KR101982602B1 - Method for producing bis (fluorosulfonyl) imide lithium salt (LiFSI) with reduced fluorine anion content (1) - Google Patents

Abstract

The present invention provides a method for manufacturing bis(fluorosulfonyl)imide lithium salt, comprising following steps of: (a) manufacturing an ammonium bis(fluorosulfonyl)imide by conducting a reaction of bis(fluorosulfonyl) imide with NH_4F(HF)n (n is 0 to 10); (b) supplying nitrogen gas to a reaction solution after completion of a reaction of the step (a) to conduct bubbling until the pH of flowing gas is 6 to 8; and (c) conducting a reaction of the ammonium bis(fluorosulfonyl)imide with a lithium base.

Description

Method for producing bis (fluorosulfonyl) imide lithium salt (LiFSI) with reduced fluorine anion content (1) (Method for producing bis (fluorosulfonyl) imide lithium salt (LiFSI)

The present invention relates to a process for producing a bis (fluorosulfonyl) imide lithium salt (LiFSI) having a reduced fluorine anion content.

With the popularization of mobile devices, the commercialization of electric vehicles, and the increasing demand for electric storage devices, secondary batteries having high output, high energy density, and high discharge voltage performance have been developed.

The lithium-ion battery includes at least a cathode, an anode, a separator, and an electrolyte. The electrolyte is generally composed of a lithium salt dissolved in a solvent which is a mixture of organic carbonates. The most widely used lithium salt is lithium hexafluorophosphate (LiPF ₆ ), which has excellent properties but has the disadvantage of being decomposed in the form of hydrofluoric acid gas.

To overcome the above disadvantages, LiTFSI (lithium bis (trifluoromethanesulfonyl) imide) and LiFSI (lithium bis (fluorosulfonyl) imide) have been developed. These salts show little or no spontaneous decomposition and are more stable to hydrolysis than LiPF ₆ .

On the other hand, LiTFSI is known to have the disadvantage of causing corrosion to an aluminum current collector, while LiFSI has not suffered from such disadvantages, and thus has attracted attention as an excellent performance as compared with other salts of the prior art.

Since the specific gravity of the lithium salt is high in the cost structure of the lithium-ion secondary battery, studies have been actively made on a method for producing a bis (fluorosulfonyl) imide lithium salt having a high purity in an economical manner.

The preparation of the conventionally known bis (fluorosulfonyl) imide lithium salt is carried out as follows:

As shown in the above reaction formula, the above production method is a method for producing a bis (fluorosulfonyl) imide compound by reacting bis (chlorosulfonyl) imide with fluoride zinc (II) (ZnF2) .

However, this reaction requires the use of expensive fluoride zinc (II), which requires the removal of sparingly soluble zinc components, and the disadvantage of producing a large amount of wastewater containing zinc components. Particularly, in order to use a bis (fluorosulfonyl) imide lithium salt in an electrolytic solution, zinc metal has to be controlled in terms of PPM.

A process for producing a bis (fluorosulfonyl) imide lithium salt as described below is also known.

This technique can be carried out by reacting bis (chlorosulfonyl) imide, which is a starting material, with NH4F (HF) n (n = 0 to 10) as a fluorination reagent to form ammonium bis (fluorosulfonyl) To produce an imide salt.

However, in the above process, most of the fluorine anion in the process of producing ammonium bis (fluorosulfonyl) imide salt by reacting bis (chlorosulfonyl) imide with NH 4 F (HF) n (n = 0 to 10) (F-) is generated, which has a disadvantage that it acts as a cause of lowering the quality of the product.

Therefore, it is required to study the method of eliminating the fluorine anion generated in this process.

Korean Patent Publication No. 10-2013-0140216

The present inventors have made intensive efforts to solve the above-mentioned problems of the prior art, and as a result, they have found that the fluorine anion (F-) generated in the course of the production of bis (fluorosulfonyl) And the present invention has been completed.

Therefore, the present invention relates to a process for producing a bis (fluorosulfonyl) imide lithium salt, which is capable of efficiently removing the fluorine anion (F-) generated in the course of the production of the bis (fluorosulfonyl) imide lithium salt by using nitrogen gas bubbling, Lt; RTI ID = 0.0 > of < / RTI > an imide lithium salt.

(Fluorosulfonyl) imide lithium salt which can provide a high-quality bis (fluorosulfonyl) imide lithium salt by sufficiently removing the fluorine anion (F-) by a simple method, And a method thereof.

In order to achieve the above object,

(a) reacting bis (chlorosulfonyl) imide with NH ₄ F (HF) n (n = 0 to 10) to prepare ammonium bis (fluorosulfonyl) imide;

(b) supplying nitrogen gas to the reaction solution after completion of the reaction of step (a) to bubble until the pH of the gas is 6 to 8; And

(c) reacting the ammonium bis (fluorosulfonyl) imide with a lithium base. The present invention also provides a process for producing a bis (fluorosulfonyl) imide lithium salt.

In one embodiment of the present invention, when the waste solid is not removed during the step (a) in the step (b), the reaction product is cooled to 50 to 70 ° C after completion of the reaction, ;

In the step (a), when the waste solid is removed, it is cooled to 0 to 20 ° C, filtered, and heated to 50 to 70 ° C, followed by nitrogen gas bubbling.

The process for producing a bis (fluorosulfonyl) imide lithium salt of the present invention is a process for producing a bis (fluorosulfonyl) imide lithium salt by reacting a fluorine anion (F < - > It is possible to efficiently remove gas bubbling.

Further, by sufficiently removing the fluorine anion (F-) by the simple method as described above, it is possible to provide a high-quality bis (fluorosulfonyl) imide lithium salt.

Hereinafter, the present invention will be described in detail.

According to the present invention,

(a) reacting bis (chlorosulfonyl) imide with NH ₄ F (HF) n (n = 0 to 10) to prepare ammonium bis (fluorosulfonyl) imide;

(b) supplying nitrogen gas to the reaction solution after completion of the reaction of step (a) to bubble until the pH of the gas is 6 to 8; And

(c) reacting the ammonium bis (fluorosulfonyl) imide with a lithium base. The present invention also relates to a method for producing a bis (fluorosulfonyl) imide lithium salt.

When an additional compound is used to reduce the fluorine anion (F < ^- >) in the course of producing bis (fluorosulfonyl) imide lithium salt, the production cost is increased and the number of steps is increased. do.

The present invention has a technical feature capable of effectively removing the fluorine anion (F < ^- >) without using any additional compound.

In fact, in the process of the following reaction formula 1, various acids are produced. Among them, HF is also generated. If it is blown in the reaction solution by nitrogen gas bubbling (if removed), the next step can be carried out with HF being removed considerably, so that the content of fluorine anions in the final product can be greatly reduced .

[Reaction Scheme 1]

However, the nitrogen gas bubbling is effected by supplying nitrogen gas to the reaction solution and bubbling the gas until the pH of the gas is 6 ~ 8.

That is, when nitrogen gas bubbling is stopped at a point where the pH of the gas is less than 6, the removal rate of HF is low. When the pH is more than 8, the amount of HF in the reaction product is rather bubbled with nitrogen gas If you do not, you may increase it.

More preferably, the nitrogen gas bubbling is stopped when the pH is from 6.5 to 7.5, and more preferably, the nitrogen gas bubbling is stopped when the pH is from 6.8 to 7.2.

If the waste solid is not removed during the step (a) in the step (b), the reaction product is cooled to 50 to 70 ° C after completion of the reaction, and then subjected to nitrogen gas bubbling; In the case of removing the waste solid in the step (a), it is preferable to perform cooling to 0 to 20 ° C, followed by filtration, heating the filtrate to 50 to 70 ° C, and then performing nitrogen gas bubbling.

The nitrogen gas bubbling in the steps (a) and (b) is carried out after the temperature is adjusted to 50 to 70 ° C. When the nitrogen bubbling is performed at this temperature, the maximum efficiency is obtained in a shorter time than when the temperature is low It is advantageous in that it can be.

It is more preferable that the nitrogen bubbling is carried out at 60 캜.

The waste solid may be any one of ammonium fluoride, ammonium halide, and impurity solid other than the above-mentioned components.

The presence of the waste solid can be confirmed by a nuclear magnetic resonance spectroscopy method.

The manufacturing method of the present invention may further include a recrystallization process after the completion of the step (b) and before the start of the step (c).

The pH of the gas discharged in the step (b) may be measured using a pH paper, but the method is not limited thereto and may be carried out by a method known in the art.

In the present invention, the processes of steps (a) and (c) are not particularly limited and can be carried out by methods known in the art.

The step (a) is a step for producing bis (fluorosulfonyl) imide by reacting bis (chlorosulfonyl) imide with NH ₄ F (HF) n (n = 0 to 10) Can be:

[Reaction Scheme 1]

Examples of the solvent include diethyl ether, diisopropyl ether, methyl-t-butyl ether, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, etc. These solvents may be used singly or in combination of two or more kinds. Can be used. Of these, butyl acetate can be more preferably used.

The reaction may be carried out in a nitrogen atmosphere.

In step (a), a nitrogen compound is bubbled through the solution, followed by filtration and concentration to obtain a crude compound. At this time, methylene chloride or the like may be added to the crude compound to perform recrystallization.

The step (c) can be carried out as shown in the following reaction formula 2:

[Reaction Scheme 2]

In step (c), examples of the solvent include diethyl ether, diisopropyl ether, methyl-t-butyl ether, methyl acetate, ethyl acetate, propyl acetate, butyl acetate and the like. Or more. Of these, butyl acetate can be more preferably used.

The (c) lithium bases include lithium hydroxide (LiOH) in step, lithium hydroxide monohydrate (LiOH · H ₂ O), lithium carbonate (Li ₂ CO _3), hydrogen carbonate, lithium (LiHCO _3), lithium chloride (LiCl), (LiCH ₃ COO), lithium oxalate (Li ₂ C ₂ O ₄ ), and the like can be used. Of these, lithium hydroxide hydrate can be preferably used.

After mixing the reactants in the step (c), nitrogen gas bubbling may be further performed.

The washing, filtration, concentration, recrystallization and the like of the obtained compound in the step (c) can be further carried out by a conventional method.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as set forth in the appended claims. Such changes and modifications are intended to be within the scope of the appended claims.

Example 1: Preparation of bis (fluorosulfonyl) imide lithium salt (in the case of formation of waste solid)

A reactor equipped with a stirrer, a condenser and a thermometer was charged with 79.57 g of ammonium fluoride and 600 g of butyl acetate purified in water under a nitrogen atmosphere at room temperature. While stirring the mixture, 100 g of bis (dichlorosulfonyl) imide was slowly added thereto, and the mixture was heated to 80 ° C and reacted for 2 hours.

The reaction product was cooled to 60 ° C in a state where the waste solid was not removed, and nitrogen gas bubbling was performed. The pH of the flammable gas was checked using a pH paper at 5 minute intervals (initial pH approx. 3) and nitrogen gas bubbling was stopped at pH 7. The temperature of the reaction was cooled to below 10 < 0 > C and filtered. To the filtered filtrate of ammonium bis (fluorosulfonyl) imide was added 25.50 g of lithium hydroxide hydrate and the mixture was stirred. Thereafter, the reaction was allowed to proceed at a temperature of less than 5 ° C for 4 hours, and the reaction was terminated.

74.97 g of distilled water was added and stirred, and then the layer was separated to remove the distilled water layer. Again, 22.49 g of distilled water was added and stirred, and the layer was separated to remove the distilled water layer. The obtained organic layer was filtered and concentrated to obtain a crude compound. Thereafter, the mixture was stirred until crystals were precipitated at a vacuum of 51 캜.

Next, 208.31 g of toluene was charged and filtered to obtain a solid, which was then vacuum dried to obtain 30.12 g of a bis (fluorosulfonyl) imide lithium salt (yield: 37%).

Example 2: Preparation of bis (fluorosulfonyl) imide lithium salt (in case of waste solid removal)

A reactor equipped with a stirrer, a condenser and a thermometer was charged with 79.57 g of ammonium fluoride and 600 g of butyl acetate purified in water under a nitrogen atmosphere at room temperature. While stirring the mixture, 100 g of bis (dichlorosulfonyl) imide was slowly added thereto, and the mixture was heated to 80 ° C and reacted for 2 hours.

The reaction product was cooled to 10 ° C or less and then filtered.

After the filtrate was heated to 60 ° C, nitrogen gas bubbling was performed. The pH of the flammable gas was checked using a pH paper at 5 minute intervals (initial pH approx. 3) and nitrogen gas bubbling was stopped at pH 7. The temperature of the reaction was cooled to below 10 < 0 > C and filtered.

To the filtered filtrate of ammonium bis (fluorosulfonyl) imide was added 25.50 g of lithium hydroxide hydrate and the mixture was stirred. Thereafter, the reaction was allowed to proceed at a temperature of less than 5 ° C for 4 hours, and the reaction was terminated.

74.97 g of distilled water was added and stirred, and then the layer was separated to remove the distilled water layer. Again, 22.49 g of distilled water was added and stirred, and the layer was separated to remove the distilled water layer. The obtained organic layer was filtered and concentrated to obtain a crude compound. Thereafter, the mixture was stirred until crystals were precipitated at a vacuum of 51 캜.

Next, 208.31 g of toluene was charged and filtered to obtain a solid, which was dried in vacuo to give 29.91 g of bis (fluorosulfonyl) imide lithium salt (yield: 37%).

Comparative Example 1: Preparation of bis (fluorosulfonyl) imide lithium salt (without nitrogen gas bubbling)

31.09 g of bis (fluorosulfonyl) imide lithium salt was obtained in the same manner as in Example 1 except that nitrogen gas bubbling was not performed during the production of bis (fluorosulfonyl) imide (Yield: 38.0 %, Purity: 99.94%).

Comparative Example 2: Preparation of bis (fluorosulfonyl) imide lithium salt

(fluorosulfonyl) imide lithium salt was obtained in the same manner as in Example 1, except that the nitrogen gas bubbling was stopped at the time when the pH became 4 without stopping the nitrogen gas bubbling at the time when the pH became 7 29.56 g of a salt were obtained (yield: 36.1% purity: 99.95%).

Comparative Example 3: Preparation of bis (fluorosulfonyl) imide lithium salt

(fluorosulfonyl) imide lithium salt was prepared in the same manner as in Example 1, except that the nitrogen gas bubbling was stopped at the time when the pH became 10 without stopping the nitrogen gas bubbling at the time when the pH became 7 30.65 g of a salt was obtained (yield: 37.41% purity: 99.95%).

Test Example 1: Measurement of the concentration of the fluorine anion (F-) contained in the bis (fluorosulfonyl) imide lithium salt

The concentration of the fluorine anion (F-) from the bis (fluorosulfonyl) imide lithium salt prepared in Examples 1 and 2 and Comparative Examples 1 to 3 was measured using a fluorimeter manufactured by Metrohm. The results of the fluorine anion (F ^- ) concentration measurement are shown in Table 1 below.

Measurement sample The state of reaction liquid containing bis (fluorosulfonyl) imide ammonium salt Fluorine anion (F ^- ) concentration (ppm) Comparative Example 1 No nitrogen gas bubbling 411.6 Comparative Example 2 Nitrogen gas bubbling (stop at pH 4) 293.6 Comparative Example 3 Nitrogen gas bubbling (stop at pH 10) 471.3 Example 1 Nitrogen gas bubbling was performed (stopped at pH 7) 1.4 Example 2 Nitrogen gas bubbling was performed (stopped at pH 7) 3.6

As shown in Table 1, in the case of the bis (fluorosulfonyl) imide lithium salt of Example 1 and Example 2 produced under nitrogen gas bubbling with sufficient acid gas removed, It was confirmed that the content of the fluorine anion (F ^- ) was remarkably reduced as compared with the bis (fluorosulfonyl) imide lithium salt prepared in Comparative Examples 1 to 3, because the acids were not much involved in the reaction.

Specifically, it was confirmed that the concentration of the fluorine anion (F ^- ) was 411.6 ppm in the bis (fluorosulfonyl) imide lithium salt of Comparative Example 1 in which nitrogen gas bubbling was not performed, The bis (fluorosulfonyl) imide lithium salt prepared in Example 1 and Example 2 in which nitrogen gas bubbling was performed was 1/11 of the bis (fluorosulfonyl) imide lithium salt prepared in Comparative Example 1 Lt; RTI ID = 0.0 > fluorine < / RTI >

On the other hand, although subjected to nitrogen gas bubbling to the reaction solution, bis (fluoro sulfonyl) imide lithium salt produced in Comparative acidic range (pH 4), stop the nitrogen gas bubbling in the Example 2 is a fluorine anion (F ^- ) concentration was found to be that the decline large as 239.6 ppm, a bis (fluoro sulfonyl) imide lithium salt prepared in a basic range (pH 10) Comparative example 3 stopped the nitrogen gas bubbling in the fluorine anion (F ^- ) Concentration of 471.3 ppm and containing a larger amount of fluorine anion (F ^- ) than that of Comparative Example 1 in which nitrogen gas bubbling was not performed.

Claims (8)

(a) reacting bis (chlorosulfonyl) imide with NH ₄ F (HF) n (n = 0 to 10) to prepare ammonium bis (fluorosulfonyl) imide;
(b) supplying nitrogen gas to the reaction solution after completion of the reaction of step (a) to bubble until the pH of the gas is 6 to 8; And
(c) reacting the ammonium bis (fluorosulfonyl) imide with a lithium base,
If the waste solid is not removed during the step (a) in the step (b), the reaction product is cooled to 50 to 70 ° C after completion of the reaction, and then subjected to nitrogen gas bubbling;
In the step (a), when the waste solid is removed, it is cooled to 0 to 20 ° C, filtered, and the temperature of the filtrate is raised to 50 to 70 ° C, followed by nitrogen gas bubbling. (Fluorosulfonyl) imide lithium salt. delete The method according to claim 1,
Wherein the waste solid is at least one of an ammonium fluoride, an ammonium halide and an impurity solid other than the above-mentioned components. The method according to claim 1,
The method for producing a bis (fluorosulfonyl) imide lithium salt according to claim 1, wherein the step (b) further comprises a recrystallization step before the step (c). The method according to claim 1,
Wherein the pH of the gas discharged in the step (b) is measured using a pH paper. The method according to claim 1,
The solvent in the steps (a) and (c) is independently selected from the group consisting of diethyl ether, diisopropyl ether, methyl-t-butyl ether, methyl acetate, ethyl acetate, propyl acetate, (Fluorosulfonyl) imide lithium salt of the formula (I). The method according to claim 1,
(C) the lithium base in step is lithium hydroxide (LiOH), lithium hydroxide monohydrate (LiOH · H ₂ O), lithium carbonate (Li ₂ CO _3), hydrogen carbonate, lithium (LiHCO _3), lithium chloride (LiCl), ethyl (Fluorosulfonyl) imide lithium salt characterized in that it is at least one selected from the group consisting of lithium (LiCH ₃ COO) and lithium oxalate (Li ₂ C ₂ O ₄ ). The method according to claim 1,
The process for producing a bis (fluorosulfonyl) imide lithium salt according to claim 1, wherein the reactant is mixed in the step (c) and further subjected to nitrogen gas bubbling.