KR102688867B1 - Process for Preparing Lithium Imidazolate Salt and Intermediate Therefor - Google Patents

Abstract

The present invention relates to a method for producing lithium imidazolate salt and intermediates used therein. According to the production method of the present invention, high purity lithium imidazolate salt can be produced efficiently and economically.

Description

Method for producing lithium imidazolate salt and intermediate therefor {Process for Preparing Lithium Imidazolate Salt and Intermediate Therefor}

The present invention relates to a method for producing lithium imidazolate salt and an intermediate therefor, and more specifically, to a method for efficiently and economically producing high purity lithium imidazolate salt and an intermediate used therefor.

Market demand for secondary batteries has been rapidly increasing recently, and in particular, as portable electronic devices such as mobile phones, laptops, and PCs are rapidly spreading, demand for lightweight and high-performance batteries that power them continues to increase. In addition, in addition to small-sized applications, it is expected to be used as a secondary battery for automobiles, and among these, lithium secondary batteries are attracting attention as high-performance batteries that meet the needs of this market.

A secondary battery consists of a positive electrode material, a negative electrode material, a separator, and an electrolyte. Among these, the electrolyte acts as a moving medium that quickly moves metal ions from the anode to the cathode during charging and from the cathode to the anode during discharging.

Lithium hexafluorophosphate (LiPF ₆ ) is commonly used as an electrolyte. However, lithium hexafluorophosphate (LiPF ₆ ) reacts with a trace amount of moisture and decomposes into hydrogen fluoride gas, which has the problem of low thermal stability. Accordingly, as a lithium salt to replace lithium hexafluorophosphate (LiPF ₆ ), lithium 2-trifluoromethyl-4,5-dicyanoimidazole (LiTDI) is very stable in moisture and shows reliable performance in various electrodes. and lithium imidazolate salts such as lithium 2-pentafluoroethyl-4,5-dicyanoimidazole (LiPDI) have been developed.

These lithium imidazolate salts contain fewer fluorine atoms than lithium hexafluorophosphate and have the advantage of containing a strong carbon-fluorine bond instead of the weak phosphorus-fluorine bond of lithium hexafluorophosphate. Additionally, these salts have very good conductivity (about 6 mS/cm), and the bond between the imidazolate anion and the lithium cation is very stable, so decomposition does not occur easily. In addition, the lithium imidazolate salt can be used as an additive to remove moisture from the electrolyte, showing excellent performance in improving the lifespan of the electrolyte.

In Korean Patent Publication No. 10-2014-0081868, diaminomaleonitrile and trifluoroacetic anhydride were reacted in dioxane under reflux, then excess water was added, and the obtained aqueous phase was extracted with ethyl acetate, A method of producing LiTDI is disclosed by extracting the organic phase with an aqueous lithium carbonate solution, separating the aqueous phase, and purifying it by treating it with activated charcoal. However, the above manufacturing method had a problem in that the purity of LiTDI was low and many purification steps were required after LiTDI was formed.

Therefore, there is an urgent need for the development of a method for efficiently and economically producing high-purity lithium imidazolate salt.

Republic of Korea Patent Publication No. 10-2014-0081868

The present inventors conducted extensive research to solve the above-mentioned problems in the production of lithium imidazolate salt, and as a result, 1H-imidazole-4,5-dicarbohydrate was obtained by reacting diaminomaleonitrile with an anhydride derivative. After forming the nitrile derivative, a small amount of water was added to the 1H-imidazole-4,5-dicarbonitrile derivative to obtain 1H-imidazole-4,5-dicarbonitrile derivative hydrate in crystal form, which was It was discovered that high-purity lithium imidazolate salt could be produced efficiently and economically through simple and easy purification, and the present invention was completed.

Therefore, the purpose of the present invention is to provide a method for efficiently and economically producing high purity lithium imidazolate salt.

Another object of the present invention is to provide an intermediate used in the above production method.

One embodiment of the present invention relates to a method for producing lithium imidazolate salt of the following formula (1), and the production method of the present invention is

(i) reacting a compound of Formula 2 below with a compound of Formula 3 below to obtain a compound of Formula 4 below;

(ii) adding water to the compound of formula 4 below to obtain a compound of formula 5 as a solid; and

(iii) reacting the compound of formula 5 below with lithium base.

[Formula 1]

[Formula 2]

[Formula 3]

[Formula 4]

[Formula 5]

In the above equation,

R is a C ₁ -C ₅ fluoroalkyl group substituted or unsubstituted with a C ₁ -C ₄ fluoroalkoxy group,

n is an integer from 1 to 2.

The fluoroalkoxy group of C ₁ -C ₄ used herein refers to a straight-chain or branched alkoxy group consisting of 1 to 4 carbon atoms substituted with one or more fluorines, and includes trifluoromethoxy, trifluoroethoxy, etc. Included but not limited to this.

As used herein, the fluoroalkyl group of C ₁ -C ₅ refers to a straight-chain or branched hydrocarbon having 1 to 5 carbon atoms substituted with one or more fluorines, for example, monofluoromethyl, difluoromethyl, triple Fluoromethyl, monofluoroethyl, difluoroethyl, trifluoroethyl, tetrafluoroethyl, pentafluoroethyl, monofluoropropyl, difluoropropyl, trifluoropropyl, tetrafluoropropyl, penta Fluoropropyl, heptafluoropropyl, monofluorobutyl, difluorobutyl, trifluorobutyl, tetrafluorobutyl, pentafluorobutyl, hexafluorobutyl, heptafluorobutyl, octafluorobutyl, nona Fluorobutyl, monofluoropentyl, difluoropentyl, trifluoropentyl, tetrafluoropentyl, pentafluoropentyl, hexafluoropentyl, heptafluoropentyl, octafluoropentyl, nonafluoropentyl, deca It includes, but is not limited to, fluoropentyl, undecafluoropentyl, etc.

In one embodiment of the invention, R is monofluoromethyl, difluoromethyl, trifluoromethyl, difluoroethyl, trifluoroethyl, tetrafluoroethyl, pentafluoroethyl, trifluoropropyl, Pentafluoropropyl, heptafluoropropyl, pentafluorobutyl, heptafluorobutyl, nonafluorobutyl, undecafluoropentyl, trifluoromethoxydifluoromethyl, trifluoromethoxydifluoroethyl, triple looromethoxytetrafluoroethyl or trifluoromethoxyhexafluoropropyl, and n may be 2.

Hereinafter, the production method of the present invention will be described in more detail with reference to Scheme 1 below. The method described in Scheme 1 below is only an example of a typically used method, and reaction reagents, reaction conditions, etc. may be changed depending on the case.

[Scheme 1]

Step 1: Synthesis of compound of formula 4

The compound of Formula 4 can be prepared by reacting the compound of Formula 2 with the compound of Formula 3.

The reaction is preferably carried out under reflux.

Dioxane, tetrahydrofuran, diethylene glycol, etc. may be used as the reaction solvent, and dioxane is particularly preferred.

A suitable reaction time is 6 hours or more, for example about 6 to 10 hours.

Step 2: Synthesis of compound of formula 5

The compound of formula 5 can be obtained by adding water to the compound of formula 4.

Specifically, the compound of Formula 5 can be obtained by adding 1 to 4 times the weight of water to the compound of Formula 4 dropwise and stirring the compound of Formula 2.

If the amount of water added is less than 1 times the weight of the compound of Formula 2, it may be difficult to form a hydrate, and if it is more than 4 times the amount of water added, the compound of Formula 4 may be dissolved in water.

The stirring time is preferably 12 hours or more, for example, about 12 to 24 hours.

The compound of formula 5 obtained in the above step is a crystalline solid that can be filtered and washed with water before being used in the preparation of the lithium imidazolate salt of formula 1.

The washed compound of Formula 5 can be purified using activated carbon.

Specifically, the washed compound of Formula 5 can be purified by dissolving it in a mixed solvent of methanol and water, adding activated carbon, stirring, and then filtering.

The compound of Formula 5 obtained in step (ii) has a purity of 99% or more.

_{In an} ±0.2, 14.2±0.2, 17.7±0.2, 20.2±0.2, 25.2±0.2, 26.1±0.2, 27.6±0.2, 28.2±0.2, 28.6±0.2 and 30.7±0.2. Romethyl)-1H-imidazole-4,5-dicarbonitrile dihydrate.

In addition to the X-ray diffraction peak, the compound of Formula 5 may additionally have weak intensity X-ray diffraction peaks at diffraction angles (2θ) of 16.3 ± 0.2, 29.4 ± 0.2, and 32.7 ± 0.2. At this time, “weak intensity” refers to a peak whose I/I ₀ (relative intensity) is less than 10%.

Step 3: Lithium of Formula 1 of imidazolate salt manufacturing

The lithium imidazolate salt of Formula 1 can be prepared by reacting the compound of Formula 5 with lithium base.

The lithium base may be lithium carbonate, lithium hydroxide, etc., and lithium carbonate is particularly preferred.

The reaction solvent may be tetrahydrofuran (THF), ethanol, methanol, water, acetonitrile, etc., and tetrahydrofuran (THF) is particularly preferable.

After the reaction is completed, methyl t-butyl ether (MTBE) is added to the reactant and concentrated to precipitate the compound of Formula 1.

One embodiment of the present invention relates to a compound of formula 5 below, which is an intermediate for the production of lithium imidazolate salt.

[Formula 5]

In the above equation,

R is a C ₁ -C ₅ fluoroalkyl group substituted or unsubstituted with a C ₁ -C ₄ fluoroalkoxy group,

n is an integer from 1 to 2.

Since the detailed description of the compound of Formula 5 is the same as the above-mentioned description regarding the preparation method of lithium imidazolate salt, detailed description is omitted to avoid duplication.

One embodiment of the present invention relates to a method for producing a compound of formula 5, which is an intermediate for the production of lithium imidazolate salt. The production method according to an embodiment of the present invention includes:

(i) reacting a compound of Formula 2 below with a compound of Formula 3 below to obtain a compound of Formula 4 below; and

(ii) adding water to the compound of formula 4 below to obtain the compound of formula 5 below as a solid.

[Formula 5]

[Formula 2]

[Formula 3]

[Formula 4]

In the above equation,

R is a C ₁ -C ₅ fluoroalkyl group substituted or unsubstituted with a C ₁ -C ₄ fluoroalkoxy group,

n is an integer from 1 to 2.

Since the detailed description of the method for producing the compound of Formula 5 is the same as the first to second steps described above with respect to the method for producing the lithium imidazolate salt, detailed description is omitted to avoid duplication.

An embodiment of the present invention relates to a method for producing a lithium imidazolate salt of Formula 1 using a compound of Formula 5, which is an intermediate for the production of lithium imidazolate salt. The production method according to an embodiment of the present invention includes:

(iii) reacting the compound of formula 5 below with lithium base.

[Formula 5]

[Formula 1]

In the above equation,

R is a C ₁ -C ₅ fluoroalkyl group substituted or unsubstituted with a C ₁ -C ₄ fluoroalkoxy group,

n is an integer from 1 to 2.

Since the detailed description of the method for producing the lithium imidazolate salt of Formula 1 is the same as the third step described above in relation to the method for producing the lithium imidazolate salt, detailed description is omitted to avoid duplication.

According to the production method of the present invention, high purity lithium imidazolate salt can be efficiently and economically produced without a complicated purification process by using 1H-imidazole-4,5-dicarbonitrile derivative hydrate, which is a crystalline solid.

Figure 1 shows the results of ¹ H NMR analysis of 2-(trifluoromethyl)-1H-imidazole-4,5-dicarbonitrile dihydrate obtained in Example 1.
Figure 2 shows the results of ¹⁹ F NMR analysis of 2-(trifluoromethyl)-1H-imidazole-4,5-dicarbonitrile dihydrate obtained in Example 1.
Figure 3 is an X-ray diffraction diagram of 2-(trifluoromethyl)-1H-imidazole-4,5-dicarbonitrile dihydrate obtained in Example 1.
Figure 4 is a thermogravimetric analysis (TGA) graph of 2-(trifluoromethyl)-1H-imidazole-4,5-dicarbonitrile dihydrate obtained in Example 1.

Hereinafter, the present invention will be described in more detail through examples. It is obvious to those skilled in the art that these examples are only for illustrating the invention and that the scope of the present invention is not limited to these examples.

Example 1: 2-( trifluoromethyl )-1H- Imidazole -4,5- Dicarbonitrile Dihydrate (TDI·2 H ₂ O )Manufacture of

42 mL (300 mmol) of trifluoroacetic anhydride, 27 g (250 mmol) of diaminomaleonitrile, and 260 mL of dioxane were added to the flask and refluxed and stirred for more than 6 hours. The end point of the reaction was confirmed by thin layer chromatography. After concentrating the dioxane in the reaction solution in a concentrator, residual trifluoroacetic anhydride was removed under high vacuum. 80 mL of water was added dropwise to the reaction product and stirred for more than 12 hours. A pale yellow solid precipitated out. The solid was filtered and washed with 50 mL of water to obtain 2-(trifluoromethyl)-1H-imidazole-4,5-dicarbonitrile dihydrate as a white solid (yield 80%).

¹ H NMR, ¹⁹ F NMR and It was confirmed that dazole-4,5-dicarbonitrile dihydrate was in crystalline form.

The characteristic _peaks shown in the The diffraction angle has a deviation range of ±0.2°.

Purity: 99.7%

No. 2θ I/I ₀ (%) No. 2θ I/I ₀ (%) One 12.521 40.2 8 27.560 10.1 2 14.179 100.0 9 28.202 13.0 3 16.298 5.4 10 28.619 10.5 4 17.661 14.9 11 29.399 5.5 5 20.178 10.9 12 30.665 13.1 6 25.218 12.5 13 32.682 6.0 7 26.101 63.0 14

Example 2: 2-( trifluoromethyl )-1H- Imidazole -4,5- Dicarbonitrile Dihydrate (TDI·2 H ₂ O ) tablets

The 2-(trifluoromethyl)-1H-imidazole-4,5-dicarbonitrile dihydrate obtained in Example 1 was dissolved in a mixed solvent of 100 mL of methanol and 100 mL of water, and then 10 g of activated carbon was added. Added and stirred at 50°C for 2 hours. After lowering the temperature to room temperature, activated carbon was removed through a filter, and then concentrated to obtain 2-(trifluoromethyl)-1H-imidazole-4,5-dicarbonitrile dihydrate as a white solid.

Purity (HPLC analysis): 99.9%

Example 3: Lithium 2- trifluoromethyl -4,5- of dicyanoimidazole (LiTDI) manufacturing

After dissolving 50 g of 2-(trifluoromethyl)-1H-imidazole-4,5-dicarbonitrile dihydrate obtained in Example 1 in 500 mL of THF, 11 g of lithium carbonate (Li ₂ CO ₃ ) was added. (0.5 eq) was added and stirred for 12 hours. After completion of the reaction, unreacted Li ₂ CO ₃ was removed through a Celite filter and concentrated. 150 mL of MTBE (methyl tertiary butyl ether) was added to the concentrate, concentrated, and the precipitated white solid was filtered. Afterwards, it was vacuum dried to obtain the target compound as a white solid (43.3 g, yield 84%).

Purity: 99.9%

Comparative example 1: Lithium 2- trifluoromethyl -4,5- of dicyanoimidazole (LiTDI) manufacturing

1.6 mL of trifluoroacetic anhydride, 1.25 g of diaminomaleonitrile, and 45 mL of 1,4-dioxane were added to the flask, stirred at 25°C for 2 hours, and then refluxed and stirred for 2 hours.

After completion of the reaction, the reaction solvent was evaporated, 60 mL of water was added, and the obtained aqueous phase was extracted with ethyl acetate (2 x 50 mL). The organic phases were then combined and extracted with an aqueous lithium carbonate solution (0.5 g Li ₂ CO ₃ in 60 mL water). Activated carbon was added to the obtained dark red aqueous phase, stirred overnight, and then heated to 45°C for 2 hours to decolorize the aqueous phase. Then, the activated carbon was removed and the aqueous phase was evaporated to prepare LiTDI as a pale yellow solid (2.01 g, yield: less than 50%).

Purity: 95%

Experiment example One: Karl Fischer analyze

Karl-Fischer analysis was performed on 2-(trifluoromethyl)-1H-imidazole-4,5-dicarbonitrile dihydrate obtained in Example 1.

Specifically, the dihydrate was dried in air at room temperature for 2 weeks, and then the contained moisture content was measured using an automatic moisture measuring device (870 KF Titrino plus).

As a result, the moisture content was found to be 16.2%, indicating that dihydrate was formed in Example 1.

Experiment example 2: thermogravity analyze( TGA )

Thermogravimetric analysis (TGA) was performed on 2-(trifluoromethyl)-1H-imidazole-4,5-dicarbonitrile dihydrate obtained in Example 1 using TGA Q50.

The results are shown in Figure 4.

In Figure 4, two inflection points where water is removed appear at 70°C (weight loss of 8.1% by weight) and 140°C (weight loss of 16.2% by weight), indicating that dihydrate was formed in Example 1.

Experiment example 3: Infrared spectroscopy (IR) analysis

In order to confirm whether the substance bound in Example 1 was a water molecule, FTIR- Infrared spectroscopy (IR) analysis was performed using a PERKIN ELMER SPECTRUM TWO.

As a result, the bending signal of water molecules appeared near 1635 cm ^-1 .

Claims (12)

(i) reacting a compound of Formula 2 below with a compound of Formula 3 below to obtain a compound of Formula 4 below;
(ii) adding water to the compound of Formula 4 in the amount of 1 to 4 times the weight of the compound of Formula 2 to obtain the compound of Formula 5 as a solid; and
(iii) A method for producing a lithium imidazolate salt of Formula 1, comprising the step of reacting a compound of Formula 5 below with a lithium base:
[Formula 2]

[Formula 3]

[Formula 4]

[Formula 5]

[Formula 1]

In the above equation,
R is a C ₁ -C ₅ fluoroalkyl group substituted or unsubstituted with a C ₁ -C ₄ fluoroalkoxy group,
n is an integer from 1 to 2. The method of claim 1, wherein R is monofluoromethyl, difluoromethyl, trifluoromethyl, difluoroethyl, trifluoroethyl, tetrafluoroethyl, pentafluoroethyl, trifluoropropyl, pentafluoromethyl, Propropyl, heptafluoropropyl, pentafluorobutyl, heptafluorobutyl, nonafluorobutyl, undecafluoropentyl, trifluoromethoxydifluoromethyl, trifluoromethoxydifluoroethyl, trifluoro A production method wherein methoxytetrafluoroethyl or trifluoromethoxyhexafluoropropyl, and n is 2. The method of claim 1, wherein in step (ii), water is added dropwise to the compound of Formula 4 and stirred to obtain the compound of Formula 5. The method of claim 1, wherein the compound of Formula 5 has a purity of 99% or more. The method of claim 1, wherein the compound of Formula 5 is in crystalline form. The method of claim 5, wherein the compound of Formula 5 has a diffraction angle (2θ) with I/I ₀ (I: intensity of the peak at each diffraction angle, I ₀ : intensity of the largest peak) of 10% or more in X-ray diffraction analysis. ) A manufacturing method wherein the values are 12.5±0.2, 14.2±0.2, 17.7±0.2, 20.2±0.2, 25.2±0.2, 26.1±0.2, 27.6±0.2, 28.2±0.2, 28.6±0.2 and 30.7±0.2. The method of claim 1, wherein the lithium base in step (iii) is lithium carbonate. delete delete delete delete delete

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