Mechanistic Insights into the Non-Equilibrium Synthesis of Highly Fluorinated Cation-Disordered Rock-Salt Cathodes: Solid-State Thermal vs. Mechanochemical Reactions
Year: 2026
Type: preprint
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.
Source: ChemRxiv
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7221800161