Chelating Agents as Electrolyte Additives for Lithium-Ion Batteries

摘要

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.