Regulating Lithium Salt to Inhibit Surface Gelation on an Electrocatalyst for High-Energy-Density Lithium-Sulfur Batteries

Xi Yao Li, Shuai Feng, Chang Xin Zhao, Qian Cheng, Zi Xian Chen, Shu Yu Sun, Xiang Chen, Xue Qiang Zhang, Bo Quan Li, Jia Qi Huang, Qiang Zhang

Research output: Contribution to journalArticlepeer-review

75 Scopus citations

Abstract

Lithium-sulfur (Li-S) batteries have great potential as high-energy-density energy storage devices. Electrocatalysts are widely adopted to accelerate the cathodic sulfur redox kinetics. The interactions among the electrocatalysts, solvents, and lithium salts significantly determine the actual performance of working Li-S batteries. Herein, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), a commonly used lithium salt, is identified to aggravate surface gelation on the MoS2 electrocatalyst. In detail, the trifluoromethanesulfonyl group in LiTFSI interacts with the Lewis acidic sites on the MoS2 electrocatalyst to generate an electron-deficient center. The electron-deficient center with high Lewis acidity triggers cationic polymerization of the 1,3-dioxolane solvent and generates a surface gel layer that reduces the electrocatalytic activity. To address the above issue, Lewis basic salt lithium iodide (LiI) is introduced to block the interaction between LiTFSI and MoS2 and inhibit the surface gelation. Consequently, the Li-S batteries with the MoS2 electrocatalyst and the LiI additive realize an ultrahigh actual energy density of 416 W h kg-1 at the pouch cell level. This work affords an effective lithium salt to boost the electrocatalytic activity in practical working Li-S batteries and deepens the fundamental understanding of the interactions among electrocatalysts, solvents, and salts in energy storage systems.
Original languageEnglish (US)
Pages (from-to)14638-14646
Number of pages9
JournalJournal of the American Chemical Society
Volume144
Issue number32
DOIs
StatePublished - Aug 17 2022
Externally publishedYes

ASJC Scopus subject areas

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

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