Non-stoichiometric Mn doping in olivine lithium iron phosphate: structure and electrochemical properties

LiFePO4 and [Li0.918(10)Fe0.01][Fe0.99Mn0.01]PO4 or 1% Mn-doped LiFePO4 were synthesized by the one-step rheological phase reaction method using inexpensive FePO4 as the main raw material. Synchrotron X-ray diffraction, neutron powder diffraction, and transmission electron microscopy were used to characterize LiFePO4 and Mn-doped LiFePO4. Particle sizes were found to be distributed in the range of 0.5 to 1 μm and the carbon-content in the as-prepared samples was around 2 wt%. Rietveld analysis suggests 1 % Mn-doping replaces 1 % Fe from the Fe (M2) site and places this fraction of Fe on the Li (M1) site. The first process on the M2 site is isovalent doping (Mn2+ for Fe2+), while the second process on M2 is supervalent doping (Fe2+ for Li+). The second process requires that Li vacancies exist for charge balance and our simultaneous refinements against neutron and synchrotron X-ray diffraction data indicate an amount of Li vacancies consistent with this requirement. This doping regime agrees with the observed enhancement of the electrochemical properties of the Mn-doped LiFePO4 compared to the undoped LiFePO4. The Mn-doped LiFePO4 cathodes exhibit higher capacity and better cycling performance than the pure LiFePO4.

Keywords

Stoichiometry, Manganese, Crystal doping, Olivine, Iron phosphates, Lithium, Chemical properties, Particles, X-ray diffraction

Citation

Feng, C., Li. H., Du, G., Guo, A., Sharma, N., Peterson, V. K., & Liu, H. (2011). Non-stoichiometric Mn doping in olivine lithium iron phosphate: structure and electrochemical properties. Poster presented to the Australian and New Zealand Institutes of Physics 35th Annual Condensed Matter and Materials Meeting, Charles Sturt University, Wagga Wagga, NSW 2nd - 4th February, 2011. Retrieved from: https://physics.org.au/wp-content/uploads/cmm/2011/

URI

https://physics.org.au/wp-content/uploads/cmm/2011/
https://apo.ansto.gov.au/dspace/handle/10238/11952

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