Mg batteries utilizing oxide cathodes can theoretically surpass the energy density of current Li-ion technologies. The absence of functional devices so far has been ascribed to impeded Mg²⁺ migration within oxides, which severely handicaps intercalation reactions at the cathode. Broadly, knowledge of divalent cation migration in solid frameworks is surprisingly deficient. Here, we present a combined experimental and theoretical study of Mg migration within three spinel oxides, which reveal critical features that influence it. Experimental activation energies for a Mg²⁺ hop to an adjacent vacancy, as low as ∼0.6 eV, are reported. These barriers are low enough to support functional electrodes based on the intercalation of Mg²⁺. Subsequent electrochemical experiments demonstrate that significant demagnesiation is indeed possible, but the challenges instead lie with the chemical stability of the oxidized states. Our findings enhance the understanding of cation transport in solid structures and renew the prospects of finding materials capable of high density of energy storage.

中文翻译：

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探测尖晶石氧化物中的Mg迁移

使用氧化物阴极的镁电池理论上可以超过当前锂离子技术的能量密度。迄今为止，由于缺少功能性器件，这归因于氧化物中Mg ^2+的迁移受阻，这严重阻碍了阴极的插层反应。广泛地讲，固体框架中二价阳离子迁移的知识令人惊讶地不足。在这里，我们提出了在三个尖晶石氧化物中的Mg迁移的实验和理论研究相结合的研究，揭示了影响它的关键特征。据报道，Mg ²⁺跃迁至相邻空位的实验活化能低至约0.6 eV。这些势垒很低，足以基于Mg ²⁺的嵌入来支撑功能性电极。随后的电化学实验表明，确实可以进行明显的脱镁，但是挑战在于氧化态的化学稳定性。我们的发现加深了对固体结构中阳离子传输的理解，并重新发现了具有高能量存储密度的材料。