Fluorosulfate Positive Electrodes for Li-Ion Batteries Made via a Solid-State Dry Process

Ionothermal synthesis has recently been used to prepare a fluorosulfate capable of reversibly intercalating Li at 3.6 V vs Li, making this material a serious contender to for HEV and electric vehicle applications. Although fluorosulfates are made from low cost and abundant starting materials, their synthesis is costly because of the use of ionic liquids as synthetic medium. Herein, we report a solid-state process by which can be synthesized without the use of ionic liquids but at the expense of both longer reaction time and weakly contaminated samples. Additionally, we show how powerful Mössbauer spectroscopy can be in the optimization of the various stages of electrode preparation as shown through the synthesis of and its implementation into an electrode. The importance of having -free hydrated precursors to routinely obtain pure samples is shown together with the need to optimize ballmilling conditions to preserve -free composites. Samples prepared via this low temperature solid-state process show battery performances approaching those of samples prepared using ionic liquids as synthetic medium. Furthermore, this process can be extended to the synthesis of the other members of the fluorosulfates family with , Na and , Co, and Ni.