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Title: Synergistic Effect of LiPF 6 and LiBF 4 as Electrolyte Salts in Lithium-Ion Cells

Recent work shows promise for LiBF 4 as an electrolyte salt for high voltage lithium-ion batteries. LiBF 4 is more hydrolytically stable than LiPF 6, and in some cases has proved to be more stable at high voltage. This work shows that 1.0 M electrolytes consisting of equal parts LiBF 4 and LiPF 6 have better performance in certain high voltage (4.35 V) lithium-ion cells than electrolytes with LiPF 6 or LiBF 4 alone. This is shown using long-term cycling and ultra-high precision coulometry on lithium-ion cells, with and without electrolyte additives. Ultra-high precision coulometry showed that electrolyte with 1:1 LiPF 6:LiBF 4 and no other additives performed as well as electrolyte with LiPF 6 and state-of-the-art additive blends in these cells. The synergism between LiPF 6 and LiBF 4 was explored using XPS, symmetric cells and EIS analysis. These show that LiBF 4 reduces impedance growth at the positive electrode, while LiPF 6 improves passivation at the negative electrode.
Authors:
 [1] ;  [2] ;  [3] ;  [4]
  1. Dalhousie Univ., Halifax (Canada). Dept. of Chemistry
  2. Dalhousie Univ., Halifax (Canada). Dept. of Physics and Atmospheric Science
  3. Idaho National Lab. (INL), Idaho Falls, ID (United States)
  4. Dalhousie Univ., Halifax (Canada). Dept. of Chemistry; Dalhousie Univ., Halifax (Canada). Dept. of Physics and Atmospheric Science
Publication Date:
Grant/Contract Number:
AC07-05ID14517
Type:
Accepted Manuscript
Journal Name:
Journal of the Electrochemical Society
Additional Journal Information:
Journal Volume: 164; Journal Issue: 12; Journal ID: ISSN 0013-4651
Publisher:
The Electrochemical Society
Research Org:
Idaho National Lab. (INL), Idaho Falls, ID (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
25 ENERGY STORAGE; additives; electrolyte; high voltage; Li-ion cells; LiBF4; LiPF6; mixtures; synergy
OSTI Identifier:
1469349