Résumé
Searching for possible new cathode materials with the ability to outperform LiFePO4, our group has recently discovered LiFeSO4F, a novel metal fluorosulphate compound. Needing no further optimization, it delivers excellent reversible capacity (~140 mAh/g) involving a 3.6 V FeII/III redox plateau. This parent fluorosulphate phase has been synthesized by three different routes, namely ionothermal synthesis, solid-state synthesis and polyol-assisted synthesis. These low temperature processing routes are described focusing on synthesis of LiFeSO4F. Furthermore, these methods were successfully employed to unravel other LiMSO4F compounds (M = Co/Ni/Mn/Zn) as well as sodium-based metal fluorosulphate NaMSO4F compounds (M = Fe/Co/Ni/Mn). These syntheses were realized at temperature not exceeding 300°C. We have discovered many interesting and at times intriguing structural, electrochemical and transport properties in these fluorosulphate materials. A few of these findings are illustrated to show the richness of the metal fluorosulphate chemistry.