Sodium–oxygen (Na–O₂) batteries exhibit a low charging overpotential owing to the reversible formation and decomposition of sodium superoxide (NaO₂) on discharge and charge cycles. However, the cycling performance of the battery system is compromised by the side reactions occurring between the reactive NaO₂ discharge product with the other components of the cell including the air electrode and the organic electrolyte. In the present study, we employ a Raman imaging technique to reveal the chemical mechanism behind the decomposition reaction of NaO₂ in the presence of diglyme-based electrolyte. Our results illustrate the formation of oxalate-based side products resulting from prolonged exposure of NaO₂ to the cell electrolyte. Moreover, we show that Na₂O₂·2H₂O is not the thermodynamically favorable side product for decomposition of NaO₂ and may only be formed under the high-energy beam used by the measuring probe. The findings of this study help to better understand the underlying chemical reaction mechanisms of Na–O₂ cells.

中文翻译：

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通过原位拉曼成像揭示NaO ₂分解的化学机理

钠氧（Na-O ₂）电池由于在放电和充电周期中可逆的超氧化钠（NaO ₂）的形成和分解而显示出较低的充电过电势。然而，电池系统的循环性能受到反应性NaO ₂放电产物与电池的其他部件（包括空气电极和有机电解质）之间发生的副反应的损害。在本研究中，我们采用拉曼成像技术来揭示在存在二甘醇二甲醚基电解质的情况下NaO ₂分解反应背后的化学机理。我们的结果表明，长时间暴露于NaO _2会形成草酸盐基副产物到细胞电解质。而且，我们表明，Na ₂ O ₂ ·2H ₂ O不是用于分解NaO ₂的热力学上有利的副产物，而只能在测量探针使用的高能束下形成。这项研究的发现有助于更好地了解Na–O ₂细胞的潜在化学反应机制。