Department of Chemistry, University of Liverpool , Liverpool L69 7ZD, United Kingdom.
Department of Physics, University of Liverpool , Liverpool L69 7ZF, United Kingdom.
J Am Chem Soc. 2016 Mar 23;138(11):3745-51. doi: 10.1021/jacs.5b12494. Epub 2016 Mar 11.
Understanding the mechanistic details of the superoxide induced solvent degradation, is important in the development of stable electrolytes for lithium-oxygen (Li-O2) batteries. Propylene carbonate (PC) decomposition on a model electrode surface is studied here using in situ attenuated total reflectance surface enhanced infrared absorption spectroscopy (ATR-SEIRAS). The sensitivity of the SEIRAS technique to the interfacial region allows investigation of subtle changes in the interface region during electrochemical reactions. Our SEIRAS studies show that the superoxide induced ring opening reaction of PC is determined by the electrolyte cation. Computational modeling of the proposed reaction pathway of superoxide with PC revealed a large difference in the activation energy barriers when Li(+) was the countercation compared with tetraethylammonium (TEA(+)), due to the coordination of Li(+) to the carbonate functionality. While the degradation of cyclic organic carbonates during the Li-O2 battery discharge process is a well-established case, understanding these details are of significant importance toward a rational selection of the Li-O2 battery electrolytes; our work signifies the use of SEIRAS technique in this direction.
了解超氧化物诱导的溶剂降解的机理细节对于开发用于锂-氧（Li-O2）电池的稳定电解质非常重要。本文使用原位衰减全反射表面增强红外吸收光谱（ATR-SEIRAS）研究了模型电极表面上碳酸丙烯酯（PC）的分解。SEIRAS 技术对界面区域的敏感性允许在电化学反应过程中研究界面区域的细微变化。我们的 SEIRAS 研究表明，超氧化物诱导的 PC 开环反应由电解质阳离子决定。超氧化物与 PC 反应途径的计算模型表明，当锂离子为抗衡离子时，与四乙基铵（TEA(+)）相比，超氧化物的活化能垒有很大差异，这是由于锂离子与碳酸酯官能团的配位。虽然在 Li-O2 电池放电过程中环状有机碳酸盐的降解是一个既定事实，但了解这些细节对于合理选择 Li-O2 电池电解质非常重要；我们的工作标志着 SEIRAS 技术在这方面的应用。
