Li2FeMn3O8 acts as a reversible cathode material by (de)lithiation in cells: Li/LiPF6, propylene carbonate/LiXFeMn3O8. Initial discharge gives a plateau centered at 4.9 V attributable to the Fe-3+,Fe-4+ couple followed by a second plateau at 4.1 V with overall discharge capacity of 125 mA h g(-1).