期刊
ELECTROCHEMISTRY
卷 89, 期 3, 页码 256-266出版社
ELECTROCHEMICAL SOC JAPAN
DOI: 10.5796/electrochemistry.21-00024
关键词
Magnesium Secondary Battery; Cathode; First-principle Calculation; Density of States
资金
- JST, ALCA-SPRING, Japan [JPMJAC1301]
- JSPS KAKENHI, Japan [20K15382]
- Grants-in-Aid for Scientific Research [20K15382] Funding Source: KAKEN
This study investigates the properties of different structures of Mg1+yCo2-xMnxO4 in the pristine and discharged states using first-principles calculations. It is found that there is strong covalency between transition metals and oxygen, and the valence of transition metals decreases with increasing Mg insertion.
In this study, the projected density of states (PDOS) of the stable normal-spinel structure and stable Mg/Co mixed-cation spinel structure of Mg1+yCo2-xMnxO4 (x = 0, 0.5; y = 0, 0.5, 1) in the pristine and discharged states are obtained using first-principles calculations. The spin state and the valence state of the transition metals are investigated. The overlaps of the d orbitals of the transition metals and the p orbitals of oxygen are large, and the covalency between the transition metal and oxygen is strong in the pristine MgCo2O4 and MgCo1.5Mn0.5O4. The M-O-6 (M = Co, Mn) octahedra become stable as a host structure. From the PDOS spectra, Co atoms are in the trivalent low-spin state in pristine MgCo2O4 and MgCo1.5Mn0.5O4 and Mn atoms are nearly tetravalent in pristine MgCo1.5Mn0.5O4. In the discharge process, the overlap of the d orbitals of the transition metals and the p orbitals of oxygen becomes narrow and the valence of the transition metals decreases with increasing Mg insertion. The results of the first-principles calculations are consistent with those of X-ray absorption near edge structure spectra. (C) The Author(s) 2021. Published by ECSJ. [GRAPHICS]
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