Journal
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
Volume 168, Issue 9, Pages -Publisher
ELECTROCHEMICAL SOC INC
DOI: 10.1149/1945-7111/ac2467
Keywords
Batteries; Lithium; Sulfur; Electrolytes
Funding
- NASA Minority University Research and Education Project (MUREP
- NASA) [NNX15AP44A, NND16AA29I]
- Sila Nanotechnologies, Inc.
- National Science Foundation [ECCS-2025462]
- NASA [NNX15AP44A, 800160] Funding Source: Federal RePORTER
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In this study, localized electrolytes based on fluorinated ethers with a total salt concentration of only 0.1 M were investigated for their performance in Li-S batteries. These electrolytes were found to suppress the formation of long-chain polysulfides, limit sulfur cathode dissolution, and improve active material utilization, leading to higher capacity and coulombic efficiency compared to traditional electrolyte solvent mixtures.
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 similar to 2.4 V plateau corresponding to the formation of long-chain polysulfide shrank, while the medium voltage similar to 2.1 V plateau corresponding to the transformation to short-chain polysulfides almost disappeared. Additionally, a third low voltage plateau (similar to 1.9 V) emerges as S transform directly to a short chain polysulfides and Li2S, 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.
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