KR101982603B1 - Method for producing bis (fluorosulfonyl) imide lithium salt (LiFSI) with reduced fluorine anion content (2) - 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); and (b) conducting a reaction of the ammonium bis(fluorosulfonyl)imide with a lithium base, wherein at least one of steps (a) and (b), after reaction, conducts a process of removing fluorine anion by adding tetraalkyl orthosilicate to a reacting solution.

Description

Method for producing bis (fluorosulfonyl) imide lithium salt (LiFSI) with reduced fluorine anion content (2) 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, 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) as a fluorination reagent, fluorine anion F-) is generated, which has a disadvantage in that it acts as a cause for lowering the quality of the product.

Various adsorbents are used to remove the fluorine anion (F-). However, since most of the adsorbents are solid adsorbents, they increase the process in actual use and generate other impurities, which is inefficient.

Therefore, there is a need for research on a method for efficiently removing fluorine anions generated in the manufacturing process.

Korean Patent Publication No. 10-2013-0140216

As a result of intensive efforts to solve the above problems of the prior art, the present inventors have found that the fluorine anion (F-) generated in the course of the production of a bis (fluorosulfonyl) imide lithium salt is highly efficient And the present invention has been completed.

Therefore, the present invention relates to a process for producing lithium bis (fluorosulfonyl) imide lithium salt which can remove fluorine anion (F-) generated in the course of the production of bis (fluorosulfonyl) imide lithium salt very efficiently using a novel adsorbent It is an object of the present invention to provide a method for producing a 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) reacting the ammonium bis (fluorosulfonyl) imide with a lithium base,

Wherein at least one of the steps (a) and (b) is carried out by adding a tetraalkyl orthosilicate to the reaction solution after the reaction to remove the fluorine anion, Sulfonyl) imide lithium salt.

As an embodiment of the present invention,

(1) after the reaction of step (a), adding tetraalkyl orthosilicate to the reaction solution and performing stirring;

(2) adding and stirring tetraalkyl orthosilicate to the reaction solution after the reaction and the washing step of step (b);

It may have a feature of performing all of the steps (1) and (2).

The process for producing the bis (fluorosulfonyl) imide lithium salt of the present invention is characterized in that a fluorine anion (F-) generated in the process of producing a bis (fluorosulfonyl) imide lithium salt by using a novel tetraalkyl orthosilicate adsorbent It provides a very efficient removal effect.

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) reacting the ammonium bis (fluorosulfonyl) imide with a lithium base,

Wherein at least one of the steps (a) and (b) is carried out by adding a tetraalkyl orthosilicate to the reaction solution after the reaction to remove the fluorine anion, Sulfonyl) imide lithium salt.

A variety of adsorbents have been used to remove fluorine anions (F < ^- >) during the preparation of bis (fluorosulfonyl) imide lithium salts, and most of them are solid adsorbents. However, the solid adsorbent has a disadvantage of increasing the process in actual use and generating other impurities, which is inefficient. In addition, known liquid adsorbents have a problem that the effect of removing fluorine anions is insufficient and it is not easy to separate them from the reaction liquid.

Tetraalkyl orthosilicate used in the present invention has a chemical reaction that the adsorption power of Si and F is much greater than the adsorption power of Si and O as shown in the following reaction formula 1, The fluorine anion can be removed very efficiently during the production of the bis (fluorosulfonyl) imide lithium salt because it forms a strong bond with the fluorine anion and is easily removed.

Specifically, when a reagent such as tetramethyl orthosilicate is used as in the following reaction formula, the concentration of the fluorine anion produced in the LiFSI production process can be significantly reduced.

[Reaction Scheme 1]

In the above, "alkyl" may be an alkyl group having 1 to 5 carbon atoms, and may be methyl, ethyl, propyl, butyl, and the like.

In the present invention, the tetraalkyl orthosilicate may be added in an amount of 0.001 to 0.01 equivalent per equivalent of bis (chlorosulfonyl) imide, preferably 0.001 to 0.008 equivalent, more preferably 0.001 to 0.005 / RTI > When it is included in the above-mentioned range, fluorine anions can be sufficiently removed, which is preferable.

In one embodiment of the present invention, the step of removing the fluorine anion

(1) after the reaction of step (a), adding tetraalkyl orthosilicate to the reaction solution and performing stirring;

(2) after the reaction and the washing step of the step (b), adding tetraalkyl orthosilicate to the reaction solution and performing stirring;

May be performed by performing all the steps (1) and (2) above.

In the case of performing the above step (1), after completion of the reaction, a step of bubbling may be further performed by supplying nitrogen gas to the reactant until the flue gas has a pH of 6-8.

The nitrogen gas bubbling may be effected by supplying nitrogen gas to the reactant 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.

The pH of the gas discharged in the step (1) may be measured using a pH paper, but is not limited to this method and may be performed by a method known in the art.

The step (2) is preferably carried out after the reaction product of step (b) is first concentrated. This is because the water content in the product is the lowest after the first concentration, and when the reaction proceeds at this time, the probability of the Si compound binding with moisture is lowest. Thus, in this case, the side reaction is the least progressed and provides the desired result.

After completion of the reaction in the step (2), a step of secondarily concentrating the reaction product may be further performed. At this time, it is also possible to carry out secondary concentration while supplying nitrogen gas to the reactant.

In the production process of the present invention, the tetraalkyl orthosilicate may be at least one selected from tetramethyl orthosilicate and tetraethyl orthosilicate.

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

(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 2]

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 (b) may be carried out in accordance with the following reaction scheme 3:

[Reaction Scheme 3]

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

A lithium base in the step (b) 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), (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.

The washing, filtration, concentration, recrystallization, and the like of the obtained compound in the step (b) 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 a reactor equipped with a stirrer, a condenser and a thermometer, 79.6 g of ammonium fluoride and 600 g of butyl acetate purified in 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 the mixture was heated to 80 ° C and reacted for 2 hours. After completion of the reaction, cool to 10 ° C or less, and then filter.

To ammonium bis (fluorosulfonyl) obtained above, 25.04 g of lithium hydroxide hydrate was added to the reactor 2 and stirred. After completion of the reaction, DIW (74.97 g, 22.49 g) was washed twice, filtered, and first concentrated.

The primary concentrate was placed in a 1000 mL 3-neck RBF, 0.75 g of TMOS (Tetramethyl orthosilicate, manufactured by Qingdao) was added, and the mixture was stirred at room temperature for 10 minutes. The reaction mixture was kept at an internal temperature of 50 캜 and concentrated under reduced pressure (second concentration).

Toluene was added to the second concentrate, and the mixture was stirred at 30 ° C for 10 minutes. The resulting solid was filtered and dried under vacuum to give 30.05 g of bis (fluorosulfonyl) imide lithium salt (Yield: 36.7%).

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

29.98 g of bis (fluorosulfonyl) imide lithium salt was obtained (yield: 36.6%) in the same manner as in Example 1, except that 0.375 g of TMOS was used instead of 0.75 g of TMOS (tetramethyl orthosilicate).

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

31.05 g of bis (fluorosulfonyl) imide lithium salt was obtained (yield: 37.9%) in the same manner as in Example 1, except that TMOS (0.15 g) was used instead of 0.75 g of TMOS (tetramethyl orthosilicate).

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

In a reactor equipped with a stirrer, a condenser and a thermometer, 79.6 g of ammonium fluoride and 600 g of butyl acetate purified in 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 the mixture was heated to 80 ° C and reacted for 2 hours. After completion of the reaction, the mixture was cooled to 60 DEG C and 3.63 g of TMOS (Tetramethyl orthosilicate, manufactured by Qingdao) was added and stirred for 10 minutes.

Nitrogen gas was supplied to the reaction solution for bubbling for 30 minutes. Next, the temperature of the reaction product was cooled to 10 DEG C or less and filtered to obtain a filtrate.

The ammonium bis (fluorosulfonyl) imide filtrate obtained above and 25.04 g of lithium hydroxide hydrate were charged into the reactor 2 and stirred. Then, nitrogen gas bubbling was performed, and the vacuum reaction was conducted for 4 hours at a temperature lower than 5 캜, and then 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 then the layer was separated to remove the distilled water layer. The obtained organic layer was filtered and concentrated to obtain a crude compound. Nitrogen gas bubbling was performed, and the mixture was stirred until crystals precipitated under a vacuum of 50 to 55 캜.

Next, 309.96 g of toluene was added thereto, and the solid was filtered to obtain 31.78 g of bis (fluorosulfonyl) imide lithium salt (yield: 38.8%).

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

30.32 g of bis (fluorosulfonyl) imide lithium salt was obtained in the same manner as in Example 4, except that 7.25 g of TMOS was used instead of 3.63 g of TMOS (tetramethyl orthosilicate) (yield: 37.0%).

Comparative Example 1: Preparation of bis (fluorosulfonyl) imide lithium salt

31.87 g of bis (fluorosulfonyl) imide lithium salt was obtained (yield: 39.0%) in the same manner as in Example 1 except that TMOS (tetramethyl orthosilicate) was not used.

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 to 5 and Comparative Example 1 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 TMOS availability and usage Fluorine anion (F ^- ) concentration (ppm) Comparative Example 1 Disable TMOS 221.9 Example 1 Using TMOS 0.75 g in step (b) 9.9 Example 2 (b), use 0.375 g of TMOS 20.6 Example 3 Use 0.15 g of TMOS in step (b) 194.9 Example 4 3.63 g of TMOS is used in step (a) 130.7 Example 5 Using TMOS 7.25 g in step (a) 16.6

As shown in Table 1, in the case where the bis (fluorosulfonyl) imide lithium salt of 1 to 5 in which the fluorine anion was removed by using TMOS was significantly reduced as compared with Comparative Example 1 in which the TMOS treatment was not performed Fluorine anion concentration.

In particular, it has been confirmed that the content of fluorine anions is inversely proportional to the amount of TMOS used in both steps (a) and (b) in which TMOS treatment is performed.

Therefore, this fact indicates that TMOS can very effectively remove fluorine anions.

Claims (9)

(a) reacting bis (chlorosulfonyl) imide with NH ₄ F (HF) n (n = 0 to 10) to prepare ammonium bis (fluorosulfonyl) imide; And
(b) reacting the ammonium bis (fluorosulfonyl) imide with a lithium base,
After the step (b), a tetraalkyl orthosilicate is added to the reaction solution to remove the fluorine anion,
Wherein the tetraalkyl orthosilicate is added in an amount of 0.375 to 0.75 g per 100 g of bis (chlorosulfonyl) imide. delete delete delete The method according to claim 1,
Wherein the addition of the tetraalkyl orthosilicate is carried out after first concentrating the reaction product of the step (b). 6. The method of claim 5,
(Fluorosulfonyl) imide lithium salt is further subjected to a step of secondarily concentrating the reaction product after the termination of the tetraalkyl orthosilicate addition reaction. The method according to claim 1,
Wherein the tetraalkyl orthosilicate is at least one selected from the group consisting of tetramethyl orthosilicate and tetraethyl orthosilicate. 2. A process for producing a bis (fluorosulfonyl) imide lithium salt according to claim 1, The method according to claim 1,
The reaction in steps (a) and (b) is carried out in a solution, and each of the solvents is independently selected from the group consisting of diethyl ether, diisopropyl ether, methyl-t-butyl ether, methyl acetate, ethyl acetate, (Fluorosulfonyl) imide lithium salt of the general formula (I), wherein R < 1 > The method according to claim 1,
The lithium base in step (b) may be lithium hydroxide (LiOH), lithium hydroxide hydrate (LiOH.H ₂ O), lithium carbonate (Li ₂ CO ₃ ), lithium hydrogen carbonate (LiHCO ₃ ), lithium chloride (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 ).