Insights into the Chemical Nature and Formation Mechanisms of Discharge Products in Na–O2 Batteries by Means of Operando X-ray Diffraction

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• 作者：R. Pinedo ; D. A. Weber ; B. Bergner ; D. Schröder ; P. Adelhelm ; J. Janek
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：April 28, 2016
• 年：2016
• 卷：120
• 期：16
• 页码：8472-8481
• 全文大小：479K
• 年卷期：0
• ISSN：1932-7455

文摘

The chemical nature of discharge products in nonaqueous Na–O₂ batteries attracts attention due to the differing electrochemical behavior of seemingly similar battery cells forming either sodium peroxide (Na₂O₂) or sodium superoxide (NaO₂). The experimental control parameters for the exclusive formation of one or the other phase during discharge are still unknown. In this paper, the important role of gas phase moisture on the chemical nature of these products is demonstrated by means of operando XRD. Operando XRD is rarely reported for alkali-O₂ systems but provides valuable real time information about the solid discharge products, growth/decomposition rates, and side reactions in the cell. In addition, the discharge/charge mechanisms of Na₂O₂·2H₂O are monitored in detail evidencing important differences from the cell reactions forming NaO₂ and Li₂O₂ and refuting previous incorrect conclusions. Moreover, the effect of the applied potential window during cycling is discussed, as it provides valuable information for the future development of Na–O₂ batteries as electrochemical energy stores.