Chelating Agents as Electrolyte Additives for Lithium-Ion Batteries

Report No. ARL-TR-1878
Authors: Foster, Donald L.; Wolfenstine, Jeff; Behl, Wishvender K.
Date/Pages: March 1999; 17 pages
Abstract: Pentamethyldiethylenetriamine (PMDT), tetraglyme, and the crown ether 12-Crown-4 (12-Cr-4) were investigated as electrolyte additives for lithium-ion cells using graphite anodes. Cyclic voltammetry at glassy carbon electrodes in 1 mol/L LiPF6/propylene carbonate (PC) solutions containing PMDT, 12-Cr-4, or tetraglyme additives showed that the PMDT additive was electrochemically oxidized at ^3.5 V versus lithium reference. The electrolytes with 12-Cr-4 and tetraglyme, on the other hand, were found to be stable up to ^4.5 V, where the control electrolyte without any additive was oxidized. Ionic conductivity measurements of the same solutions showed that all three additives enhanced the conductivity of 1 mol/L LiPF6/PC solution at 25 deg C. Lithium cycling studies in PC solutions using graphite electrodes showed that the 12-Cr-4 and tetraglyme additives allowed reversible lithium intercalation into graphite; whereas, the PMDT additive did not have any effect. However, the PMDT additive was found to reduce the irreversible capacity loss on the first cycle in ethylene carbonate- propylene carbonate electrolyte solutions.
Distribution: Approved for public release
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Last Update / Reviewed: March 1, 1999