GLYCEROL ACETAL POLYETHERS AND USE THEREOF IN LITHIUM CELLS

Abstract

The invention relates to glycerol acetal polyethers of general formula (I) or (II), wherein R1, R2, R3, R4, R5, and n have the meaning specified in the description. Said glycerol acetal polyethers are suitable as electrolyte solvents in a lithium cell, in particular a lithium-sulfur cell. The hydroxyl content of said glycerol acetal polyethers is preferably less than 0.2 wt %. In a method for producing said glycerol acetal polyethers, glycerol acetal polyether alcohols are reacted with a C1-C18 mono- or dialkyl sulfate or C1-C18 mono- or dialkyl sulfonate in the presence of an alkaline earth.

Claims

1-14. (canceled)

15. A glyceryl acetal polyether of the general formula I or II ##STR00006## wherein R.sup.1 and R.sup.2 are each independently H or C.sub.1-C.sub.4 alkyl or R.sup.1 and R.sup.2 together are C.sub.3-C.sub.5 alkylene, R.sup.3 and R.sup.4 are each independently H or C.sub.1-C.sub.4 alkyl, R.sup.5 is C.sub.1-C.sub.12 alkyl and n is an integer from 2 to 18, wherein the glyceryl acetal polyether has a hydroxyl content of less than 0.2% by weight.

16. The glyceryl acetal polyether according to claim 15, wherein R.sup.1 and R.sup.2 are each H.

17. The glyceryl acetal polyether according to claim 15, in which R.sup.3 and R.sup.4 are each independently selected from H and methyl.

18. The glyceryl acetal polyether according to claim 15, in which R.sup.3 and R.sup.4 are each H.

19. The glyceryl acetal polyether according to claim 15, in which R.sup.5 is methyl.

20. The glyceryl acetal polyether according to claim 15, in which n is an integer from 2 to 18.

21. A process for preparing glyceryl acetal polyethers of the formula I and/or II ##STR00007## where R.sup.1 and R.sup.2 are each independently H or C.sub.1-C.sub.4 alkyl or R.sup.1 and R.sup.2 together are C.sub.3-C.sub.5 alkylene, R.sup.3 and R.sup.4 are each independently H or C.sub.1-C.sub.4 alkyl, R.sup.5 is C.sub.1-C.sub.12 alkyl and n is an integer from 2 to 18, which comprises reacting alcohols of the general formulae III and/or IV ##STR00008## wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are each as already defined with a C.sub.1-C.sub.18 mono- or dialkyl sulfate or C.sub.1-C.sub.18 mono- or dialkylsulfonate in the presence of an alkaline earth metal oxide.

22. The process according to claim 21, wherein the reaction in a reaction solvent selected from polar aprotic solvents.

23. The process according to claim 21, wherein the reaction solvent is selected from cyclic ethers.

24. The process according to claim 21, wherein the reaction solvent is selected from the group consisting of oxirane, tetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 1,4-dioxane and crown ethers.

25. The process according to claim 21, wherein the alkylating agent is selected from C.sub.1-C.sub.18 dialkyl sulfates.

26. The process according to claim 21, wherein the alkaline earth metal oxide is selected from the group consisting of MgO, CaO, SrO and BaO.

27. A lithium cell comprising the glyceryl acetal polyether according to claim 15 as electrolyte solvent.

28. The lithium cell according to claim 27, wherein the cell is a lithium-sulfur cell.

Description

GENERAL WORKING METHODS

[0052] Nuclear resonance spectroscopy

[0053] The nuclear resonance spectra were recorded on the Varian instruments at 300 K. The chemical shifts are reported as δ values (ppm) and refer to the shift relative to TMS as internal standard. In the assignment of the signals and for the signal multiplicities, the following abbreviations were used: s-singlet, d-doublet, t-triplet, q-quartet, m-multiple, b-broad, virt.-virtual. In the event of coincidental equivalence of the coupling constants of non-equivalent protons, the coupling pattern was assigned according to the rules of 1st order spectra. The coupling constants J reported are reported as mean values of those found experimentally.

[0054] The Karl Fischer titration was conducted with the Metrohm Coulometer 831 according to the manufacturer's instructions. Traces of water and hydroxyl groups were determined quantitatively with a detection limit of 50 ppm for an amount of sample of at least 200 mg.

EXAMPLE 1

Methoxy (PEG-2) Glyceryl Formal

[0055] At room temperature, a mixture of ethoxylated (n=2) glyceryl 1,2-formal and 1,3-formal (60.0 g) was dissolved in 1,3-dioxolane (200 mL) comprising dimethyl sulfate (41.3 g, 327 mmol). Over a period of 75 minutes, barium oxide (49.0 g, 320 mmol) was added in small portions. In the course of this, the temperature rose to 30° C. On completion of addition, the reaction mixture was stirred at room temperature for 24 hours and then filtered through Celite. Celite was washed with dichloromethane and the crude product was filtered through basic alumina (100 g, Fluka 5016A). The solvent was removed under reduced pressure and the crude product was purified by distillation. At 0.1 mbar, the product fractions were collected at a boiling point of 64° C. to 125° C. The yield of the mixture of end-capped glyceryl formal polyethers was 50.0 g.

[0056] The hydroxyl content of the product was less than 0.2%.

.sup.1H NMR (CDCl.sub.3): δ(ppm)=3.38 (s, 3 H), 3.45-3.55 (m, 3 H), 3.60-3.73 (m, 8 H), 3.96 (t, 0.4 H), 4.09 (dd, 1.2 H), 4.23 (m, 0.4 H), 4.69 (dd, 0.6 H), 4.88 (m, 1 H), 5.02 (d, 0.4 H).

EXAMPLE 2

Methoxy (PEG-5) Glyceryl Formal

[0057] At room temperature, a mixture of ethoxylated (n=5) glyceryl 1,2-formal and 1,3-formal (25.0 g) was dissolved in 1,3-dioxolane (50 mL) comprising dimethyl sulfate (11.3 g, 89.5 mmol). Over a period of 75 minutes, barium oxide (12.8 g, 83.4 mmol) was added in small portions. In the course of this, the temperature rose to 30° C. On completion of addition, the reaction mixture was stirred at room temperature for 24 hours and then filtered through Celite. Celite was washed with dichloromethane and the crude product was filtered through basic alumina (100 g, Fluke 5016A). The solvent was removed under reduced pressure and the crude product was purified by distillation (0.1 mbar, 170° C.). The yield of the mixture of end-capped glyceryl formal polyethers was 20.1 g. The hydroxyl content of the product was less than 0.2%.

.sup.1H NMR (CDCl.sub.3): δ(ppm)=3.35 (s, 3 H), 3.42-3.55 (m, 3 H), 3.60-3.74 (m, 20 H), 3,94 (t, 0.4 H), 4.08 (dd, 1.2 H), 4.18 (m, 0.4 H), 4.64 (dd, 0.6 H), 4.82 (m, 1 H), 4.98 (d, 0.4 H).

EXAMPLE 3

Methoxy (PEG-10) Glyceryl Formal

[0058] At room temperature, a mixture of ethoxylated (n=10) glyceryl 1,2-formal and 1,3-formal (40.0 g) was dissolved in 1,3-dioxolane (80 mL) comprising dimethyl sulfate (11.4 g, 90.4 mmol) and water (0.18 g, 10.0 mmol). Over a period of 75 minutes, barium oxide (14.7 g, 95.9 mmol) was added in small portions. In the course of this, the temperature rose to 30° C. On completion of addition, the reaction mixture was stirred at room temperature for two days and then filtered through magnesium sulfate and Celite. Celite was washed with diethyl ether, and the solvent and volatile constituents were removed under reduced pressure, The residue was cooled, diethyl ether was added and the mixture was filtered through basic alumina (100 g, Fluka 5016A). After removal of the diethyl ether under reduced pressure, a mixture of the end-capped glyceryl formal polyethers was obtained in a yield of 20.6 g. The hydroxyl content of the product was less than 0.2%.

[0059] .sup.1H NMR (CDCI.sub.3): δ(ppm)=3.40; (s, 3 H), 3.45-3.58; (m, 3 H), 3.60-3.78; (m, 40 H), 3.96; (t, 0.4 H), 4.10; (dd, 1.2 H), 4.24; (m, 0.4 H), 4.70; (dd, 0.6 H), 4.88; (m, 1 H), 5.04; (d, 0.4 H).

EXAMPLE 4

Methoxy (PEG-15) Glyceryl Formal

[0060] At room temperature, a mixture of ethoxylated (n=15) glyceryl 1,2-formal and 1,3-formal (40.0 g) was dissolved in 1,3-dioxolane (80 mL) comprising dimethyl sulfate (8.10 g, 64.2 mmol) and water (0.10 g, 5.56 mmol). Over a period of 75 minutes, barium oxide (13.0 g, 84.8 mmol) was added in small portions. In the course of this, the temperature rose to 30° C. On completion of addition, the reaction mixture was stirred at room temperature for five days and then filtered through magnesium sulfate and Celite. Celite was washed with diethyl ether, and the solvent and volatile constituents were removed under reduced pressure. The residue was cooled, diethyl ether was added and the mixture was filtered through basic alumina (100 g, Fluka 5016A). After removal of the diethyl ether under reduced pressure, a mixture of the end-capped glyceryl formal polyethers was obtained in a yield of 16.1 g. The hydroxyl content of the product was less than 0.2%.

[0061] .sup.1H NMR (CDCI.sub.3): δ(ppm)=3.49; (s, 3 H), 3.42-3.58; (m, 3 H), 3.60-3.78; (m, 60 H), 3.98; (t, 0.4 H), 4.10; (dd, 1.2 H), 4.25; (m, 0.4 H), 4.70; (dd, 0.6 H), 4.92; (m, 1 H), 5.05; (d, 0.4 H).