The Mechanism of Fluorine Doping for the Enhanced Lithium Storage Behavior in Cation-Disordered Cathode Oxide

Sichen Jiao, Yujian Sun, Junyang Wang, Dekai Shi, Yapei Li, Xiangkang Jiang, Fangwei Wang, Yuanpeng Zhang, Jue Liu, Xuelong Wang, Xiqian Yu, Hong Li, Liquan Chen, Xuejie Huang

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12 Scopus citations

Abstract

Li-rich cation-disordered rock-salt (DRX) materials have emerged as promising candidates for high-capacity oxide cathodes. Their fluorinated variants have shown improved cycling stability with effectively suppressed oxygen loss. However, a comprehensive understanding of how fluorination impacts the multiscale structure and lithium transportation in DRX remains elusive in experiments. Herein, the neutron total scattering technique in conjunction with the advanced reverse Monte Carlo (RMC) fitting method is employed to characterize the intricate structure of Li1.16Ti0.37Ni0.37Nb0.1O2 (LTNNO) and the fluorinated Li1.2Ti0.35Ni0.35Nb0.1O1.8F0.2 (LTNNOF). Through rigorous statistical analysis, the multiscale structural evolution upon fluorination is quantified from atomic (≤5 Å) to long-range scale (≈100 Å). The local Li-rich environments around F induce a modest 2.4% increment in the number of fast Li 0TM (transition metal) channels. Crucially, at a broader scale, the proportion of 0TM channels participating in percolation increases significantly from 2.9% in LTNNO to 8.7% in LTNNOF. Fluorination improves the capacity release mainly through merging isolated fast Li channels into the percolation network. This work experimentally unravels the multiscale mechanism of fluorination-induced performance improvement in DRX materials and highlights the necessity of adopting an advanced RMC fitting method to obtain a full view of the complex structural features in developing high-capacity DRX cathodes.

Original languageEnglish
Article number2301636
JournalAdvanced Energy Materials
Volume13
Issue number47
DOIs
StatePublished - Dec 15 2023

Funding

S.J., Y.S., and J.W. contributed equally to this work. The work was supported by funding from the National Natural Science Foundation of China (grant nos. U1932220, 52325207, and 22239003), CAS Project for Young Scientists in Basic Research (Grant no. YSBR‐058), and the National Key Research and Development Program of China (No. 2021YFB2500300). This work had been partially supported by UT‐Battelle, LLC, under Contract No. DE‐AC05‐00OR22725 with the US Department of Energy. S.J., Y.S., and J.W. contributed equally to this work. The work was supported by funding from the National Natural Science Foundation of China (grant nos. U1932220, 52325207, and 22239003), CAS Project for Young Scientists in Basic Research (Grant no. YSBR-058), and the National Key Research and Development Program of China (No. 2021YFB2500300). This work had been partially supported by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the US Department of Energy.

Keywords

  • cathodes
  • cation-disordered oxide
  • fluorine doping
  • lithium-ion batteries
  • neutron total scattering

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