Different solid state and sol-gel preparations of undoped and Mn substituted cathode material LiFePO4 are 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.

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

BINI, MARCELLA;MOZZATI, MARIA CRISTINA;GALINETTO, PIETRO;CAPSONI, DORETTA;FERRARI, STEFANIA;MASSAROTTI, VINCENZO
2009

Abstract

Different solid state and sol-gel preparations of undoped and Mn substituted cathode material LiFePO4 are 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.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11571/202971
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