Determining the crystal and electronic structures of the magnesium secondary battery cathode material MgCo2−xMnxO4 using first-principles calculations and a quantum beam during discharge

• Published in: Journal of materials science Vol. 55; no. 28; pp. 13852 - 13870
• Main Authors: Ishibashi, Chiaki, Ishida, Naoya, Kitamura, Naoto, Idemoto, Yasushi
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.10.2020; Springer Nature B.V
• Subjects: Cathodes; Characterization and Evaluation of Materials; Chemical bonds; Chemistry and Materials Science; Classical Mechanics; Computation & Theory; Crystal structure; Crystallography and Scattering Methods; Discharge; Electrode materials; Electron density; First principles; Halites; Insertion; Magnesium; Materials Science; Mathematical analysis; Polymer Sciences; Solid Mechanics; Spinel; Storage batteries
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-020-04979-8

The stable structures of the spinel compounds MgCo 2 O 4 and MgCo 1.5 Mn 0.5 O 4 following the insertion of Mg atoms into vacant 16 c sites during discharge were investigated using first-principles calculations. During this insertion, Mg atoms at 8 a sites were found to migrate to other vacant 16 c sites, such that the spinel form transitioned to a rock salt structure. The structural change from the standard spinel phase to a rock salt form was minimal in the case of MgCo 2 O 4 , since this change required the insertion of numerous Mg atoms. In contrast, a more pronounced structural change from the normal spinel to a rock salt form occurred in the MgCo 1.5 Mn 0.5 O 4 , as this change required fewer Mg atom insertions. The data suggest that the electron density and bond length between Mg atoms at 8 a sites and O atoms in MgCo 1.5 Mn 0.5 O 4 are both reduced compared to that in MgCo 2 O 4 . The Mg atoms in MgCo 1.5 Mn 0.5 O 4 were determined to readily undergo intercalation as a result of the substitution of Mn atoms. Graphic abstract