State Key Laboratory of Advanced Special Steel & Shanghai Key Laboratory of Advanced Ferrometallurgy & School of Materials Science and Engineering, Shanghai University, Shanghai, 200444, China.
State Key Laboratory of Physical Chemistry of Solid Surfaces, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.
Angew Chem Int Ed Engl. 2023 Mar 27;62(14):e202217354. doi: 10.1002/anie.202217354. Epub 2023 Feb 21.
LiI and LiBr have been employed as soluble redox mediators (RMs) in electrolytes to address the sluggish oxygen evolution reaction kinetics during charging in aprotic Li-O batteries. Compared to LiBr, LiI exhibits a redox potential closer to the theoretical one of discharge products, indicating a higher energy efficiency. However, the reason for the occurrence of solvent deprotonation in LiI-added electrolytes remains unclear. Here, by combining ab initio calculations and experimental validation, we find that it is the nucleophile that triggers the solvent deprotonation and LiOH formation via nucleophilic attack, rather than the increased solvent acidity or the elongated C-H bond as previously suggested. As a comparison, the formation of in LiBr-added electrolytes is found to be thermodynamically unfavorable, explaining the absence of LiOH formation. These findings provide important insight into the solvent deprotonation and pave the way for the practical application of LiI RM in aprotic Li-O batteries.
碘化锂和溴化锂已被用作非质子型 Li-O 电池电解液中的可溶性氧化还原介质（RM），以解决充电过程中氧气析出反应动力学缓慢的问题。与溴化锂相比，碘化锂的氧化还原电位更接近放电产物的理论值，表明其具有更高的能量效率。然而，在添加碘化锂的电解液中溶剂去质子化发生的原因仍不清楚。在这里，我们通过结合从头算计算和实验验证，发现是亲核试剂通过亲核进攻引发了溶剂去质子化和 LiOH 的形成，而不是如先前所建议的那样，增加了溶剂酸度或伸长了 C-H 键。相比之下，发现添加溴化锂的电解液中 的形成在热力学上是不利的，这解释了为什么没有 LiOH 的形成。这些发现为溶剂去质子化提供了重要的见解，并为在非质子型 Li-O 电池中实际应用碘化锂 RM 铺平了道路。
