Perfluoro Aryl Boronic Esters as Chemical Shuttle Additives in Lithium Ion Batteries
- EnerDel Inc., Greenfield, IN (United States); Enerdel, Incorporated
Redox shuttles could provide an added measure of control for lithium ion batteries beyond that which is provided by the battery management system. Redox shuttles, which are electrolyte additives, provide electrochemical overcharge protection. Since they possess a reduction-oxidation potential that is slightly above the maximum cathode potential during normal use, they should cause no degradation in cell performance during normal operation, but should shuttle excess electrons during overcharge conditions, effectively limiting the full cell voltage. The goals of the Chemical Shuttle Additives program were to discover and implement a redox shuttle that is compatible with large format lithium ion cells utilizing LiNi1/3Mn1/3Co1/3O2 (NMC) cathode material and to understand the mechanism of redox shuttle action. Many redox shuttles, both commercially available and experimental, were tested and much fundamental information regarding the mechanism of redox shuttle action was discovered. In particular, studies surrounding the mechanism of the reduction of the oxidized redox shuttle at the carbon anode surface were particularly revealing. Shuttles that were evaluated in various lithium ion cell chemistries include: • 2-(pentafluorophenyl)-tetrafluoro-1,3,2-benzodioxaborole (BDB) supplied by Argonne National Laboratory (ANL), Lemont, Illinois; • 2,5-di-tert-butyl-1,4-dimethoxybenzene (DDB) supplied by 3M, St. Paul, Minnesota; • Li2B12F12 supplied by Air Products, Allentown, Pennsylvania (pure compound) and Showa Denko, Japan (in electrolyte); • 1,4-bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene (ANL-RS2) supplied by Argonne National Laboratory (ANL), Lemont, Illinois; and • A 4.5V class redox shuttle supplied by Argonne National Laboratory (ANL), Lemont, Illinois Although redox shuttles with an appropriate redox potential and sufficient chemical and electrochemical stability for cells utilizing cathodes with potentials higher and lower than that of NMC, a redox shuttle that is viable for use in large format lithium ion cells with NMC cathodes was not found. The effect of the anode on the capacity loss of lithium ion cells with redox shuttles in cells utilizing lithium, lithium titanate, or graphite cells was studied. Molecular imprinting of the redox shuttle molecule during solid electrolyte interphase (SEI) layer formation likely contributes to the successful reduction of oxidized redox shuttle species at carbon anodes. This helps understand how a carbon anode covered with an SEI layer, that is supposed to be electrically insulating, can reduce the oxidized form of a redox shuttle.
- Research Organization:
- EnerDel Inc., Greenfield, IN (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- EE0001938
- OSTI ID:
- 1163216
- Report Number(s):
- DOE-ENERDEL--0001938
- Country of Publication:
- United States
- Language:
- English
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