Ren Jing, Huang Zhimei, Kalambate Pramod K, Shen Yue, Huang Yunhui
State Key Laboratory of Material Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology (HUST) Wuhan 430074 Hubei P. R. China
RSC Adv. 2018 Aug 10;8(50):28496-28502. doi: 10.1039/c8ra03416h. eCollection 2018 Aug 7.
The development of the rechargeable Li-O battery (LOB) has encountered several bottlenecks till date. One of the biggest challenges is to lower the oxidation potential of LiO, which is the insulating and insoluble discharge product. A possible solution to this problem is to use high acceptor number (AN) or donor number (DN) solvents to increase the solubility of LiO, so that the dissolved LiO can diffuse to the cathode surface and get oxidized at a relatively low potential. Herein, we explored the efficiency and side-reactions in the LOB charge process with different LiO soluble electrolytes. The relationship between the solubility of LiO and charging rate was analyzed quantitatively with ultraviolet-visible (UV-Vis) spectroscopy and rotating disk electrode experiments. As a result, electrolytes with high AN usually have higher solubility for LiO than electrolytes with high DN, and thus exhibit higher LiO oxidation rates. Nevertheless, higher LiO solubility in high AN electrolytes also induces more severe side reactions and easily passivates the electrode surface. The trade-off between charging reaction rate and electrolyte stability is a key issue to be considered when designing high performance LOB electrolytes.
迄今为止，可充电锂氧电池（LOB）的发展遇到了几个瓶颈。最大的挑战之一是降低LiO的氧化电位，LiO是绝缘且不溶的放电产物。解决这个问题的一个可能方法是使用高受体数（AN）或供体数（DN）的溶剂来增加LiO的溶解度，这样溶解的LiO就可以扩散到阴极表面并在相对较低的电位下被氧化。在此，我们研究了使用不同的LiO可溶电解质时LOB充电过程中的效率和副反应。通过紫外可见（UV-Vis）光谱和旋转圆盘电极实验定量分析了LiO的溶解度与充电速率之间的关系。结果表明，高AN的电解质通常比高DN的电解质对LiO具有更高的溶解度，因此表现出更高的LiO氧化速率。然而，在高AN电解质中较高的LiO溶解度也会引发更严重的副反应，并容易使电极表面钝化。在设计高性能LOB电解质时，充电反应速率与电解质稳定性之间的权衡是一个需要考虑的关键问题。
