Abstract
Recently in the Li-ion battery community there has been an intense amount of attention focusing on developing 22 positive electrodes which operate on the Fe2+/Fe3+ redox potential given that the environmental and economic 23 advantages of Fe-based compounds compared to other transitionmetals are tremendous.Herewe report thatwe 24 have succeeded in preparing for the first time LiFeSO4F in the triplite structurewhich shows an open circuit volt- 25 age of 3.9 V versus Li with a reversible capacity of approximately 85mA h g 26 −1, still well below the theoretical value of 148 mA h g 27 −1 due to poor electrode kinetics. Nevertheless, we additionally found that the volume change on removal of Li is 0.6%. Once optimized, this triplite phase of LiFeSO4F could stand as a promising con- 28 tender to LiFePO4.