KR102259983B1 - Method for producing bis (fluorosulfonyl) imide lithium salt (LiFSI) with reduced fluorine anion content - Google Patents

Abstract

the present invention
(a) Bis(chlorosulfonyl)imide and NH ₄ F(HF)n (n=0~10) under a nitrogen atmosphere were mixed with diethyl ether, diisopropyl ether, methyl-t-butyl ether, methyl acetate, acetic acid preparing ammonium bis(fluorosulfonyl)imide by reacting in at least one solvent selected from the group consisting of ethyl, propyl acetate, and butyl acetate;
(b) After the completion of the reaction in step (a), the reaction result is cooled to 50-70° C., and then the pH of the gas blown by supplying nitrogen gas to the reaction solution is measured using a pH paper, and the pH is 6- bubbling until 8;
(c) reacting the ammonium bis(fluorosulfonyl)imide obtained in step (b) with a lithium base to prepare a bis(fluorosulfonyl)imide lithium salt;
(d) adding the lithium salt of bis(fluorosulfonyl)imide prepared in step (c) and an antisolvent to the reactor;
(e) adding lithium methoxide or lithium methoxide solution to the reactor and stirring; and
(f) filtering the solution stirred in step (e), and drying the filtrate; provides a method for preparing a lithium salt of bis (fluorosulfonyl) imide comprising a.

Description

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

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

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

A lithium-ion battery includes at least a negative electrode, a positive electrode, a separator and an electrolyte. The electrolyte consists of a lithium salt dissolved in a solvent, which is usually a mixture of organic carbonates. The most widely used lithium salt is lithium hexafluorophosphate (LiPF ₆ ). This lithium salt has excellent performance, 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 exhibit little or no spontaneous decomposition and are more stable to hydrolysis than _{LiPF 6 .}

On the other hand, LiTFSI is known to have a disadvantage of causing corrosion to an aluminum current collector, whereas LiFSI does not have the above disadvantages, so it is attracting attention for its excellent performance compared to other conventional salts.

Since the specific gravity of lithium salts in the cost structure of lithium-ion secondary batteries is high, research on a method for economically manufacturing high-purity bis(fluorosulfonyl)imide lithium salts is being actively conducted.

A conventionally known method for preparing a lithium salt of bis(fluorosulfonyl)imide is carried out as follows:

As shown in the scheme above, in the preparation method, in step (1), bis(chlorosulfonyl)imide is reacted with zinc(II) fluoride (ZnF2) to prepare a bis(fluorosulfonyl)imide compound. have characteristics.

However, the above reaction has disadvantages in that expensive zinc (II) fluoride must be used, a poorly soluble zinc component must be removed, and a large amount of wastewater containing a zinc component is generated. In particular, in order to use the bis(fluorosulfonyl)imide lithium salt in the electrolyte, it has a disadvantage in that the zinc metal must be adjusted in PPM units.

In addition, a method for producing a bis(fluorosulfonyl)imide lithium salt carried out as follows is also known.

As shown in the reaction scheme, the above technique reacts bis(chlorosulfonyl)imide, a starting material, with NH4F(HF)n (n=0~10), a fluorination reagent, to form ammonium bis(fluorosulfonyl) as an intermediate product. It is characterized in that the imide salt is prepared.

However, in the above method, most of the fluoride anions are produced by reacting bis(chlorosulfonyl)imide with NH4F(HF)n (n=0 to 10) as a fluorination reagent to prepare ammonium bis(fluorosulfonyl)imide salt. (F-) is generated, which has a disadvantage in that it acts as a cause of lowering the quality of the product.

Therefore, research on a method for removing fluoride anions generated in this process is required.

The ammonium fluoride (NH ₄ F(HF)n) is relatively safe and is a useful fluorine source that can be used for industrial mass synthesis, but the excess ammonium fluoride and ammonium chloride remaining after the fluorination reaction is bis(fluorosulfur) Phonyl)imide lithium salt increases the acidity, turbidity, chloride ion concentration, and sulfonic acid anion concentration of the final product, thereby reducing the quality of the product and reducing the life of the battery.

That is, in the case of the above reaction in the above reaction scheme, the following impurities are generated:

In addition, in the case of the following reaction in the above reaction scheme, the following impurities are generated:

Therefore, in manufacturing LiFSI (lithium bis(fluorosulfonyl)imide), research on a method for minimizing impurities is required.

Republic of Korea Patent Publication No. 10-2013-0140216

The present inventors, as a result of earnest efforts to solve the above problems of the prior art, found a method for efficiently removing fluorine anions (F-) and impurities generated during the preparation of bis(fluorosulfonyl)imide lithium salt Found and completed the present invention.

Therefore, the present invention provides a bis(fluorosulfonyl)imide lithium salt that can efficiently remove fluorine anions (F-) and impurities generated during the production process by nitrogen gas bubbling and purification by lithium methoxide. An object of the present invention is to provide a method for preparing a fluorosulfonyl)imide lithium salt.

In addition, the present invention provides a lithium bis(fluorosulfonyl)imide lithium salt capable of providing a high-quality bis(fluorosulfonyl)imide lithium salt by sufficiently removing a fluorine anion (F-) and impurities by a simple method. An object of the present invention is to provide a method for preparing a salt.

In order to achieve the above object, the present invention,

(a) Bis(chlorosulfonyl)imide and NH ₄ F(HF)n (n=0~10) under a nitrogen atmosphere were mixed with diethyl ether, diisopropyl ether, methyl-t-butyl ether, methyl acetate, acetic acid preparing ammonium bis(fluorosulfonyl)imide by reacting in at least one solvent selected from the group consisting of ethyl, propyl acetate, and butyl acetate;

(b) After the completion of the reaction in step (a), the reaction result is cooled to 50-70° C., and then the pH of the gas blown by supplying nitrogen gas to the reaction solution is measured using a pH paper, and the pH is 6- bubbling until 8;

(c) reacting the ammonium bis(fluorosulfonyl)imide obtained in step (b) with a lithium base to prepare a bis(fluorosulfonyl)imide lithium salt;

(d) adding the lithium salt of bis(fluorosulfonyl)imide prepared in step (c) and an antisolvent to the reactor;

(e) adding lithium methoxide or lithium methoxide solution to the reactor and stirring; and

(f) filtering the solution stirred in step (e), and drying the filtrate; provides a method for preparing a lithium salt of bis (fluorosulfonyl) imide comprising a.

The method for preparing bis(fluorosulfonyl)imide lithium salt of the present invention is a method for preparing bis(fluorosulfonyl)imide lithium salt by nitrogen gas bubbling and lithium methoxy fluorine anion (F-) and impurities generated during the production process. It provides the effect of being able to remove efficiently by purification by side.

In addition, it provides the effect of providing a high-quality bis(fluorosulfonyl)imide lithium salt by sufficiently removing the fluorine anion (F-) and impurities by the simple method as described above.

Hereinafter, the present invention will be described in detail.

The present invention is

(a) Bis(chlorosulfonyl)imide and NH ₄ F(HF)n (n=0~10) under a nitrogen atmosphere were mixed with diethyl ether, diisopropyl ether, methyl-t-butyl ether, methyl acetate, acetic acid preparing ammonium bis(fluorosulfonyl)imide by reacting in at least one solvent selected from the group consisting of ethyl, propyl acetate, and butyl acetate;

(b) After the completion of the reaction in step (a), the reaction result is cooled to 50-70° C., and then the pH of the gas blown by supplying nitrogen gas to the reaction solution is measured using a pH paper, and the pH is 6- bubbling until 8;

(c) reacting the ammonium bis(fluorosulfonyl)imide obtained in step (b) with a lithium base to prepare a bis(fluorosulfonyl)imide lithium salt;

(d) adding the lithium salt of bis(fluorosulfonyl)imide prepared in step (c) and an antisolvent to the reactor;

(e) adding lithium methoxide or lithium methoxide solution to the reactor and stirring; and

(f) filtering the solution stirred in step (e), and drying the filtrate; relates to a method for producing a bis(fluorosulfonyl)imide lithium salt comprising a.

In the process of Scheme 1 below, various acids are produced. Among them, HF is also generated, and if it is blown out (if removed) in the reaction solution by bubbling nitrogen gas, the following process can be performed in a state in which HF is significantly removed, so the content of fluoride anions in the final product can be greatly reduced .

[Scheme 1]

However, in the nitrogen gas bubbling, the desired effect can be obtained only when nitrogen gas is supplied to the reaction solution and bubbling is performed until the pH of the blown gas becomes 6-8.

That is, if nitrogen gas bubbling is stopped when the pH of the flying gas is less than 6, the removal rate of HF is low. When the pH exceeds 8, the amount of HF in the reactant is rather nitrogen gas bubbling. It may be higher than if you didn't.

It is more preferable to stop bubbling nitrogen gas when the pH becomes 6.5 to 7.5, and even more preferably to stop bubbling nitrogen gas when the pH becomes 6.8 to 7.2.

If the waste solids are not removed during the process of step (a) in step (b), after the reaction is completed, the reaction product is cooled to 50-70° C., followed by bubbling nitrogen gas; In the case of removing the waste solids during the process of step (a), it is preferable to cool to 0-20°C, filter, and then heat the filtrate to 50-70°C, followed by nitrogen gas bubbling.

In step (b), the nitrogen gas bubbling is carried out after adjusting the temperature to 50 to 70 ° C. In the case of nitrogen bubbling at this temperature, the maximum efficiency can be obtained in a shorter time than when the temperature is low. because it is advantageous.

In the above, nitrogen bubbling is more preferably carried out at 55 to 65 ℃.

In the above, the waste solid may be any one of ammonium fluoride and ammonium halide and other impurity solids other than the above components.

The existence of the waste solid may be confirmed by nuclear magnetic resonance spectroscopy.

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

Specifically, after bubbling nitrogen gas in step (b), a crude compound can be obtained by filtration and concentration, and in this case, diethyl ether, diisopropyl ether, and methyl-t-butyl are added to the crude compound. Recrystallization may be performed by adding methylene chloride or the like together with one or more solvents selected from ether, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, and the like.

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

In the present invention, the processes of steps (a) and (c) that are not related to the technical features of the present invention may be performed by methods known in the art.

The step (a) is a step of preparing bis(fluorosulfonyl)imide by reacting bis(chlorosulfonyl)imide with NH ₄ F(HF)n (n=0 to 10), which is represented by Scheme 1 below. can be:

[Scheme 1]

Examples of the solvent in the reaction include diethyl ether, diisopropyl ether, methyl-t-butyl ether, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, and the like, and these may be used alone or in combination of two or more. can be used Among these, butyl acetate can be used more preferably.

As the NH ₄ F(HF)n (n=0 to 10), NH ₄ F may be more preferably used.

The reaction may be carried out in a nitrogen atmosphere.

Step (c) may be carried out as in Scheme 2:

[Scheme 2]

As the solvent in the reaction of step (c), diethyl ether, diisopropyl ether, methyl-t-butyl ether, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, etc. may be mentioned, and these may be used alone or in two It can be used in combination of more than one species. Among these, butyl acetate can be used more preferably.

As the lithium base in step (c), lithium hydroxide (LiOH), lithium hydroxide hydrate (LiOH·H ₂ O), lithium carbonate (Li ₂ CO ₃ ), lithium hydrogen carbonate (LiHCO ₃ ), lithium chloride (LiCl), At least one selected from the group consisting of lithium acetate (LiCH ₃ COO) and lithium oxalate (Li ₂ C ₂ O _{4 ) may be used.} Among these, lithium hydroxide hydrate can be preferably used.

After mixing the reactants in step (c), nitrogen gas bubbling may be further performed. Specifically, the nitrogen gas bubbling may be performed in the same manner as the above-described method.

Washing of the compound obtained in step (c), concentration by filtration, recrystallization, etc. may be further carried out by a conventional method.

In step (d), the antisolvent may be added in an amount of 50 to 500 parts by weight, more preferably 80 to 300 parts by weight, based on 100 parts by weight of the bis(fluorosulfonyl)imide lithium salt. .

If the amount of the anti-solvent is less than the above range, it is not preferable because the problem that impurities do not fall into the filtrate may occur, and if it exceeds the above range, the effect does not increase, and it is not preferable because it may be difficult to the stirrer.

In step (d), the antisolvent may be at least one selected from the group consisting of toluene, hexane, heptane, chloroform, dichloromethane, and the like.

In step (e), the lithium methoxide or lithium methoxide solution is 0.03 to 2.0 parts by weight, more preferably 0.06 to 1.5 parts by weight based on lithium methoxide based on 100 parts by weight of the bis(fluorosulfonyl)imide lithium salt. may be added as parts. When included in less than the above range, it is difficult to obtain the desired effect, and when included in excess of the above range, lithium methoxide remains, which is not preferable.

In step (e), the lithium methoxide solution may be a solution of lithium methoxide dissolved in alcohol, and the alcohol may be a C1-C4 lower alcohol. In particular, methanol can be preferably used.

The concentration of the lithium methoxide solution is not particularly limited, but a lithium methoxide solution having a concentration of 5 to 20% (w/w), more preferably 8 to 12% (w/w) may be preferably used.

The stirring in step (f) is preferably carried out at 100 ~ 500 rpm, more preferably, may be stirred at 250 ~ 350 rpm.

When the stirring speed is performed less than the above range, a problem of poor reactivity may occur, and if it exceeds the above range, the desired effect does not increase, and it is not preferable because it may strain the stirrer.

Agitation in step (f) may be performed using a magnetic bar.

The stirring time in step (f) may be carried out for 0.1 to 4 hours, preferably for 1 to 2.5 hours.

Hereinafter, preferred examples are presented to help the understanding of the present invention, but the following examples are merely illustrative of the present invention, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present invention, It goes without saying that such changes and modifications fall within the scope of the appended claims.

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

In a reactor equipped with a stirring device, a condenser and a thermometer, 79.57 g of ammonium fluoride and 600 g of butyl acetate, which were purified from water under a nitrogen atmosphere, were added at room temperature. While stirring the mixture, 100 g of bis(dichlorosulfonyl)imide was slowly added thereto, and then the temperature was raised to 80° C. and reacted for 2 hours.

The temperature was cooled to 60° C. without removing waste solids from the reactant, and nitrogen gas bubbling was performed. The pH of the flying gas was checked using a pH paper at 5 minute intervals (initial pH about 3), and nitrogen gas bubbling was stopped when the pH reached 7. The temperature of the reaction was cooled to below 10° C. and filtered. 25.50 g of lithium hydroxide hydrate was added to the filtered ammonium bis(fluorosulfonyl)imide filtrate and stirred. Then, the reaction was terminated after proceeding the reaction at less than 5 ℃ for 4 hours.

After adding 74.97 g of distilled water and stirring, the layers were separated to remove the distilled water layer. After adding 22.49 g of distilled water again and stirring, the layers were 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 under vacuum conditions at 51° C. until crystals were precipitated.

Next, 208.31 g of toluene was added, filtered to obtain a solid, and vacuum dried to obtain a bis(fluorosulfonyl)imide lithium salt.

43.34 g of the bis(fluorosulfonyl)imide lithium salt obtained above was added to the reactor together with 100 ml of toluene as an antisolvent.

0.4 ml of a 10% (w/w) methanol solution of lithium methoxide was added to the reactor, and stirred at 300 rpm for 2 hours using a Mechanical Overhead Stirrer.

After the stirring was completed, the crystals obtained by filtration were dried to prepare 39.43 g of purified bis(fluorosulfonyl)imide lithium salt.

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

In a reactor equipped with a stirring device, a condenser and a thermometer, 79.57 g of ammonium fluoride and 600 g of butyl acetate, which were purified from water under a nitrogen atmosphere, were added at room temperature. While stirring the mixture, 100 g of bis(dichlorosulfonyl)imide was slowly added thereto, and then the temperature was raised to 80° C. and reacted for 2 hours.

The reactant was cooled to 10° C. or less and then filtered to remove waste solids.

After raising the temperature of the filtered filtrate to 60°C, nitrogen gas bubbling was performed. The pH of the flying gas was checked using a pH paper at 5 minute intervals (initial pH about 3), and nitrogen gas bubbling was stopped when the pH reached 7. The temperature of the reaction was cooled to below 10° C. and filtered.

25.50 g of lithium hydroxide hydrate was added to the filtered ammonium bis(fluorosulfonyl)imide filtrate and stirred. Then, the reaction was terminated after proceeding the reaction at less than 5 ℃ for 4 hours.

After adding 74.97 g of distilled water and stirring, the layers were separated to remove the distilled water layer. After adding 22.49 g of distilled water again and stirring, the layers were 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 under vacuum conditions at 51° C. until crystals were precipitated.

Next, 208.31 g of toluene was added, filtered to obtain a solid, and vacuum dried to obtain a bis(fluorosulfonyl)imide lithium salt.

43.34 g of the bis(fluorosulfonyl)imide lithium salt obtained above was added to the reactor together with 100 ml of toluene as an antisolvent.

4 ml of a 10% (w/w) methanol solution of lithium methoxide was added to the reactor, and stirred at 300 rpm for 2 hours using a Mechanical Overhead Stirrer.

After the stirring was completed, the crystals obtained by filtration were dried to prepare a purified bis(fluorosulfonyl)imide lithium salt.

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

Purification was carried out in the same manner as in Example 2, except that 0.04 ml of lithium methoxide methanol solution was added instead of 0.4 ml of lithium methoxide in Example 2 to prepare a purified lithium bis(fluorosulfonyl)imide salt.

Example 4: Preparation of bis(fluorosulfonyl)imide lithium salt

Purification was performed in the same manner as in Example 2, except that a magnetic bar was used when stirring at 300 rpm in Example 2 to prepare a purified lithium bis(fluorosulfonyl)imide salt.

Example 5: Preparation of bis(fluorosulfonyl)imide lithium salt

Purification was carried out in the same manner as in Example 2, except that 0.04 g of lithium methoxide was used instead of 10% (w/w) lithium methoxide in methanol solution in Example 2, and the purified bis(fluorosulfonyl) already de lithium salt was prepared.

Comparative Example 1: Preparation of bis(fluorosulfonyl)imide lithium salt (no nitrogen gas bubbling)

A lithium salt of bis(fluorosulfonyl)imide was obtained in the same manner as in Example 2, except that nitrogen gas bubbling and purification by lithium methoxide were not performed during the preparation of bis(fluorosulfonyl)imide. did.

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

The same as in Example 2, except that nitrogen gas bubbling was not stopped when the pH became 7, nitrogen gas bubbling was stopped when the pH became 4, and purification with lithium methoxide was not performed. A lithium salt of bis(fluorosulfonyl)imide was obtained by this method.

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

The same method as in Example 2, except that nitrogen gas bubbling was not stopped when the pH became 7, nitrogen gas bubbling was stopped at the pH 10, and purification with lithium methoxide was not performed. bis(fluorosulfonyl)imide lithium salt was obtained.

Test Example 1: Measurement of Concentration of Fluoride Anion (F-) in Lithium Salt of Bis(fluorosulfonyl)imide

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

measurement sample State of the reaction solution containing bis(fluorosulfonyl)imide lithium salt Fluoride Anion (F ^- ) Concentration (ppm) Comparative Example 1 No nitrogen gas bubbling and lithium methoxide purification 411.6 Comparative Example 2 With nitrogen gas bubbling (stopped at pH 4) and without lithium methoxide purification 293.6 Comparative Example 3 With nitrogen gas bubbling (stopped at pH 10) and without lithium methoxide purification 471.1 Example 1 Nitrogen gas bubbling (stopped at pH 7) and lithium methoxide purification 1.1 Example 2 Nitrogen gas bubbling (stopped at pH 7) and lithium methoxide purification 2.3

As shown in Table 1 above, in the case of the bis(fluorosulfonyl)imide lithium salts of Examples 1 and 2, which were sufficiently removed by nitrogen gas bubbling and purified using lithium methoxide, In the final process, undesirable acids do not participate much in the reaction, and by repurifying using lithium methoxide, the fluorine anion (F) compared to the bis(fluorosulfonyl)imide lithium salt prepared in Comparative Examples 1 to 3 ^It was confirmed that the content of - ) was significantly reduced.

Test Example 2: Acidity analysis of bis(fluorosulfonyl)imide lithium salt

The acidity of the bis(fluorosulfonyl)imide lithium salt prepared in Examples 1 to 5 and Comparative Example 1 was measured by a dynamic u titration method using a potentiometric titrator (888 Titrando) and an LCO NaOH method with 0.02N NaOH, The results are shown in Table 1 below.

In addition, the turbidity of the bis(fluorosulfonyl)imide lithium salt prepared in Examples 1 to 5 and Comparative Example 1 was measured by diluting 5 g of the bis(fluorosulfonyl)imide lithium salt in 45 g of ethylmethyl carbonate to obtain a 2100an turbidimeter. ) and the results are shown in Table 2 below.

sample Acidity analysis result turbidity Example 1 10ppm 0.66 Example 2 4ppm 1.12 Example 3 23ppm 1.15 Example 4 4ppm 0.99 Example 5 32ppm 1.07 Comparative Example 1 134ppm 2.91

As shown in Table 2, the bis(fluorosulfonyl)imide lithium salts prepared by the methods of Examples 1 to 5 of the present invention were bis(fluorine) of Comparative Example 1 in which bubbling and lithium methoxide purification were not performed. It can be seen that the sulfonyl)imide lithium salt has significantly lower acidity and turbidity compared to the lithium salt. Therefore, these results indicate that the method of the present invention is very effective for the purification of the bis(fluorosulfonyl)imide lithium salt.

Test Example 3: Test of change with time of bis(fluorosulfonyl)imide lithium salt

The bis(fluorosulfonyl)imide lithium salt prepared in Examples 1 to 5 and Comparative Example 1 was placed in an airtight container, stored in a desiccator, maintained at 50% humidity, and the acidity level after 1 month was measured by the dynamic u titration method using the LCO NaOH method using a potentiometric titrator (888 Titrando) and 0.02N NaOH, and the results are shown in Table 3 below.

sample Result of acidity analysis before storage Acidity analysis result after storage for 1 month Example 1 10ppm 21ppm Example 2 4ppm 10ppm Example 3 23ppm 56ppm Example 4 4ppm 9ppm Example 5 32ppm 69ppm Comparative Example 1 134ppm 561ppm

As shown in Table 2, the bis(fluorosulfonyl)imide lithium salts prepared by the method of Examples 1 to 5 were bis(fluorosulfonyl) of Comparative Example 1 in which bubbling and lithium methoxide purification were not performed. It can be seen that the decomposition rate is significantly lower than that of the lithium imide salt.

Claims (3)

(a) Bis(chlorosulfonyl)imide and NH ₄ F(HF)n (n=0~10) under a nitrogen atmosphere were mixed with diethyl ether, diisopropyl ether, methyl-t-butyl ether, methyl acetate, acetic acid After reacting in one or more solvents selected from the group consisting of ethyl, propyl acetate, and butyl acetate, the reactant is cooled to 0-20° C. and filtered to remove waste solids to prepare ammonium bis (fluorosulfonyl) imide to do;
(b) heating the filtrate of step (a) to 50-70° C. and then bubbling until the pH of the gas blown by supplying nitrogen gas becomes 6-8;
(c) reacting the ammonium bis(fluorosulfonyl)imide with a lithium base;
(d) adding the lithium salt of bis(fluorosulfonyl)imide prepared in step (c) and an antisolvent to the reactor;
(e) adding lithium methoxide or lithium methoxide solution to the reactor and stirring; and
(f) filtering the solution stirred in step (e), and drying the filtrate;
The pH of the gas blown out in step (b) is measured using a pH paper,
In step (e), the lithium methoxide or lithium methoxide solution is added in an amount of 0.06 to 1.5 parts by weight based on lithium methoxide based on 100 parts by weight of the bis(fluorosulfonyl)imide lithium salt. A method for preparing a sulfonyl)imide lithium salt. According to claim 1,
As the solvent in step (c), at least one selected from the group consisting of diethyl ether, diisopropyl ether, methyl-t-butyl ether, methyl acetate, ethyl acetate, propyl acetate, and butyl acetate is used A method for producing a bis (fluorosulfonyl) imide lithium salt comprising: According to claim 1,
The lithium base of step (c) is lithium hydroxide (LiOH), lithium hydroxide hydrate (LiOH·H ₂ O), lithium carbonate (Li ₂ CO ₃ ), lithium hydrogen carbonate (LiHCO ₃ ), lithium chloride (LiCl), acetic acid Lithium (LiCH ₃ COO) and lithium oxalate (Li ₂ C ₂ O ₄ ) A method for producing a bis(fluorosulfonyl)imide lithium salt, characterized in that at least one selected from the group consisting of.