Zinc-based spinel cathode materials for magnesium rechargeable batteries: toward the reversible spinel-rocksalt transition
Zinc-based spinel cathode materials for magnesium rechargeable batteries: toward the reversible spinel-rocksalt transition
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DOI：
10.1039/c9ta02281c
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发表时间：
2019-05-21
影响因子：
11.9
通讯作者：
Ichitsubo, Tetsu
中科院分区：
文献类型：
--
作者：
Shimokawa, Kohei;Atsumi, Taruto;Ichitsubo, Tetsu
放电时镁插入尖晶石氧化物中的尖晶石到岩盐的转变可用作镁可充电电池的阴极反应。然而，由此产生的坚固岩盐相的形成可能对可循环性有害，因为恢复到原始尖晶石结构的速度很慢。在这项工作中，我们表明，通过用更喜欢四面体环境的 Zn 稳定尖晶石结构，可以在充电时促进岩盐到尖晶石的反向转变。我们的从头计算研究证实，锌基尖晶石氧化物（空间群#227）有利于正尖晶石构型，因为四面体 8a 位点中 Zn-O 的共价性，而阳离子无序或从 8a 到 16c 位点的迁移在热力学和动力学方面往往是不利的。基于这一理论预测，我们通过实验证明，这种稳定的正常尖晶石结构（即 ZnCo2O4 和 ZnFe2O4）因此允许在充电和放电时发生可逆的尖晶石-岩盐转变。此外，ZnFe2O4在充放电过程中的体积变化比钴基尖晶石氧化物小得多，可以提供由丰富元素组成的近乎零应变的正极材料。
The spinel-to-rocksalt transition with Mg insertion into spinel oxides upon discharge can be utilized as a cathode reaction for magnesium rechargeable batteries. However, the formation of the resulting robust rocksalt phase can be harmful to the cyclability, in that it is sluggish to revert to the original spinel structure. In this work, we show that the inverse rocksalt-to-spinel transition can be facilitated upon charge by stabilizing the spinel structure with Zn preferring a tetrahedral environment. Our ab initio calculation study substantiates that Zn-based spinel oxides (space group #227) favor a normal-spinel configuration owing to covalency of Zn-O in the tetrahedral 8a site and cation disordering or migration from 8a to 16c sites tends to be unfavorable in terms of thermodynamics and kinetics. Based on this theoretical prediction, we show experimentally that such a stabilized normal spinel structure (i.e., ZnCo2O4 and ZnFe2O4) consequently allows the reversible spinel-rocksalt transition upon charge and discharge. Furthermore, the volume change of ZnFe2O4 in discharge/charge is much smaller than that of Co-based spinel oxides, which can provide a nearly zero-strain cathode material consisting of abundant elements.