Browsing by Author "Feng, C"

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    Non-stoichiometric Mn doping in olivine lithium iron phosphate: structure and electrochemical properties
    (Australian Institute of Physics, 2011-02-02) Feng, C; Li, HH; Du, GD; Guo, ZP; Sharma, N; Peterson, VK; Li, HJ
    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.