Li₅FeO₄ and its analogues as electrode of lithium ion batteries

The anti-fluorite type materials, Li₅FeO₄ were prepared and studied as a cathode for lithium secondary battery. 1.2 equivalent lithium was deintercalated from Li₅FeO₄ and reversibly intercalated, which corresponds to the capacity of 200mAh/g in Li/Li ₅FeO₄ cell(4V-2V). In the first charge, the structure changes to amorphous-like phase which dominates in the following cycles. In the initial few cycles, the discharge capacity was lower than the charged capacity and the efficiency became 100% after the fifth cycle. The Mössbauer effect measurement shows that the valence state of oxidized iron did not coincide with the charge transferred in the Li/Li₅FeO₄ cell. The participation of electrons belonging to oxide ions was suggested.