Process for the preparation of lithium or sodium bis(fluorosulphonyl)imide

Abstract

A process for the preparation of a bis(sulphonato)imide salt of formula: (III) (SO.sub.3.sup.)N.sup.(SO.sub.3.sup.) 3C.sup.+where C.sup.+ represents a monovalent cation, comprising the reaction of amidosulphuric acid of formula: (I) (OH)SO.sub.2NH.sub.2 with a halosulphonic acid of formula: (II) (OH)SO.sub.2X where X represents a halogen atom, and comprising a reaction with a base which is a salt formed with the cation C.sup.+. Also, a process for the preparation of bis(fluorosulphonyl)imide acid of formula: (V) F(SO.sub.2)NH(SO.sub.2)F and to a process for the preparation of lithium bis(fluorosulphonyl)imide salt of formula: (VII) F(SO.sub.2)N.sup.(SO.sub.2)F Li.sup.+.

Claims

1. An electrolyte comprising the bis(fluorosulphonyl)imide salt of formula (VII) made by the process for the preparation of bis(fluorosulphonyl)imide salt of formula:
F(SO.sub.2)N.sup.(SO.sub.2)F M.sup.+(VII) wherein M is Li or Na, the process comprising the preparation of bis(fluorosulphonyl)imide acid of formula (V)
F(SO.sub.2)NH(SO.sub.2)F(V) by fluorination of a bis(chlorosulfonyl)imide acid of formula:
Cl(SO.sub.2)NH(SO.sub.2)Cl; and purifying the bis(fluorosulfonyl)imide acid of formula (V) by extraction, wherein the extraction comprises extraction with an organic solvent; wherein the fluorination is carried out with hydrogen fluoride as a fluorinating agent and then the reaction of the bis(fluorosulphonyl)imide acid with a lithium or sodium base, wherein the lithium or sodium base comprises lithium hydroxide, lithium carbonate, sodium hydroxide or sodium carbonate, wherein, when M is Li: wherein LiCI, LiF and FSO.sub.3Li are each present in the lithium bis(fluorosulphonyl)imide, and wherein the lithium bis(flourosulphonyl)imide comprises at most 1000 ppm of each of the LiCl, LiF and FSO.sub.3Li.

2. An electrolyte comprising the bis(fluorosulphonyl)imide salt of formula: F(SO.sub.2)N.sup.(SO.sub.2)F M.sup.+made by the process for the preparation of bis(fluoro-sulphonyl)imide salt of formula: F(SO.sub.2)N.sup.(SO.sub.2)F M.sup.+, wherein M is Li or Na, the process comprising: fluorination of a bis(chlorosulfonyl)imide acid of formula: Cl(SO.sub.2)NH(SO.sub.2)Cl to form bis(fluorosulphonyl)imide acid of formula: F(SO.sub.2)NH(SO.sub.2)F; reaction of the bis(fluorosulphonyl)imide acid with a lithium or sodium base to form the F(SO.sub.2)N.sup.(SO.sub.2)F M.sup.+; wherein the fluorination is carried out with hydrogen fluoride as a fluorinating agent, wherein, when M is Li: wherein LiCI, LiF and FSO.sub.3Li are each present in the lithium bis(fluorosulphonyl)imide, and wherein the lithium bis(fluorosulphonyl)imide comprises at most 1000 ppm of each of the LiCI, LiF and FSO.sub.3Li.

3. A process for the preparation of a bis(fluorosulfonyl)imide acid of formula:
F(SO.sub.2)NH(SO.sub.2)F(V) by fluorination of a bis(chlorosulfonyl)imide acid of formula:
Cl(SO.sub.2)NH(SO.sub.2)Cl; the process comprising fluorinating a starting mixture of Cl(SO.sub.2)NH(SO.sub.2)Cl and KCl, wherein the fluorination is carried out with hydrogen fluoride as a fluorinating agent.

4. The electrolyte of claim 1, wherein, when M is Na: wherein NaCl, NaF and FSO.sub.3Na are each present in the sodium bis(fluorosulphonyl)imide, and wherein the sodium bis(fluorosulphonyl)imide comprises at most 1000 ppm of each of the NaCl, NaF and FSO.sub.3Na.

5. The electrolyte of claim 2, wherein, when M is Na: wherein NaCl, NaF and FSO.sub.3Na are each present in the sodium bis(fluorosulphonyl)imide, and wherein the sodium bis(fluorosulphonyl)imide comprises at most 1000 ppm of each of the NaCl, NaF and FSO.sub.3Na.

Description

DETAILED DESCRIPTION OF EMBODIMENTS

(1) The invention is now described in more detail and without implied limitation in the description which follows:

(2) The invention provides for the preparation of the lithium bis(fluorosulphonyl)imide salt according to the following general scheme in three parts:
(OH)SO.sub.2NH.sub.2+(OH)SO.sub.2X.fwdarw.(SO.sub.3.sup.)N.sup.(SO.sub.3.sup.) 3C.sup.+1)
(SO.sub.3.sup.)N.sup.(SO.sub.3.sup.) 3C.sup.+.fwdarw.F(SO.sub.2)NH(SO.sub.2)F2)
F(SO.sub.2)NH(SO.sub.2)F.fwdarw.F(SO.sub.2)N.sup.(SO.sub.2)F M.sup.+3)
1st PartPreparation of the bis(sulphonato)imide trisalt

(3) Two alternative forms are envisaged for this first part. The first alternative form corresponds to the following reaction scheme:
(OH)SO.sub.2NH.sub.2+(OH)SO.sub.2X+zC.sub.xB.sub.y.fwdarw.(SO.sub.3.sup.)N.sup.(SO.sub.3.sup.)3C.sup.++zB.sub.yH.sub.x+CX

(4) In the preceding scheme, (OH)SO.sub.2NH.sub.2 is amidosulphuric acid, the formula of which is denoted (I); (OH)SO.sub.2X is a halosulphonic acid (X representing a halogen atom), the formula of which is denoted (II); and C.sub.xB.sub.y is a non-nucleophilic base (that is to say, an organic base which is not capable of interfering with the reaction by permanently adding to (OH)SO.sub.2X), C.sup.+ representing the monovalent cation resulting from this base, and x, y, z, x, y and z are integral or fractional numbers such that the product zx and the product zx are equal to 4.

(5) The formula of the trisalt (SO.sub.3.sup.)N.sup.(SO.sub.3.sup.) 3C.sup.+is denoted (III).

(6) Preferably, X represents chlorine.

(7) C.sup.+ represents, for example, the potassium ion K.sup.+. C.sub.xB.sub.y represents, for example, potassium carbonate K.sub.2CO.sub.3. In this case, C represents potassium K, B represents CO.sub.3, x has the value 2, y has the value 1, z has the value 2, x has the value 2, y has the value 1 and z has the value 2.

(8) Alternatively, C.sup.+can represent, for example, the sodium ion Na.sup.+, the cesium ion Cs.sup.+, the lithium ion Li.sup.+ or the H.sup.+ ion.

(9) The above reaction can, for example, be carried out at a temperature from 0 to 150 C. (preferably from 0 to 50 C., more particularly preferably from 10 to 40 C. and in particular from 15 to 30 C.) and at a pressure ranging from atmospheric pressure up to 15 bar. Sulfamic acid is preferably the limiting reactant and the halosulphonic acid (OH)SO.sub.2X can be used in excess (1 to 3 equivalents).

(10) The second alternative form corresponds to the following reaction scheme:
(OH)SO.sub.2NH.sub.2+(OH)SO.sub.2X+B.fwdarw.(OH)SO.sub.2NHSO.sub.2(OH)+BH.sup.+X.sup.
(OH)SO.sub.2NHSO.sub.2(OH)+zC.sub.xB.sub.y.fwdarw.(SO.sub.3.sup.)N.sup.(SO.sub.3.sup.) 3C.sup.++zB.sub.y+H.sub.x

(11) In this scheme, (OH)SO.sub.2NHSO.sub.2(OH) is bis(sulphonyl)imide, the formula of which is denoted (IV); X still represents a halogen atom; B is a nucleophilic or non-nucleophilic base; C.sub.xB.sub.y is a nucleophilic or non-nucleophilic base, C.sup.+ representing the monovalent cation resulting from this base, and x, y, z, x, y and z are integral or fractional numbers such that the product zx and the product zx are equal to 3. In the above reaction scheme, the two stages are successive stages and the bis(sulphonyl)imide of formula (IV) is not isolated.

(12) In the case where C.sup.+ is a proton H.sup.+, the second alternative form comprises only the first stage.

(13) Preferably, X represents chlorine.

(14) C.sup.+ represents, for example, the potassium ion K.sup.+.

(15) C.sub.xB.sub.y represents, for example, potassium hydroxide (KOH), sodium hydroxide (NaOH) or potassium carbonate (K.sub.2CO.sub.3).

(16) B represents, for example, triethylamine (NEt.sub.3).

(17) The above reaction scheme can, for example, be carried out at a temperature from 0 to 150 C. (preferably from 0 to 50 C., more particularly preferably from 10 to 40 C. and in particular from 15 to 30 C.) and at a pressure ranging from atmospheric pressure to 15 bar. Sulfamic acid is preferably the limiting reactant and the halosulphonic acid (OH)SO.sub.2X can be used in excess (1 to 3 equivalents). The base B is also used as reaction solvent and the base C.sub.xB.sub.y is added in excess until a basic pH from 8 to 14 is obtained.

(18) On conclusion of this first part, the compound (trisalt or acid) of formula (III) is preferably purified. This is because the trisalt (III) or acid is relatively insoluble in water, whereas the impurities formed during the reaction are very soluble in water under basic conditions. The purification can also be carried out from other polar solvents, such as alcohols.

(19) 2nd Part-Preparation of bis (fluorosulphonyl)imide Acid

(20) Two alternative forms are envisaged for this second part. The first alternative form comprises a chlorination and then a fluorination, whereas the second alternative form comprises a direct fluorination.

(21) The first alternative form corresponds to the following reaction scheme:
(SO.sub.3.sup.)N.sup.(SO.sub.3.sup.) 3C.sup.++xA.sub.1.fwdarw.Cl(SO.sub.2)N.sup.(SO.sub.2)Cl C.sup.++A.sub.2
Cl(SO.sub.2)N.sup.(SO.sub.2)Cl C.sup.++3HF.fwdarw.F(SO.sub.2)NH(SO.sub.2)F+2HCl+CF

(22) In this scheme, F(SO.sub.2)NH(SO.sub.2)F is bis(fluorosulphonyl)imide acid, the formula of which is denoted (V); A.sub.1 represents a chlorinating agent; A.sub.2 generically represents one or more products from the chlorination reaction; C.sup.+ still represents the monovalent cation described above; x is an integral or fractional number; and Cl(SO.sub.2)N.sup.(SO.sub.2)Cl C.sup.+ is a bis(chlorosulphonyl)imide salt, the formula of which is denoted (VI).

(23) A.sub.1 can, for example, be thionyl chloride SOCl.sub.2 (x=1), in which case A.sub.2 represents 2KCl+2SO.sub.2, if C.sup.+ is the potassium ion.

(24) A.sub.1 can also be phosphorus pentachloride (PCl.sub.5), phosphorus oxychloride (POCl.sub.3) or oxalyl chloride.

(25) The chlorination reaction can, for example, be carried out at a temperature from 0 to 150 C. and at a pressure ranging from atmospheric pressure up to 15 bar. The chlorinating agent is preferably used in excess and generally acts as solvent. The temperature of the reaction is advantageously in the vicinity of the boiling point of the solvent. For example, in the case of thionyl chloride, the boiling point is in the vicinity of 76 C. and the temperature of the reaction will thus, for example, be from 60 to 90 C. or from 70 to 80 C.

(26) As regards the fluorination reaction proper, the latter can, for example, be carried out at a temperature from 0 to 350 C. (preferably from 0 to 50 C., more particularly preferably from 10 to 40 C. and in particular from 15 to 30 C.) and at a pressure ranging from atmospheric pressure to 15 bar.

(27) It is also possible to use other fluorinating agents in place of HF, such as diethylaminosulphur trifluoride (DAST) or sulphur tetrafluoride (SF.sub.4), or alternatively fluoride salts of formula C.sub.xF.sub.y, where x and y are positive integers and C is a cation. For example, C.sub.xF.sub.y can be zinc fluoride ZnF.sub.2, as described in the document WO 2009/123328.

(28) The second alternative form corresponds, for example, to the following reaction scheme:
(SO.sub.3.sup.)N.sup.(SO.sub.3.sup.)3C.sup.++5HF.fwdarw.F(SO.sub.2)NH(SO.sub.2)F+2H.sub.2O+3CF

(29) In this scheme, C.sup.+ still represents the monovalent cation described above, for example K.sup.+.

(30) The reaction can, for example, be carried out at a temperature from 0 to 350 C. (preferably from 0 to 50 C., more particularly preferably from 10 to 40 C. and in particular from 15 to 30 C.) and at a pressure ranging from atmospheric pressure up to 15 bar. The hydrogen fluoride is generally used in excess. The reaction is carried out without solvent.

(31) It is possible to use, in place of hydrogen fluoride, other fluorinating agents, such as diethylaminosulphur trifluoride (DAST) or sulphur tetrafluoride (SF.sub.4).

(32) As such fluorinating agents are more reactive than hydrogen fluoride, they can be used in a smaller excess than hydrogen fluoride, within the same pressure and temperature ranges.

(33) The bis(fluorosulphonyl)imide acid is subsequently purified; at the end of the reaction, the acid is extracted from the residual solid using an organic solvent as the impurities are not soluble or are only slightly soluble in organic solvents. This organic solvent is preferably dimethyl carbonate.

(34) 3rd PartPreparation of the MFSI

(35) This third part corresponds to the following reaction scheme:
F(SO.sub.2)NH(SO.sub.2)F+MB.fwdarw.F(SO.sub.2)N.sup.(SO.sub.2)F M.sup.++BH

(36) F(SO.sub.2)N.sup.(SO.sub.2)F M.sup.+ is LiFSI or NaFSI, the formula of which is denoted (VII). MB is a lithium or sodium base, that is to say a base in the form of a salt formed from the lithium cation Li.sup.+ or sodium cation Na.sup.+ and from an anion B. This base can, for example, be lithium hydroxide, sodium hydroxide, lithium carbonate or sodium carbonate.

(37) The reaction can, for example, be carried out at a temperature from 25 C. to 80 C. The lithium or sodium base is used in a proportion of 1 to 1.5 equivalents, preferably in water, or also in a polar solvent, such as an alcohol.

(38) According to the present invention, the purity of the lithium or sodium bis(fluorosulphonyl)imide (MFSI) is preferably at least equal to 99.5% by weight, advantageously at least equal to 99.9% by weight.

(39) The impurities, such as LiCI, LiF and FSO.sub.3Li or NaCl, NaF and FSO.sub.3Na, present in the bis(sulphonato)imide salt each preferably represent at most 1000 ppm and advantageously at most 500 ppm.

(40) Whatever the method of preparation, FSO.sub.3Li preferably represents at most 5 ppm.

(41) According to any embodiment of the present invention, the lithium or sodium bis(fluorosulphonyl)imide (MFSI) preferably do neither contain moisture nor impurities consisting of salts from a cation of group 11 to 15 and period 4 to 6 of the Periodic Table(such as Zn, Cu, Sn, Pb, Bi). Due to their electrochemical activity, these impurities have a negative effect on the capacity of the Li or Na-ion battery.

(42) Preparation of an Electrolyte

(43) The MFSI prepared as described above can be used in the preparation of an electrolyte by dissolving it in an appropriate solvent.

(44) For example, as is described in the document J. Electrochemical Society, 2011, 158, A74-82, the LiFSI can be dissolved at a concentration of 1 mol/l in a 5:2:3 by volume mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC); such an electrolyte exhibits a very good conductivity, a good cycling stability and a corrosion of the aluminum above 4.2 V.

(45) This electrolyte can subsequently be used in the manufacture of batteries or battery cells by positioning it between a cathode and an anode, in a way known per se.

EXAMPLES

(46) The following examples illustrate the invention without limiting it.

Example 1

Synthesis of potassium bis(sulphonato)imide trisalt

(47) The reaction is carried out without solvent in a dry round-bottomed glass flask. 1.1 ml of chlorosulphonic acid are added to 1.61 g of sulfamic acid with stirring. Subsequently, 2 ml of triethylamine are added. The reaction mixture is left stirring for 1 day. The reaction is halted by the addition of 20 ml of water. Subsequently, 2.79 g of potassium hydroxide are added. The final product precipitates and is recovered by filtration and washed with 230 ml of CH.sub.2Cl.sub.2.

Example 2

Synthesis of potassium bis(chlorosulphonyl)imide

(48) 15.3 g of the trisalt are added to a 250 ml round-bottomed flask. 60 ml of oxalyl chloride are subsequently added dropwise, followed by 1 ml of dimethylformamide. The reaction medium is stirred at reflux for 3 hours and the solution becomes yellow in color. At the end of the reaction, the solution is filtered and a white solid (w=19.0 g) is obtained which comprises the chlorinated compound and potassium chloride.

Example 3

Synthesis of bis(fluorosulphonyl)imide

(49) 19.0 g of the mixture of potassium bis(chlorosulphonyl)imide and potassium chloride are added to a 800 ml autoclave. 20 g of hydrogen fluoride are subsequently added at ambient temperature. The reaction medium is stirred for 3 hours. The excess hydrogen fluoride and the hydrogen chloride given off are subsequently removed by a stream of air. A solid having a golden yellow color is then obtained.