Investigation of solid electrolyte interphases (SEIs) on negative electrode surfaces is essential to improve the stable charge-discharge performance of rechargeable lithium-air batteries (Li-O2 batteries). In this study, a direct investigation of SEI films is conducted using analytical transmission electron microscopy (TEM). A thin Cu specimen is pre-fabricated for TEM observation, and is utilised as a model substrate for SEI formation. The electrochemical cell constructed using dissolved oxygen in the electrolyte exhibits a greater electrochemical overpotential during the Li-metal deposition process than that constructed with a pristine electrolyte. This suggests that different electrochemical passivation features occur in each different electrochemical cell. TEM observation confirms that the surface film formed by O2 dissolute electrolyte is a polycrystalline Li2O film with a thickness of approximately 5 nm, whereas the film formed by the pristine electrolyte is organic-based, amorphous-like, and 20-50 nm thick. The dissolved oxygen molecules are more easily reduced than the components of the electrolyte, leading to the formation of Li2O as a stable passivation SEI film, which is expected to exhibit good charge-discharge features during the operation of the Li-O2 battery.

中文翻译：

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Li-O2电池电解液固体电解质界面的分析透射电子显微镜研究

研究负极表面上的固体电解质界面（SEI）对于提高可充电锂空气电池（Li-O2 电池）的稳定充放电性能至关重要。在这项研究中，使用分析透射电子显微镜 (TEM) 对 SEI 薄膜进行了直接研究。预制薄铜样品用于 TEM 观察，并用作 SEI 形成的模型基板。在锂金属沉积过程中，使用电解质中溶解氧构建的电化学电池比使用原始电解质构建的电化学电池表现出更大的电化学过电位。这表明在每个不同的电化学电池中出现不同的电化学钝化特征。TEM观察证实O2溶解电解质形成的表面膜是多晶Li2O膜，厚度约为5nm，而原始电解质形成的膜是有机基的、非晶状的，厚度为20-50nm。溶解氧分子比电解液的成分更容易被还原，导致形成 Li2O 作为稳定的钝化 SEI 膜，有望在 Li-O2 电池的运行过程中表现出良好的充放电特性。