Effect of the Hydrofluoroether Cosolvent Structure in Acetonitrile-Based Solvate Electrolytes on the Li+ Solvation Structure and Li-S Battery Performance.

Journal Article · Wed Nov 15 04:00:00 EST 2017 · ACS Applied Materials and Interfaces

DOI:https://doi.org/10.1021/acsami.7b11566· OSTI ID:1420080

Shin, Minjeong; Wu, Heng-Liang; Narayanan, Badri; See, Kimberly A.; Assary, Rajeev S.; Zhu, Lingyang; Haasch, Richard T.; Zhang, Shuo; Zhang, Zhengcheng; Curtiss, Larry A.; Gewirth, Andrew A.

We evaluate hydrofluoroether (HFE) cosolvents with varying degrees of fluorination in the acetonitrile-based solvate electrolyte to determine the effect of the HFE structure on the electrochemical performance of the Li-S battery. Solvates or sparingly solvating electrolytes are an interesting electrolyte choice for the Li-S battery due to their low polysulfide solubility. The solvate electrolyte with a stoichiometric ratio of LiTFSI salt in acetonitrile, (MeCN)(2)-LiTFSI, exhibits limited polysulfide solubility due to the high concentration of LiTFSI. We demonstrate that the addition of highly fluorinated HFEs to the solvate yields better capacity retention compared to that of less fluorinated HFE cosolvents. Raman and NMR spectroscopy coupled with ab initio molecular dynamics simulations show that HFEs exhibiting a higher degree of fluorination coordinate to Li+ at the expense of MeCN coordination, resulting in higher free MeCN content in solution. However, the polysulfide solubility remains low, and no crossover of polysulfides from the S cathode to the Li anode is observed.

• Research Organization: Argonne National Laboratory (ANL)
• Sponsoring Organization: USDOE Office of Science - Office of Basic Energy Sciences - Materials Sciences and Engineering Division; USDOE Office of Science; USDOE Office of Science - Office of Basic Energy Sciences - Joint Center for Energy Storage Research (JCESR)
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 1420080
• Journal Information: ACS Applied Materials and Interfaces, Journal Name: ACS Applied Materials and Interfaces Journal Issue: 45 Vol. 9; ISSN 1944-8244
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

X-ray photoelectron spectroscopy
hydrofluoroether cosolvent
lithium-sulfur battery
solvate electrolyte
sparingly solvating electrolyte
variable-temperature NMR spectroscopy