Synthesis and Electrode Performance of Li₄MoO₅-LiFeO₂ Binary System as Positive Electrode Materials for Rechargeable Lithium Batteries

A binary system, x Li4MoO5–(1 − x) LiFeO2, is studied as electrode materials for rechargeable lithium batteries. A sample of single phase is obtained at x = 0.5, and it is found that Li1.42Mo0.29Fe0.29O2 (x = 0.5) crystalizes into Li5ReO6-type structure. Although an initial charge capacity of Li1.42Mo0.29Fe0.29O2 reaches 350 mAh g−1, irreversible phase transition associated with oxygen loss and molybdenum migration on charge is evidenced by X-ray diffraction and X-ray absorption spectroscopy. The irreversible phase transition inevitably results in large polarization on discharge as electrode materials in Li cells. These findings provide the basis for the development of high-capacity electrode materials with solid-state redox reaction of oxide ions.