SOLVENT-FREE PROCESS FOR PREPARING A SALT OF BIS(FLUOROSULFONYL)IMIDE

Abstract

The present disclosure relates to a method for preparing salts of bis(fluorosulfonyl)imide and to a method for preparing alkali metal salts of bis(fluorosulfonyl)imide from said bis(fluorosulfonyl)imide salts. More specifically. the invention provides a new method for producing these salts of bis(fluorosulfonyl)imide which is implementable at industrial scale and providing high-purity bis(fluorosulfonyl)imide salts.

Claims

1. A process for preparing a salt of bis(fluorosulfonyl)imide of formula (I):
[F(SO.sub.2)N.sup.?(SO.sub.2)F].sub.nX.sub.1n.sup.+(I) wherein: X.sub.1.sup.n+ is a cation selected from the group consisting of K.sup.+, Na.sup.+ and an onium cation, and n is 1 representing the valence of the cation, the process comprising the fluorination of a bis(chlorosulfonyl)imide of formula (II):
Cl(SO.sub.2)NH(SO.sub.2)Cl (II) or salt thereof with a fluorinating agent represented by formula (III):
X.sub.1.sup.n+(F.sup.?).sub.n(HF).sub.p wherein: p varies between 0 and 10, wherein the process is carried out in molten salt of bis(fluorosulfonyl)imide of formula (I), in the absence of solvent or in the presence of an amount of solvent less than 5 wt. % based on the total weight of the reaction mixture.

2. The process of claim 1, which is carried out under reduced pressure.

3. The process of claim 1, wherein the stoichiometry amount of fluorinating agent (III) is between 1 to 10 equivalents per 1 mol of bis(chlorosulfonyl)imide (II).

4. The process of claim 1, comprising the steps of: (i) heating a quantity Q.sub.0 of the salt of bis(fluorosulfonyl)imide (I) at a temperature Ta(? C.) higher than its melting point Tm.sub.(I), to produce a molten salt of bis(fluorosulfonyl)imide (I), and (ii) adding the fluorinating agent (III) and the bis(chlorosulfonyl)imide (II) to the molten salt of bis(fluorosulfonyl)imide (I).

5. The process of claim 4, wherein step (ii) comprises: (ii1) adding the fluorinating agent (III) to the molten salt of bis(fluorosulfonyl)imide (I), (ii2) optionally removing the residual amount of water or aqueous liquid from the fluorinating agent (III), and (ii3) adding the bis(chlorosulfonyl)imide (II) to the reaction mixture.

6. The process of claim 5, wherein the process comprises a step (ii2) carried out by distillation of the water.

7. The process of claim 1, wherein the quantity Q.sub.0 is not less than 20 wt. % of the total weight of the reaction mixture when all the reactive materials have been added.

8. The process of any one of claims 1 7 claim 1, which is carried out at a temperature of less than 100? C.

9. A salt of bis(fluorosulfonyl)imide of formula (I):
[F(SO.sub.2)N.sup.?(SO.sub.2)F].sub.nX.sub.1n.sup.+(I) wherein: X.sub.1.sup.n+ is a cation selected from the group consisting of K.sup.+, Na.sup.+ and an onium cation, and n is 1 representing the valence of the cation, obtainable by the process claim 1, wherein the amount of solvent is less than 100 ppm.

10. The salt of claim 9, wherein the amount of solvent is less than 50 ppm.

11. A process for preparing an alkali salt of bis(fluorosulfonyl)imide of formula (V),
F(SO.sub.2)NX.sub.3(SO.sub.2)F (IV) wherein X.sub.3 represents Li or Cs, comprising the steps of: (a) preparing a salt of bis(fluorosulfonyl)imide of formula (I) according to claim 1, and (b) reacting the salt of bis(fluorosulfonyl)imide (I) obtained in step (a) with an alkali agent consisting in a lithium salt or a cesium salt.

12. The process of claim 11, wherein step (b) is carried out in an organic reaction medium comprising at least one organic solvent, said organic solvent being selected from the aprotic organic solvents.

13. A salt of bis(fluorosulfonyl)imide of formula (IV):
F(SO.sub.2)NX.sub.3(SO.sub.2)F (IV) wherein X.sub.3 represents Li or Cs, obtainable by the process of claim 11.

14. A method comprising incorporating the salt of bis(fluorosulfonyl)imide of formula (IV) of claim 13 in a battery electrolyte solution.

Description

EXAMPLES

[0182] The invention will be now described in more detail with reference to the following examples, whose purpose is merely illustrative and not intended to limit the scope of the disclosure.

Example 1Bis(fluorosulfonyl)imide Ammonium Salt Formation

[0183] Under nitrogen, 63.5 g of NH.sub.4F (1.71 mol, 4.4 eq vs HCSI) was mixed with 250 g of NH.sub.4FSI (1.26 mol) and stirred for 1 hour at 90? C. Liquid HCSI was then added continuously to the reaction mixture at a rate of 40 g/h and up to 83.3 g (0.39 mol) using a feeding funnel with a heat belt. The stirring was continued for 12 hours. The temperature of the reaction was continuously monitored and kept below 100? C. The reaction mixture was then cooled to 60? C. in 1 hour. 320 g of TFE was then added to the mixture. The solid was isolated by filtration. The filtrated solution was then cooled to 10? C. in 2 hours. Crystals were isolated by filtration at 25? C., then washed with 160 g of fresh TFE. The solid was dried under vacuum at room temperature for 12 hours.

[0184] The product was then analysed.

[0185] The conversion was 87.6%, as measured by 19F NMR (FSI-).

Example 2Bis(fluorosulfonyl)imide Lithium Salt Formation

[0186] Under nitrogen atmosphere, a solution of 6.9 g NH.sub.4FSI (0.35 mmol), as obtained form Example 1, was prepared in 60 g of Ethyl Methyl Carbonate (EMC). 14.6 g of solid LiOH.Math.H.sub.2O (0.35 mmol) was added to the vessel at room temperature in 10 minutes. After 1 hour of stirring, the conversion of NH.sub.4.sup.+ ions (as measured by a NaOH titration) was greater than 90%. The medium was concentrated a first time under reduced pressure (P=20 mbar, T=0? C.). 120 mL of EMC was added and the concentration was performed a second time under the same conditions. The concentrated solution was dried under vacuum pressure at 30? C. for 24 hours. 5 g of a viscous transparent liquid was obtained. .sup.19F NMR analysis indicated a purity above 99 wt. %. No other fluorinated species was detected.