Phase diagram of Lix(MnyFe1-y)PO4(0 ≤ x, y ≤ 1)

The room temperature (x, y) two-dimensional phase diagram of the olivine-type solid-solution, Li 3 (Mn x Fe 1-x )PO 4 (0 ≤ x, y ≤ 1, orthorhombic, D 16 2h : Pmnb), is determined. The x-dependent changes in the unit cell dimensions at various fixed Mn contents y are analyzed in detail. The manganese substitution for iron in the octahedral 4c sites induces I. the two-phase Mn 3+ /Mn 2 redox region with a potential of 4.1 V vs. Li/Li + ; 2. a partial conversion of the form of the Fe 3+ /Fe 2+ redox reaction (3.4 V vs. Li/Li + ) from two-phase to single-phase; and 3, phase instability at the composition region close to the point (x, y) = (0, 1) caused by the Jahn-Teller effect of Mn 3+ . The conversion, 2, is complete at around y = 0.6. The phase instability, 3, makes the Mn-rich phase (y > 0.8) unsuitable for battery applications. The local lattice deformation around Mn 3+ is severe enough to induce significant selective damping in the extended X-ray absorption tine structure for Mn 3+ .