Recent studies indicate that concentrated electrolyte solutions can enhance the stability of organic solvents during the charge/discharge processes in lithium–oxygen (Li–O₂) batteries. However, the effects of electrolyte concentration on the solvation structures of lithium ions (Li-ions) at the electrode surface and their implications for oxygen reduction and evolution reactions (ORR/OER) remain poorly understood. In this study, we investigate the solvation structures of Li-ions in bulk solutions and on a gold electrode surface at various concentrations of acetonitrile (CH₃CN) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) electrolytes, using in situ Raman and surface-enhanced Raman spectroscopy. Our findings show that increasing electrolyte concentration decreases the number of free CH₃CN molecules, significantly altering solvation structures at the electrode surface. Decomposed CH₃CN species predominate the gold electrode surface, while the irreversible side reactions are suppressed in highly concentrated electrolytes. This research highlights the importance of electrolyte concentration in optimizing solvation structures and enhancing the electrolyte stability of Li–O₂ batteries.

中文翻译：

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从本体到表面：Li-O2 电池浓乙腈电解质中溶剂化结构的拉曼光谱分析


最近的研究表明，浓电解质溶液可以增强锂氧 （Li-O₂） 电池充放电过程中有机溶剂的稳定性。然而，电解质浓度对电极表面锂离子 （Li-ions） 溶剂化结构的影响及其对氧还原和析出反应 （ORR/OER） 的影响仍然知之甚少。在这项研究中，我们使用原位拉曼和表面增强拉曼光谱研究了不同浓度的乙腈 （CH₃CN） 和双（三氟甲磺酰）酰亚胺锂 （LiTFSI） 电解质下本体溶液和金电极表面锂离子的溶剂化结构。我们的研究结果表明，增加电解质浓度会减少游离 CH₃CN 分子的数量，从而显着改变电极表面的溶剂化结构。分解的 CH₃CN 物质在金电极表面占主导地位，而不可逆的副反应在高浓度电解质中被抑制。这项研究强调了电解质浓度在优化 Li-O₂ 电池的溶剂化结构和增强电解质稳定性方面的重要性。