KR102007476B1 - New purification method of bis(fluorosulfonyl)imide lithium salt) - Google Patents

Abstract

The present invention provides a purification method of a bis(fluorosulfonyl)imide lithium salt, comprising steps of: (a) adding the bis(fluorosulfonyl)imide lithium salt and an antisolvent to a reactor; (b) putting lithium methoxide or a lithium methoxide solution to the reactor and stirring the same; and (c) filtering a solution stirred in the step (b) and drying a filtrate. The method for purifying the bis(fluorosulfonyl)imide lithium salt of the present invention provides an effect of effectively removing impurities contained in the bis(fluorosulfonyl)imide lithium salt by a simple method.

Description

New purification method of bis (fluorosulfonyl) imide lithium salt}

The present invention relates to a novel process for purifying bis (fluorosulfonyl) imide lithium salt (LiFSI).

BACKGROUND 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 have been developed.

Lithium-ion batteries include at least a cathode, a cathode, 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 salts include lithium hexafluorophosphate (LiPF ₆ ), which has excellent performance but has the disadvantage of being decomposed in the form of hydrofluoric acid gas.

In order 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 degradation and are more stable to hydrolysis than LiPF ₆ .

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

Due to the high specific gravity of lithium salts in the cost structure of lithium-ion secondary batteries, researches on a method of producing bis (fluorosulfonyl) imide lithium salts of high purity economically have been actively conducted.

Examples of conventionally known methods for preparing bis (fluorosulfonyl) imide lithium salts include the following methods:

As described in the above scheme, the bis (chlorosulfonyl) imide, a starting material, is reacted with NH ₄ F (HF) n (n = 1-10), a fluorination reagent, to form ammonium bis (fluorosulfonate) as an intermediate product. It is characterized by producing a polyyl) imide salt.

The ammonium fluoride (NH ₄ F (HF) n) is a relatively safe and useful source of fluorine for use in industrial mass synthesis, but the excess ammonium fluoride and ammonium chloride remaining after the fluorination reaction is bis (fluorosulfonate). Phenyl) imide Lithium salt Increases the acidity, turbidity, chlorine ion concentration and sulfonic acid anion concentration of the final product, not only to reduce the quality of the product but also to be a major cause of battery life.

In addition, the acidity is increased in the process of removing the ammonium salt and introducing lithium ions, which not only leads to a decrease in quality but also lowers the purity of lithium hydroxide, thereby lowering the economics of the synthesis.

In other words, in the above reaction, the following impurities are generated:

In addition, in the following reactions, the following impurities occur:

Therefore, in preparing 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 have made diligent efforts to solve the above-mentioned problems of the prior art and, as a result, can effectively remove impurities generated in the manufacturing process and contained in bis (fluorosulfonyl) imide lithium salt (LiFSI) by a simple method. A novel purification method that can be found has been completed to complete the present invention.

Therefore, an object of the present invention is to provide a novel method for preparing a bis (fluorosulfonyl) imide lithium salt which can effectively remove impurities contained in the bis (fluorosulfonyl) imide lithium salt by a simple method. do.

In order to achieve the above object,

The present invention,

(a) adding bis (fluorosulfonyl) imide lithium salt and antisolvent to the reactor;

(b) adding a lithium methoxide or lithium methoxide solution to the reactor and stirring the solution; And

(c) filtering the solution stirred in step (b), and drying the filtrate; provides a method for purifying bis (fluorosulfonyl) imide lithium salt comprising a.

The purification method of the bis (fluorosulfonyl) imide lithium salt of the present invention provides the effect that the impurities contained in the bis (fluorosulfonyl) imide lithium salt can be effectively removed by a simple method.

Hereinafter, the present invention will be described in detail.

The present invention,

(a) adding bis (fluorosulfonyl) imide lithium salt and antisolvent to the reactor;

(b) adding a lithium methoxide or lithium methoxide solution to the reactor and stirring the solution; And

(c) filtering the solution stirred in step (b) and drying the filtrate; and relates to a method for purifying a bis (fluorosulfonyl) imide lithium salt comprising a.

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

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

The antisolvent in step (a) may be one or more selected from the group consisting of toluene, hexane, heptane, chloroform, dichloromethane and the like.

In step (b), 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 100 parts by weight of the bis (fluorosulfonyl) imide lithium salt. May be added in portions. When included in the above-described range, it is difficult to obtain the desired effect, and when included in the above-described range, it is not preferable because lithium methoxide remains.

In step (b), the lithium methoxide solution may be a solution in which lithium methoxide is dissolved in alcohol, and the alcohol may be C1 to 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 of 5 to 20% (w / w), more preferably 8 to 12% (w / w), may be preferably used.

In the step (c), the stirring is preferably carried out at 100 to 500 rpm, more preferably, it may be stirred at 250 to 350 rpm.

If the stirring speed is carried out below the above-mentioned range may cause a problem of poor reactivity, if it exceeds the above-mentioned range, the desired effect does not increase, it is not preferable because it may be a bunch on the stirrer.

In the step (c), the stirring may be performed using a magnetic bar.

In the step (c), the stirring time may be performed for 0.1 to 4 hours, and preferably for 1 to 2.5 hours.

In the purification method of the present invention, the bis (fluorosulfonyl) imide lithium salt in step (a), for example, may be prepared by a method comprising the following (a) and (b) step. However, it is not limited to this method.

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

(B) reacting the ammonium bis (fluorosulfonyl) imide with a lithium base to obtain a bis (fluorosulfonyl) imide lithium salt; it may be prepared by a method comprising a.

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) to be represented by Scheme 1 below. Can:

Scheme 1

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

The reaction may be carried out in a nitrogen atmosphere.

After performing nitrogen gas bubbling in the step (A), the crude compound can be obtained by filtration and concentration. In this case, recrystallization may be performed by adding methylene chloride and the like to the crude compound together with a solvent.

Step (b) may be carried out with Scheme 2 below:

Scheme 2

The solvent in the step (b) may include diethyl ether, diisopropyl ether, methyl t-butyl ether, methyl acetate, ethyl acetate, propyl acetate, butyl acetate isobutyl propionate, isobutyl acetate, and the like. These may be used alone or in combination of two or more thereof. Among these, butyl acetate can be used more preferably.

In the step (b), the lithium base includes lithium hydroxide (LiOH), lithium hydroxide hydrate (LiOHH ₂ O), lithium carbonate (Li ₂ CO ₃ ), lithium carbonate (LiHCO ₃ ), lithium chloride (LiCl), One or more selected from the group consisting of lithium acetate (LiCH ₃ COO), lithium oxalate (Li ₂ C ₂ O ₄ ), and the like may be used. Among these, lithium hydroxide hydrate can be preferably used.

After the reactants are mixed in step (b), nitrogen gas bubbling may be further performed.

The washing of the compound obtained in step (b), filtration concentration, recrystallization, etc. may be further carried out in a conventional manner.

Hereinafter, preferred examples are provided to help the understanding of the present invention, but the following examples are merely illustrative of the present invention, and various changes and modifications within the scope and spirit of the present invention are apparent to those skilled in the art. It is natural that such changes and modifications fall within the scope of the appended claims.

Preparation Example 1 Preparation of Bis (Fluorosulfonyl) imide Lithium Salt

Into a reactor equipped with a stirrer, a condenser and a thermometer, 51.91 g of anhydrous ammonium fluoride and 1000 g of butyl acetate were purified at room temperature under a nitrogen atmosphere. While stirring the mixture, 100 g of bis (dichlorosulfonyl) imide was slowly added thereto, followed by reaction for 2 hours while raising the temperature to 70 ° C. After completion of the reaction, the temperature of the reaction was lowered to room temperature, filtered and concentrated to obtain 83.32 g of crude compound.

222.20 g of butyl acetate was added to the crude compound, followed by stirring. Then, 843.16 g of methylene chloride was added and recrystallized. After filtering, the solid was vacuum dried for at least 2 hours to obtain 74.06 g of ammonium bis (fluorosulfonyl) imide. (Yield: 80%).

74.06 g of the ammonium bis (fluorosulfonyl) imide and 444.39 g of butyl acetate were added to Reactor 1 and stirred. 41.96 g of LiOHH ₂ O and 220.63 g of butyl acetate were added to Reactor 2 and stirred. The solution of Reactor 1 was slowly added dropwise to Reactor 2. After completion of the reaction, the reaction was cooled to room temperature, filtered and concentrated.

200 g of methylene chloride was added to the concentrate and stirred at room temperature for 20 minutes. The resulting solid was filtered and dried under vacuum to give 43.34 g of bis (fluorosulfonyl) imide lithium salt (yield: 62%).

Example 1 Purification of Bis (Fluorosulfonyl) imide Lithium Salt

43.34 g of the bis (fluorosulfonyl) imide lithium salt obtained in Preparation Example 1 was added to the reactor together with 100 ml of toluene as an antisolvent.

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

After stirring was complete, filtered crystals were dried to prepare 39.43 g of purified bis (fluorosulfonyl) imide lithium salt.

Example 2: Purification of Bis (Fluorosulfonyl) imide Lithium Salt

In Example 1, except that 4 ml of lithium methoxide methanol solution was added instead of 0.4 ml, the purification was carried out in the same manner as in Example 1, to obtain 42.1 g of purified bis (fluorosulfonyl) imide lithium salt. It was.

Example 3: Purification of Bis (Fluorosulfonyl) imide Lithium Salt

41.9 g of purified bis (fluorosulfonyl) imide lithium salt was prepared in the same manner as in Example 1, except that 0.04 ml was added instead of 0.4 ml of the lithium methoxide methanol solution in Example 1. It was.

Example 4 Purification of Bis (Fluorosulfonyl) imide Lithium Salt

41.6 g of purified bis (fluorosulfonyl) imide lithium salt was prepared in the same manner as in Example 1, except that the magnetic bar was used when stirring at 300 rpm in Example 1.

Example 5: Purification of Bis (Fluorosulfonyl) imide Lithium Salt

Except for using 0.04 g of lithium methoxide in place of 10% (w / w) lithium methoxide methanol solution in Example 1, 42.03 g of purified bis (fluorosulfonate) was purified in the same manner as in Example 1. Phonyl) imide lithium salt was prepared.

Comparative Example 1: Bis (Fluorosulfonyl) imide Lithium Salt

The bis (fluorosulfonyl) imide lithium salt obtained in Preparation Example 1 was used as a comparative example.

Test Example 1 Acidity Analysis of Bis (Fluorosulfonyl) imide Lithium Salt

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

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

sample PH analysis result Turbidity Example 1 12 ppm 0.78 Example 2 5 ppm 1.27 Example 3 28 ppm 1.24 Example 4 56 ppm 1.09 Example 5 36 ppm 1.12 Comparative Example 1 134 ppm 2.91

As shown in Table 1, the bis (fluorosulfonyl) imide lithium salts prepared by the methods of Examples 1 to 5 of the present invention are the bis (fluorosulfonyl) imide lithium of Comparative Example 1 without purification. It can be seen that it has a significantly lower acidity and turbidity compared to salts.

Therefore, these results indicate that the method of the present invention is very effective for the purification of bis (fluorosulfonyl) imide lithium salts.

Test Example 2 Test of Change over Time of Bis (Fluorosulfonyl) imide Lithium Salt

After containing the bis (fluorosulfonyl) imide lithium salts prepared in Examples 1 to 5 and Comparative Example 1 in a sealed container, stored in a desiccator, and maintaining a humidity of 50%, the acidity after 1 month Was measured by the dynamic u titration method by the LCO NaOH method using a potentiometric titrator (888 Titrando) and 0.02N NaOH, and the results are shown in Table 2 below.

sample Results of pH analysis before storage Results of pH analysis after 1 month storage Example 1 12 ppm 23 ppm Example 2 5 ppm 11 ppm Example 3 28 ppm 59 ppm Example 4 56 ppm 89 ppm Example 5 36 ppm 72 ppm Comparative Example 1 134 ppm 561 ppm

As shown in Table 2, the bis (fluorosulfonyl) imide lithium salts prepared by the method of Examples 1 to 3 were compared with the bis (fluorosulfonyl) imide lithium salt of Comparative Example 1, which was not purified. It can be seen that the decomposition rate is significantly lower.

Claims (8)

(a) adding bis (fluorosulfonyl) imide lithium salt and antisolvent to the reactor;
(b) adding a lithium methoxide or lithium methoxide solution to the reactor and stirring the solution; And
(c) filtering the solution stirred in step (b) and drying the filtrate;
In step (b), the lithium methoxide or lithium methoxide solution is based on 100 parts by weight of the bis (fluorosulfonyl) imide lithium salt, based on lithium methoxide, based on 0.06 to 1.5 parts by weight of bis (fluorosulfur). Purification method of the fonyl) imide lithium salt. The method of claim 1,
The antisolvent in step (a) is a method for purifying bis (fluorosulfonyl) imide lithium salt, which is added at 50 to 500 parts by weight based on 100 parts by weight of the bis (fluorosulfonyl) imide lithium salt. . The method of claim 1,
The antisolvent in step (a) is at least one selected from the group consisting of toluene, hexane, heptane, chloroform, and dichloromethane, the method for purifying bis (fluorosulfonyl) imide lithium salt. delete The method of claim 1,
The lithium methoxide solution in step (b) is a method for purifying bis (fluorosulfonyl) imide lithium salt, characterized in that the solution of lithium methoxide dissolved in alcohol. The method of claim 5,
The alcohol is a purification method of bis (fluorosulfonyl) imide lithium salt, characterized in that methanol. The method of claim 1,
In the step (c), the agitation is a method for purifying bis (fluorosulfonyl) imide lithium salt, which is performed at 100 to 500 rpm. The method of claim 1,
In step (a), the bis (fluorosulfonyl) imide lithium salt is
(A) reacting bis (chlorosulfonyl) imide with NH ₄ F (HF) n (n = 0-10) to prepare ammonium bis (fluorosulfonyl) imide; And
(B) reacting the ammonium bis (fluorosulfonyl) imide with a lithium base to obtain a bis (fluorosulfonyl) imide lithium salt; bis (fluorosulfonyl), characterized in that it was prepared by a method including Purification method of an imide lithium salt.