WO2019229367A1

WO2019229367A1 - Composition based on lithium bis(fluorosulfonyl)imide salt

Info

Publication number: WO2019229367A1
Application number: PCT/FR2019/051245
Authority: WO
Inventors: Grégory Schmidt
Original assignee: Arkema France
Priority date: 2018-06-01
Filing date: 2019-05-28
Publication date: 2019-12-05
Also published as: FR3081722A1

Abstract

The present invention relates to a composition comprising: at least 99.75% by weight of a lithium bis(fluorosulfonyl)imide salt; - CL- chlorides in a content by weight of strictly less than 20 ppm; - F- fluorides in a content by weight of strictly greater than 0 ppm; wherein: [S04^2-] + [CI^- ] + [F^-] ≤<150 ppm.

Description

Composition based on bis (fluorosulfonyl) imide lithium salt

FIELD OF THE INVENTION

The present invention relates to a bis (fluorosulfonyl) imide lithium salt composition.

TECHNICAL BACKGROUND

Anions of sulfonylimide type, by their very low basicity, are increasingly used in the field of energy storage in the form of inorganic salts in batteries, or organic salts in supercapacitors or in the field of liquids ionic. As the battery market is booming and the reduction of battery manufacturing costs becomes a major issue, a large-scale and low-cost synthesis process for this type of anion is necessary.

In the specific field of Li-ion batteries, the salt currently most used is LiPF ₆ but this salt shows numerous disadvantages such as limited thermal stability, sensitivity to hydrolysis and therefore lower battery safety. . Recently, new salts having the FSO ₂ group have been studied and have demonstrated many advantages such as better ionic conductivity and resistance to hydrolysis. One of these salts, LiFSI (LiN (FSO ₂ ) ₂ ) has shown very interesting properties that make it a good candidate to replace LiPF ₆ .

The identification and quantification of impurities in salts and / or electrolytes, and the understanding of their impacts on battery performance become paramount. For example, impurities having a mobile proton, due to their interference with electrochemical reactions, lead to lower overall performance and stability of the Li-ion batteries. Other impurities can induce corrosion of battery components, such as electrodes and / or current collector.

There is therefore a need for novel bis (fluorosulfonyl) imide lithium salt compositions to overcome, at least partially, at least one of the aforementioned disadvantages.

In particular, there is a need for novel bis (fluorosulfonyl) lithium salt compositions having an improved lifetime and / or having a limited impact on the corrosion of the constituents of the battery (eg current collector, ...). DESCRIPTION OF THE INVENTION

The present invention relates to a composition comprising:

at least 99.75%, preferably at least 99.85%, advantageously at least 99.95%, still more advantageously 99.99% by weight of a bis (fluorosulfonyl) imide lithium salt;

chlorides Cl, in a mass content strictly less than 20 ppm;

fluorides F- in a mass content strictly greater than 0 ppm;

in which :

[S0 ₄ ² ] + [CI] + [F] <150 ppm

In the context of the invention, the following expression:

[S0 ₄ ² ] + [CI] + [F] <150 ppm

means that the sum of the total mass contents of sulfates (SO ² ), chlorides (CI) and fluorides (F) is less than or equal to 150 ppm, relative to the total mass of the composition.

In the context of the invention, the terms "lithium salt of bis (fluorosulfonyl) imide", "lithium bis (sulfonyl) imide", "LiFSI", "LiN (FSO ₂ ) _2" are used in an equivalent manner, " bis (sulfonyl) imide lithium, or lithium bis (fluorosulfonyl) imide.

In the context of the invention, the term "ppm" or "part per million" means ppm by weight.

Preferably, the aforementioned composition is such that [S0 ² ] + [Cl] + [F] <120 ppm, preferably [S0 ² ] + [Cl] + [F] <100 ppm, advantageously [S0 ² ] + [Cl] ] + [F] <80 ppm, still more advantageously [S0 ² ] + [CI] + [F] <50 ppm, in particular [S0 ² ] + [CI] + [F] <30 ppm, and for example [ S0 ² ] + [CI] + [F] <20 ppm.

The composition may comprise a mass content of sulphates of less than or equal to 150 ppm, preferably less than or equal to 100 ppm, preferably less than or equal to 50 ppm, advantageously less than or equal to 30 ppm, even more advantageously less than or equal to 20 ppm , in particular less than or equal to 10 ppm, relative to the total mass of the composition.

Preferably, the composition is such that the mass content of sulphates is strictly greater than 0 ppm, preferably greater than or equal to 0.1 ppm, relative to the total mass of the composition.

For example, the composition is such that the mass content of sulphates ranges from 0.1 ppm to 100 ppm, preferably from 0.1 ppm to 80 ppm, preferentially from 0.1 ppm to 50 ppm, advantageously from 0.1 ppm. at 20 ppm, more preferably from 0.1 ppm to 10 ppm, and in particular from 0.1 ppm to 5 ppm, based on the total weight of the composition. According to a preferred embodiment, the mass content of Cl chlorides in the composition is less than or equal to 18 ppm, preferably less than or equal to 15 ppm, preferably less than or equal to 12 ppm, advantageously less than or equal to 10 ppm relative to to the total mass of the composition.

Preferably, the mass content of Cl chlorides in the composition is strictly greater than 0, preferably greater than or equal to 0.1 ppm, preferably greater than or equal to 0.5 ppm, even more preferably greater than or equal to 1 ppm, advantageously greater than or equal to 2 ppm, still more preferably greater than or equal to 3 ppm, and in particular greater than or equal to 4 ppm relative to the total mass of the composition.

In particular, the mass content of chlorides CI in the composition ranges from 0.1 ppm to less than 20 ppm, preferably from 0.1 ppm to 18 ppm, preferentially from 0.1 ppm to 15 ppm, advantageously from 0.1. ppm at 12 ppm, and in particular from 0.1 ppm to 10 ppm relative to the total mass of the composition.

According to a preferred embodiment, the mass content of fluorides F in the composition is greater than or equal to 0.1 ppm, preferably greater than or equal to 0.5 ppm, preferably greater than or equal to 1 ppm, advantageously greater than or equal to 2 ppm, still more preferably greater than or equal to 3 ppm, and in particular greater than or equal to 4 ppm relative to the total mass of the composition.

The mass content of fluorides in the composition may be less than or equal to 100 ppm, preferably less than or equal to 80 ppm, preferably less than or equal to 60 ppm, advantageously less than or equal to 50 ppm, even more advantageously less than or equal to 30 ppm. ppm relative to the total mass of the composition.

In particular, the mass content of fluorides F in the composition ranges from 0.1 ppm to 100 ppm, preferably from 0.1 ppm to 80 ppm, preferentially from 0.1 ppm to 60 ppm, advantageously from 0.1 ppm to 50 ppm, and in particular from 0.1 ppm to 30 ppm relative to the total mass of the composition.

The composition may comprise less than 200 ppm K ⁺ , preferably less than 150 ppm, preferably less than 100 ppm, advantageously less than 50 ppm, still more preferably less than 30 ppm, and in particular less than 10 ppm by weight relative to to the total mass of the composition.

Preferably, the composition comprises strictly more than 0 ppm of K ⁺ , preferably of strictly more than 0 ppm to less than 100 ppm, advantageously of strictly more than 0 ppm to less than 50 ppm, still more advantageously of strictly more than 0 ppm at less than 30 ppm, and in particular from strictly more than 0 ppm to less than 10 ppm by weight relative to the total mass of the composition.

According to one embodiment, the composition is characterized in that: [S0 ₄ ² ] + [CI] + [F] + [K ⁺ ] <150 ppm

In the context of the invention, the following expression:

[S0 ₄ ² ] + [CI] + [F] + [K ⁺ ] <150 ppm

means that the sum of the total mass contents of sulphates (SO ₄ ² ), chlorides (CI), fluorides (F) and potassium ions (K ⁺ ) is less than or equal to 150 ppm, relative to the total mass of the composition.

Preferably, the aforementioned composition is such that [S0 ₄ ² ] + [Cl] + [P] + [K ⁺ ] <120 ppm, preferably [S0 ₄ ² ] + [Cl] + [P] + [K ⁺ ] <100 ppm, advantageously [S0 ₄ ² ] + [CI] + [P] + [K ⁺ ] <80 ppm, even more advantageously [S0 ₄ ² ] + [CI] + [P] + [K ⁺ ] <50 ppm, in particular [S0 ₄ ² ] + [CI] + [F] + [K ⁺ ] <30 ppm, and for example [S0 ₄ ² ] + [CI] + [F] + [K ⁺ ] <20 ppm .

The composition may also comprise less than 200 ppm of water, preferably less than 150 ppm, preferably less than 100 ppm, advantageously less than 50 ppm, even more advantageously less than 30 ppm, and in particular less than 10 ppm by weight. water relative to the total mass of the composition.

Preferably, the composition comprises strictly more than 0 ppm of water, preferably of strictly more than 0 ppm to less than 100 ppm, advantageously of strictly more than 0 ppm to less than 50 ppm, even more advantageously of strictly more than 0 ppm. at less than 30 ppm, and in particular from strictly more than 0 ppm to less than 10 ppm by weight relative to the total mass of the composition.

The composition according to the invention can be obtained by a process for purifying a bis (fluorosulfonyl) imide lithium salt in solution in an organic solvent S1, said process possibly comprising the following steps:

a) liquid-liquid extraction of said salt from the solution containing the organic solvent S1 and the salt, with deionized water to form an aqueous solution of said bis (fluorosulfonyl) imide salt;

a ') possible concentration of said aqueous solution;

b) liquid-liquid extraction of the bis (fluorosulfonyl) imide lithium salt from said aqueous solution (obtained in step a) or step a ')), with an organic solvent S2; c) concentration of the bis (fluorosulfonyl) imide lithium salt obtained in step b) to form a composition C,

d) crystallizing the bis (fluorosulfonyl) imide lithium salt from composition C;

e) possible filtration step, to lead to the composition according to the invention,

said process being characterized in that the composition C comprises at least 30% by weight of a dry extract ES, said dry extract ES being characterized in that:

it comprises the lithium salt of bis (fluorosulfonyl) imide, preferably at a content greater than or equal to 99.90% by weight relative to the total weight of said solids ES;

the sum of the total mass contents of chlorides, sulphates and fluorides is strictly greater than 0 and less than or equal to 500 ppm, preferably less than or equal to 300 ppm, advantageously less than or equal to 200 ppm by weight relative to the total weight of said dry extract ES.

The measurement of dry extract is typically carried out on a Metler Toledo thermobalance type HR73 according to the following steps:

- (i) an aluminum nacelle is placed in the Metler Toledo HR73 thermobalance device;

- ii) the nacelle is then tared;

iii) a fiberglass disk is placed on the boat and is dried at 110 ° C. until a constant weight is obtained;

- iv) the nacelle and the fiberglass disc are tared;

v) the disc is soaked with 1 g of solution to be analyzed and is heated to 110.degree.

vi) the dry extract is obtained when the weight becomes constant.

According to one embodiment, the total mass content of chlorides in the above-mentioned composition C is greater than 20 ppm, preferably greater than or equal to 30 ppm, preferably greater than or equal to 50 ppm, advantageously greater than or equal to 100 ppm, for example greater than or equal to 150 ppm.

Preferably, the composition C is characterized in that the sum of the total mass contents of chlorides, sulphates, fluorides and potassium ion is greater than or equal to 100 ppm, preferably greater than or equal to 150 ppm, advantageously greater than or equal to 180 ppm.

According to one embodiment, the composition C comprises at least 35% by weight of said dry extract ES, preferably at least 40% by weight, and advantageously at least 50% by weight, relative to the total weight of the composition C.

The lithium salt of bis (fluorosulfonyl) imide in solution in the organic solvent S1 can be obtained by any known method for preparing said salt, for example as described in WO2015 / 158979 or WO2009 / 1233328. The LiFSI salt can be obtained either in solid form or in the form of a solution in an organic solvent S1. The composition according to the invention can be obtained by a process comprising the following steps:

i) a process for preparing the lithium salt of bis (fluorosulfonyl) imide, said salt possibly being solid or in solution in an organic solvent S1;

ii) a step of contacting with an organic solvent S1 in the case where the LiFSI salt obtained in step i) is solid;

iii) purification process as described above.

The above-mentioned organic solvent S 2 may be selected from the group consisting of esters, nitriles, ethers, chlorinated solvents, aromatic solvents, and mixtures thereof. Preferably, the solvent S 2 is chosen from dichloromethane, ethyl acetate, butyl acetate, tetrahydrofuran, acetonitrile, diethyl ether, and mixtures thereof. Preferably, the organic solvent S 2 is butyl acetate.

According to the invention, each of the above steps a) and b) can be repeated at least once.

According to one embodiment, the organic solvent S1 is selected from the group consisting of esters, nitriles, ethers, chlorinated solvents, aromatic solvents, and mixtures thereof. Preferably, the solvent S1 is chosen from ethers, esters, and mixtures thereof. For example, mention may be made of methyl t-butyl ether, cyclopentyl methyl ether, ethyl acetate, propyl acetate, butyl acetate, dichloromethane, tetrahydrofuran, acetonitrile and diethyl ether, and their mixtures. Preferably, the solvent SOI is chosen from methyl-t-butyl ether, cyclopentyl methyl ether, ethyl acetate, propyl acetate and butyl acetate, and mixtures thereof, the organic solvent S 1 being preferentially butyl acetate.

The above-mentioned step c) can be carried out in two stages:

a pre-concentration preferably carried out at a temperature ranging from 25 ° C. to 45 ° C., preferably from 30 ° C. to 40 ° C .;

a concentration step carried out in a short-path thin-film evaporator under the following conditions:

temperature between 30 ° C and 95 ° C, preferably between 30 ° C and 90 ° C, preferably between 40 ° C and 85 ° C, in particular between 60 ° C and 80 ° C,

pressure between 10 ³ mbar abs and 5 mbar abs, and in particular between 5.10 ¹ and 2 mbar abs;

- residence time less than or equal to 5 min, preferably less than or equal to 3 min.

Preferably, the pre-concentration step is carried out under reduced pressure, for example at a pressure of less than or equal to 50 mbar abs, in particular at a pressure of less than or equal to 30 mbar abs. The pre-concentration step can be carried out by any means allowing the concentration, for example using an evaporator.

In the context of the invention, and unless otherwise stated, the term "residence time" means the time that elapses between the entry of the lithium salt solution of bis (fluorosulfonyl) imide (in particular obtained at the result of step b) above) in the evaporator and the outlet of the first drop of the solution.

According to a preferred embodiment, the temperature of the condenser of the short-path thin-film evaporator is between -50 ° to 5 ° C., preferably between -35 ° C. and 5 ° C. In particular, the temperature of the condenser is -5 ° C.

Short-path thin-film evaporators according to the invention are also known under the name "Wiped film short path" (WFSP). They are typically so called because the vapors generated during evaporation make a "short trip" (short distance) before being condensed to the condenser.

Among the short-path thin film evaporators, there may be mentioned evaporators marketed by the companies Buss SMS Ganzler ex Luwa AG, UIC Gmbh or VTA Process.

Typically, short-path thin-film evaporators may include a solvent vapor condenser positioned within the apparatus itself (particularly in the center of the apparatus), unlike other types of film evaporators. thin (which are not short path) in which the condenser is located outside the device.

In this type of apparatus, the formation of a thin film of product to be distilled on the internal hot wall of the evaporator can typically be provided by continuously spreading on the evaporation surface by mechanical means. specified below.

The evaporator may in particular be provided at its center, an axial rotor on which are mounted the mechanical means that allow the formation of the film on the wall. They may be rotors equipped with fixed blades: three-blade or four-blade lobed rotors in flexible or rigid materials, distributed over the entire height of the rotor or rotors equipped with moving blades, pallets, scrapers, guided rubbers. In this case, the rotor may be constituted by a succession of articulated pallets on pivot mounted on a shaft or axis via radial supports. Other rotors may be equipped with mobile rollers mounted on secondary axes and said rollers are pressed on the wall by centrifugation. The rotational speed of the rotor which depends on the size of the apparatus can be readily determined by those skilled in the art. The various mobiles can be made of various materials, for example metal, steel, alloy steel (stainless steel), aluminum, or polymers, for example polytetrafluoroethylene PTFE or glass materials (enamel); metallic materials coated with polymeric materials. The crystallization step d) can be carried out by contacting the composition obtained at the end of step c) with an organic solvent ("crystallization solvent") chosen from chlorinated solvents, such as, for example, dichloromethane, and aromatic solvents, such as, for example, toluene.

Preferably, the crystallization is carried out at a temperature of less than or equal to 25 ° C., preferably less than or equal to 15 ° C.

The present application also relates to the use of the composition according to the invention, in a battery, for example a Li-ion battery, in particular at a temperature greater than or equal to 25 ° C, preferably between 25 ° C and 80 ° C. C, and / or in particular at a voltage between 3.5 and 5 volts, preferably between 4.2 and 4.5 volts. For example, the use is in mobile devices, for example mobile phones, cameras, tablets or laptops, in electric vehicles, or in the storage of renewable energy.

The present invention also relates to a method of charging / discharging a battery, in particular a Li-ion battery, said method comprising:

a charging step up to a voltage Tsup of between 4 and 4.7 volts, preferably between 4.2 and 4.5 volts; and

a discharge step up to a voltage Tint of between 2.5 and 3.5 volts, said battery comprising the composition as defined above.

The charge step / discharge step cycles can be repeated several times.

The present invention also relates to the use of the composition according to the invention for improving the life of a battery, in particular a Li-ion battery, said battery preferably operating at a usage voltage of between 3.5. and 5 volts, preferably between 4.2 and 4.5 volts.

The composition according to the invention advantageously has at least one of the following advantages:

- improved battery life;

- Reduction or elimination of corrosion of the constituents of the battery, such as the AI collector.

In the context of the invention, "between x and y" or "ranging from x to y" means an interval in which the terminals x and y are included. For example, the temperature "between -20 and 80 ° C" includes in particular the values -20 ° C and 80 ° C.

All the embodiments described above can be combined with each other. The present invention is illustrated by the following example, to which it is however not limited.

EXPERIMENTAL PART

Preparation of the LiFSI of Examples 1 and 2:

Crude LiFSI in solution in butyl acetate is obtained at the end of the process described in WO 2015/158979. The LiFSI solution is subjected to a purification process comprising the liquid-liquid extraction of said salt with deionized water to form an aqueous solution, and then the liquid-liquid extraction of the bis (fluorosulfonyl) imide lithium salt from from said aqueous solution with butyl acetate. The solution obtained was subjected to a concentration step to give a composition comprising more than 30% by weight of a dry extract characterized in that it comprises more than 99.75% by weight of LiFSI and in that the sum of the total mass contents of chlorides, sulphates and fluorides is strictly greater than 0 and less than 500 ppm. The composition is then subjected to a crystallization and filtration step to give the LiFSI of Example 1.

The LiFSI of Example 2 was obtained according to a similar method.

Preparation of the LiFSI of Example 3

Crude LiFSI in solution in butyl acetate is obtained at the end of the process described in WO 2015/158979. The LiFSI solution is subjected to a purification process comprising the liquid-liquid extraction of said salt with deionized water to form an aqueous solution, and then the liquid-liquid extraction of the bis (fluorosulfonyl) imide lithium salt from from said aqueous solution with butyl acetate. The solution obtained was subjected to a concentration step to give a composition comprising a dry extract characterized in that it comprises less than 99.75% by weight of LiFSI, and in that the sum of the total chloride mass contents. in sulphates and fluorides is strictly greater than 600 ppm. The composition is then subjected to a crystallization and filtration step to give the LiFSI of Example 3.

tests

Cyclic voltammetry tests were performed. For this purpose CR2032 button cells were manufactured with a 20 mm diameter aluminum foil as working electrode, a 8 mm diameter lithium metal pellet as reference electrode and a fiberglass separator. 18 mm diameter impregnated with 12 drops (0.6 mL) of a LiFSI solution of different compositions at 1 mol / L in a solvent mixture composed of ethylene carbonate and methyl ethyl carbonate (CAS = 623-53-0) in a ratio of 3/7 by volume.

Then a voltage sweep is performed at the terminals of the button cell at 4.5 V. Two preliminary sweeps are performed allowing the formation of passivation layers such as SEI and passivation of aluminum. Then, the oxidation current at 4.5V (after the two scans) generated was measured and recorded. The values are as follows:

The oxidation current observed can reflect many phenomena: aluminum corrosion, degradation of the electrolyte and the formation of lithium dendrites. All these phenomena are responsible for the degradation of the life of Li-ion batteries. The lower the current, the longer the life of the battery is improved. At 4.5 V, the results show that the use of a LiFSI having in particular a chloride content of less than 20 ppm advantageously makes it possible to reduce this oxidation current with respect to a LiFSI having a chloride content of 20 ppm, and therefore improve the life of Li-ion batteries.

Claims

1. Composition comprising:

chlorides Cl, in a mass content strictly less than 20 ppm;

fluorides F- in a mass content strictly greater than 0 ppm;

in which :

[S0 ₄ ² ] + [CI] + [F] <150 ppm

2. Composition according to claim 1, characterized in that:

[S0 ₄ ² ] + [Cl] + [P] <120 ppm, preferentially [S0 ₄ ² ] + [Cl] + [P] <100 ppm, advantageously [S0 ₄ ² ] + [Cl] + [P] < 80 ppm, still more advantageously [S0 ₄ ² ] + [Cl] + [P] <50 ppm, in particular [S0 ₄ ² ] + [Cl] + [P] <30 ppm, and for example [S0 ₄ ² ] + [CI] + [P] <20 ppm.

3. Composition according to any one of claims 1 or 2, wherein the mass content of sulphates is less than or equal to 150 ppm, preferably less than or equal to 100 ppm, preferably less than or equal to 50 ppm, advantageously less than or equal to at 30 ppm, more preferably less than or equal to 20 ppm, in particular less than or equal to 10 ppm, relative to the total mass of the composition.

4. Composition according to any one of claims 1 to 3, wherein the mass content of sulphates is strictly greater than 0 ppm, preferably greater than or equal to 0.1 ppm, relative to the total mass of the composition.

5. Composition according to any one of claims 1 to 4, wherein the mass content of Cl chlorides is less than or equal to 18 ppm, preferably less than or equal to 15 ppm, preferably less than or equal to 12 ppm, preferably less or equal to 10 ppm relative to the total mass of the composition.

6. Composition according to any one of claims 1 to 5, wherein the mass content of chlorides CI is strictly greater than 0 ppm, preferably greater than or equal to 0.1 ppm, preferably greater than or equal to 0.5 ppm, even more preferably greater than or equal to 1 ppm, advantageously greater than or equal to 2 ppm, still more advantageously greater than or equal to 3 ppm, and in particular greater than or equal to 4 ppm relative to the total mass of the composition.

7. Composition according to any one of claims 1 to 6, wherein the mass content of chlorides Cl ranges from 0.1 ppm to less than 20 ppm, preferably from 0.1 ppm to 18 ppm, preferably from 0.1. ppm at 15 ppm, advantageously from 0.1 ppm to 12 ppm, and in particular from 0.1 ppm to 10 ppm relative to the total weight of the composition.

8. Composition according to any one of claims 1 to 7, wherein the mass content of fluorides F is greater than or equal to 0.1 ppm, preferably greater than or equal to 0.5 ppm, preferably greater than or equal to 1 ppm. , advantageously greater than or equal to 2 ppm, still more preferably greater than or equal to 3 ppm, and in particular greater than or equal to 4 ppm relative to the total weight of the composition.

9. Composition according to any one of claims 1 to 8, wherein the mass content of fluorides is less than or equal to 100 ppm, preferably less than or equal to 80 ppm, preferably less than or equal to 60 ppm, preferably less than or equal to at 50 ppm, still more preferably less than or equal to 30 ppm relative to the total mass of the composition.

10. Composition according to any one of claims 1 to 9, characterized in that it comprises less than 200 ppm K ⁺ , preferably less than 150 ppm, preferably less than 100 ppm, preferably less than 50 ppm, even more advantageously less than 30 ppm, and in particular less than 10 ppm by weight relative to the total mass of the composition.

1. Composition according to any one of Claims 1 to 10, characterized in that it comprises strictly more than 0 ppm of K ⁺ , preferably of strictly more than 0 ppm to less than 100 ppm, advantageously of strictly more than 0 ppm. ppm to less than 50 ppm, still more preferably from strictly more than 0 ppm to less than 30 ppm, and in particular from strictly more than 0 ppm to less than 10 ppm by weight relative to the total mass of the composition.

12. Composition according to any one of claims 1 to 1 1, characterized in that

[S0 ₄ ² ] + [CI] + [F] + [K ⁺ ] <150 ppm

13. Composition according to any one of claims 1 to 12, characterized in that it comprises less than 200 ppm of water, preferably less than 150 ppm, preferably less than 100 ppm, preferably less than 50 ppm, even more advantageously less than 30 ppm, and in particular less than 10 ppm by weight of water relative to the total mass of the composition.

14. Composition according to any one of claims 1 to 13, characterized in that it comprises strictly more than 0 ppm of water, preferably from strictly more than 0 ppm to less than 100 ppm, preferably strictly more than 0 ppm at less than 50 ppm, still more preferably from strictly more than 0 ppm to less than 30 ppm, and in particular from strictly more than 0 ppm to less than 10 ppm by weight based on the total mass of the composition.

15. Process for the preparation of the composition as defined in any one of claims 1 to 14, comprising a process for purifying a lithium salt of bis (fluorosulfonyl) imide in solution in an organic solvent S1, said method of purification t comprising the following steps:

a ') possible concentration of said aqueous solution;

b) liquid-liquid extraction of the bis (fluorosulfonyl) imide lithium salt from said aqueous solution (obtained in step a or in step a '), with an organic solvent S2;

c) concentration of the bis (fluorosulfonyl) imide lithium salt obtained in step b) to form a composition C,

e) possible filtration step,

to give the composition as defined in any one of claims 1 to 14,

said purification process being characterized in that the composition C comprises at least 30% by weight of a dry extract ES, said dry extract ES being characterized in that: it comprises the lithium salt of bis (fluorosulfonyl) imide, preferably at a content greater than or equal to 99.90% by weight relative to the total weight of said dry extract ES;

the sum of the total mass contents of chlorides, sulphates and fluorides is strictly greater than 0 and less than or equal to 500 ppm, preferably less than or equal to 300 ppm, preferably less than or equal to 200 ppm by weight relative to the total weight of said dry extract ES.

16. Use of the composition as defined in any one of claims 1 to 14 in a battery, for example a Li-ion battery, in particular at a temperature greater than or equal to 25 ° C, preferably between 25 ° C and 25 ° C. ° C and 80 ° C, and / or in particular at a tenson between 3.5 and 5 volts, preferably between 4.2 and 4.5 volts.

17. Use of the composition as defined in any one of claims 1 to 14, to improve the life of a battery.