Mössbauer Studies of LixFe1/3Mn1/3Ni1/3PO4 Cathode Materials

Abstract

We report on the crystallographic and magnetic properties of LixFe1/3Mn1/3Ni1/3 PO4 (x = 0, 1) using x-ray diffraction (XRD), a vibrating sample magne- tometer (VSM), and Mossbauer spectroscopy. XRD analysis confirmed that the samples have an orthorhombic structure with space group Pnma. From the VSM measurements the samples exhibited an antiferromagnetic behavior with a Curie–Weiss temperature θ = − 162 K for x = 1, and θ = − 303 K for x = 0. The Neel temperature (TN) and spin reorientation temperature (TS) were determined to be 40 K and 10 K for x = 1, and 66 K and 25 K for x = 0. The hyperfine field (Hhf) of LiFe1/3Mn1/3Ni1/3PO4 had smaller values than that of Fe1/3Mn1/3Ni1/3PO4 due to the magnitude of the nearest-neighbor superexchange interaction. Isomer shift (δ) values indicate that the charge states of LiFe1/3Mn1/3Ni1/3PO4 are ferrous (Fe2+), and that of Fe1/3Mn1/3Ni1/3PO4 are ferric (Fe3+). The larger values of the electric quadrupole splitting (δEQ) for the Fe2+ phase compared to the Fe3+ phased originated from the different lattice and valence electron contributions due to the crystalline field and valence transition. Debye temperatures (θD) of 338 ± 5 K (x = 1), and 370 ± 5 K (x = 0) were obtained for the samples.