Structural and electronic properties of spinel type Mg1+yCo2-x-yMnxO4 for cathode applications in magnesium rechargeable batteries

JOURNAL OF POWER SOURCES

卷:482

Article

Idemoto, Yasushi¹  Ichiyama, Mai¹  Ishida, Naoya¹  Kitamura, Naoto¹ 

[1] Tokyo Univ Sci, Fac Sci & Technol, 2641 Yamazaki, Noda, Chiba 2788510, Japan

关键词: Magnesium secondary battery;    Cathode;    Spinel type structure;    Crystal structure;    Synchrotron X-ray source;    Neutron diffraction;   

DOI  :  10.1016/j.jpowsour.2020.228920

来源: Elsevier

【 摘 要 】

Mg1+yCo2-x-yMnxO4 (x = 0, 0.4, 0.5, 0.6; y = 0, 0.04, 0.05, 0.4) was synthesized by the reverse co-precipitation method. Powder X-ray diffraction measurements of the obtained product indicated a spinel structure with the space group Fd (3) over barm. The compositional homogeneity of the synthesized material was confirmed by scanning transmission electron microscopy-energy dispersive X-ray spectroscopy mapping. Charge and discharge cycle tests showed a discharge capacity higher than 220 mAh g(-1) at 90 degrees C with a cut-off voltage ranging from 0.345 to -1.055 V vs. Ag/Ag+ (2.945-1.545 V vs. Mg/Mg2+). The electronic structure was analyzed by the maximum-entropy method (MEM) based on Rietveld analysis results, which showed that Mg insertion was easier in Mg1+yCo2-x-yMnxO4 than in MgCo2O4, and that the strong covalency of M(16d)-O in Mg1+yCo2-x-yMnxO4 enabled Mg ion conduction at the 8a sites. The strain in MO6 octahedra decreased with increasing Mn substitution. The valence of the transition metals was examined by X-ray absorption fine structure (XAFS) measurements, and the Co and Mn K-edge spectra revealed that Co and Mn are present as trivalent to bivalent and tetravalent to trivalent species, respectively. Both Co and Mn redox processes are considered to contribute to the specific capacity during the first charge-discharge process. Rietveld analysis after charge/discharge confirmed a partly reversible phase transition from the spinel phase to the rock salt type phase.

【 授权许可】

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