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| Home > Publications database > Coordination of the Mn$^{4+}$-Center in Layered Li[Co$_{0.98}$Mn$_{0.02}$]O$_{2}$ Cathode Materials for Lithium-Ion Batteries |
| Journal Article | FZJ-2017-02879 |
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2017
De Gruyter
Berlin
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Please use a persistent id in citations: doi:10.1515/zpch-2016-0909
Abstract: The local coordination of the manganese in Li[Co0.98Mn0.02]O2 cathode materials for lithium-ion batteries has been investigated by means of a joint XRD and multi-frequency electron paramagnetic resonance (EPR) characterization approach. EPR showed the manganese being in a tetravalent high-spin Mn4+-oxidation state with S=32. The set of spin-Hamiltonian parameters obtained from the multi-frequency EPR analysis with Larmor frequencies ranging between 9.4 and 406 GHz is transformed into structural information by means of the recently introduced Monte-Carlo Newman-superposition modeling. Based on this analysis, the Mn4+ are shown being incorporated for the Co3+-sites, i.e. acting as donor-type functional centers Mn∙Co. In that respect, for Mn4+ the negative sign of the axial second-order fine-structure interaction parameter B02 is indicative of an elongated oxygen octahedron in its first coordination sphere, whereas B02>0 rather points to a compressed octahedron coordinated about the Mn4+-centers. Furthermore, the results obtained here suggest that the oxygen octahedron about the Mn4+-ion is slightly distorted as compared to the CoO6 octahedron. Concerning the coordination to next-nearest neighbor ions, part of the manganese resides in manganese-rich domains, whereas the for the remaining centers the Co3+-site is randomly occupied with Co/Mn according to the effective stoichiometry of the compound. Finally, a structural stability range emerges from the Newman-modeling that supports the discussed ability of manganese to act as an structure-stabilizing element in layered oxides.
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