Spinel intercalation hosts are well known to to facilitate high rate capability and high voltage Li-ion batteries. A recent experimental study has shown that Mg can reversibly intercalate in spinel TiS₂, demonstrating the viability of Li intercalation host crystal structures for Mg-ion batteries [Sun, X.; Energy Environ. Sci. 2016, 9, 2273−2277]. We report on a first-principles statistical mechanics study of Mg insertion into spinel TiS₂, accounting for occupancy on both octahedrally and tetrahedrally coordinated interstitial sites. In contrast to Li-containing spinels, we predict mixed octahedral and tetrahedral site occupancy at nondilute Mg concentrations consistent with the recent experimental study of Sun et al. The onset of mixed occupancy is correlated with an increase in the spinel volume upon Mg insertion, which is more pronounced in Mg_xTiS₂ than in its Li counterpart. The results in this study suggest that the degree of mixed occupancy could be controlled through the volume of the host with addition of electrochemically inactive species.

中文翻译：

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尖晶石MgTiS ₂作为阴极材料的第一性原理研究

众所周知，尖晶石插层主机可促进高倍率能力和高压锂离子电池。最近的一项实验研究表明，Mg可以可逆地插入尖晶石TiS _2中，证明了用于Mg离子电池的Li嵌入主体晶体结构的可行性[孙X; 能源环境。科学 2016，9，2273年至2277年]。我们报告了镁插入尖晶石TiS ₂的第一性原理统计力学研究，说明了八面体和四面体协调的间隙位置上的占有率。与含锂尖晶石相反，我们预测在未稀释的Mg浓度下八面体和四面体的混合位点占有率与Sun等人最近的实验研究一致。混合占据的发生与插入Mg时尖晶石体积的增加相关，这在Mg _x TiS _2中更为明显比其李同行。这项研究的结果表明，可以通过添加电化学惰性物质来控制宿主的体积，从而控制混合占用的程度。