Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1998-11-12
2000-08-22
Lambkin, Deborah C.
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
429198, C07D20504, H01M 604
Patent
active
061074934
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the preparation of cyclic perfluoroalkanebis(sulfonyl)imides and salts thereof.
Cyclic perfluoroalkanebis(sulfonyl)imides, and salts of these compounds, which contain at least two ring carbon atoms are known from EP 0 057 327 B1. Compounds of this type can be obtained from corresponding open-chain precursors by a cyclization reaction. According to the patent specification mentioned, the compounds are prepared by passing gaseous ammonia through a solution of a corresponding perfluoroalkane-bis-sulfonyl fluoride. Ring compounds which are initially obtained in the form of the ammonium salts are formed by this procedure. The imides or imide salts with other cations can be obtained by an exchange reaction.
It is known from WO 88/03331 that cyclic perfluoroalkanebis(sulfonyl)imide salts prepared in this way, such as, in particular, the corresponding lithium salts, can be employed as conductive salts in non-aqueous electrolytes for lithium secondary batteries.
It can be seen from EP 0 057 327 B1 that the preparation process described therein gives only product yields which are not very satisfactory. Our studies confirm this, and furthermore show that the target products are obtained in a form contaminated with undesirable by-products and other impurities, from which they can be separated off only with difficulty and with further losses in yield. However, a high and reproducible purity of these compounds is of essential importance for use as a constituent of battery electrolytes.
SUMMARY OF THE INVENTION
It has now been found that cyclic perfluoroalkanebis(sulfonyl)imides and salts thereof can be obtained in a virtually quantitative yield and in a form which is largely free from by-products and impurities if a solution of the corresponding perfluoroalkane-bis-sulfonyl fluoride is metered slowly and with intensive thorough mixing into liquid ammonia.
It has furthermore been found that the compound cyclo-difluoromethanebis(sulfonyl)imide, which is new per se, and salts thereof can be obtained by the process according to the invention.
The invention thus relates to a process for the preparation of cyclic perfluoroalkanebis(sulfonyl)imides and salts thereof by a cyclization reaction of corresponding perfluoroalkane-bis-sulfonyl fluorides in which a solution of the perfluoroalkane-bis-sulfonyl fluoride is metered slowly and with intensive thorough mixing into liquid ammonia.
The invention furthermore relates to the new ammonium and lithium salts of cyclo-difluoromethanebis(sulfonyl)imide.
The invention moreover relates to the use of lithium cyclo-difluoromethanebis(sulfonyl)imide as a conductive salt in non-aqueous electrolytes for lithium secondary batteries.
The invention finally relates to non-aqueous electrolytes for lithium secondary batteries which comprise the compound lithium cyclo-difluoromethanebis(sulfonyl)imide, and lithium secondary batteries which comprise such electrolytes.
The process according to the invention starts from the same non-cyclic starting compounds and is based in principle on the same cyclization reaction as the known processes. However, an essential difference is that in this case the starting compound is cyclized in and at the temperature of liquid ammonia, the reaction partner ammonia always being present in excess in the course of the reaction because of the reaction conditions chosen. The formation of by-products and impurities is presumably largely suppressed by this excess ammonia and the low reaction temperature.
Liquid ammonia is produced in a manner known per se by condensation of ammonia gas with appropriate cooling. The temperature of the liquid ammonia is -70.degree. C. or even lower. Cooling which is suitable for the laboratory to pilot plant scale can be effected with the aid of dry ice (solid carbon dioxide), mezhanol/dry ice refrigerating mixtures or with liquid nitrogen. The liquefaction is carried out by condensing the ammonia gas into the cooled reaction vessel.
The perfluoroalkanebis(sulfonyl)imide is employed in the form of a
REFERENCES:
patent: 4429093 (1984-01-01), Koshar
patent: 5021308 (1991-06-01), Armand et al.
patent: 5652072 (1997-07-01), Lamanna et al.
F. Dallacker, Justus Liebigs Annalen Der Chemie, vol. 689, pp. 179-188 (Dec. 3, 1965).
D. Viets et al., Chemische Berichte, vol. 124, No. 6, pp. 1353-1356 (Jun. 6, 1991).
Hilarius Volker
Jueschke Ralf
Pohl Ludwig
Sartori Peter
Lambkin Deborah C.
Merck Patent Gesellschaft mit beschrankter Haftung
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