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Combined use of EPR and 23Na MAS NMR spectroscopy for assessing the properties of mixed cobalt-nickel-manganese layers of P3-NayCo1-2xNixMnxO2

Abstract

The knowledge on the formation of mixed transition metal layers on lithium and sodium transition metal oxides, Li/Na(Co,Ni,Mn,)O2, determines the ability to control their electrochemical properties as electrode materials in alkaline ion batteries. Taking into account this, herein we combine the EPR and 23Na MAS NMR spectroscopic techniques in order to gain insight into the structural peculiarities of mixed cobalt-nickel-manganese layers of NayCo1-2xNixMnxO2 with a three-layer stacking (P3-type of structure). Two types of compositions are examined where diamagnetic Co3+ and paramagnetic Ni3+ and Mn4+ are stabilized: Na2/3Co1/3Ni1/3Mn1/3O2 and Na1/2Ni1/2Mn1/2O2. EPR spectroscopy operating in the X- and Q-band region is applied with an aim to improve the spectra resolution and, on the other hand, to provide straightforward information on coordination of transition metal ions inside the layers. The analysis of EPR spectra is based on the reference for Mn4+ and Ni2+ ions occurring simultaneously in oxides with two layer stacking, P2-Na2/3Ni1/3Mn2/3O2. Complementary to EPR, 23Na MAS NMR at high spinning rates is undertaken to assess the local structure of Na nucleus in layered P3-NayCo1-2xNixMnxO2 oxides. All results are discussed taking into account the EPR and NMR data for well-known lithium analogues O3-LiCo1/3Ni1/3Mn1/3O2 and O3-LiNi1/2Mn1/2O2. Finally, the structure peculiarities of the transition metal layers extracted from EPR and NMR methods are demonstrated by electrochemical intercalation of Li+ ions into P3-NayCo1-2xNixMnxO2.

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Publication details

The article was received on 18 Jul 2017, accepted on 07 Sep 2017 and first published on 08 Sep 2017


Article type: Paper
DOI: 10.1039/C7CP04849A
Citation: Phys. Chem. Chem. Phys., 2017, Accepted Manuscript
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    Combined use of EPR and 23Na MAS NMR spectroscopy for assessing the properties of mixed cobalt-nickel-manganese layers of P3-NayCo1-2xNixMnxO2

    M. Kalapsazova, S. Ivanova, R. Kukeva, S. Simova, S. Wegner, E. Zhecheva and R. Stoyanova, Phys. Chem. Chem. Phys., 2017, Accepted Manuscript , DOI: 10.1039/C7CP04849A

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