Joint Center for Energy Storage Research, Pacific Northwest National Laboratory , Richland, Washington 99354, United States.
ACS Appl Mater Interfaces. 2017 Feb 8;9(5):4290-4295. doi: 10.1021/acsami.6b04158. Epub 2016 Jul 1.
In rechargeable Li-S batteries, the uncontrollable passivation of electrodes by highly insulating LiS limits sulfur utilization, increases polarization, and decreases cycling stability. Dissolving LiS in organic electrolyte is a facile solution to maintain the active reaction interface between electrolyte and sulfur cathode, and thus address the above issues. Herein, ammonium salts are demonstrated as effective additives to promote the dissolution of LiS to 1.25 M in DMSO solvent at room temperature. NMR measurements show that the strong hydrogen binding effect of N-H groups plays a critical role in dissolving LiS by forming complex ligands with S anions coupled with the solvent's solvating surrounding. Ammonium additives in electrolyte can also significantly improve the oxidation kinetics of LiS, and therefore enable the direct use of LiS as cathode material in Li-S battery system in the future. This provides a new approach to manage the solubility of lithium sulfides through cation coordination with sulfide anion.
在可充式 Li-S 电池中，高度绝缘的 LiS 会使电极不可控地钝化，从而限制硫的利用率、增加极化并降低循环稳定性。将 LiS 溶解在有机电解液中是一种简单的解决方案，可以维持电解液和硫阴极之间的活性反应界面，从而解决上述问题。在此，铵盐被证明是一种有效的添加剂，可以促进 LiS 在室温下于 DMSO 溶剂中溶解至 1.25M。NMR 测量表明，N-H 基团的强氢键作用通过与阴离子形成配合物发挥关键作用，同时溶剂的溶剂化环境也对溶解 LiS 起到了辅助作用。电解液中的铵添加剂还可以显著提高 LiS 的氧化动力学，从而使 LiS 可以直接用作 Li-S 电池系统中的阴极材料。这为通过阳离子与硫化物阴离子的配位来控制硫化锂的溶解度提供了一种新方法。
