Syntheses of novel delocalized cations and fluorinated anions, new fluorinated solvents and additives for lithium ion batteries

To improve the properties of rechargeable lithium ion batteries, like conductivity, SEI-formation, thermal and electrochemical stability, low and high temperature performance and safety new electrolyte salts, novel solvents (co-solvents) and additives have been synthesized. All new anions, solvents and additives contain fluorine proving the importance of this element for the electrolyte system. Tetrafluoroborates having bulky delocalized nitrogen-, phosphorus and sulfur-centered counter-cations containing tetramethylguanidyl substituents, like [(Me2N)2CNC(NMe2)2]+, have been prepared to improve the conductivity in polymer electrolytes. The hitherto unknown lithium sulfonate, MeOCF2CF2SO3Li, has been successfully synthesized along with further analogs, and also MeOCF2CF(CF3)SO3Li was obtained, both from precursors, FO2SCF2C(O)F or FO2SCF(CF3)C(O)F accessible by ring opening reactions from the respective sultones. For the lithium salt CF3OCF(CF3)SO3Li, a new simple synthetic pathway was found where CF3OCFCF2 and SO2F2 were used as precursors. Novel possible redox shuttles, namely (CF3)5C6OLi and fluorinated pyridine-N-oxides have been prepared. A neutral cyclic carben-PF5 adduct turned out to be a very effective overcharge protection additive. The family of cyclic and acyclic carbonates playing a key-role as electrolyte solvents in lithium ion batteries could be extended by derivatives of 1,1,1,4,4,4-hexafluorobutandiol. Reaction products from perfluoropropene oxide and alcohols, ROC(F)CF3C(O)OR (R = CH2CF3, CH2CH2, CH(CF3)2) were obtained according to new optimized methods. New cyclic sulfonamides synthesized from FO2SCF2C(O)F and FO2SCF(CF3)C(O)F could be successfully identified as versatile electrolyte additives.