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Fluoride in the SEI Stabilizes the Li Metal Interface in Li–S Batteries with Solvate Electrolytes

Ware, Skyler D. and Hansen, Charles J. and Jones, John-Paul and Hennessy, John and Bugga, Ratnakumar V. and See, Kimberly A. (2021) Fluoride in the SEI Stabilizes the Li Metal Interface in Li–S Batteries with Solvate Electrolytes. ACS Applied Materials & Interfaces, 13 (16). pp. 18865-18875. ISSN 1944-8244. doi:10.1021/acsami.1c02629.

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Lithium–sulfur (Li–S) batteries offer high theoretical gravimetric capacities at low cost relative to commercial lithium-ion batteries. However, the solubility of intermediate polysulfides in conventional electrolytes leads to irreversible capacity fade via the polysulfide shuttle effect. Highly concentrated solvate electrolytes reduce polysulfide solubility and improve the reductive stability of the electrolyte against Li metal anodes, but reactivity at the Li/solvate electrolyte interface has not been studied in detail. Here, reactivity between the Li metal anode and a solvate electrolyte (4.2 M LiTFSI in acetonitrile) is investigated as a function of temperature. Though reactivity at the Li/electrolyte interface is minimal at room temperature, we show that reactions between Li and the solvate electrolyte significantly impact the solid electrolyte interphase (SEI) impedance, cyclability, and capacity retention in Li–S cells at elevated temperatures. Addition of a fluoroether cosolvent to the solvate electrolyte results in more fluoride in the SEI which minimizes electrolyte decomposition, reduces SEI impedance, and improves cyclability. A 6 nm AlF₃ surface coating is employed at the Li anode to further improve interfacial stability at elevated temperatures. The coating enables moderate cyclability in Li–S cells at elevated temperatures but does not protect against capacity fade over time.

Item Type:Article
Related URLs:
URLURL TypeDescription
Ware, Skyler D.0000-0002-3249-1946
Hansen, Charles J.0000-0003-4981-9087
Hennessy, John0000-0002-0135-0219
See, Kimberly A.0000-0002-0133-9693
Additional Information:© 2021 American Chemical Society. Received: February 7, 2021; Accepted: April 4, 2021; Published: April 15, 2021. This research was carried out at the Jet Propulsion Laboratory and the California Institute of Technology under a contract with the National Aeronautics and Space Administration and funded through the President’s and Director’s Fund Program. XPS data were collected at the Molecular Materials Research Center in the Beckman Institute of the California Institute of Technology. The authors thank N. Gu for assistance with collecting temperature-controlled UV–vis spectra. The authors declare no competing financial interest.
Funding AgencyGrant Number
JPL President and Director's FundUNSPECIFIED
Subject Keywords:Li−S battery, solvate electrolyte, Li metal SEI, fluoroether cosolvent, AlF3, protective coating, acetonitrile−LiTFSI electrolyte
Issue or Number:16
Record Number:CaltechAUTHORS:20210419-130016948
Persistent URL:
Official Citation:Fluoride in the SEI Stabilizes the Li Metal Interface in Li–S Batteries with Solvate Electrolytes. Skyler D. Ware, Charles J. Hansen, John-Paul Jones, John Hennessy, Ratnakumar V. Bugga, and Kimberly A. See. ACS Applied Materials & Interfaces 2021 13 (16), 18865-18875; DOI: 10.1021/acsami.1c02629
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:108758
Deposited By: Tony Diaz
Deposited On:19 Apr 2021 21:08
Last Modified:03 May 2021 17:51

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