence of the core excitation process in resonant X-ray inelastic scattering, for which the possible scenarios of the dissociation of ‘M-(O–O)’-like species on beam excitation must be considered. Collectively, our results reconcile the conflicting reported results on the (non-)observation of molecular O2 signal collected from different beamlines and suggest that molecular O2 is not the energetic engine of new battery oxide cathodes.