Synthesis and crystal chemistry of the NaMSO4F family (M = Mg, Fe, Co, Cu, Zn)

Our work in metal fluorosulphate chemistry, which was triggered by the discovery of the tavorite-phase of LiFeSO4F, has unveiled many novel Li- and Na-based phases with desirable electrochemical and/or transport properties. Further exploring this rich crystal chemistry, we have synthesized the Na-based magnesium, copper and zinc fluorosulphates, which crystallise in the maxwellite (tavorite-like framework) structure just as their Fe and Co counterparts, which were previously reported. These phases show ionic conductivities in the range of ∼10−7 S cm−1 or ∼10−11 S cm−1 depending upon their synthesis process and no reversible electrochemical activity versus Na.

Graphical abstractObservation of Jahn-Teller distortion in NaCuSO4F system.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Discovery of three novel Na-based fluorosulphate compounds, namely NaMgSO4F, NaCuSO4F and NaZnSO4F. ► Solving the maxwellite crystal structure. ► Observation of Jahn–Teller distortion in NaCuSO4F phase, the first such example in metal fluorosulphate family.