Mechanistic Insights into the Non-Equilibrium Synthesis of Highly Fluorinated Cation-Disordered Rock-Salt Cathodes: Solid-State Thermal vs. Mechanochemical Reactions
12 affiliations
- 1Materials Sciences Division
- 2Lawrence Berkeley National Laboratory
- 3School of Engineering and Sciences
- 4SRM University-AP
- 5Department of Chemical Engineering
- 6Columbia University
- 7Advanced Light Source
- 8Earth and Planetary Sciences
- 9University of California
- 10Applied Materials Division
- 11Argonne National Laboratory
- 12Department of Materials Science and Engineering
Abstract
Fluorination is an effective strategy to improve the stability of high-capacity cation-disordered rock-salt (DRX) cathodes, yet incorporating substantial fluorine through conventional thermal synthesis remains challenging. Although mechanochemical milling enables highly fluorinated compositions, the reaction pathways underlying this capability remain poorly understood. This study compares the thermal and mechanochemical synthesis of Li2Mn0.5Ti0.5O2F from identical precursors using in situ thermal and custom-made quasi in situ mechanochemical synchrotron X-ray diffraction. Thermal synthesis proceeds through a Ti-rich DRX intermediate followed by Mn incorporation. Subsequent LiF incorporation coincides with MnO segregation, while further heating induces phase decomposition and substantial fluorine loss. In contrast, mechanochemical milling generates a transient amorphous intermediate that coexists with Ti-rich DRX during progressive MnO incorporation and subsequently transforms into highly fluorinated DRX. Elemental analysis combined with 19F solid-state nuclear magnetic resonance shows estimated fluorine contents of 1.00–1.06 F per formula unit of DRX after mechanochemical synthesis, compared with 0.32–0.41 after thermal synthesis. These findings support an amorphous-mediated pathway for accommodating Mn and F within metastable DRX, highlighting control over transient intermediates as a strategy for accessing highly fluorinated oxyfluoride cathodes.
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BibTeX
@misc{avvaru2026mechanistic,
title = {{Mechanistic Insights into the Non-Equilibrium Synthesis of Highly Fluorinated Cation-Disordered Rock-Salt Cathodes: Solid-State Thermal vs. Mechanochemical Reactions}},
author = {Venkata Sai Avvaru and Seonghun Jeong and Harshita Lohani and Sean Alexander Fernandez and Bora Kalkan and Camille Molsick-Gibson and Martin Kunz and Mateusz Zuba and Ozgenur Kahvecioglu and Lauren E. Marbella and Haegyeom Kim},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv.15010431/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010431/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Mechanistic Insights into the Non-Equilibrium Synthesis of Highly Fluorinated Cation-Disordered Rock-Salt Cathodes: Solid-State Thermal vs. Mechanochemical Reactions
AU - Venkata Sai Avvaru
AU - Seonghun Jeong
AU - Harshita Lohani
AU - Sean Alexander Fernandez
AU - Bora Kalkan
AU - Camille Molsick-Gibson
AU - Martin Kunz
AU - Mateusz Zuba
AU - Ozgenur Kahvecioglu
AU - Lauren E. Marbella
AU - Haegyeom Kim
PY - 2026
DA - 2026/10/13
PB - ChemRxiv
DO - 10.26434/chemrxiv.15010431/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010431/v1
AB - Fluorination is an effective strategy to improve the stability of high-capacity cation-disordered rock-salt (DRX) cathodes, yet incorporating substantial fluorine through conventional thermal synthesis remains challenging. Although mechanochemical milling enables highly fluorinated compositions, the reaction pathways underlying this capability remain poorly understood. This study compares the thermal and mechanochemical synthesis of Li2Mn0.5Ti0.5O2F from identical precursors using in situ thermal and custom-made quasi in situ mechanochemical synchrotron X-ray diffraction. Thermal synthesis proceeds through a Ti-rich DRX intermediate followed by Mn incorporation. Subsequent LiF incorporation coincides with MnO segregation, while further heating induces phase decomposition and substantial fluorine loss. In contrast, mechanochemical milling generates a transient amorphous intermediate that coexists with Ti-rich DRX during progressive MnO incorporation and subsequently transforms into highly fluorinated DRX. Elemental analysis combined with 19F solid-state nuclear magnetic resonance shows estimated fluorine contents of 1.00–1.06 F per formula unit of DRX after mechanochemical synthesis, compared with 0.32–0.41 after thermal synthesis. These findings support an amorphous-mediated pathway for accommodating Mn and F within metastable DRX, highlighting control over transient intermediates as a strategy for accessing highly fluorinated oxyfluoride cathodes.
ER -