The Mg battery cathode material, thiospinel Mg_xZr₂S₄ (0 ≤ x ≤ 1), exhibits negligible volume change (ca. 0.05%) during electrochemical cycling, providing valuable insight into the limiting factors in divalent cation intercalation. Rietveld refinement of XRD data for Mg_xZr₂S₄ electrodes at various states of charge, , coupled with EDX analysis, demonstrates that Mg²⁺ can be inserted into Zr₂S₄ at 60 °C up to x = 0.7 at a C/10 rate (up to x = 0.9 at very slow rates) and cycled with a high Coulombic efficiency of 99.75%. HAADF-STEM studies provide clear visual evidence of Mg-ion occupation in the lattice, whereas XAS studies show that Zr⁴⁺ was reduced upon Mg²⁺ intercalation. Operando and synchrotron XRD studies reveal the creation of two phases during the latter stages of discharge (x > 0.5) as the lattice fills and Mg²⁺ ions begin occupying tetrahedral (8a) sites in addition to octahedral (16c) interstitial sites. Compared to the isostructural Ti₂S₄ thiospinel, Zr₂S₄ presents a slightly larger cell volume and hence an almost ideal zero-strain lattice on Mg²⁺ insertion. Nonetheless, its 4-fold lower electronic conductivity results in a diffusion coefficient for Mg²⁺ ions (D_Mg; 1 × 10^–10 to 1 × 10^–9 cm²/s) that is more than a factor of 10 lower than in Ti₂S₄. This shows that delocalization of the electron charge carriers in the framework is a very important factor in governing multivalent ion diffusivity in the thiospinel framework and, by extension, in other materials.

中文翻译：

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零应变材料中Mg ²⁺嵌入的洞察力：硫喷松Mg _x Zr ₂ S ₄

镁电池的正极材料，thiospinel的Mg _X的Zr ₂小号₄（0≤ X ≤1），显示出在电化学循环期间可忽略不计的体积变化（约0.05％），提供有价值的洞察二价阳离子嵌入的限制因素。对Mg _x Zr ₂ S ₄电极在不同电荷状态下的XRD数据进行Rietveld精修，结合EDX分析，表明Mg ²⁺可以在60°C的情况下插入Zr ₂ S ₄，直到在C时x = 0.7 / 10率（最高x= 0.9（非常慢的速度）并以99.75％的高库仑效率循环。HAADF-STEM研究提供了镁离子在晶格中占据的清晰视觉证据，而XAS研究表明，随着Mg ^2+的插入，Zr ⁴⁺会减少。Operando和同步加速器XRD研究表明，在放电的后期阶段（x > 0.5）产生了两个相，这是因为晶格填充和Mg ²⁺离子开始占据八面体（16c）间隙位置之外的四面体（8a）位置。与同构Ti ₂ S ₄硫代松油相比，Zr ₂ S ₄呈现出稍大的晶胞体积，因此在Mg ²⁺插入时几乎理想的零应变晶格。但是，其低4倍的电导率导致Mg ²⁺离子的扩散系数（D _Mg； 1×10 ^–10到1×10 ^–9 cm ² / s），比Mg ²⁺离子的扩散系数低10倍以上。 Ti ₂ S ₄。这表明在框架中电子载流子的离域化是控制硫代松油框架中以及进而扩展到其他材料中的多价离子扩散性的一个非常重要的因素。