KR20200137147A - Process for Preparing Lithium Imidazolate Salt and Intermediate Therefor - Google Patents

Abstract

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

Description

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

The present invention relates to a method for preparing a lithium imidazolate salt and an intermediate therefor, and more particularly, to a method for efficiently and economically preparing a lithium imidazolate salt of high purity, and an intermediate used therein.

The market demand for secondary batteries is increasing rapidly in recent years, and in particular, as portable electronic devices such as mobile phones, notebook computers, and PCs are rapidly spreading, demand for lightweight and high-performance batteries for driving them continues to increase. In addition, it is expected to be used as secondary batteries for automobiles in addition to small-sized applications, among which lithium secondary batteries are attracting attention as a high-performance battery that satisfies such market demand.

The secondary battery is composed of a positive electrode material, a negative electrode material, a separator, and an electrolyte. Among these, the electrolyte acts as a moving medium that rapidly moves metal ions from the anode to the cathode during charging and from the cathode to the anode during discharge.

Lithium hexafluorophosphate (LiPF ₆ ) is commonly used as an electrolyte. However, lithium hexafluorophosphate (LiPF ₆ ) reacts with a trace amount of moisture to decompose in the form of hydrogen fluoride gas, and exhibits low thermal stability. Thus, lithium 2-trifluoromethyl-4,5-dicyanoimidazole (LiTDI), which is a lithium salt to replace lithium hexafluorophosphate (LiPF ₆ ), which 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 including strong carbon-fluorine bonds instead of the weak phosphorus-fluorine bonds of lithium hexafluorophosphate. Further, 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 that decomposition does not occur easily. In addition, the lithium imidazolate salt is used as an additive for removing moisture from an electrolyte, and thus may exhibit excellent performance in improving electrolyte life.

Korean Patent Application Laid-Open No. 10-2014-0081868 discloses that diaminomaleonitrile and trifluoroacetic anhydride are reacted in dioxane under reflux, an excess of water is added, and the obtained aqueous phase is extracted with ethyl acetate, A method of preparing LiTDI is disclosed by extracting the organic phase with an aqueous lithium carbonate solution to separate the aqueous phase and then treating it with activated charcoal for purification. However, the above manufacturing method has a problem in that the purity of LiTDI is low, and after LiTDI is formed, many purification steps are required.

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

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

As a result of intensive research and examination to solve the above problems in the preparation of lithium imidazolate salts, the present inventors reacted diaminomaleonitrile with an anhydride derivative to obtain 1H-imidazole-4,5-dicarbohydrate. After forming the nitrile derivative, a small amount of water was added to the 1H-imidazole-4,5-dicarbonitrile derivative to obtain a 1H-imidazole-4,5-dicarbonitrile derivative hydrate in crystal form, which By simply and easily purifying, it was found that high purity lithium imidazolate salt can be efficiently and economically produced, and the present invention was completed.

Accordingly, it is an object of the present invention to provide a method for efficiently and economically producing a high purity lithium imidazolate salt.

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

One embodiment of the present invention relates to a method for preparing a lithium imidazolate salt represented by the following formula (1),

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

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

(iii) reacting the compound of Formula 5 with a lithium base.

[Formula 1]

[Formula 2]

[Formula 3]

[Formula 4]

[Formula 5]

In the above formula,

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

n is an integer of 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 fluorine, and trifluoromethoxy, trifluoroethoxy, etc. Included, but not limited to this.

The C ₁ -C ₅ fluoroalkyl group used herein refers to a straight-chain or branched hydrocarbon having 1 to 5 carbon atoms substituted with one or more fluorine, for example, monofluoromethyl, difluoromethyl, triple Rooromethyl, 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 Fluoropentyl, undecafluoropentyl, and the like are included, but are not limited thereto.

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

Hereinafter, the manufacturing method of the present invention will be described in more detail with reference to Scheme 1 below. The method described in Reaction Scheme 1 below is merely an example of a representatively used method, and the reaction reagent, reaction conditions, etc. may be changed as much as desired.

[Scheme 1]

Step 1: Synthesis of the 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.

The reaction time is preferably 6 hours or more, such as about 6 to 10 hours.

Step 2: Synthesis of the 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 dropwise addition of 1 to 4 times of water based on the weight of the compound of Formula 2 to the compound of Formula 4 and stirring.

When the amount of water to be added is less than 1 times by weight based on the weight of the compound of Formula 2, it may be difficult to form a hydrate, and when it is greater than 4 times, the compound of Formula 4 may be dissolved in water.

The stirring time is preferably 12 hours or more, such as about 12 to 24 hours.

The compound of Formula 5 obtained in the above step may be filtered and washed with water before being used in the preparation of the lithium imidazolate salt of Formula 1 as a crystalline solid.

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

Specifically, after the washed compound of Formula 5 is dissolved in a mixed solvent of methanol and water, activated carbon is added thereto, stirred, and then filtered to purify.

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

In X-ray diffraction analysis, the compound of Formula 5 has a diffraction angle (2θ) of 10% or more with I/I ₀ (I: intensity of the peak at each diffraction angle, I ₀ : intensity of the largest peak) of 12.5. Crystalline 2-(trifluoro), characterized in that ±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 further have an X-ray diffraction peak at diffraction angles (2θ) of 16.3±0.2, 29.4±0.2, and 32.7±0.2 with a weak intensity. At this time, "weak intensity" refers to a peak in which I/I ₀ (relative intensity) is less than 10%.

Step 3: Lithium of Formula 1 Imidazolate salt Produce

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

Lithium carbonate, lithium hydroxide, etc. may be used as the lithium base, and lithium carbonate is particularly preferred.

As the reaction solvent, tetrahydrofuran (THF), ethanol, methanol, water, acetonitrile, and the like may be used, and tetrahydrofuran (THF) is particularly preferred.

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

One embodiment of the present invention relates to a compound represented by the following formula (5), which is an intermediate for producing a lithium imidazolate salt.

[Formula 5]

In the above formula,

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

n is an integer of 1 to 2.

Since the detailed description of the compound of Formula 5 is the same as the description above in relation to the method for preparing the lithium imidazolate salt, detailed descriptions are omitted to avoid redundancy.

One embodiment of the present invention relates to a method for preparing a compound of Formula 5, which is an intermediate for preparing a lithium imidazolate salt, and a method according to an embodiment of the present invention is

(i) reacting a compound of formula 2 with a compound of formula 3 to obtain a compound of formula 4; And

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

[Formula 5]

[Formula 2]

[Formula 3]

[Formula 4]

In the above formula,

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

n is an integer of 1 to 2.

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

An embodiment of the present invention relates to a method for preparing a lithium imidazolate salt of Formula 1 using a compound of Formula 5, which is an intermediate for preparing a lithium imidazolate salt, and the manufacturing method according to an embodiment of the present invention

(iii) reacting the compound of Formula 5 with a lithium base.

[Formula 5]

[Formula 1]

In the above formula,

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

n is an integer of 1 to 2.

Since the detailed description of the method for preparing the lithium imidazolate salt of Chemical Formula 1 is the same as the third step described above with respect to the method for preparing the lithium imidazolate salt, a detailed description will be omitted to avoid redundancy.

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

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

Hereinafter, the present invention will be described in more detail by examples. It will be apparent to those skilled in the art that these examples are for illustrative purposes only, 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 ) Of manufacture

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

¹ H NMR, ¹⁹ F NMR, and X-ray diffraction analysis of the obtained dihydrate were performed, and the results are shown in Figs. 1, 2 and 3, respectively, from which 2-(trifluoromethyl)-1H-imi It was confirmed that dazole-4,5-dicarbonitrile dihydrate was in crystalline form.

To the characteristic peaks (peak) appeared in the X-ray diffraction in Fig. 3 also showed in Table 1, where it '2θ' is 'I / I _0' the diffraction angle, denotes the relative intensity of the peaks (peak). 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 ) Of tablets

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. Then, it was 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) Produce

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 ) (0.5 eq) was added and stirred for 12 hours. After completion of the reaction, unreacted Li ₂ CO ₃ was removed with a Celite filter and concentrated. 150 mL of MTBE (methyl tertiary butyl ether) was added to the concentrate, and the precipitated white solid was filtered. Thereafter, it was dried in vacuo 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) Produce

To the flask was added 1.6 mL of trifluoroacetic anhydride, 1.25 g of diaminomaleonitrile, and 45 mL of 1,4-dioxane, and stirred at 25° C. for 2 hours, followed by refluxing for 2 hours.

After completion of the reaction, the reaction solvent was evaporated, water 60 mL 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 of Li ₂ CO _{3 in} 60 mL of water). Activated carbon was added to the dark red-colored aqueous phase, stirred overnight, and then heated to 45° C. for 2 hours to decolorize the aqueous phase. Thereafter, 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%

Experimental example One: Karl Fisher analysis

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

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

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

Experimental example 2: Thermal weight analysis( TGA )

The 2-(trifluoromethyl)-1H-imidazole-4,5-dicarbonitrile dihydrate obtained in Example 1 was subjected to thermogravimetric analysis (TGA) using TGA Q50.

The results are shown in FIG. 4.

In FIG. 4, it was found that dihydrate was formed in Example 1 as the two inflection points from which water was removed were shown at 70° C. (8.1 wt% weight reduction) and 140° C. (16.2 wt% weight reduction).

Experimental example 3: Infrared spectroscopy (IR) analysis

In order to confirm whether the substance bound in Example 1 is a water molecule, FTIR- for 2-(trifluoromethyl)-1H-imidazole-4,5-dicarbonitrile dihydrate obtained in Example 1 above. Infrared spectroscopy (IR) analysis was performed using PERKIN ELMER SPECTRUM TWO.

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

Claims (12)

(i) reacting a compound of formula 2 with a compound of formula 3 to obtain a compound of formula 4;
(ii) adding water to the compound of the following formula 4 to obtain a compound of the following formula 5 as a solid; And
(iii) A method for preparing a lithium imidazolate salt of the following formula 1 comprising the step of reacting a compound of formula 5 with a lithium base
[Formula 2]

[Formula 3]

[Formula 4]

[Formula 5]

[Formula 1]

In the above formula,
R is a C ₁ -C ₅ fluoroalkyl group substituted or unsubstituted with a C ₁ -C ₄ fluoroalkoxy group,
n is an integer of 1 to 2. The method of claim 1, wherein R is monofluoromethyl, difluoromethyl, trifluoromethyl, difluoroethyl, trifluoroethyl, tetrafluoroethyl, pentafluoroethyl, trifluoropropyl, pentafluoro Lopropyl, heptafluoropropyl, pentafluorobutyl, heptafluorobutyl, nonafluorobutyl, undecafluoropentyl, trifluoromethoxydifluoromethyl, trifluoromethoxydifluoroethyl, trifluoroethyl Methoxytetrafluoroethyl or trifluoromethoxyhexafluoropropyl, and n is 2. The method of claim 1, wherein in step (ii), 1 to 4 times by weight of water is added dropwise to the compound of Formula 2 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) of 10% or more in I/I ₀ (I: intensity of the peak at each diffraction angle, I ₀ : intensity of the largest peak) in X-ray diffraction analysis. ) Values of 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. Compounds of Formula 5:
[Formula 5]

In the above formula,
R is a C ₁ -C ₅ fluoroalkyl group substituted or unsubstituted with a C ₁ -C ₄ fluoroalkoxy group,
n is an integer of 1 to 2. The method of claim 8, wherein R is monofluoromethyl, difluoromethyl, trifluoromethyl, difluoroethyl, trifluoroethyl, tetrafluoroethyl, pentafluoroethyl, trifluoropropyl, pentafluoro Lopropyl, heptafluoropropyl, pentafluorobutyl, heptafluorobutyl, nonafluorobutyl, undecafluoropentyl, trifluoromethoxydifluoromethyl, trifluoromethoxydifluoroethyl, trifluoroethyl The compound of formula (5), wherein methoxytetrafluoroethyl or trifluoromethoxyhexafluoropropyl, and n is 2. The method of claim 8, wherein in X-ray diffraction analysis, I/I ₀ (I: intensity of the peak at each diffraction angle, I ₀ : intensity of the largest peak) is 10% or more, and the value of the diffraction angle (2θ) is 12.5. Compounds of formula 5, which are ±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. (iii) A method for preparing a lithium imidazolate salt of the following formula 1 comprising the step of reacting a compound of formula 5 with a lithium base
[Formula 5]

[Formula 1]

In the above formula,
R is a C ₁ -C ₅ fluoroalkyl group substituted or unsubstituted with a C ₁ -C ₄ fluoroalkoxy group,
n is an integer of 1 to 2. The method of claim 11, wherein the compound of Formula 5 has a diffraction angle (2θ) of 10% or more in I/I ₀ (I: intensity of the peak at each diffraction angle, I ₀ : intensity of the largest peak) in X-ray diffraction analysis. ) Values of 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.

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