Cation-Directed Selective Polysulfide Stabilization in Alkali Metal-Sulfur Batteries

Qingli Zou, Zhuojian Liang, Guan Ying Du, Chi You Liu, Elise Y. Li, Yi Chun Lu*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

66 Citations (Scopus)


Alkali metal sulfur redox chemistry offers promising potential for high-energy-density energy storage. Fundamental understanding of alkali metal sulfur redox reactions is the prerequisite for rational designs of electrode and electrolyte. Here, we revealed a strong impact of alkali metal cation (Li+, Na+, K+, and Rb+) on polysulfide (PS) stability, redox reversibility, and solid product passivation. We employed operando UV-vis spectroscopy to show that strongly negatively charged short-chain PS (e.g., S4 2-/S3 2-) is more stabilized in the electrolyte with larger cation (e.g., Rb+) than that with the smaller cation (e.g., Li+), which is attributed to a stronger cation-anion electrostatic interaction between Rb+ and S4 2-/S3 2- owing to its weaker solvation energy. In contrast, Li+ is much more strongly solvated by solvent and thus exhibits a weaker electrostatic interaction with S4 2-/S3 2-. The stabilization of short-chain PS in K+-, Rb+-sulfur cells promotes the reduction of long-chain PS to short-chain PS, leading to high discharge potential. However, it discourages the oxidation of short-chain PS to long-chain PS, leading to poor charge reversibility. Our work directly probes alkali metal-sulfur redox chemistry in operando and provides critical insights into alkali metal sulfur reaction mechanism.

Original languageEnglish
Pages (from-to)10740-10748
Number of pages9
JournalJournal of the American Chemical Society
Issue number34
Publication statusPublished - 2018 Aug 29

ASJC Scopus subject areas

  • Catalysis
  • General Chemistry
  • Biochemistry
  • Colloid and Surface Chemistry


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