Minimizing Long-Chain Polysulfide Formation in Li-S Batteries by Using Localized Low Concentration Highly Fluorinated Electrolytes. Issue 9 (23rd September 2021)

• Record Type: Journal Article
• Authors: Glaser, Rebecca; Borodin, Oleg; Johnson, Billy; Jhulki, Samik; Yushin, Gleb
• Is Part Of: Journal of the Electrochemical Society. Volume 168:Issue 9(2021)
• Publication Date: 2021-09-23
• Subjects: Batteries - Lithium -- Sulfur -- Electrolytes; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/1945-7111/ac2467
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : Electrolytes that suppress the formation of long-chain polysulfides and limit the sulfur (S) cathode dissolution and polysulfide shuttle effect, while maintaining high active material utilization and long cycle life, have long been sought for advancing Li-S battery applications. Here we demonstrate that localized electrolytes based on fluorinated ethers with the total salt concentration of only 0.1 M show remarkable performance characteristics. By systematically reducing the fraction of sulfolane (SL) as a cosolvent with 1, 1, 2, 2-tetrafluoroethyl 2, 2, 3, 3-tetrafluoropropylether (HFE), we reveal a dramatic change in the cell discharge behavior. The higher voltage ∼2.4 V plateau corresponding to the formation of long-chain polysulfide shrank, while the medium voltage ∼2.1 V plateau corresponding to the transformation to short-chain polysulfides almost disappeared. Additionally, a third low voltage plateau (∼1.9 V) emerges as S transform directly to a short chain polysulfides and Li2 S, which have significantly lower solubilities. This plateau extended with increasing HFE and became a dominant process. When compared with the traditional dimethoxyethane/1, 3-dioxolane (DME/DIOX) electrolyte solvent mixture, the reported electrolytes offer substantially higher capacity and coulombic efficiency due to decreased solubility for Li + in the HFE, causing a shift to favoring short chain length polysulfides in the discharge reaction.