Reaction Mechanism of the Olivine-Type Li[sub x](Mn[sub 0.6]Fe[sub 0.4])PO[sub 4] (0≤x≤1)

The charge-discharge reaction mechanism of the olivine-type a possible 4 V class cathode material for lithium batteries, was investigated using equilibrium voltage measurements, X-ray diffraction, Mössbauer spectroscopy, and X-ray absorption spectroscopy. The flat two-phase region with an open-circuit voltage (OCV) of ca. 4.1 V (region I: and the S-curved single-phase region with (region II: were clearly identified together with the corresponding change in the unit cell dimensions of the orthorhombic lattice. These features show significant differences from the reaction mechanism of in which the whole reaction proceeds in a two-phase manner with a flat voltage profile at 3.4 V. © 2001 The Electrochemical Society. All rights reserved.