Improved Performance of Lithium-ion Cells at Low Temperature

The widespread uses of hybrid electric vehicles (HEVs) and electric vehicles (EVs), which use rechargeable batteries as the power source, could significantly reduce U.S. dependence on foreign oil. Lithium-ion batteries have great potential for such applications but need improvement in low temperature performance. Therefore, this project will develop technology to improve this low temperature performance by incorporating anion receptor additives in the battery electrolytes. These additives should be highly effective in dissociating ion-pairs and forming complexes with the electrolyte anions, thereby improving ionic conductivity and interfacial impedance. In Phase I, several different types of electrolytes were prepared and their ionic conductivity and electrode/electrolyte interfacial impedance were measured at different low temperatures. Prototype 200 mAh lithium-ion cells were developed with these electrolytes, and their performance was evaluated at both ambient temperatures and low temperatures. Phase II will: (1) prepare electrolytes with different combinations of salts, solvents, and anion-receptor additives, (2) optimize salts, solvents, and additive combinations, (3) characterize the developed electrolytes, (4) evaluate the electrolytes for lithium-ion battery applications, and (5) develop prototype lithium-ion cells and evaluate their performance. Commercial Applications and other Benefits as described by the awardee: The technology should lead to the development of a highly effective, low-temperature-performance electrolyte for lithium-ion batteries.