Crystal and Electronic Structures of MgCo2−xMnxO4 as Cathode Material for Magnesium Secondary Batteries Using First-Principles Calculations and Quantum Beam Measurements

The stable structure of the spinels MgCo2O4 and MgCo1.5Mn0.5O4, as Mg secondary battery cathode materials, was investigated by first-principles calculations. The calculated stable structures were compared with the crystal structures obtained by quantum beam measurements. The effect on the electronic...

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Published inBulletin of the Chemical Society of Japan Vol. 92; no. 12; pp. 1950 - 1959
Main Authors Ishibashi, Chiaki, Mizutani, Yusuke, Ishida, Naoya, Kitamura, Naoto, Idemoto, Yasushi
Format Journal Article
LanguageEnglish
Published Tokyo The Chemical Society of Japan 15.12.2019
Chemical Society of Japan
Subjects
Bonding strength
Cathodes
Crystal structure
Crystals
Discharge
Distribution functions
Electrode materials
Electron density
Electronic structure
First principles
Magnesium
Manganese
Mathematical analysis
Spinel
Storage batteries
Substitutes
Synchrotron radiation
Electronic structures
Magnesium secondary battery
First-principle calculation
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Summary:The stable structure of the spinels MgCo2O4 and MgCo1.5Mn0.5O4, as Mg secondary battery cathode materials, was investigated by first-principles calculations. The calculated stable structures were compared with the crystal structures obtained by quantum beam measurements. The effect on the electronic structure of the substitution of Mn in MgCo2O4 was examined. Pair distribution function fitting of the normal spinel of MgCo1.5Mn0.5O4 gave a better agreement with experiments than that of MgCo2O4. It was found that Mg/Co cation mixing decreased by the substitution of Mn, as found for the Rietveld analysis of the synchrotron X-ray diffraction. From electron density analysis, it was expected that the Mn-O6 octahedra were more stable than the Co-O6 octahedra because Mn is more attracted to an O atom than a Co atom, that is, the Mn-O bond was stronger than the Co-O bond. The Mg in MgCo1.5Mn0.5O4 was more easily inserted and moved than in MgCo2O4 because the Mg-O bonds near Mn became weak. This fact is consistent with the fact that the first discharge capacity and cycling performance of MgCo1.5Mn0.5O4 were improved over those of MgCo2O4 in charge and discharge tests.
ISSN:0009-2673
1348-0634
DOI:10.1246/bcsj.20190207