The incorporation of fluorine into oxide has been reported to improve the performance of disordered rock salt type cathodes , as it offers another knob for tuning the valence of the transition metal cations, and being more electronegative than oxygen leads to higher voltages . Anions that are less electronegative can be oxidised more easily than O-, which could favour anionic redox and leads to higher capacities . For chalcogenide anions (S 2-and Se 2-), the increased polarizability also give rise to better electronic conductivity than the oxide and polyanion based materials, which often poses limitations for fast and reversible Li cycling.