Kitta Mitsunori, Sano Hikaru
Research Institute of Electrochemical Energy, Department of Energy and Environment, National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan.
Microscopy (Oxf). 2020 Jul 30;69(4):227-233. doi: 10.1093/jmicro/dfaa012.
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 prefabricated 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 ~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.
研究负极表面的固体电解质界面（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。在本研究中，使用分析透射电子显微镜（TEM）对SEI膜进行了直接研究。制备了一个薄铜样品用于TEM观察，并将其用作SEI形成的模型基板。与使用原始电解质构建的电化学电池相比，使用电解质中溶解氧构建的电化学电池在锂金属沉积过程中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会出现不同的电化学钝化特征。TEM观察证实，由溶解氧电解质形成的表面膜是厚度约为5nm的多晶Li₂O膜，而由原始电解质形成的膜是基于有机的、类似非晶的且厚度为20-50nm。溶解的氧分子比电解质的成分更容易还原，导致形成Li₂O作为稳定的钝化SEI膜，预计该膜在Li-O₂电池运行期间将表现出良好的充放电特性。
