期刊
ACS APPLIED MATERIALS & INTERFACES
卷 9, 期 45, 页码 39357-39370出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsami.7b11566
关键词
lithium-sulfur battery; solvate electrolyte; sparingly solvating electrolyte; hydrofluoroether cosolvent; variable-temperature NMR spectroscopy; X-ray photoelectron spectroscopy
资金
- Joint Center for Energy Storage Research, an Energy Innovation Hub - U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences
- U.S. Department of Energy Office of Science laboratory [DE-AC02-06CH113.57]
- DOE Office of Science [DE-AC02-06CH11357]
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-AC02-06CH11357]
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.
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