Structural, spectroscopic and magnetic investigation of the LiFe1-xMnxPO4 (x=0-0.18) solid solution

Different solid state and sol-gel preparations of undoped and Mn substituted cathode material LiFePO4 ;re investigated. Li3PO4, Fe2P2O7 and Li4P2O7 are detected and quantified by XRPD only in solid state synthesis. In addition, micro-Raman spectra reveal low amount of different iron oxides Clusters. EPR data, combined with the results of magnetization measurements, evidence signals from Fe3+ ions in maghemite nanoclusters, and in Li3Fe2(PO4)(3). The sol-gel synthesis, showing the lowest amount of impurity phases, seems the most suitable to obtain a promising cathode material. The structural refinement gives new insights into the cation distribution of the Mn doped triphylite structure: (i) about 85% of Mn2+ ions Substitutes Fe2+, the remaining 15% being located on the Li site, thus suggesting a structural disorder also confirmed by EPR and micro-Raman results; (ii) Mn ions on the Li site are responsible for the observed slight cell volume expansion. (C) 2009 Elsevier Inc. All rights reserved.