Ceramic synthesis of disordered lithium rich oxyfluoride materials

Disordered lithium-rich transition metal oxyfluorides with a general formula Li$_{1+x}$MO$_{2}$F$_{x}$ (M being a transition metal) are gaining more attention due to their high specific capacity which can be delivered from the facecentered cubic (fcc) structure. The most common synthesis procedure involves use of mechanosynthesis. In this work, ceramic synthesis of lithium rich iron oxyfluoride and lithium rich titanium oxyfluoride are reported. Two ceramic synthesis routes are developed each leading to the different level of doping with Li and F and different levels of cationic disorder in the structure. Three different Li$_{1+x}$MO$_{2}$F$_{x}$ samples (x ¼ 0.25, 0.3 and 1) are compared with a sample prepared by mechanochemical synthesis and non-doped LiFeO2 with fcc structure. The obtained lithium rich iron oxyfluoride are characterized by use of M€ossbauer spectroscopy, X-ray absorption spectroscopy, NMR and TEM. Successful incorporation of Li and F have been confirmed and specific capacity that can be obtained from the samples is in the correlation with the level of disorder introduced with doping, nevertheless oxidation state of iron in all samples is very similar. ... mehrConclusions obtained from lithium rich iron oxyfluoride are validated by lithium rich titanium oxyfluoride.