Exploring Gas-Solid Phase Diagrams: Novel Methods for Oxyfluorination of Mn3O4 and Mn2O3 with Molecular Fluorine

Fluorinated, manganese-redox cation-disordered rocksalts are promising candidates for high-performance cobalt-free Li-ion cathode active material. A need for reactive fluorinated precursors was however identified. While manganese oxyfluorides are promising precursor candidates, none stable at room temperature was reported prior to 2023. The key to their recent synthesis by reacting molecular fluorine with MnO was a procedure to continuously scan the temperature axis in search of activation temperatures. In line with this philosophy of continuous exploration of the chemical space, two experimental procedures are reported to scan the stoichiometry axis of a gas-solid phase diagram in search of transitions and intermediate compounds. Their application to F-2 - Mn3O4 and F-2 - Mn2O3 phase diagrams resulted in the discovery of two new ranges of stable manganese oxyfluorides of respective compositions MnO1.33-0.13xFx with x<0.5 and MnO1.5-0.22xFx with x<1.