Notable Reactivity of Acetonitrile Towards Li2O2/LiO2 Probed by NAP XPS During Li–O2 Battery Discharge
Notable Reactivity of Acetonitrile Towards Li2O2/LiO2 Probed by NAP XPS During Li–O2 Battery Discharge
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DOI：
10.1007/s11244-018-1072-5
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发表时间：
2018-10
影响因子：
3.6
通讯作者：
Tatiana K. Zakharchenko;A. I. Belova;A. Frolov;O. Kapitanova;J. Velasco‐Vélez;A. Knop‐Gericke;D. Vyalikh;D. Itkis;L. Yashina
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文献类型：
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作者：
Tatiana K. Zakharchenko;A. I. Belova;A. Frolov;O. Kapitanova;J. Velasco‐Vélez;A. Knop‐Gericke;D. Vyalikh;D. Itkis;L. Yashina
锂离子电池可循环性差的关键因素之一是电解质与放电产物li2o2和/或中间物LiO2发生不可逆反应产生副产物。在用作锂氧电池电解质成分的许多溶剂中，乙腈（MeCN）被认为是相对稳定的氧化溶剂。利用近环境压力x射线光发射光谱（NAP XPS）表征了MeCN在li - o2电池中的反应性。为此，我们设计了用固体电解质组装的电化学电池模型。我们先在o2中释放它，然后暴露在MeCN蒸气中。进一步，在O2+ MeCN混合物中进行了放电。我们已经证明，当与li - o2放电产物接触时，MeCN会氧化。这就产生了与表面结合较弱且易于解吸的物质。这就是为什么它们不能被传统的XPS探测到。我们的结果表明，相应的化学过程很可能不会引起电极钝化，但会大大降低电池的库仑效率。
One of the key factors responsible for the poor cycleability of Li–O2batteries is a formation of byproducts from irreversible reactions between electrolyte and discharge product Li2O2and/or intermediate LiO2. Among many solvents that are used as electrolyte component for Li–O2batteries, acetonitrile (MeCN) is believed to be relatively stable towards oxidation. Using near ambient pressure X-ray photoemission spectroscopy (NAP XPS), we characterized the reactivity of MeCN in the Li–O2battery. For this purpose, we designed the model electrochemical cell assembled with solid electrolyte. We discharged it first in O2and then exposed to MeCN vapor. Further, the discharge was carried out in O2+ MeCN mixture. We have demonstrated that being in contact with Li–O2discharge products, MeCN oxidizes. This yields species that are weakly bonded to the surface and can be easily desorbed. That’s why they cannot be detected by the conventional XPS. Our results suggest that the respective chemical process most probably does not give rise to electrode passivation but can decrease considerably the Coulombic efficiency of the battery.