Synthesis and crystal chemistry of the NaMSO ₄F family (M = Mg, Fe, Co, Cu, Zn)

Our work in metal fluorosulphate chemistry, which was triggered by the discovery of the tavorite-phase of LiFeSO ₄F, 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.