Recently, an anti-perovskite structured oxysulphide Li 2 FeSO (Pm 3m) was synthesised and found to have reasonably good electrochemical performance with a theoretical cationic redox capacity of 223 mAh/g, and a voltage of 2.5 V against graphite electrodes . A subsequent computational study suggests that the anti-perovskite framework provides low lithium-diffusion barriers, and substituting Fe with other transition metal ions could lead to improved performance . Replacing half of the Fe by Mn has been reported to improved the structural stability, although it leads to a decreased specific capacity . Meanwhile, iron oxysulphide based cathodes have also been explored for applications in sodium-ion battery batteries .