Reversibility of Noble Metal-Catalyzed Aprotic Li-O2 Batteries

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• 作者：Shunchao Ma ; Yang Wu ; Jiawei Wang ; Yelong Zhang ; Yantao Zhang ; Xinxiu Yan ; Yang Wei ; Peng Liu ; Jiaping Wang ; Kaili Jiang ; Shoushan Fan ; Ye Xu ; Zhangquan Peng
• 刊名：Nano Letters
• 出版年：2015
• 出版时间：December 9, 2015
• 年：2015
• 卷：15
• 期：12
• 页码：8084-8090
• 全文大小：514K
• ISSN：1530-6992

文摘

The aprotic Li-O₂ battery has attracted a great deal of interest because, theoretically, it can store far more energy than today鈥檚 batteries. Toward unlocking the energy capabilities of this neotype energy storage system, noble metal-catalyzed high surface area carbon materials have been widely used as the O₂ cathodes, and some of them exhibit excellent electrochemical performances in terms of round-trip efficiency and cycle life. However, whether these outstanding electrochemical performances are backed by the reversible formation/decomposition of Li₂O₂, i.e., the desired Li-O₂ electrochemistry, remains unclear due to a lack of quantitative assays for the Li-O₂ cells. Here, noble metal (Ru and Pd)-catalyzed carbon nanotube (CNT) fabrics, prepared by magnetron sputtering, have been used as the O₂ cathode in aprotic Li-O₂ batteries. The catalyzed Li-O₂ cells exhibited considerably high round-trip efficiency and prolonged cycle life, which could match or even surpass some of the best literature results. However, a combined analysis using differential electrochemical mass spectrometry and Fourier transform infrared spectroscopy, revealed that these catalyzed Li-O₂ cells (particularly those based on Pd-CNT cathodes) did not work according to the desired Li-O₂ electrochemistry. Instead the presence of noble metal catalysts impaired the cells鈥?reversibility, as evidenced by the decreased O₂ recovery efficiency (the ratio of the amount of O₂ evolved during recharge/that consumed in the preceding discharge) coupled with increased CO₂ evolution during charging. The results reported here provide new insights into the O₂ electrochemistry in the aprotic Li-O₂ batteries containing noble metal catalysts and exemplified the importance of the quantitative assays for the Li-O₂ reactions in the course of pursuing truly rechargeable Li-O₂ batteries.