title: Intercalation and Push-Out Process with Spinel-to-Rocksalt Transition on Mg Insertion into Spinel Oxides in Magnesium Batteries.
abstract: On the basis of the similarity between spinel and rocksalt structures, it is shown that some spinel oxides (e.g., MgCo2O4, etc) can be cathode materials for Mg rechargeable batteries around 150 °C. The Mg insertion into spinel lattices occurs via "intercalation and push-out" process to form a rocksalt phase in the spinel mother phase. For example, by utilizing the valence change from Co(III) to Co(II) in MgCo2O4, Mg insertion occurs at a considerably high potential of about 2.9 V vs. Mg2+/Mg, and similarly it occurs around 2.3 V vs. Mg2+/Mg with the valence change from Mn(III) to Mn(II) in MgMn2O4, being comparable to the ab initio calculation. The feasibility of Mg insertion would depend on the phase stability of the counterpart rocksalt XO of MgO in Mg2X2O4or MgX3O4(X = Co, Fe, Mn, and Cr). In addition, the normal spinel MgMn2O4and MgCr2O4can be demagnesiated to some extent owing to the robust host structure of Mg1-xX2O4, where the Mg extraction/insertion potentials for MgMn2O4and MgCr2O4are both about 3.4 V vs. Mg2+/Mg. Especially, the former "intercalation and push-out" process would provide a safe and stable design of cathode materials for polyvalent cations.
authors.affiliation: Department of Materials Science and Engineering Kyoto University Kyoto 606-8501 Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Okamoto
authors.affiliation: Department of Materials Science and Engineering Kyoto University Kyoto 606-8501 Japan.
authors.forename: Tetsu
authors.initials: T
authors.lastname: Ichitsubo
authors.affiliation: Department of Materials Science and Engineering Kyoto University Kyoto 606-8501 Japan.
authors.forename: Tomoya
authors.initials: T
authors.lastname: Kawaguchi
authors.affiliation: Materials Research Center for Element Strategy Tokyo Institute of Technology Yokohama 226-8503 Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Kumagai
authors.affiliation: Department of Materials Science and Engineering Kyoto University Kyoto 606-8501 Japan; Materials Research Center for Element Strategy Tokyo Institute of Technology Yokohama 226-8503 Japan.
authors.forename: Fumiyasu
authors.initials: F
authors.lastname: Oba
authors.affiliation: Nanoscience and Nanotechnology Research Center Osaka Prefecture University Osaka 599-8570 Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Yagi
authors.affiliation: Department of Materials Science and Engineering Kyoto University Kyoto 606-8501 Japan.
authors.forename: Kohei
authors.initials: K
authors.lastname: Shimokawa
authors.affiliation: Department of Materials Science and Engineering Kyoto University Kyoto 606-8501 Japan.
authors.forename: Natsumi
authors.initials: N
authors.lastname: Goto
authors.affiliation: Department of Molecular Chemistry and Biochemistry Doshisha University Kyoto 610-0321 Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Doi
authors.affiliation: Department of Materials Science and Engineering Kyoto University Kyoto 606-8501 Japan.
authors.forename: Eiichiro
authors.initials: E
authors.lastname: Matsubara