KR101955093B1 - Preparing method of electrolyte additives with lowered acidity - Google Patents

Abstract

[화학식 2]

본 발명에 따른 산도가 줄어든 전해액 첨가제 제조방법은 리튬 비스(플루오로술포닐)이미드 화합물 또는 디플루오로인산리튬 화합물에 알칼리 시약을 첨가함으로써 위험한 공정 없이 간단한 방법으로 고순도 및 고수율의 산도가 줄어든 부식성 없는 전해액 첨가제 및 그를 포함하는 고온안정성과 장기보관 안정성이 확보되는 용액 조성을 제조할 수 있는 장점이 있다.The present invention relates to a method for preparing an electrolyte additive having reduced acidity, and more particularly, to a method for preparing an electrolyte additive comprising the steps of: preparing a mixture by mixing a lithium bis (fluorosulfonyl) imide compound or a lithium difluorophosphate compound as an electrolyte additive and a solvent; Adding an alkali reagent to the mixture, and stirring and reacting; And separating the reaction product by filtration, followed by washing and drying to obtain a lithium bis (fluorosulfonyl) imide compound represented by the following formula (1) or a lithium difluorophosphate compound represented by the following formula (2) ; And a method for producing a solution which can be used for an electrolytic solution containing the electrolytic solution additive.
[Chemical Formula 1]

(2)

The method for preparing an electrolyte additive with reduced acidity according to the present invention is characterized in that an alkaline reagent is added to a lithium bis (fluorosulfonyl) imide compound or a lithium difluorophosphate compound so that a high-purity and high- There is an advantage that it is possible to produce a solution composition in which a corrosion-resistant electrolyte additive and its high-temperature stability and long-term storage stability are ensured.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preparing an electrolyte additive having reduced acidity,

The present invention relates to a method for producing an electrolyte additive having reduced acidity, and more particularly, to a process for producing an electrolyte additive by reducing the acidity by treating a lithium salt used for an electrolyte for a lithium secondary battery in a simple manner at a high purity and a high yield without an economically dangerous process And a method for producing an electrolyte additive having no corrosiveness.

With the commercialization of various types of mobile devices, the need for high performance secondary batteries is increasing. Commercialization of electric vehicles and hybrid electric vehicles, and development of electric storage devices have resulted in the development of high output, high energy density and high discharge voltage A secondary battery was required.

The importance of the lithium salt in the composition of the electrolytic solution suitable for this has been raised, and it has been found that the lithium bis (fluorosulfonyl) imide compound and the lithium difluorophosphate compound have excellent performance.

In addition, lithium rechargeable batteries for electric vehicles require more than 10 years of harsh conditions while satisfying the requirements without degradation, while conventional secondary batteries (mobile devices such as notebooks and smart phones) are used for two years. A necessity for manufacturing a secondary battery material becomes more urgent.

Item standard water 99.5% or more Foshan (HF) 50 ppm or less Chlorine (Cl) 5 ppm or less moisture 100 ppm or less The metals (Na, K, Ca, Fe) 10 ppm or less

Table 1 shows a standard for sufficiently exhibiting the performance required in a secondary battery of a lithium bis (fluorosulfonyl) imide compound, which is a main material used as an electrolyte additive for a lithium secondary battery.

Item standard water 99.0% or more Foshan (HF) 1000 ppm or less Chlorine (Cl) 100 ppm or less moisture 200 ppm or less The metals (Na, K, Ca, Fe) 10 ppm or less

Table 2 shows a product standard for sufficiently exhibiting the performance required in a secondary battery of a lithium difluorophosphate compound which is a main material used as an electrolyte additive of a lithium secondary battery.

Particularly, the acidity of a secondary battery represented by the HF content is known to cause a problem of shortening the battery life due to corrosion in the battery during continuous use of the lithium secondary battery.

It is very important to control the hydrofluoric acid (HF) content to below the standard (1000 ppm) shown in Table 2, and the less the acidity of the secondary battery is, the more advantageous it is.

Also, since chlorine (Cl) is also involved in corrosion, it is also advantageous that the content in the secondary battery is smaller.

However, since there is no research to reduce the content of hydrofluoric acid (HF) or chlorine (Cl) of the main material used as an electrolyte additive for a lithium secondary battery, research and development thereof is urgent.

Korean Patent No. 1521069

Disclosure of the Invention An object of the present invention is to solve the problems of the prior art as described above and to provide a lithium bis (fluorosulfonyl) imide compound and a lithium difluorophosphate compound, which are lithium salts used in an electrolyte solution for a middle- or large- And which is capable of reducing corrosion resistance by reducing the acidity by treating it in a simple manner at a high purity and a high yield without the use of an acid catalyst.

In order to accomplish the above object, the present invention provides a method for preparing a lithium secondary battery, comprising the steps of: preparing a mixture by mixing a lithium bis (fluorosulfonyl) imide compound or a lithium difluorophosphate compound as an electrolyte additive and a solvent; Adding an alkali reagent to the mixture, and stirring and reacting; And separating the reaction product by filtration, followed by washing and drying to obtain a lithium bis (fluorosulfonyl) imide compound represented by the following formula (1) or a lithium difluorophosphate compound represented by the following formula (2) ; And a method for producing an electrolyte additive having reduced acidity.

[Chemical Formula 1]

(2)

The present invention also relates to an electrolyte solution comprising an electrolyte additive having reduced acidity, in which the electrolyte additive is dissolved and contained in a solvent.

The method for preparing an electrolyte additive with reduced acidity according to the present invention is characterized in that an alkaline reagent is added to a lithium bis (fluorosulfonyl) imide compound or a lithium difluorophosphate compound so that a high purity and a high yield can be obtained There is an advantage that it is possible to produce a solution composition in which a corrosive electrolyte-containing additive and its high-temperature stability and long-term storage stability are ensured.

Hereinafter, a method for producing an electrolyte additive with reduced acidity of the present invention will be described in more detail.

The inventors of the present invention have found that by reducing the content of hydrofluoric acid (HF) or chlorine (Cl) by adding an alkali reagent to a lithium bis (fluorosulfonyl) imide compound or a lithium difluorophosphate compound as an electrolyte additive, It is possible to produce an electrolytic solution composition containing the electrolytic solution with high purity and high purity without decreasing the acidity of the electrolytic solution. The present invention has been completed based on this finding.

The present invention relates to a method for preparing a lithium secondary battery, comprising the steps of: preparing a mixture by mixing a lithium bis (fluorosulfonyl) imide compound or a lithium difluorophosphate compound, which is an electrolyte additive, Adding an alkali reagent to the mixture, and stirring and reacting; And separating the reaction product by filtration, followed by washing and drying to obtain a lithium bis (fluorosulfonyl) imide compound represented by the following formula (1) or a lithium difluorophosphate compound represented by the following formula (2) ; And a method for producing an electrolyte additive having reduced acidity.

[Chemical Formula 1]

(2)

The solvent may be an equivalent ratio of 0.5 to 100 to the lithium bis (fluorosulfonyl) imide compound or the lithium difluorophosphate compound, but is not limited thereto.

The solvent is any one selected from the group consisting of diethyl ether, diisopropyl ether, and methyl-t-butyl ether; Alkoxyethanes of dimethoxyethane and diethoxyethane; Esters of any one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; Nitriles selected from the group consisting of acetonitrile, propionitrile, and butyronitrile; Hydrocarbons selected from the group consisting of pentane, hexane, and heptane; Alcohols selected from the group consisting of methanol, ethanol, propanol, and butanol; Ketones selected from the group consisting of acetone, methyl ethyl ketone, and methyl isopropyl ketone; And dialkyl carbonates selected from the group consisting of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; and the like, but are not limited thereto. In particular, when a dialkyl carbonate group which can be used for a double electrolyte solution is used as a solvent, there is an advantage that a solution of an electrolytic solution composition having a low acidity and ensuring high temperature stability and long-term storage stability can be produced.

The alkali reagent may be in an equivalent ratio of 0.0001 to 0.01 relative to lithium bis (fluorosulfonyl) imide compound or lithium difluorophosphate compound, but is not limited thereto.

The alkali reagent may be an amine such as ammonia, alkylamine, arylamine, dialkylamine, diarylamine, alkylarylamine, trialkylamine, dialkylarylamine, alkyldiarylamine; And a hydroxide salt, hydride salt, carbonate salt, hydrogen carbonate salt, alkyl salt, and aryl salt of an alkali (I) metal or alkaline earth (II) metal, no.

The alkaline reagent is lithium hydroxide (LiOH), lithium hydroxide hydrate (LiOH · H ₂ O), lithium carbonate (Li ₂ CO _3), hydrogen carbonate, lithium (LiHCO _3), lithium acetate (LiCH ₃ COO), or oxalic acid lithium (Li ₂ C ₂ O ₄ ), but the present invention is not limited thereto.

The reaction may be carried out by adding an alkali reagent to the mixture, stirring the mixture at 45 to 75 rpm, and reacting the mixture at -10 to 60 ° C.

The reaction conditions such as the reaction temperature and the like are not particularly limited and may be carried out under arbitrary conditions depending on the circumstances, but the upper limit of the reaction temperature is preferably 60 占 폚, more preferably 40 占 폚 or lower, Deg.] C, more preferably 0 [deg.] C or higher. At a temperature lower than 0 ° C, the reaction proceeds slowly, which is not economical.

The step of producing a lithium bis (fluorosulfonyl) imide compound represented by the following Chemical Formula 1 or a lithium difluorophosphate compound represented by the following Chemical Formula 2 in which the acidity is reduced may be carried out by maintaining the reaction product at 15 to 25 ° C, It may be washed and dried after separation, and it is more preferable to keep the reaction product at 20 캜.

The present invention also relates to an electrolyte solution comprising an electrolyte additive having reduced acidity, in which the electrolyte additive is dissolved and contained in a solvent.

The solvent is any one selected from the group consisting of diethyl ether, diisopropyl ether, and methyl-t-butyl ether; Alkoxyethanes of dimethoxyethane and diethoxyethane; Esters of any one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; And carbonates selected from the group consisting of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, and propylene carbonate; and the like, but is not limited thereto.

Hereinafter, a method for preparing an electrolyte additive having reduced acidity and a method for producing a solution thereof according to the present invention will be described in more detail with reference to the following examples. However, the present invention is not limited by these examples.

≪ Example 1 > Synthesis of lithium carbonate (Li ₂ CO ₃ ) To prepare a lithium bis (fluorosulfonyl) imide compound having reduced acidity

90.0 g of a lithium bis (fluorosulfonyl) imide compound (purity: 99.5%; hydrofluoric acid (HF) content: 35 ppm) and 210.0 g of dimethyl carbonate were added to a 1,000 ml Teflon material flask equipped with a stirrer, a condenser and a thermometer under a nitrogen atmosphere. g at 20 < [deg.] > C to prepare a mixture.

The mixture was stirred and dissolved at 20 rpm at 60 rpm and 35.5 mg (equivalent to 0.0010 of lithium bis (fluorosulfonyl) imide compound) of lithium carbonate (Li ₂ CO ₃ ) powder was added thereto. To prepare a reaction product.

After the completion of the reaction, the insoluble matter generated was filtered out with filter paper and then washed with 21.0 g of dimethyl carbonate.

(Yield: 98%, purity: 99.5%, hydrofluoric acid (HF) content: 0 ppm) was obtained as a white powder by washing with water, followed by concentration and drying to obtain a lithium bis (fluorosulfonyl) imide compound.

< Example  2> lithium hydroxide hydrate ( LiOH · H ₂ O) to prepare a lithium bis (fluorosulfonyl) imide compound having reduced acidity

90.0 g of a lithium bis (fluorosulfonyl) imide compound (purity: 99.5%; hydrofluoric acid (HF) content: 35 ppm) and 210.0 g of butylated nitrate (hereinafter abbreviated as HF) were added to a 1,000 ml Teflon material flask equipped with a stirrer, a condenser and a thermometer under a nitrogen atmosphere. g at 20 &lt; [deg.] &gt; C to prepare a mixture.

The mixture was stirred and dissolved at 20 rpm at 60 rpm and then 20.2 mg of lithium hydroxide hydrate (LiOH.H ₂ O) powder (equivalent ratio of 0.0010 to lithium bis (fluorosulfonyl) imide compound) The reaction product was prepared by stirring and reacting.

After completion of the reaction, the insoluble matter generated was filtered out with a filter paper and then washed with 21.0 g of butyl acetate.

(Yield: 97%, purity: 99.4%, hydrofluoric acid (HF) content: 5 ppm) was obtained as a white powder by washing with water, followed by concentration and drying to obtain a lithium bis (fluorosulfonyl) imide compound.

Comparative Example 1 Preparation of lithium bis (fluorosulfonyl) imide compound having reduced acidity using ammonia (ammonia)

90.0 g of a lithium bis (fluorosulfonyl) imide compound (purity: 99.5%; hydrofluoric acid (HF) content: 35 ppm) and 210.0 g of dimethyl carbonate were added to a 1,000 ml Teflon material flask equipped with a stirrer, a condenser and a thermometer under a nitrogen atmosphere. g at 20 &lt; [deg.] &gt; C to prepare a mixture.

The mixture was stirred and dissolved at 45 rpm at 45 rpm, and then 32.7 mg of 25% ammonia water (equivalent ratio of 0.0010 to lithium bis (fluorosulfonyl) imide compound) was added thereto. The product was prepared.

After the completion of the reaction, the insoluble matter generated was filtered out with filter paper and then washed with 21.0 g of dimethyl carbonate.

(Yield: 93%, purity: 99.3%, hydrofluoric acid (HF) content: 9 ppm) was obtained as a white powder by washing with water, followed by concentration and drying to obtain a lithium bis (fluorosulfonyl) imide compound.

&Lt; Comparative Example 2 > ₃ N) to prepare a lithium bis (fluorosulfonyl) imide compound having reduced acidity

90.0 g of a lithium bis (fluorosulfonyl) imide compound (purity: 99.5%; hydrofluoric acid (HF) content: 35 ppm) and 210.0 g of dimethyl carbonate were added to a 1,000 ml Teflon material flask equipped with a stirrer, a condenser and a thermometer under a nitrogen atmosphere. g at 20 &lt; [deg.] &gt; C to prepare a mixture.

The mixture was stirred and dissolved at 20 rpm at 60 rpm and reacted by adding 48.7 mg of triethylamine (Et ₃ N) (equivalent ratio of 0.0010 to lithium bis (fluorosulfonyl) imide compound) and stirring at 20 ° C The reaction product was prepared.

After the completion of the reaction, the insoluble matter generated was filtered out with filter paper and then washed with 21.0 g of dimethyl carbonate.

(Yield: 95%, purity: 99.3%, hydrofluoric acid (HF) content: 15 ppm) was obtained as a white powder by washing with water, followed by concentration and drying to obtain a lithium bis (fluorosulfonyl) imide compound.

Comparative Example 3 Preparation of lithium bis (fluorosulfonyl) imide compound having reduced acidity using aniline

90.0 g of a lithium bis (fluorosulfonyl) imide compound (purity: 99.5%; hydrofluoric acid (HF) content: 35 ppm) and 210.0 g of dimethyl carbonate were added to a 1,000 ml Teflon material flask equipped with a stirrer, a condenser and a thermometer under a nitrogen atmosphere. g at 20 &lt; [deg.] &gt; C to prepare a mixture.

The mixture was stirred and dissolved at 60 rpm at 60 rpm, and then the reaction product was prepared by adding 44.8 mg of aniline (equivalent ratio of 0.0010 to lithium bis (fluorosulfonyl) imide compound) and stirring at 20 ° C Respectively.

After the completion of the reaction, the insoluble matter generated was filtered out with filter paper and then washed with 21.0 g of dimethyl carbonate.

(Yield: 95%, purity: 99.1%, hydrofluoric acid (HF) content: 18 ppm) was obtained as a white powder by washing with water, followed by concentration and drying to obtain a lithium bis (fluorosulfonyl) imide compound.

&Lt; Comparative Example 4 > Lithium bicarbonate (LiHCO ₃ ) To prepare a lithium bis (fluorosulfonyl) imide compound having reduced acidity

90.0 g of a lithium bis (fluorosulfonyl) imide compound (purity: 99.5%; hydrofluoric acid (HF) content: 35 ppm) and 210.0 g of dimethyl carbonate were added to a 1,000 ml Teflon material flask equipped with a stirrer, a condenser and a thermometer under a nitrogen atmosphere. g at 20 &lt; [deg.] &gt; C to prepare a mixture.

The mixture was stirred and dissolved at 20 rpm at 60 rpm, and 32.7 mg (0.0010 equivalent to lithium bis (fluorosulfonyl) imide compound) of lithium hydrogen carbonate (LiHCO ₃ ) was added thereto. The reaction product was prepared.

After completion of the reaction, the insoluble matter generated was filtered out with a filter paper and then washed with a small amount of dimethyl carbonate.

(Yield: 96%, purity: 99.5%, hydrofluoric acid (HF) content: 12 ppm) was obtained as a white powder by washing with water, followed by concentration and drying.

Experimental Example 1 Analysis of HF Content in Lithium Bis (fluorosulfonyl) imide Compound by Treatment with Various Alkali Reagents

The hydrofluoric acid (HF) content in the lithium bis (fluorosulfonyl) imide compound treated according to Examples 1 to 2 and Comparative Examples 1 to 4 was analyzed and the results are shown in Table 3 Respectively.

Alkali reagent Quality change after treatment water(%) Fluoric acid (HF) (ppm) Example 1 Lithium carbonate 99.5 0 Example 2 Lithium hydroxide hydrate 99.4 5 Comparative Example 1 25% ammonia water 99.3 9 Comparative Example 2 Triethylamine 99.3 15 Comparative Example 3 aniline 99.1 18 Comparative Example 4 Lithium bicarbonate 99.5 12

Specifically, referring to Table 3, when the content of hydrofluoric acid (HF) remaining in the lithium bis (fluorosulfonyl) imide compound when using lithium carbonate (Li ₂ CO ₃ ) in various alkali reagents (Example 1) Was 0 ppm and the effect of decreasing the hydrofluoric acid (HF) content was the best.

In particular, it was confirmed that the content of hydrofluoric acid (HF) can be completely reduced by only an equivalent ratio of 0.0010, which is a trace amount, so that a lithium bis (fluorosulfonyl) imide compound having no corrosiveness can be produced.

&Lt; Example 3 > Lithium carbonate (Li ₂ CO ₃ ) To prepare a lithium difluorophosphate compound having reduced acidity

100.0 g of a lithium difluorophosphate compound (purity: 99.4%; hydrofluoric acid (HF) content: 650 ppm; chlorine (Cl) content: 9.3 ppm) was added to a 1,000 ml Teflon flask equipped with a stirrer, a condenser and a thermometer, 150.0 g of dimethyl carbonate was added at 20 占 폚 to prepare a mixture.

The mixture was stirring at 20 ℃ to 50 rpm In the lithium carbonate (Li ₂ CO ₃₎ (equivalent ratio of 0.0010 compared to lithium phosphate compound difluoromethyl) powder 68.5 mg preparing a reaction product by reacting the mixture was stirred at 20 ℃.

After completion of the reaction, the generated salt was filtered with filter paper and then washed with 15.0 g of dimethyl carbonate.

(Yield: 97%, purity: 99.4%, hydrofluoric acid (HF) content: 379 ppm, chlorine (Cl) content: 6.9 ppm) as a white powder, .

< Example  4> lithium hydroxide hydrate ( LiOH · H ₂ O) was used to reduce the pH Lithium difluorophosphate  Preparation of compounds

100.0 g of a lithium difluorophosphate compound (purity: 99.4%; hydrofluoric acid (HF) content: 650 ppm; chlorine (Cl) content: 9.3 ppm) was added to a 1,000 ml Teflon flask equipped with a stirrer, a condenser and a thermometer, 150.0 g of butyl acetate was added at 20 캜 to prepare a mixture.

38.9 mg of lithium hydroxide hydrate (LiOH.H ₂ O) powder (equivalent ratio of 0.0010 to lithium difluorophosphate compound) was added to the reaction product while stirring the mixture at 20 ° C and 60 rpm, followed by stirring at 20 ° C to react The product was prepared.

After completion of the reaction, the resulting salt was filtered with a filter paper, and then washed with 15.0 g of butyl acetate.

(Yield: 93%, purity: 99.0%, hydrofluoric acid (HF) content: 474 ppm, chlorine (Cl) content: 7.3 ppm) was obtained as a white powder by recovering the washed salt. .

&Lt; Comparative Example 5 > Preparation of lithium difluorophosphate compound with reduced acidity using ammonia (ammonia)

100.0 g of a lithium difluorophosphate compound (purity: 99.4%; hydrofluoric acid (HF) content: 650 ppm; chlorine (Cl) content: 9.3 ppm) was added to a 1,000 ml Teflon flask equipped with a stirrer, a condenser and a thermometer, 150.0 g of dimethyl carbonate was added at 20 占 폚 to prepare a mixture.

The mixture was stirred at 45 rpm at 20 DEG C, and a reaction product was prepared by adding 63.1 mg of 25% ammonia water (equivalent ratio of 0.0010 to lithium difluorophosphate compound) and stirring at 20 deg.

After completion of the reaction, the generated salt was filtered with filter paper and then washed with 15.0 g of dimethyl carbonate.

(Yield: 94%, purity: 99.2%, hydrofluoric acid (HF) content: 547 ppm, chlorine (Cl) content: 9.1 ppm) was obtained as a white powder by recovering the washed salt. .

&Lt; Comparative Example 6 > ₃ N) to prepare a lithium difluorophosphate compound having a reduced acidity

100.0 g of a lithium difluorophosphate compound (purity: 99.4%; hydrofluoric acid (HF) content: 650 ppm; chlorine (Cl) content: 9.3 ppm) was added to a 1,000 ml Teflon flask equipped with a stirrer, a condenser and a thermometer, 150.0 g of dimethyl carbonate was added at 20 占 폚 to prepare a mixture.

While stirring the mixture at 20 to 60 rpm In ℃ triethylamine (Et ₃ N), 93.7 mg (equivalent ratio of 0.0010 compared to lithium phosphate compound-difluoro), which was prepared by reacting the reaction product was stirred at 20 ℃.

After completion of the reaction, the generated salt was filtered with filter paper and then washed with 15.0 g of dimethyl carbonate.

(Yield: 93%, purity: 99.1%, hydrofluoric acid (HF) content: 576 ppm, chlorine (Cl) content: 8.9 ppm) was obtained as a white powder by recovering the washed salt. .

&Lt; Comparative Example 7 > Preparation of lithium difluorophosphate compound with reduced acidity using aniline

100.0 g of a lithium difluorophosphate compound (purity: 99.4%; hydrofluoric acid (HF) content: 650 ppm; chlorine (Cl) content: 9.3 ppm) was added to a 1,000 ml Teflon flask equipped with a stirrer, a condenser and a thermometer, 150.0 g of dimethyl carbonate was added at 20 占 폚 to prepare a mixture.

The reaction mixture was prepared by adding 86.3 mg of aniline (equivalent ratio of 0.0010 to lithium difluorophosphate) while stirring at 20 DEG C and 75 rpm, and stirring at 20 DEG C for reaction.

After completion of the reaction, the generated salt was filtered with filter paper and then washed with 15.0 g of dimethyl carbonate.

(Yield: 91%, purity: 99.1%, hydrofluoric acid (HF) content: 580 ppm, chlorine (Cl) content: 9.0 ppm) was obtained as a white powder by recovering the washed salt. .

&Lt; Comparative Example 8 > Lithium bicarbonate (LiHCO ₃ ) To prepare a lithium difluorophosphate compound having reduced acidity

100.0 g of a lithium difluorophosphate compound (purity: 99.4%; hydrofluoric acid (HF) content: 650 ppm; chlorine (Cl) content: 9.3 ppm) was added to a 1,000 ml Teflon flask equipped with a stirrer, a condenser and a thermometer, 150.0 g of dimethyl carbonate was added at 20 占 폚 to prepare a mixture.

In the mixture of lithium carbonate and stirred at 20 ℃ to 60 rpm (LiHCO ₃₎ powder 63.0 mg (equivalent ratio of 0.0010 compared to lithium phosphate compound-difluoro), which was prepared by reacting the reaction product was stirred at 20 ℃.

After completion of the reaction, the generated salt was filtered with filter paper and then washed with 15.0 g of dimethyl carbonate.

(Yield: 96%, purity: 99.3%, hydrofluoric acid (HF) content: 560 ppm, chlorine (Cl) content: 7.8 ppm) was obtained as a white powder by recovering the washed salt. .

<Experimental Example 2> Analysis of the content of hydrofluoric acid (HF) contained in the lithium difluorophosphate compound by treatment with various alkali reagents

The hydrofluoric acid (HF) content in the lithium difluorophosphate compounds treated according to Examples 3 to 4 and Comparative Examples 5 to 8 was analyzed, and the results are shown in Table 4 below.

Alkali reagent Quality change after treatment water(%) Fluoric acid (HF) (ppm) Example 3 Lithium carbonate 99.4 379 Example 4 Lithium hydroxide hydrate 99.0 474 Comparative Example 5 25% ammonia water 99.2 547 Comparative Example 6 Triethylamine 99.1 576 Comparative Example 7 aniline 99.1 580 Comparative Example 8 Lithium bicarbonate 99.3 560

Specifically, referring to Table 4, when the lithium carbonate (Li ₂ CO ₃ ) was used in various alkali reagents (Example 3), the amount of hydrofluoric acid (HF) remaining in the lithium difluorophosphate compound was 379 ppm (HF) content of 99.4% and HF content of 650 ppm) before the treatment with alkali reagents was taken into consideration.

&Lt; Example 5 > Synthesis of lithium carbonate (Li ₂ CO ₃ ) To prepare a lithium difluorophosphate compound having reduced acidity

100.0 g of a lithium difluorophosphate compound (purity: 99.4%; hydrofluoric acid (HF) content: 650 ppm; chlorine (Cl) content: 9.3 ppm) was added to a 1,000 ml Teflon flask equipped with a stirrer, a condenser and a thermometer, 150.0 g of dimethyl carbonate was added at 20 占 폚 to prepare a mixture.

The mixture was stirring at 20 ℃ to 60 rpm In the lithium carbonate (Li ₂ CO ₃₎ powder, 102.7 mg (difluoromethyl an equivalent ratio of 0.0015 compared to lithium phosphate compound) preparing a reaction product by reacting the mixture was stirred at 20 ℃.

After completion of the reaction, the generated salt was filtered with filter paper and then washed with 15.0 g of dimethyl carbonate.

(Yield: 96%, purity: 99.0%, hydrofluoric acid (HF) content: 278 ppm, chlorine (Cl) content: 5.2 ppm) was obtained as a white powder by recovering the washed salt. .

Example 6 Synthesis of lithium carbonate (Li ₂ CO ₃ ) To prepare a lithium difluorophosphate compound having reduced acidity

100.0 g of a lithium difluorophosphate compound (purity: 99.4%; hydrofluoric acid (HF) content: 650 ppm; chlorine (Cl) content: 9.3 ppm) was added to a 1,000 ml Teflon flask equipped with a stirrer, a condenser and a thermometer, 150.0 g of dimethyl carbonate was added at 20 占 폚 to prepare a mixture.

The mixture was stirring at 20 ℃ to 60 rpm In the lithium carbonate (Li ₂ CO ₃₎ powder, 136.9 mg (difluoromethyl an equivalent ratio of 0.0020 compared to lithium phosphate compound) preparing a reaction product by reacting the mixture was stirred at 20 ℃.

After completion of the reaction, the generated salt was filtered with filter paper and then washed with 15.0 g of dimethyl carbonate.

(Yield: 96%, purity: 99.2%, hydrofluoric acid (HF) content: 202 ppm, chlorine (Cl) content: 4.5 ppm) was obtained as a white powder by recovering the washed salt. .

&Lt; Example 7 > Synthesis of lithium carbonate (Li ₂ CO ₃ ) To prepare a lithium difluorophosphate compound having reduced acidity

100.0 g of a lithium difluorophosphate compound (purity: 99.4%; hydrofluoric acid (HF) content: 650 ppm; chlorine (Cl) content: 9.3 ppm) was added to a 1,000 ml Teflon flask equipped with a stirrer, a condenser and a thermometer, 150.0 g of dimethyl carbonate was added at 20 占 폚 to prepare a mixture.

The mixture was stirring at 20 ℃ to 60 rpm In the lithium carbonate (Li ₂ CO ₃₎ powder, 205.4 mg (difluoromethyl an equivalent ratio of 0.0030 compared to lithium phosphate compound) preparing a reaction product by reacting the mixture was stirred at 20 ℃.

After completion of the reaction, the generated salt was filtered with filter paper and then washed with 15.0 g of dimethyl carbonate.

(Yield: 97%, purity: 99.1%, hydrofluoric acid (HF) content: 120 ppm, chlorine (Cl) content: 3.1 ppm) was obtained as a white powder by recovering the washed salt. .

<Example 8> Synthesis of lithium carbonate (Li ₂ CO ₃ ) To prepare a lithium difluorophosphate compound having reduced acidity

100.0 g of a lithium difluorophosphate compound (purity: 99.4%; hydrofluoric acid (HF) content: 650 ppm; chlorine (Cl) content: 9.3 ppm) was added to a 1,000 ml Teflon flask equipped with a stirrer, a condenser and a thermometer, 150.0 g of dimethyl carbonate was added at 20 占 폚 to prepare a mixture.

The mixture was stirring at 20 ℃ to 60 rpm In the lithium carbonate (Li ₂ CO ₃₎ powder, 308.1 mg (difluoromethyl an equivalent ratio of 0.0045 compared to lithium phosphate compound) preparing a reaction product by reacting the mixture was stirred at 20 ℃.

After completion of the reaction, the generated salt was filtered with filter paper and then washed with 15.0 g of dimethyl carbonate.

(Yield: 98%, purity: 99.1%, hydrofluoric acid (HF) content: 49 ppm, chlorine (Cl) content: 2.0 ppm) was obtained as a white powder by recovering the washed salt. .

<Example 9> Synthesis of lithium carbonate (Li ₂ CO ₃ ) To prepare a lithium difluorophosphate compound having reduced acidity

100.0 g of a lithium difluorophosphate compound (purity: 99.4%; hydrofluoric acid (HF) content: 650 ppm; chlorine (Cl) content: 9.3 ppm) was added to a 1,000 ml Teflon flask equipped with a stirrer, a condenser and a thermometer, 150.0 g of dimethyl carbonate was added at 20 占 폚 to prepare a mixture.

The mixture was stirring at 20 ℃ to 60 rpm In the lithium carbonate (Li ₂ CO ₃₎ powder, 410.8 mg (difluoromethyl an equivalent ratio of 0.0060 compared to lithium phosphate compound) preparing a reaction product by reacting the mixture was stirred at 20 ℃.

After completion of the reaction, the generated salt was filtered with filter paper and then washed with 15.0 g of dimethyl carbonate.

(Yield: 98%, purity: 99.3%, hydrofluoric acid (HF) content: 0 ppm, chlorine (Cl) content: 0.8 ppm) was obtained as a white powder by recovering the washed salt. .

<Experimental Example 3> A lithium carbonate (Li (Li) was added to the lithium difluorophosphate compound ₂ CO ₃ ) HF content analysis of residual lithium difluorophosphate according to equivalence ratio

In the various alkali reagents according to Experimental Example 2, when the lithium carbonate (Li ₂ CO ₃ ) was treated, the amount of hydrofluoric acid remaining in the lithium difluorophosphate compound in the same equivalent ratio (equivalent ratio of 0.0010 to lithium difluorophosphate compound) (HF) content could be applied to middle- or large-sized lithium secondary batteries, and the effect of reducing HF according to the amount of lithium carbonate (Li ₂ CO ₃ ) was further analyzed.

Alkali reagent Throughput Quality change after treatment water(%) Fluoric acid (HF) (ppm) Example 3 Lithium carbonate 0.0010 99.4 379 Example 5 Lithium carbonate 0.0015 99.0 278 Example 6 Lithium carbonate 0.0020 99.2 202 Example 7 Lithium carbonate 0.0030 99.1 120 Example 8 Lithium carbonate 0.0045 99.1 49 Example 9 Lithium carbonate 0.0060 99.3 0

Specifically, referring to Table 5, it can be confirmed that the hydrofluoric acid (HF) content decreases depending on the throughput of lithium carbonate (Li ₂ CO ₃ ).

Particularly, when lithium carbonate (Li ₂ CO ₃ ) is added at an equivalent ratio of 0.0045 to the lithium difluorophosphate compound, the content of hydrofluoric acid (HF) can be lowered to 50 ppm or less. According to Example 9, a lithium difluorophosphate It was confirmed that when lithium carbonate (Li ₂ CO ₃ ) was added at an equivalence ratio of 0.0060, the lithium difluorophosphate compound reached 0 ppm and thus the lithium difluorophosphate compound was not corrosive.

Considering that the amount of hydrofluoric acid (HF) in the lithium bis (fluorosulfonyl) imide compound is about 20 to 50 ppm, and that in the case of lithium difluorophosphate is about 200 to 800 ppm, Lithium bis (fluorosulfonyl) imide compound or lithium difluorophosphate compound which can be applied to a small-sized lithium secondary battery can be applied. However, when it is applied to a middle- or large-sized lithium secondary battery (electric vehicle, energy storage device, ESS) It can be understood that it is insufficient due to the problem of.

However, in view of the above experimental results, it can be understood that the electrolyte additive having reduced acidity prepared according to the present invention is an excellent invention applicable to a mid-to large-sized lithium secondary battery.

Example 10 Synthesis of lithium carbonate (Li ₂ CO ₃ ) To prepare a solution of lithium bis (fluorosulfonyl) imide compound having reduced acidity

90.0 g of a lithium bis (fluorosulfonyl) imide compound (purity: 99.5%; hydrofluoric acid (HF) content: 35 ppm) and 210.0 g of dimethyl carbonate were added to a 1,000 ml Teflon material flask equipped with a stirrer, a condenser and a thermometer under a nitrogen atmosphere. g at 20 &lt; [deg.] &gt; C to prepare a mixture.

The mixture was stirred and dissolved at 20 rpm at 60 rpm and 35.5 mg (equivalent to 0.0010 of lithium bis (fluorosulfonyl) imide compound) of lithium carbonate (Li ₂ CO ₃ ) powder was added thereto. To prepare a reaction product.

After the completion of the reaction, the insoluble matter generated was filtered out with filter paper and then washed with 21.0 g of dimethyl carbonate.

(Yield: 98%, purity: 99.5%, hydrofluoric acid (HF) content: 0 ppm, concentration: 27.6 (molar ratio), and the mixture was filtered to obtain a colorless transparent dimethyl carbonate solution containing lithium bis (fluorosulfonyl) imide compound. %).

EXPERIMENTAL EXAMPLE 4 Comparative Analysis of High Temperature Stability / Long Term Storage Stability according to HF Content of Solutions of Lithium Bis (fluorosulfonyl) imide and lithium difluorophosphate

A solution containing lithium bis (fluorosulfonyl) imide and a lithium difluorophosphate compound obtained in Example 1 and Example 9 respectively in 30% and 1% concentration, and lithium obtained in Example 10 Three kinds of colorless transparent dimethyl carbonate solution (concentration 27.6%) containing bis (fluorosulfonyl) imide compound were compared with the same concentration of dimethyl carbonate solution of untreated sample and stability stability at high temperature / long-term storage.

The mixture was allowed to stand at 70 ° C for 72 hours, and the difference in color and pH of the solution was confirmed. Unlike small batteries, it is necessary to maintain stability even at high temperature, which is the battery operating environment, for medium and large-sized lithium secondary batteries. Typically, small- and mid-sized batteries should be stable for more than 10 years. The results are summarized in Table 6 below.

start 70 ° C / 72 hours stability 6 months 12 months #One Colorless transparent (pH: 7.0) Colorless transparent (pH: 6.8) Colorless transparent (pH: 7.0) Colorless transparent (pH: 7.0) #2 Colorless transparent (pH: 6.5) Pale yellow (pH: 4.0) Colorless transparent (pH: 6.4) Colorless transparent (pH: 6.1) # 3 Colorless transparent (pH: 7.0) Colorless transparent (pH: 7.0) Colorless transparent (pH: 7.0) Colorless transparent (pH: 7.0) #4 Colorless transparent (pH: 6.7) Colorless transparent (pH: 5.0) Colorless transparent (pH: 6.7) Colorless transparent (pH: 6.4) # 5 Colorless transparent (pH: 7.0) Colorless transparent (pH: 7.0) Colorless transparent (pH: 7.0) Colorless transparent (pH: 7.0)

# 1: 30.0% dimethyl carbonate solution of lithium bis (fluorosulfonyl) imide obtained in Example 1

# 2: 30.0% dimethyl carbonate solution of lithium bis (fluorosulfonyl) imide used in Example 1

# 3: A 1.0% dimethyl carbonate solution of lithium difluorophosphate obtained in Example 9

# 4: 1.0% dimethyl carbonate solution of lithium difluorophosphate used in Example 9

# 5: A 27.6% dimethyl carbonate solution of the lithium bis (fluorosulfonyl) imide obtained in Example 10

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It is to be understood that various modifications and changes may be made without departing from the scope of the appended claims.

Claims (9)

Preparing a mixture by mixing a lithium bis (fluorosulfonyl) imide compound or a lithium difluorophosphate compound as an electrolyte additive and a solvent;
Adding lithium alkali reagent to the mixture, stirring at 45 to 75 rpm, and reacting at -10 to 60 ° C; And
Separating the reaction product by filtration, washing and drying to prepare a lithium bis (fluorosulfonyl) imide compound represented by Formula 1 or a lithium difluorophosphate compound represented by Formula 2 below;
/ RTI &gt;
Wherein the lithium alkali reagent is added in an equivalent ratio of 0.0045 to 0.01 based on the lithium bis (fluorosulfonyl) imide compound or the lithium difluorophosphate compound.
[Chemical Formula 1]

(2)

The method according to claim 1,
The solvent may be,
(Fluorosulfonyl) imide compound or lithium difluorophosphate compound in an equivalent ratio of 0.5 to 100, based on the total weight of the electrolyte solution. The method according to claim 1,
The solvent may be,
Ethers selected from the group consisting of diethyl ether, diisopropyl ether, and methyl-t-butyl ether; Alkoxyethanes of dimethoxyethane and diethoxyethane; Esters of any one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; Nitriles selected from the group consisting of acetonitrile, propionitrile, and butyronitrile; Hydrocarbons selected from the group consisting of pentane, hexane, and heptane; Alcohols selected from the group consisting of methanol, ethanol, propanol, and butanol; Ketones selected from the group consisting of acetone, methyl ethyl ketone, and methyl isopropyl ketone; And carbonates which are selected from the group consisting of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. delete delete The method according to claim 1,
The lithium alkali reagent may be,
Lithium hydroxide (LiOH), lithium hydroxide hydrate (LiOH · H ₂ O), lithium carbonate (Li ₂ CO _3), hydrogen carbonate, lithium (LiHCO _3), lithium acetate (LiCH ₃ COO), or oxalic acid lithium (Li ₂ C ₂ &gt; O &lt; ₄ &gt;). delete delete delete