KR20240070173A - Producing method for solution of lithium bis(fluorosulfony)imide containing reduced content of acid and water - Google Patents

Abstract

The present invention relates to a method for producing a lithium bis(fluorosulfonyl)imide carbonate solution, and particularly to a method for producing a lithium bis(fluorosulfonyl)imide carbonate solution with reduced acid component and moisture content. It's about.

Description

Producing method for solution of lithium bis(fluorosulfony)imide containing reduced content of acid and water}

The present invention relates to a method for producing a lithium bis(fluorosulfonyl)imide solution, and particularly to a method for producing a lithium bis(fluorosulfonyl)imide solution with reduced acid component and moisture content. .

With the popularization of mobile devices, commercialization of electric vehicles, and increasing demand for electric storage devices, secondary batteries with performance such as high output, high energy density, and high discharge voltage are being developed. In particular, lithium-ion secondary batteries have a high energy density, so they are used as power sources for mobile communication devices and portable information terminals, and their market is growing rapidly along with the spread of terminals. Since these lithium secondary batteries operate at a high driving voltage, aqueous electrolytes that are highly reactive with lithium cannot be used. Non-aqueous electrolyte solution, that is, organic electrolyte solution, is used in lithium secondary batteries.

A lithium secondary battery includes a negative electrode, positive electrode, and separator along with a non-aqueous electrolyte solution.

In lithium secondary batteries, the non-aqueous electrolyte serves as a medium for the movement of lithium ions between the anode and the cathode and improves the thermal, electrical, and physical safety of the battery. It works together with non-aqueous solvents and salts to improve the thermal, electrical, and physical safety of the battery. It consists of various additives. Additives exist in numerous quantities and are involved in the creation of solid electrolyte interphase (SEI). LiPF ₆ is mainly used as a salt, but recently, the use of bis(fluorosulfonyl)imide alkali metal salt, which has excellent performance such as excellent low temperature, instantaneous high output, and low resistance value, is increasing, and the representative material is lithium. It is bis(fluorosulfonyl)imide (LiFSI).

As a method for producing bis(fluorosulfonyl)imide lithium salt, Canadian Patent Publication No. 2527802 involves reacting bis(fluorosulfonyl)imide with lithium fluoride in an autoclave in the presence of hydrogen fluoride, with a yield of 99%. The above describes obtaining bis(fluorosulfonyl)imide lithium salt in solid phase. However, this method uses hydrogen fluoride, which is highly corrosive to the reaction vessel, and the hydrogen fluoride remains in the bis(fluorosulfonyl)imide lithium salt, making it difficult to prepare an electrolyte using this bis(fluorosulfonyl)imide lithium salt. There is a disadvantage in that hydrogen fluoride remains in the electrolyte. In registered patent 10-2443835, bis(fluorosulfonyl)imide salt is prepared in butyl acetate solvent to obtain solid bis(fluorosulfonyl)imide salt, and then mixed with the bis(fluorosulfonyl)imide salt as an electrolyte solvent. In obtaining the electrolyte material by adding a method, a method is disclosed that is characterized in that the solution containing the fluorosulfonylimide salt and the electrolyte solvent is reduced in pressure and/or heated to remove the remaining butylacetate solvent.

Canadian Patent Publication No. 2527802 Registered Patent 10-2443835

In order for bis(fluorosulfonyl)imide salt to be used as an electrolyte salt in a secondary battery, it must have thermal stability, high conductivity, low corrosiveness, and be free from impurities, especially acidic impurities, moisture, and residual solvents. Acidic impurities, moisture, and residual solvents reduce the withstand voltage of the electrolyte and corrode secondary battery components, reducing battery life.

However, the registered patent 10-2443835 method requires additional energy as it requires reduced pressure and/or heating to remove the residual butylacetate solvent, and also generates impurities due to decomposition of the bis(fluorosulfonyl)imide salt during the heating process. There is a problem with it remaining in the advance payment amount.

Accordingly, the object of the present invention is to provide lithium bis(fluorosulfonyl)imide that does not require removal of hydrogen fluoride or organic solvents that may remain in the production of bis(fluorosulfonyl)imide salt and can be used as is in the electrolyte solution. It provides a method for manufacturing a (LiFSI) solution, in which impurities, especially acidic impurities and moisture that affect battery life, are reduced and a lithium bis(fluorosulfonyl)imide solution that can be used as is in the electrolyte solution is manufactured. It provides a way to do it.

In addition, the object of the present invention is to provide a manufacturing method in which lithium bis(fluorosulfonyl)imide and a solvent prepared without a solvent removal process can be used as an electrolyte in producing lithium bis(fluorosulfonyl)imide, , At this time, a method is provided to reduce the content of acid components such as hydrogen fluoride and sulfuric acid, which are by-products that greatly affect battery life.

In order to achieve the above object, the present invention,

Step 1) reacting lithium fluoride (LiF) in a carbonate solvent at a ratio of less than 1 equivalent to 1 equivalent of bis(fluorosulfonyl)imide (HFSI), and

It provides a method for producing a carbonate solution of lithium bis(fluorosulfonyl)imide (LiFSI), which includes the step 2) of treating the reaction solution of step 1) with Li ₂ CO ₃ .

The present invention provides a method for producing a lithium bis(fluorosulfonyl)imide (LiFSI) solution, characterized in that there is no recovery process for the produced lithium bis(fluorosulfonyl)imide to a solid phase.

The production method of the present invention may include a purification process of filtering the reaction solution after step 2).

The production method of the present invention may include the step of removing volatile substances in the reaction solution by reducing pressure and/or heating during or after the reaction in step 1).

The production method of the present invention may include a process of filtering the reaction solution and then removing moisture through azeotropic distillation.

The carbonate solution of lithium bis(fluorosulfonyl)imide (LiFSI) prepared by the method of the present invention is a carbonate solvent used in the non-aqueous electrolyte solution of lithium secondary batteries. Since it is obtained in the form of a solution containing

In addition, lithium bis(fluorosulfonyl)imide is not recovered as a solid, but is used as a raw material for electrolyte in solution, and the content of acidic components such as F ^- , Cl ^- and sulfate ions is low, especially fluorosulfonic acid and It has a low sulfamate ion content and low moisture content, so when it is used to produce an electrolyte, it has the effect of extending the life of the battery. It also has the effect of suppressing battery corrosion.

According to the present invention, since the process of removing the solvent to obtain lithium bis(fluorosulfonyl)imide as a solid is not included after the reaction, the lithium bis(fluorosulfonyl)imide generated during the solvent removal process by heating is eliminated. It has the effect of reducing the generation of decomposition by-products and also reducing energy costs for solvent removal. In addition, it has the effect of preventing solid-phase lithium bis(fluorosulfonyl)imide from contacting moisture.

The present invention has the advantage that by reacting a small amount of LiF compared to bis(fluorosulfonyl)imide, LiF does not remain after the reaction, so a step to remove LiF is not necessary.

Hereinafter, the present invention will be described in detail. Terms or words used in the specification and claims should not be construed as limited to their ordinary or dictionary meanings, and the inventor may appropriately define the concept of terms in order to explain his or her invention in the best way. It must be interpreted with meaning and concept consistent with the technical idea of the present invention based on the principle that it is.

The present inventors prepared lithium bis(fluorosulfonyl)imide through the reaction of bis(fluorosulfonyl)imide and lithium fluoride in a reaction solvent that does not contain HF, and then produced lithium bis(fluorosulfonyl)imide. In order to use the solution produced without the process of recovering lithium bis(fluorosulfonyl)imide into a solid phase in an electrolyte solution, a method of producing a carbonate solution of lithium bis(fluorosulfonyl)imide was developed using a carbonate solvent as a reaction solvent. I wanted to do it.

In particular, the present invention sought to prepare a solution with sufficiently reduced impurities without the process of recovering lithium bis(fluorosulfonyl)imide as a solid phase and to use it directly in the electrolyte solution.

Accordingly, the present invention

Step 1) reacting lithium fluoride (LiF) in a carbonate solvent at a ratio of less than 1 equivalent to 1 equivalent of bis(fluorosulfonyl)imide (HFSI), and

It provides a method for producing a carbonate solution of lithium bis(fluorosulfonyl)imide (LiFSI), which includes the step 2) of treating the reaction solution of step 1) with Li ₂ CO ₃ .

The production method of the present invention does not include a recovery process for the produced lithium bis(fluorosulfonyl)imide into a solid phase.

In the present invention, in step 1), lithium fluoride (LiF) is reacted with bis(fluorosulfonyl)imide (HFSI) in a carbonate solvent to prepare a carbonate solution of lithium bis(fluorosulfonyl)imide. At this time, HF is generated as a by-product, and volatilization can be performed to remove HF. Through the volatilization operation, low boiling point HF is primarily removed.

The present inventors found that when LiF is used in excess of 1 equivalent compared to bis(fluorosulfonyl)imide in the reaction between bis(fluorosulfonyl)imide and LiF, LiF remains in the carbonate solution after the reaction, and the remaining LiF It was discovered that it had the disadvantage of not being easy to remove, such as requiring a long time for removal as it had to be removed with a fine filter. Accordingly, the present inventors used less than 1 equivalent of LiF compared to 1 equivalent of bis(fluorosulfonyl)imide, so that the probability of LiF remaining after the reaction between bis(fluorosulfonyl)imide and LiF is low, and therefore, it is necessary to remove LiF. The present invention was completed after discovering that a filter process was not necessary.

In the reaction between bis(fluorosulfonyl)imide and LiF of the present invention, the equivalent ratio of LiF to bis(fluorosulfonyl)imide is less than 1.0, preferably 0.7 or more to less than 1.0, more preferably 0.8 or more. to 0.99 or less. If the equivalence ratio of LiF to bis(fluorosulfonyl)imide is less than 0.7, there is a disadvantage in that too much unreacted bis(fluorosulfonyl)imide remains.

As a result of reacting a small amount of LiF with bis(fluorosulfonyl)imide, unreacted bis(fluorosulfonyl)imide may remain in the carbonate solution. If bis(fluorosulfonyl)imide remains in this way, the pH of the lithium bis(fluorosulfonyl)imide carbonate solution decreases and decomposes to produce fluorosulfonic acid, sulfamic acid, sulfuric acid, etc. It can be. When a lithium bis(fluorosulfonyl)imide solution containing bis(fluorosulfonyl)imide is used as an electrolyte for a secondary battery, the remaining bis(fluorosulfonyl)imide reduces the efficiency of the secondary battery, especially moisture. When in contact with the above-mentioned various acids, etc. may be generated, which may cause corrosion problems in secondary batteries in the future.

Additionally, if the by-product HF is not completely removed in the reaction in step 1) and remains, the pH of the lithium bis(fluorosulfonyl)imide carbonate solution may be lowered, thereby producing a weakly acidic solution with a pH of less than 6.5. If the lithium bis(fluorosulfonyl)imide carbonate solution is a weakly acidic solution with a pH of less than 6.5, when used as an electrolyte, it may corrode secondary battery electrodes and devices and reduce battery capacity.

Accordingly, the production method of the present invention includes the step of treating the reaction solution with Li ₂ CO ₃ in step 2) after step 1). When the reaction solution is treated with Li ₂ CO ₃ , Li ₂ CO ₃ acts as a Li ion source for producing LiFSI and reacts with the remaining unreacted HFSI to produce LiFSI. In addition, when the reaction solution is treated with Li ₂ CO _{3 ,} Li ₂ CO ₃ acts as a base and sufficiently removes acid components such as HF and sulfuric acid generated as by-products, thereby reducing acid components such as HF or sulfuric acid in the final solution. .

The amount of Li ₂ CO ₃ added in step 2) is preferably the value of the following formula (1). When Li ₂ CO ₃ is used in the above content, LiFSI can be produced by reacting with the remaining HFSI, and lithium bis (fluorosulphate) is finally produced by sufficiently removing acid components such as HF and sulfuric acid present as impurities. There is an advantage that the carbonate solution of ponyl)imide can be used directly in the electrolyte solution.

Equation (1)

Equivalent amount of Li ₂ CO ₃ used = 1 - ax Equivalent amount of LiF used

a is a number from 0.6 to 0.9, preferably from 0.7 to 0.9.

When a is a number of 0.6 to 0.9, it can sufficiently react with the remaining HFSI to produce LiFSI and also neutralize the remaining HF or sulfuric acid to prevent the pH of the solution from lowering.

In the present invention, in the production of a carbonate solution of lithium bis(fluorosulfonyl)imide, HFSI and LiF are first reacted and then Li ₂ CO ₃ is reacted, and LiF and Li ₂ CO ₃ are added to the HFSI-containing solution. If added at the same time, Li ₂ CO ₃ acts first as a Li ion source and is exhausted, making it difficult to remove the acid as a base. Therefore, the acid component present as a by-product or impurity in the carbonate solution of lithium bis(fluorosulfonyl)imide cannot be sufficiently removed. Accordingly, the present invention reacts less than 1 equivalent of LiF per 1 equivalent of bis(fluorosulfonyl)imide (LiFSI) in a carbonate solvent and then reacts Li ₂ CO ₃ . After reacting solid Li ₂ CO ₃ to remove acidic components, the remaining Li ₂ CO ₃ and the generated insoluble salt can be removed by filtration.

As a result, the present invention can obtain a lithium bis(fluorosulfonyl)imide carbonate solution with a pH of 6.5 to 7.5.

According to the production method of the present invention, a carbonate solution of lithium bis(fluorosulfonyl)imide (LiFSI) with reduced concentrations of F ^- ions, SO ₄ ^2- ions, and Cl ^- ions can be obtained. The present invention provides a bis (fluorosulphate) in which the F ^- ion content is reduced to 0-30 ppm, more preferably 0-20 ppm, the SO ₄ ^{2 -} ion content is reduced to 0-30 ppm, and the Cl ^- ion content is reduced to 1 ppm or less. A carbonate solution of ponyl)imide (LiFSI) can be obtained. In addition, the present invention can obtain a carbonate solution of lithium bis(fluorosulfonyl)imide (LiFSI) with reduced contents of fluorosulfonic acid (FSO ₃ H) and sulfamic acid (NH ₂ SO ₃ H) as acid components. The present invention can obtain a carbonate solution of lithium bis(fluorosulfonyl)imide (LiFSI) containing 0-30ppm of fluorosulfonic acid (FSO ₃ H). The present invention can obtain a carbonate solution of lithium bis(fluorosulfonyl)imide (LiFSI) containing 0-50ppm, preferably 0-40ppm, of sulfamic acid (NH ₂ SO ₃ H).

The lower limit of the content of acid impurities in the present invention is preferably 0, but may be at least 0.1 ppm.

In the method for producing a carbonate solution of lithium bis(fluorosulfonyl)imide (LiFSI) of the present invention, when treated with Li ₂ CO ₃ , most of Li ₂ CO ₃ reacts with HFSI to produce LiFSI, but some of it reacts with HF and H. It can react with ₂ SO ₄ , FSO ₃ H, and NH ₂ SO ₃ H to produce water. When the generated water is small, the added Li ₂ CO ₃ acts as a moisture adsorbent, and water can be removed from the carbonate solution of lithium bis(fluorosulfonyl)imide (LiFSI). However, when the manufacturing process is scaled up or the generated water is excessive, a process to remove it is necessary.

Therefore, the present invention may include an azeotropic distillation step from step 2) to step 3) to prepare a carbonate solution of lithium bis(fluorosulfonyl)imide (LiFSI) with reduced moisture. Water can be removed by azeotropic distillation of the carbonate solvent and water through the azeotropic distillation step.

In the method for producing lithium bis(fluorosulfonyl)imide carbonate solution of the present invention, commercially available bis(fluorosulfonyl)imide can be used as the starting material, and it can be synthesized and used by a known method. For example, there is a method of synthesizing bis(fluorosulfonyl)imide from bis(chlorosulfonyl)imide using a fluorinating agent. There is also a method of synthesizing bis(fluorosulfonyl)imide using urea and fluorosulfonic acid.

The solvent used in the preparation of the lithium bis(fluorosulfonyl)imide carbonate solution of the present invention contains one or two or more types selected from carbonate solvents, and contains moisture to prevent moisture remaining in the final solution. It is preferred to use this reduced anhydrous carbonate.

The carbonate solvent may be a linear or cyclic carbonate.

Linear carbonates include dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate (MEC).

Cyclic carbonates include ethylene carbonate (EC) and propylene carbonate (PC).

Considering the generated by-products or azeotropic distillation, the carbonate may be dimethyl carbonate (DMC), diethyl carbonate (DEC), or ethylmethyl carbonate (EMC), and may be a mixed solvent of two or more of these and ethylene carbonate or propylene carbonate. You can. For example, the carbonate solvent may be dimethyl carbonate alone or a mixture of dimethyl carbonate and another carbonate.

The present invention is a lithium bis(fluorosulfonyl)imide that can sufficiently dissolve lithium bis(fluorosulfonyl)imide produced by using carbonate solvents as a reaction solvent and easily remove unreacted substances and by-products. A carbonate solution can be obtained.

In the present invention, by using carbonate solvents as the reaction solvent, the lithium bis(fluorosulfonyl)imide carbonate solution can be prepared and then used as an electrolyte without removing the reaction solvent. When the carbonate solvent of the present invention is used as an electrolyte for a secondary battery, it can effectively stabilize both the positive and negative electrodes, increase the electrochemical stability of the electrolyte, suppress consumption, and improve the efficiency of the lithium metal secondary battery. .

In the production method of the present invention, the carbonate solvent for bis(fluorosulfonyl)imide is 1 to 5 weight, preferably 1.5 to 4 weight, more preferably, based on 1 weight of bis(fluorosulfonyl)imide. It may be 1.5 to 3 weight. When carbonate solvents are used in the above amounts, LiF and HFSI can be sufficiently dissolved to sufficiently proceed with the lithium bis(fluorosulfonyl)imide production reaction, and an appropriate concentration of lithium bis(fluorosulfonyl)imide can be produced without removal of the solvent after the reaction. There is an advantage in that a sulfonyl)imide carbonate solution can be prepared and used as an electrolyte.

The content of lithium bis(fluorosulfonyl)imide in the carbonate solution of lithium bis(fluorosulfonyl)imide (LiFSI) obtained by the method of the present invention is 20 to 60% by weight. If the content is as above, it can be used as an electrolyte for secondary batteries, etc., as is or by simple dilution. The electrolyte has a reduced content of acid components such as hydrogen fluoride, sulfuric acid, fluorosulfonic acid, and sulfamic acid, and moisture, so when used in the electrolyte, the performance of the battery can be improved and the lifespan can be extended.

The reaction temperature between bis(fluorosulfonyl)imide and lithium fluoride is preferably 10°C to 100°C rather than 0°C to 200°C. If the reaction temperature is lower than 0°C, the reaction rate decreases, and if the reaction temperature is higher than the above, there is a risk of by-products being generated, which is not preferable. The time required for the reaction varies depending on the scale of the reaction, but is preferably 0.1 to 48 hours, more preferably 0.5 to 24 hours.

The reaction can be carried out under normal pressure, but if carried out under reduced pressure, HF produced as a by-product is removed and the target product is easily synthesized. The reaction pressure is not particularly limited, but is preferably less than atmospheric pressure - 0.01 atm, and a degree of pressure reduction such that the solvent refluxes at 0°C - 100°C is more preferable.

The production method of the present invention may include removing volatile substances in the reaction solution by reducing pressure and/or heating. HF, which is produced as a by-product in the present invention, exists as a gas above 19.5°C and can be removed by reducing pressure and heating.

In the present invention, nitrogen gas bubbling can be performed to smoothly remove HF during or after the reaction between bis(fluorosulfonyl)imide and lithium fluoride. Bubbling of nitrogen gas can be performed until the pH of the gas discharged from the reaction solution reaches 6-8. It is more preferable to stop bubbling nitrogen gas when the pH reaches 6.5-7.5, and it is even more preferable to stop bubbling nitrogen gas when the pH reaches 6.8-7.2. When nitrogen gas bubbling is performed in this way, the content of fluorine anions in the final product can be greatly reduced. When nitrogen gas bubbling is performed after the reaction of bis(fluorosulfonyl)imide and lithium fluoride, it can be performed at 50-70°C.

The present invention obtains a carbonate solution containing lithium bis(fluorosulfonyl)imide by reacting bis(fluorosulfonyl)imide with lithium fluoride, and then treats the solution with Li ₂ CO ₃ to remove unreacted It can prevent the residue of bis(fluorosulfonyl)imide and further remove acid components such as hydrogen fluoride, fluorosulfonic acid, sulfamic acid, hydrochloric acid, and sulfuric acid remaining in the solution.

The treatment with Li ₂ CO ₃ may be a step of adding Li ₂ CO ₃ to the reaction solution after step 1) and stirring. The stirring may be performed at room temperature for 0.1 hours - 10 hours, preferably 0.2 hours - 5 hours. When performed as above, unreacted HFSI can be sufficiently converted to LiFSI and acids such as hydrogen fluoride, fluorosulfonic acid, sulfamic acid, hydrochloric acid, and sulfuric acid present as impurities can be removed.

In the present invention, a filtration process may be performed to remove Li ₂ CO ₃ and/or other insoluble components remaining after step 2).

The filtration process of the present invention first removes coarse particles using a filter with a pore diameter of 0.3 to 1.0 ㎛, and then secondarily filters the filtrate through a filter with a pore diameter of less than 0.3 ㎛, preferably more than 0.1 but less than 0.3 ㎛. Particles can be removed efficiently. In the present invention, the remaining Li ₂ CO ₃ and other impurities are sufficiently removed by filtering the Li ₂ CO ₃ reaction using a fine filter as described above, and the filtered solution can be used as is in a secondary battery electrolyte solution.

The filtration step may be performed at normal pressure, increased pressure, or reduced pressure, but when reduced-pressure filtration is performed at a pressure of 0.1 atmosphere or less, the filtration time can be shortened. You can also proceed by pressurizing the reaction solution injection side and depressurizing the filtrate side.

The present invention allows the carbonate solution containing the produced lithium bis(fluorosulfonyl)imide to be used directly as an electrolyte without removing the solvent. If fine particles remain in the reaction solution, they are dispersed in the electrolyte and increase the turbidity of the electrolyte. As a result, the lifespan may be shortened, including a decrease in the number of times the battery can be charged and discharged, so it is desirable to perform the filtration process as described above.

The production method of the present invention may include an azeotropic distillation step as step 3) to remove moisture remaining in the carbonate solution of lithium bis(fluorosulfonyl)imide after the filtration process. The carbonate solvent can be azeotropically distilled with water, and through the azeotropic distillation, the moisture remaining in the solution and a portion of the carbonate solvent are removed, and as a result, a carbonate solution of lithium bis(fluorosulfonyl)imide containing no moisture is provided. You can.

Azeotropic distillation can be performed at a temperature of 20 to 80˚C under reduced pressure of 0.1 to 200 Torr. When azeotropic distillation is carried out under the above conditions, moisture can be removed without adding excessive energy and without decomposition of the produced LiFSI.

In the present invention, after preparing a carbonate solution of lithium bis(fluorosulfonyl)imide, the solvent is not removed from the solution (if an azeotropic distillation step is included, part of the carbonate is removed), and the solvent is used as is in the electrolyte solution for a secondary battery, thereby eliminating the need for a solvent removal process. Battery manufacturing can be done efficiently, and the creation and mixing of impurities that occur during the solvent removal process can be prevented. In addition, it can solve the deliquescence problem of lithium bis(fluorosulfonyl)imide absorbing moisture during or after drying, or the residual problem of unnecessary organic solvents.

By the production method of the present invention, a solution containing lithium bis(fluorosulfonyl)imide and carbonate is obtained without going through the recovery and drying process of lithium bis(fluorosulfonyl)imide in the solid phase, which is then added to the electrolyte solution. It can be used in the preparation of. The present invention provides a non-aqueous electrolyte solution containing the above solution.

The electrolyte solution obtained by the production method of the present invention can be used in batteries with charge/discharge mechanisms such as lithium ion secondary batteries and fuel cells, electrolytic capacitors, electric double layer capacitors, solar cells, electrochromic display devices, etc.

Hereinafter, preferred embodiments of the present invention will be described in detail as follows. However, in describing the present invention, descriptions of already known conditions or configurations will be omitted to make the gist of the present invention clear.

Example 1

In a PFA (fluororesin) reaction vessel equipped with a stirrer, condenser, and thermometer, 24.7 g (0.95 mol) of LiF and 362 g (weight ratio 2) of dimethyl carbonate as a solvent were added at room temperature under a nitrogen atmosphere. 181 g (1 mol) of HFSI [bis(fluorosulfonyl)imide] was added. After that, the reaction solution was stirred at 25°C and normal pressure for 5 hours to carry out the reaction. Afterwards, the pressure was reduced to 0.1 atm and the remaining HF was removed for 0.5 hours. Afterwards, 7.4 g (0.1 mol) of Li ₂ CO ₃ was added to the reaction solution and stirred at room temperature for 1 hour.

Afterwards, the reaction solution was first filtered at room temperature through a filter with a pore diameter of 0.45㎛, and then secondarily filtered through a filter with a pore diameter of 0.2㎛. The filtrate was azeotropically distilled at a pressure of 20 Torr and a temperature of 40 ˚C to remove moisture, and the final dimethyl carbonate solution of lithium bis(fluorosulfonyl)imide was obtained.

The content of LiFSI was calculated by F-NMR.

pH was measured with a pH meter.

F ^- , SO ₄ ^2- , Cl ^- , NH ₄ ⁺ , FSO ₃ ^- and H ₂ NSO ₃ ^- contents were measured by ion chromatography.

Acidity was measured by titrimetric method.

Moisture was measured using the Karl Fischer measurement method.

The LiFSI content, pH, and impurity content of the solution are shown in Table 1 below.

Example 2

In a PFA (fluororesin) reaction vessel equipped with a stirrer, condenser, and thermometer, 23.9 g (0.92 mol) of LiF and 362 g (weight ratio 2) of ethylmethyl carbonate as a solvent were added at room temperature under a nitrogen atmosphere. 181 g (1 mol) of HFSI [bis(fluorosulfonyl)imide] was added. An ethylmethyl carbonate solution of LiFSI was obtained in the same manner as in Example 1, except that 11.1 g (0.15 mol) of Li ₂ CO ₃ was added.

The LiFSI content, pH, and impurity content of the solution are shown in Table 1 below.

Example 3

In a PFA (fluororesin) reaction vessel equipped with a stirrer, condenser, and thermometer, 23.4 g (0.90 mol) of LiF and 362 g (weight ratio 2) of dimethyl carbonate as a solvent were added at room temperature under a nitrogen atmosphere. 181 g (1 mol) of HFSI [bis(fluorosulfonyl)imide] was added. A dimethyl carbonate solution of LiFSI was obtained in the same manner as Example 1, except that 11.1 g (0.15 mol) of Li ₂ CO ₃ was added.

The LiFSI content, pH, and impurity content of the solution are shown in Table 1 below.

Example 4

Into a PFA (fluororesin) reaction vessel equipped with a stirrer, condenser, and thermometer, 24.7 g (0.95 mol) of LiF and 362 g (weight ratio 2) of diethyl carbonate as a solvent were added at room temperature under a nitrogen atmosphere. 181 g (1 mol) of HFSI [bis(fluorosulfonyl)imide] was added. A LiFSI diethyl carbonate solution was obtained in the same manner as in Example 1, except that 7.4 g (0.1 mol) of Li ₂ CO ₃ was added.

The LiFSI content, pH, and impurity content of the solution are shown in Table 1 below.

Example 5

In a PFA (fluororesin) reaction vessel equipped with a stirrer, condenser, and thermometer, 24.7 g (0.95 mol) of LiF and 362 g (weight ratio 2) of dimethyl carbonate as a solvent were added at room temperature under a nitrogen atmosphere. 181 g (1 mol) of HFSI [bis(fluorosulfonyl)imide] was added. After that, the reaction solution was stirred at 25°C and normal pressure for 5 hours to carry out the reaction. Afterwards, the remaining HF was removed for 0.5 hours while bubbling nitrogen gas. Afterwards, 7.4 g (0.1 mol) of Li ₂ CO ₃ was added and stirred at room temperature for 1 hour.

Afterwards, the reaction solution was first filtered through a filter with a pore diameter of 0.45㎛, and then secondarily filtered through a filter with a pore diameter of 0.2㎛, to obtain a dimethyl carbonate solution of LiFSI.

The LiFSI content, pH, and impurity content of the solution are shown in Table 1 below.

Comparative example 1

In a PFA (fluororesin) reaction vessel equipped with a stirrer, condenser, and thermometer, 28.6 g (1.1 mol) of LiF and 362 g (weight ratio 2) of dimethyl carbonate as a solvent were added at room temperature under a nitrogen atmosphere. 181 g (1 mol) of HFSI [bis(fluorosulfonyl)imide] was added. After that, the reaction solution was stirred at 25°C and normal pressure for 5 hours to carry out the reaction. Afterwards, the pressure was reduced to 0.1 atm to remove remaining HF for 1 hour, and the reaction solution was first filtered at room temperature through a filter with a pore diameter of 0.45㎛, and then secondarily filtered through a filter with a pore diameter of 0.2㎛ to remove lithium bis(fluorosulfonyl). ) A dimethyl carbonate solution of imide was obtained.

The LiFSI content, pH, and impurity content of the solution are shown in Table 1 below.

Comparative Example 2

In a PFA (fluororesin) reaction vessel equipped with a stirrer, condenser, and thermometer, 23.4 g (0.9 mol) of LiF and 362 g (weight ratio 2) of dimethyl carbonate as a solvent were added at room temperature under a nitrogen atmosphere. 181 g (1 mol) of HFSI [bis(fluorosulfonyl)imide] was added. After that, the reaction solution was stirred at 25°C and normal pressure for 5 hours to carry out the reaction. Afterwards, the pressure was reduced to 0.1 atm to remove remaining HF for 1 hour, and the reaction solution was first filtered at room temperature through a filter with a pore diameter of 0.45㎛, and then secondarily filtered through a filter with a pore diameter of 0.2㎛ to remove lithium bis(fluorosulfonyl). ) A dimethyl carbonate solution of imide was obtained.

The LiFSI content, pH, and impurity content of the solution are shown in Table 1 below.

division LiFSI content
(g) LiFSI concentration
(weight%) F ^- (ppm) SO ₄ ^2-
(ppm) Cl ^-
(ppm) ^NH ₄₊
(ppm) FSO ₃ ^-
(ppm) H ₂ NSO ₃ ^-
(ppm) acidity
(ppm) moisture
(ppm) pH standard 30 30 One 20 30 50 10 20 6.5~7.5 Example 1 185 35.8 11 14 < 1 7 16 15 4 14 7.0 Example 2 182 35.5 18 22 < 1 11 13 21 8 16 6.9 Example 3 181 35.4 19 28 < 1 6 9 32 7 16 6.9 Example 4 180 35.2 13 17 < 1 9 28 27 7 18 7.0 Example 5 186 40.0 13 11 < 1 18 23 22 5 17 7.1 Comparative Example 1 187 34.6 370 52 < 1 26 64 41 56 37 6.2 Comparative Example 2 168 32.3 632 67 < 1 15 72 129 80 44 6.0

According to Table 1, in the production method of the present invention, LiFSI is produced by reacting HFSI and LiF in a carbonate solvent, and then the solution is treated with Li ₂ CO ₃ and there is no process of recovering LiFSI in a solid phase, so it is sufficient. While LiFSI is produced in high yield, acid components such as HF and sulfuric acid are removed, and in particular, the content of fluorosulfonic acid and sulfamic acid is reduced, making it possible to obtain a carbonate solution of lithium bis(fluorosulfonyl)imide whose pH becomes neutral. In particular, a carbonate solution of lithium bis(fluorosulfonyl)imide with reduced moisture content can be obtained. On the other hand, in Comparative Example 1, in which more than 1 equivalent of lithium fluoride was reacted with respect to 1 equivalent of bis(fluorosulfonyl)imide, it was difficult to remove the remaining LiF by filtration, and hydrogen fluoride, sulfuric acid, fluorosulfonic acid, and sulfamic acid were present in the solution. It can be seen that the content of acid components and moisture is high. In addition, in Comparative Example 2, where less than 1 equivalent of lithium fluoride was reacted with respect to 1 equivalent of bis(fluorosulfonyl)imide, but there was no subsequent treatment with Li ₂ CO ₃ , it was found that the content of acid components in the solution was high. You can.

Claims (11)

Step 1) reacting lithium fluoride (LiF) in a carbonate solvent at a ratio of less than 1 equivalent to 1 equivalent of bis(fluorosulfonyl)imide (HFSI), and
2) A method for producing a carbonate solution of lithium bis(fluorosulfonyl)imide (LiFSI) comprising the step of treating the reaction solution of step 1) with Li ₂ CO ₃ . The method of claim 1, wherein the carbonate solvent is a carbonate of lithium bis(fluorosulfonyl)imide (LiFSI), one or more types selected from dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, ethylene carbonate, and propylene carbonate. Solution preparation method. The method of claim 1, wherein the carbonate solution of lithium bis(fluorosulfonyl)imide (LiFSI) has a pH of 6.5 to 7.5. The method of claim 1, wherein in step 1), lithium fluoride (LiF) is reacted at a ratio of 0.7 equivalent to less than 1 equivalent with respect to 1 equivalent of bis(fluorosulfonyl)imide (HFSI). Method for producing carbonate solution of rosulfonyl)imide (LiFSI). The method of claim 1, wherein the carbonate solvent content for bis(fluorosulfonyl)imide in step 1) is 1 to 5 weight of lithium bis(fluorosulfonyl)imide based on 1 weight of bis(fluorosulfonyl)imide. Method for producing carbonate solution of imide (LiFSI). The method of claim 1, wherein the amount of Li ₂ CO ₃ used in step 2) is the value of the following formula (1).
Equation (1)
Equivalent amount of Li ₂ CO ₃ used = 1 - ax Equivalent amount of LiF used
a is a number from 0.6 to 0.9. The method of claim 1, wherein the step of treating with Li ₂ CO ₃ includes adding Li ₂ CO ₃ and stirring. The method of claim 1, comprising a purification process of filtering the reaction solution after step 2). The method of claim 8, wherein the filtration purification process first removes coarse particles through a filter with a pore diameter of 0.3 to 0.7 ㎛, and then secondarily filters the filtrate through a filter with a pore diameter of less than 0.3 ㎛. Method for producing carbonate solution of ponyl)imide (LiFSI). The method of claim 8, comprising the step of removing moisture by azeotropic distillation in step 3) after the purification process of filtering the reaction solution. A non-aqueous electrolyte solution containing a carbonate solution of lithium bis(fluorosulfonyl)imide (LiFSI) prepared by the production method of claim 1.