Okamoto Shinya, Ichitsubo Tetsu, Kawaguchi Tomoya, Kumagai Yu, Oba Fumiyasu, Yagi Shunsuke, Shimokawa Kohei, Goto Natsumi, Doi Takayuki, Matsubara Eiichiro
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.
Adv Sci (Weinh). 2015 Jun 10;2(8):1500072. doi: 10.1002/advs.201500072. eCollection 2015 Aug.
On the basis of the similarity between spinel and rocksalt structures, it is shown that some spinel oxides (e.g., MgCoO, 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 MgCoO, Mg insertion occurs at a considerably high potential of about 2.9 V vs. Mg/Mg, and similarly it occurs around 2.3 V vs. Mg/Mg with the valence change from Mn(III) to Mn(II) in MgMnO, 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 MgXO or MgXO (X = Co, Fe, Mn, and Cr). In addition, the normal spinel MgMnO and MgCrO can be demagnesiated to some extent owing to the robust host structure of MgXO, where the Mg extraction/insertion potentials for MgMnO and MgCrO are both about 3.4 V vs. Mg/Mg. Especially, the former "intercalation and push-out" process would provide a safe and stable design of cathode materials for polyvalent cations.
基于尖晶石结构与岩盐结构之间的相似性，研究表明一些尖晶石氧化物（如MgCoO等）在150℃左右可作为镁可充电电池的正极材料。镁插入尖晶石晶格是通过“嵌入和推出”过程进行的，从而在尖晶石母相中形成岩盐相。例如，通过利用MgCoO中Co(III)到Co(II)的价态变化，镁在相对于Mg/Mg约2.9V的相当高的电位下发生插入，类似地，在MgMnO中，随着Mn(III)到Mn(II)的价态变化，镁在相对于Mg/Mg约2.3V左右发生插入，这与从头算计算结果相当。镁插入的可行性将取决于MgXO或MgXO（X = Co、Fe、Mn和Cr）中MgO的对应岩盐XO的相稳定性。此外，由于MgXO的坚固主体结构，正常尖晶石MgMnO和MgCrO可以在一定程度上去镁化，其中MgMnO和MgCrO的镁提取/插入电位相对于Mg/Mg均约为3.4V。特别是，前一种“嵌入和推出”过程将为多价阳离子正极材料提供安全稳定的设计。
