NEW HEAT TRANSFER LIQUID FOR COOLING LITHIUM STORAGE BATTERIES

Abstract

Substantially water-free antifreezes and coolants are useful for cooling lithium rechargeable batteries.

Claims

1. A method of cooling a lithium-ion rechargeable battery, the method comprising: transferring heat through a heat-transfer liquid comprising a component (A) and a component (B), wherein component (A) comprises at least one alkylene glycol derivative of formula (I) ##STR00009## where R.sup.1 is hydrogen or C.sub.1- to C.sub.4-alkyl, R.sup.2 is C.sub.1- to C.sub.4-alkyl, R.sup.3 is hydrogen or methyl, and n is on arithmetic average a number from 3.0 to 4.0; and wherein component (B) comprises at least one corrosion inhibitor selected from the group consisting of (Ba) an orthosilicate ester and/or an alkoxyalkylsilane, (Bb) an azole derivative, and (Bc) a compound of general formula (II) ##STR00010## where R.sup.4 is an organic radical having 6 to 10 carbon atoms, p and q are independently of one another a positive integer from 1 to 30, and each X.sub.i for i=1 to p and 1 to q are independently of one another selected from the group consisting of —CH.sub.2—CH.sub.2—O—, —CH.sub.2—CH(CH.sub.3)—O—, —CH(CH.sub.3)—CH.sub.2—O—, —CH.sub.2—C(CH.sub.3).sub.2—O—, —C(CH.sub.3).sub.2—CH.sub.2—O—, —CH.sub.2—CH(C.sub.2H.sub.5)—O—, —CH(C.sub.2H.sub.5)—CH.sub.2—O—, —CH(CH.sub.3)—CH(CH.sub.3)—O—, —CH.sub.2—CH.sub.2—CH.sub.2—O— and —CH.sub.2—CH.sub.2—CH.sub.2—CH.sub.2—O—; and wherein the heat-transfer liquid comprises as an electrolyte (E) at least one compound selected from the group consisting of lithium hexafluorophosphate (LiPF.sub.6), lithium tetrafluoroborate (LiBF.sub.4), lithium perchlorate (LiClO.sub.4), lithium phosphate (Li.sub.3PO.sub.4), and lithium bis(oxalato)borate (LiBOB), and wherein the heat-transfer liquid comprises less than 1 wt % of water.

2. The method according to claim 1, wherein the electrolyte is LiPF.sub.6.

3. The method according to claim 1, wherein the lithium-ion rechargeable battery is a lithium cobalt dioxide rechargeable battery, a lithium titanate rechargeable battery, a lithium manganese rechargeable battery, a lithium nickel cobalt aluminum rechargeable battery or a lithium iron phosphate rechargeable battery.

4. The method according to claim 1, wherein the electrolyte is dissolved in an aprotic organic solvent (Eb).

5. The method according to claim 4, wherein the aprotic organic solvent (Eb) is an open-chain or cyclic carbonate.

6. The method according to claim 4, wherein the aprotic organic solvent (Eb) is a compound of formula (VII) ##STR00011## where R.sup.2 and R.sup.3 are as defined above for the component (A) and r and s are on arithmetic average numbers from 3.0 to 4.0, wherein R.sup.2 and R.sup.3 may independently of one another for each r and s be identical or different.

7. The method according to claim 1, wherein the heat-transfer liquid has a kinematic viscosity at minus 40° C. according to ASTM D445 of not more than 600 mm.sup.2/s.

8. The method according to claim 1, wherein the heat-transfer liquid has a specific heat capacity at 50° C. of at least 2.0 kJ/kg×K.

9. The method according to claim 1, wherein the heat-transfer liquid has a thermal conductivity of at least 0.15 W/m×K.

10. The method according to claim 1, wherein the at least one corrosion inhibitor comprises a compound of the general formula (II), and wherein the structural element R.sup.4−N< of the general formula (II) is derived from at least one amine selected from the group consisting of n-hexylamine, 2-methylpentylamine, n-heptylamine, 2-heptylamine, iso-heptylamine, 1-methylhexylamine, n-octylamine, 2-ethylhexylamine, 2-aminooctane, 6-methyl-2-heptylamine, n-nonylamine, iso-nonylamine, n-decylamine, 2-propylheptylamine, and mixtures thereof.

11. The method according to claim 1, wherein the at least one corrosion inhibitor comprises an azole derivative, and wherein the azole derivative is selected from the group consisting of benzimidazole, benzotriazole, tolyltriazole, and hydrogenated tolyltriazole.

12. The method according to claim 1, wherein the heat-transfer liquid comprises: 95 to 99.9 wt % of the component (A) and 0.1 to 5 wt % of the component (B).

13. The method according to claim 1, wherein the component (A) comprises more than one of the alkylene glycol derivative of formula (I), and wherein a ratio of alkylene glycol derivatives of formula (I) where n=3 to those where n=4 is from 100:0 to 40:60.

14. The method according to claim 1, wherein the heat-transfer liquid consists of the component (A), the component (B), optionally at least one further corrosion inhibitor (C) distinct from the component (B), and optionally at least one further compound selected from the group consisting of a dye, a defoamer, and an antioxidant.

15. The method according to claim 1, wherein in the component (A), R.sup.1 is hydrogen.

16. The method according to claim 1, wherein in the component (A), R.sup.2 is methyl.

17. The method according to claim 1, wherein in the component (A), R.sup.3 is hydrogen.

18. The method according to claim 1, wherein in the component (B), R.sup.4 is a straight-chain alkyl or alkenyl radical having 8 carbon atoms.

19. The method according to claim 1, wherein in the component (B), p and q are independently of one another 1 or 2.

20. The method according to claim 1, wherein in the component (B), X.sub.i is —CH.sub.2—CH.sub.2—O—.

Description

EXAMPLES

[0239] To determine the reactivity of the components (A) with the electrolyte (E) online and in noninvasive fashion, 500 MHz .sup.1H-, 470 MHz .sup.19F- and 202 MHz .sup.31P-NMR spectra of the components individually and/or in admixture were determined in a Bruker AV3-500p NMR spectrometer at 298 K against an external DMSO standard.

[0240] The electrolyte liquid employed was Selectylite® LP 57 which, according to WO 2016/149442 A1, is a 1 M solution of LiPF.sub.6 in 30:70 (w/w) ethylene carbonate:ethyl methyl carbonate.

[0241] The component (A) employed was the following additized mixture of triethylene glycol monomethyl ether and tetraethylene glycol monomethyl ether:

TABLE-US-00001 Triethylene glycol monomethyl ether 86.2 Tetraethylene glycol monomethyl ether 10 Octyldiethanolamine 1.8 Additive mixture: Tolyltriazole* 0.05 Antioxidant** 0.03 Emulsifiers*** 0.25 Triethylene glycol monomethyl ether 1.67 Defoamer 0.001 Sum 100 The components employed in the additive mixture have the following activity: *Tolyltriazole as an inhibitor against non-ferrous metal corrosion **Antioxidant for preventing/reducing oxidation of the alkylene glycol ethers ***Mixture of fatty alcohol ethoxylates

Example 1—Spectra of the Electrolyte Liquid Alone

[0242] The .sup.1H-NMR showed only the signals of the solvent mixture.

[0243] The .sup.31P-NMR showed a heptet at −144 ppm of LiPF.sub.6 and weak signals at −19 and −34 ppm which indicate traces of difluorophosphoric acid and phosphoryl fluoride.

[0244] The .sup.19F-NMR spectrum showed a doublet at −74 ppm and weak doublets at −85 and −90 ppm which indicate traces of difluorophosphoric acid and phosphoryl fluoride.

Example 2—Mixture of Components (A) and (E)

[0245] The electrolyte solution and the above-described mixture of components (A) were mixed at ambient temperature in a ratio of about 50:50 (v/v) and stored at this temperature for 7 days before NMR spectra were recorded at 298 K and 333 K.

[0246] The .sup.1H-NMR showed not only the signals of the solvent mixture from example 1 but also the signals of the components (A).

[0247] The .sup.31P-NMR showed no further signals relative to the spectrum from example 1. The weak signals at −19 and −34 ppm visible in example 1 were no longer detectable, presumably due to dilution with the component (A).

[0248] The .sup.19F-NMR spectrum showed no further signals relative to the spectrum from example 1. The weak signals at −85 and −90 ppm visible in example 1 were no longer detectable, presumably due to dilution with the component (A).

[0249] Since no strengthening of the signals for difluorophosphoric acid and phosphoryl fluoride or appearance of new signals indicating phosphoric esters was observed in the NMR spectra it is apparent that at ambient temperature over a period of 7 days and NMR measurement at 298 K and 333 K no reaction between the component (A) and LiPF.sub.6 has taken place. The disappearance of the signals for difluorophosphoric acid and phosphoryl fluoride previously observed in example 1 after mixing with component (A) in example 2 is attributable to the effect of dilution.

Examples 3 to 7—Mixture of Components (A) and (E) with Further Customary Constituents of Coolants

[0250] The electrolyte solution and the above-described mixture of the components (A) were mixed in the volume ratio indicated in the table at ambient temperature (about 20° C.) and stored at this temperature for 7 days before .sup.31P- and .sup.19F-NMR spectra were recorded at 298 K and 333 K.

TABLE-US-00002 Electrolyte Component Monoethylene Diethylene Triethylene Example liquid (E) (A) Water glycol glycol glycol Glycerol 1 100 2 50 50 3 50 40 10 4 50 40 10 5 50 40 10 6 50 40 10 7 50 40 10

[0251] The observations in examples 3 to 7 corresponded to those of example 2; no strengthening of the signals for difluorophosphoric acid and phosphoryl fluoride or appearance of new signals indicating phosphoric esters was observed in the NMR spectra. It is thus apparent that at ambient temperature over a period of 7 days and NMR measurement at 298 K and 333 K no reaction between LiPF.sub.6 and the component (A) or the additionally added constituents has taken place.