| abstract |
The present invention provides a lithium ion electrochemical cell comprising: a positive electrode comprising a lithium metal oxide or a lithium metal phosphate, a negative electrode capable of intercalating lithium or forming an alloy with lithium, and an electrolyte including an additive. The additive comprises a polyfunctional anion having the formula X-SO2-Rf'-SO2-Y, wherein X and Y are independently O- or RfSO2N-, and Rf is a linear or branched chain fluorine having 1 to 6 carbon atoms Alkyl moieties and optionally containing one or more intrachain heteroatoms, wherein Rf' is a straight or branched chain or cyclic fluoro extender having from 1 to 10 carbon atoms and optionally containing one or more intrachain heteroatoms Alkyl, and wherein both Rf and Rf' have up to 20% non-fluorinated substituents. The additives provided provide improved performance, hydrolytic stability, and thermal stability of the provided electrochemical cells. |