New Electrolytes for Lithium-ion Cells

Commercially available lithium-ion cells use electrolytes containing a mixture of organic carbonate solvents combined with lithium hexafluorophosphate salt. These electrolytes have significant disadvantages limiting the performance and safety of large li-ion batteries for automotive applications: regular electrolytes are flammable and the instability of the salt causes battery performance degradation and limits the cycle life. We propose to develop a novel Li-ion battery electrolyte composed of thermally stable lithium imide salt and non-flammable solvents. Use of this advanced electrolyte is coupled by employment of graphite foil as a cathode current collector, which unlike aluminum, does not corrode in lithium imide salts solutions. During our Phase I effort we prepared and tested lithium imide-based electrolyte formulations incorporating 80% of non-flammable components, such as fluorinated ethers and ionic liquids, and demonstrated drastically improved safety in 2.4Ah pouch cells with cathodes coated on graphite foil current collector. During the Phase II effort we will expand our development into a number of promising non-flammable fluorinated solvents and imide anion ionic liquids. We will optimize electrolyte formulations and overall cell design to meet rate capability requirements. New electrolytes will be evaluated for performance and safety in large 10Ah pouch cells designed for automotive applications. Commercial Applications and Other Benefits: Success of this program will lead to new generation of safer, longer lasting Li-ion cells. These Li-ion batteries will find use in many applications, including HEV, PHEV and EV. That will in turn help accelerate the growth of this market and the acceptance of these new vehicles by the buying public.