The presence of H₂O has been linked to enhancements in the reactivity of cathodes for Mg²⁺ electrochemistry. If the enhancements were mimicked by nonaqueous solvents, they could enable Mg batteries with transformational energy density. However, the extent to which H₂O may boost actual intercalation of Mg²⁺, as opposed to competing reactions, has not been elucidated. Here, we evaluate its role as additive in the electrochemistry of a tunnel polymorph of V₂O₅ in a nonaqueous Mg²⁺ electrolyte. The electrochemical response and V reduction in the cathodes positively correlated with H₂O concentration, but it was not concurrent with commensurate changes in cell volume and Mg content. These observations indicate that H₂O does not enhance Mg²⁺ intercalation, but rather, it promotes competing pathways. This work shows the importance of accurately probing reactions in multivalent electrolytes. Importantly, it indicates that H₂O is not a universal solution to the challenge of Mg²⁺ intercalation in oxides.

中文翻译：

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水会增强镁在氧化物中的嵌入吗？隧道框架案例

H ₂ O的存在与提高阴极对Mg ²⁺电化学的反应性有关。如果增强作用被非水溶剂模拟，它们可以使Mg电池具有转化能量密度。然而，与竞争反应相反，H ₂ O可以促进Mg ^2+的实际插入的程度尚未阐明。在这里，我们评估其在非水Mg ²⁺电解质中V ₂ O ₅的隧道多晶型物的电化学中作为添加剂的作用。阴极的电化学响应和V还原与H ₂正相关O浓度，但与细胞体积和Mg含量没有相应变化。这些观察结果表明，H ₂ O不会增强Mg ^2+的嵌入，但是会促进竞争途径。这项工作表明了在多价电解质中准确探测反应的重要性。重要的是，这表明H ₂ O并不是应对Mg ²⁺嵌入氧化物的挑战的通用解决方案。