Impurity remover for removing fluorosulfonic acid from bisfluorosulfonyl imide and purification method for crude bisfluorosulfonyl imide containing fluorosulfonic acid

Abstract

This application provides a scavenger for removing fluorosulfonic acid from bisfluorosulfonyl imide and a method for purifying crude bisfluorosulfonyl imide containing fluorosulfonic acid. The scavenger comprises a liquid organic amine. Thus, using the scavenger to purify crude bisfluorosulfonyl imide containing fluorosulfonic acid improves the removal of fluorosulfonic acid without introducing other impurity ions, thereby increasing the purity of the bisfluorosulfonyl imide.

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular to an impurity remover for removing fluorosulfonic acid from bisfluorosulfonyl imide and a method for purifying crude bisfluorosulfonyl imide containing fluorosulfonic acid. Background Art

[0002] Lithium bis(fluorosulfonyl)imide (LiBISM) is an important lithium battery material. Its usage has been increasing in recent years, with a trend toward becoming the primary electrolyte salt, rather than an electrolyte additive. Currently, bis(fluorosulfonyl)imide is primarily used to prepare lithium bis(fluorosulfonyl)imide. Therefore, the impurity level in bis(fluorosulfonyl)imide largely determines the quality of lithium bis(fluorosulfonyl)imide. Fluorosulfonic acid (FSA) is a major impurity in bis(fluorosulfonyl)imide. Related technologies primarily remove FSA through distillation or the introduction of salts, but this is inefficient and results in a high FSA content in bis(fluorosulfonyl)imide. Summary of the Invention

[0003] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0004] In a first aspect, the present application provides an impurity remover for removing fluorosulfonic acid from bisfluorosulfonyl imide, the impurity remover comprising a liquid organic amine. Thus, using the impurity remover to purify crude bisfluorosulfonyl imide containing fluorosulfonic acid can improve the removal of fluorosulfonic acid without introducing other impurity ions, thereby increasing the purity of the bisfluorosulfonyl imide.

[0005] According to some embodiments of the present application, the organic amine includes at least one of aliphatic amine, aromatic amine, and alicyclic amine.

[0006] According to some embodiments of the present application, the impurity remover satisfies at least one of the following conditions: the aliphatic amine includes at least one of triethylamine, diethylamine, and n-butylamine; the aromatic amine includes at least one of aniline and diphenylamine; the alicyclic amine includes at least one of cyclohexylamine, morpholine, and piperidine.

[0007] Therefore, the reaction between the above-mentioned organic amines and the crude bis(fluorosulfonyl)imide is a homogeneous reaction, which can improve the reaction efficiency and the removal effect of fluorosulfonic acid.

[0008] According to some embodiments of the present application, the organic amine includes at least one of triethylamine, diethylamine, and n-butylamine. Thus, these saturated fatty amines produce fewer side reactions during the removal of fluorosulfonic acid, thereby improving the removal efficiency of fluorosulfonic acid and reducing the fluorosulfonic acid content in bisfluorosulfonimide.

[0009] The second aspect of the present application provides a method for purifying a crude bisfluorosulfonyl imide containing fluorosulfonic acid, comprising mixing the crude bisfluorosulfonyl imide containing fluorosulfonic acid with the impurity remover provided in the first aspect of the present application in a reactor, heating to obtain a mixture containing ammonium fluorosulfonic acid and bisfluorosulfonyl imide, wherein the molar ratio of the amine group in the organic amine to the fluorosulfonic acid is 1.5-4; and subjecting the mixture to reduced pressure distillation to obtain the bisfluorosulfonyl imide. Thus, by adjusting the molar ratio of the amine group in the organic amine to the fluorosulfonic acid within the above range, the removal effect of the fluorosulfonic acid can be improved, the content of the fluorosulfonic acid in the bisfluorosulfonyl imide can be reduced, and the purity of the bisfluorosulfonyl imide can be improved.

[0010] According to some embodiments of the present application, the molar ratio of the amino group in the organic amine to the fluorosulfonic acid is 1.5-2.0, thereby improving the removal effect of the fluorosulfonic acid and the yield of the bis(fluorosulfonyl)imide.

[0011] According to some embodiments of the present application, the heating temperature is 20° C.-130° C. Thus, the removal efficiency of fluorosulfonic acid is improved.

[0012] According to some embodiments of the present application, the method satisfies at least one of the following conditions: the pressure during the vacuum distillation is 0-40 KPa; the temperature during the vacuum distillation is 80° C.-130° C. Thus, the removal efficiency of fluorosulfonic acid is improved.

[0013] According to some embodiments of the present application, the method further includes: before mixing the crude bis(fluorosulfonyl)imide containing the fluorosulfonic acid with the organic amine in the reactor, introducing an inert gas or nitrogen into the reactor to prevent moisture from entering the system and avoid hydrolysis of the bis(fluorosulfonyl)imide to generate additional impurities.

[0014] According to some embodiments of the present application, after the crude bisfluorosulfonyl imide containing fluorosulfonic acid is purified by the purification method, the content of fluorosulfonic acid in the obtained bisfluorosulfonyl imide is less than or equal to 1000 ppm. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0016] Figure 1 A schematic diagram of the process for purifying crude bis(fluorosulfonyl)imide according to one embodiment of the present application is shown. DETAILED DESCRIPTION

[0017] The following embodiments of the present invention are described in detail. The embodiments described below are exemplary and are only used to explain the present invention, and are not to be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this field or the product specifications are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be obtained commercially.

[0018] In the related art, there are two main methods for purifying crude bis(fluorosulfonyl)imide. The first is a conventional distillation method, which uses the difference in boiling points between fluorosulfonic acid and bis(fluorosulfonyl)imide to remove fluorosulfonic acid. The second is to introduce salt into the crude bis(fluorosulfonyl)imide, and use the salt to preferentially react with fluorosulfonic acid to obtain a high-boiling-point fluorosulfonate salt, which then remains in the heavy component, thereby achieving the purpose of removing the fluorosulfonate ion.

[0019] For the first method, because the boiling points of fluorosulfonic acid and bis(fluorosulfonyl)imide are very close, the number of distillation stages required is high, resulting in high equipment and construction costs. Furthermore, the distillation tower operation is extremely complex, with a high reflux ratio, resulting in high overall energy consumption and low efficiency.

[0020] For the second method, the main optional halogenated salts (such as sodium chloride, potassium chloride, etc.), sulfates (sodium sulfate, potassium sulfate, etc.), organic acid salts (sodium acetate, potassium acetate) are used as impurity removers. Fluorosulfonic acid is an impurity. Compared with the bis(fluorosulfonyl)imide product, its content is relatively low. Too much impurity remover will lead to product loss, and insufficient addition will lead to high residual fluorosulfonic acid. Therefore, the amount of impurity remover needs to be precisely controlled to achieve a better deacidification effect. However, the current impurity removers are all solids, and the amount added is difficult to precisely control. In addition, the water content of commercially available salts is generally difficult to reach the ppm level, and a certain amount of water is contained therein. The introduction of water will cause the bis(fluorosulfonyl)imide to decompose and produce additional impurities. Again, using salt for impurity removal will also introduce other acidic substances, such as chlorides will produce hydrogen chloride tail gas, sulfates will produce sulfuric acid, and acetates will produce acetic acid. These will more or less cause the waste gas and waste liquid components to be more complicated, resulting in safety and environmental protection problems.

[0021] In a first aspect, the present application provides an impurity remover for removing fluorosulfonic acid from bisfluorosulfonyl imide, comprising a liquid organic amine. Thus, using the impurity remover to purify crude bisfluorosulfonyl imide containing fluorosulfonic acid can improve the removal of fluorosulfonic acid without introducing other impurity ions, thereby reducing the fluorosulfonic acid content in the bisfluorosulfonyl imide and improving the purity of the bisfluorosulfonyl imide.

[0022] The principle by which this method can achieve the above-mentioned beneficial effects is described in detail below:

[0023] This application uses a liquid organic amine to remove the fluorosulfonic acid from bisfluorosulfonyl imide. Fluorosulfonic acid and bisfluorosulfonyl imide react rapidly with the organic amine simultaneously to produce the corresponding ammonium salt. Since the crude product contains a large amount of bisfluorosulfonyl imide and a small amount of fluorosulfonate, upon initial addition, a large amount of the organic amine reacts with the bisfluorosulfonyl imide to form the corresponding ammonium salt, while the fluorosulfonic acid does not fully react to form the ammonium fluorosulfonate salt.

[0024]

[0025] As the reaction proceeds, the fluorosulfonic acid that hasn't yet reacted will collide with the ammonium salt of bis(fluorosulfonyl)imide. Because fluorosulfonic acid is more acidic than bis(fluorosulfonyl)imide, an ion exchange reaction occurs based on the principle of strong acid converting weak acid, producing ammonium fluorosulfonic acid and bis(fluorosulfonyl)imide. This ensures that all fluorosulfonic acid in the crude product is converted into the high-boiling-point ammonium salt, which can then be separated from the bis(fluorosulfonyl)imide by distillation.

[0026]

[0027] According to some embodiments of the present application, the organic amine includes at least one of aliphatic amine, aromatic amine, and alicyclic amine.

[0028] As an example, the aliphatic amine includes at least one of triethylamine, diethylamine, and n-butylamine.

[0029] As an example, the aromatic amine includes at least one of aniline and diphenylamine.

[0030] As an example, the alicyclic amine includes at least one of cyclohexylamine, morpholine, and piperidine.

[0031] Therefore, the reaction between the above-mentioned types of organic amines and the crude bisfluorosulfonyl imide is a homogeneous reaction, which can increase the reaction rate between fluorosulfonic acid and liquid organic amine, and between bisfluorosulfonyl imide and liquid organic amine, improve the removal effect of fluorosulfonic acid, thereby reducing the content of fluorosulfonic acid in bisfluorosulfonyl imide and improving the purity of bisfluorosulfonyl imide.

[0032] According to some embodiments of the present application, the organic amine includes at least one of triethylamine, diethylamine, and n-butylamine. Thus, these saturated fatty amines can, on the one hand, improve the removal of fluorosulfonic acid and reduce the fluorosulfonic acid content in bisfluorosulfonyl imide; and, on the other hand, these saturated fatty amines have no other active groups besides the amino group, making side reactions less likely to occur during the impurity removal process.

[0033] The second aspect of the present application provides a method for purifying a crude bisfluorosulfonyl imide containing fluorosulfonic acid, comprising mixing the crude bisfluorosulfonyl imide containing fluorosulfonic acid with the impurity remover provided in the first aspect of the present application in a reactor, heating to obtain a mixture containing ammonium fluorosulfonic acid and bisfluorosulfonyl imide, wherein the molar ratio of the amine group in the organic amine to the fluorosulfonic acid is 1.5-4; and subjecting the mixture to reduced pressure distillation to obtain the bisfluorosulfonyl imide. Thus, the purification method is simple, has high reaction efficiency, does not require the introduction of other anionic impurities, can reduce the content of fluorosulfonic acid in the bisfluorosulfonyl imide, and improves the purity of the bisfluorosulfonyl imide.

[0034] The following is a detailed description of each step of the method, refer to Figure 1 , the method comprising:

[0035] S10: Mixing the crude bis(fluorosulfonyl)imide containing fluorosulfonic acid with an organic amine in a reactor and heating to obtain a mixture containing ammonium fluorosulfonate and bis(fluorosulfonyl)imide.

[0036] According to some embodiments of the present application, the molar ratio of the amino group in the organic amine to the fluorosulfonic acid is 1.5-4. Thus, by controlling the molar ratio of the amino group in the organic amine to the fluorosulfonic acid, the removal effect of the fluorosulfonic acid is improved, the content of the fluorosulfonic acid in the bisfluorosulfonyl imide is reduced, and the purity of the bisfluorosulfonyl imide is increased.

[0037] According to some embodiments of the present application, the molar ratio of the amine group in the organic amine to the fluorosulfonic acid is 1.5-4. For example, it can be 1.5, 1.8, 2.1, 2.4, 2.7, 3.0, 3.3, 3.6, 3.9 or 4, or it can be a range composed of any of the above numerical values. Thus, while improving the removal effect of fluorosulfonic acid, the risk of excessive organic amine continuing to react with bisfluorosulfonyl imide is reduced, thereby improving the yield of bisfluorosulfonyl imide. According to some embodiments of the present application, the molar ratio of the amine group in the organic amine to the fluorosulfonic acid is 1.5-2.0.

[0038] According to some specific embodiments of the present application, the heating temperature is 20°C-130°C. For example, it can be 20°C, 50°C, 70°C, 100°C, or 130°C, or any range thereof. This increases the rate of the homogeneous reaction and the efficiency of removing the fluorosulfonic acid impurity.

[0039] According to some specific embodiments of the present application, the method may further include: introducing an inert gas or nitrogen into the reactor before mixing the crude bis(fluorosulfonyl)imide containing the fluorosulfonic acid with the organic amine in the reactor. Thus, introducing the inert gas or nitrogen in advance can prevent moisture from entering the system and avoid the hydrolysis of the bis(fluorosulfonyl)imide to produce additional impurities.

[0040] S20: The mixture is subjected to reduced pressure distillation to obtain the bis(fluorosulfonyl)imide

[0041] According to some embodiments of the present application, the pressure during the reduced pressure distillation is 0-40 KPa, and the temperature during the reduced pressure distillation is 80° C.-130° C.

[0042] As an example, the pressure during the reduced pressure distillation can be 10 KPa, 20 KPa, 30 KPa, or 40 KPa, or can be within a range consisting of any of the above values. This improves the separation efficiency of the bis(fluorosulfonyl)imide in the mixture, shortens the distillation time, and reduces energy consumption.

[0043] For example, the temperature during the reduced pressure distillation can be 80° C., 90° C., 100° C., 110° C., 120° C., or 130° C., or any range thereof. This improves the separation efficiency of the bis(fluorosulfonyl)imide in the mixture, shortens the distillation time, and reduces energy consumption.

[0044] According to some embodiments of the present application, the content of fluorosulfonic acid in the bisfluorosulfonyl imide is less than or equal to 1000 ppm, thereby reducing the content of fluorosulfonic acid in the bisfluorosulfonyl imide.

[0045] The following embodiments of the present invention are described in detail. The embodiments described below are exemplary and are only used to explain the present invention, and are not to be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this field or the product specifications are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be obtained commercially.

[0046] Example 1

[0047] A 500 mL stainless steel flask was placed in an oil bath. After nitrogen replacement, 400 g of crude bis(fluorosulfonyl)imide (8600 ppm of fluorosulfonate, equivalent to 3.44 g of fluorosulfonic acid, 34.4 mmol, as determined by ion chromatography) was added. Stirring was started, and 6.25 g of triethylamine (61.8 mmol) was added. The reaction was maintained at 50°C for 30 min.

[0048] Vacuum distillation: Install a still, condenser, and receiving flask in the reactor and connect it to a vacuum pump. Once the pressure stabilizes below 4 kPa, raise the temperature to 95°C. Liquid begins to flow out, which is then collected to yield high-quality bis(fluorosulfonyl)imide. When the liquid ceases to flow, 394.8 g of high-quality bis(fluorosulfonyl)imide has been collected (yield 98.7%, ion chromatography analysis reveals 330 ppm of fluorosulfonate). The residue in the reactor becomes liquid upon cooling.

[0049] The methods in Examples 2 to 15 are the same as those in Example 1, with the differences shown in Table 1.

[0050] Comparative Example 1

[0051] The purification method is the same as that in Example 1, except that the molar ratio of the amino group in the organic amine to the fluorosulfonic acid is 1.1:1.

[0052] Comparative Example 2

[0053] The purification method is the same as that of Example 1, except that the molar ratio of the amino group in the organic amine to fluorosulfonic acid is 4.5:1.

[0054] Comparative Example 3

[0055] Get same batch of crude bis(fluorosulfonyl)imide 400g among embodiment 1, be placed in the 500mL stainless steel flask through nitrogen replacement, load onto the stainless steel rectifying column that the high φ 20 of 60cm contains tetrafluoro filler, connect vacuum pump, open vacuum pump, when system internal pressure is evacuated to below 4kPa and stable, start to be warming up to and reflux occurs in the rectifying column, now, flask temperature is 95 ℃, reflux stabilizes for a period of time in system continuation, after flask temperature, rectifying column top temperature are stable, start to carry out rectification under reduced pressure, collect fraction under different temperatures.When column top temperature is 60 ℃, some liquid is had to come out, and 325.2g liquid (detected through ion chromatography, wherein fluorosulfonate radical 10600ppm) is collected altogether.When column top temperature is 64 ℃, liquid is again flowed out, and 28.2g liquid (detected through ion chromatography, wherein fluorosulfonate radical 4700ppm) is collected altogether, and remainder is the still residue that can not steam out.

[0056] Comparative Example 4

[0057] A 500 mL stainless steel flask was placed in an oil bath. After nitrogen replacement, 400 g of crude bis(fluorosulfonyl)imide (from the same batch as in Example 1, ion chromatography analysis showed 8600 ppm of fluorosulfonate, equivalent to 3.44 g and 34.4 mmol of fluorosulfonic acid) was added. Stirring was started, and 5.03 g of sodium chloride (86.0 mmol) was added. The reaction was maintained at 50 ° C for 30 min to complete.

[0058] The reactor was equipped with a distillation head, condenser, and receiving flask, and a vacuum pump was connected. The vacuum pump was turned on and the pressure was stabilized below 4 kPa. The temperature was then raised to 95°C. Liquid began to flow out and was collected to obtain high-quality bis(fluorosulfonyl)imide. When no liquid flowed out, a total of 378.4 g of high-quality bis(fluorosulfonyl)imide was collected (yield 94.6%, ion chromatography analysis showed 970 ppm of fluorosulfonate). The residue in the reactor cooled to a paste-like solid.

[0059] Table 1

[0060]

[0061]

[0062] Performance Testing

[0063] Determination of Fluorosulfonic Acid Content in Bis(Fluorosulfonyl)imide

[0064] Take a certain amount of bis(fluorosulfonyl)imide, dilute it a certain multiple, and test it by anion chromatography to obtain the fluorosulfonate peak area. Then compare it with the peak area of ​​a fluorosulfonate standard solution of known concentration to calculate the fluorosulfonate content in the bis(fluorosulfonyl)imide sample.

[0065] The test results of Examples 1 to 15 and Comparative Examples 1 to 4 are shown in Table 2.

[0066] Table 2

[0067]

[0068] Comparison of Examples 1-15 with Comparative Examples 1-4 demonstrates that, by adding an organic amine during the purification process and controlling the amount of the organic amine added, the present invention can simultaneously improve the removal of fluorosulfonic acid and the yield of bis(fluorosulfonyl)imide. This indicates that the addition of the organic amine can convert all fluorosulfonic acid in the crude product into a high-boiling-point ammonium salt, which is then separated from the bis(fluorosulfonyl)imide by distillation, thereby improving the removal of fluorosulfonic acid.

[0069] It can be seen from Examples 1 to 8 that the addition of different types of organic amines can achieve the effect of removing fluorosulfonic acid in bis(fluorosulfonyl)imide.

[0070] As can be seen from the comparison between Examples 9 to 12 and Comparative Examples 1 and 2, by controlling the amount of organic amine added, the removal effect of fluorosulfonic acid can be improved while increasing the yield of bis(fluorosulfonyl)imide, so that the yield of bis(fluorosulfonyl)imide is greater than or equal to 96%, thereby reducing production costs and improving production efficiency.

[0071] From the comparison between Examples 1 to 3 and Examples 4 to 8, it can be seen that the use of aliphatic amines for purification can further improve the removal effect of fluorosulfonic acid compared to the use of aromatic amines and alicyclic amines.

[0072] It can be seen from Examples 1, 9 and 10 that when the molar ratio of the amino group in the organic amine to the fluorosulfonic acid is in the range of 1.5-2.0, bisfluorosulfonyl imide with low fluorosulfonic acid content and high yield can be obtained.

[0073] It can be seen from Examples 13 to 15 that by controlling the reaction temperature of the crude bis(fluorosulfonyl)imide and the organic amine, the reaction rate and reaction degree can be increased, thereby improving the removal effect of fluorosulfonic acid.

[0074] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0075] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for purifying a crude bis(fluorosulfonyl)imide product containing fluorosulfonic acid, characterized in that: The crude bisfluorosulfonyl imide containing fluorosulfonic acid is mixed with an impurity remover in a reactor and heated to obtain a mixture containing ammonium fluorosulfonic acid and bisfluorosulfonyl imide, wherein the impurity remover comprises a liquid organic amine, and the molar ratio of the amino group in the organic amine to the fluorosulfonic acid is 1.5-4; The mixture is subjected to reduced pressure distillation to obtain the bisfluorosulfonyl imide.

2. The method for purifying a crude bisfluorosulfonyl imide containing fluorosulfonic acid according to claim 1, characterized in that: The organic amine includes at least one of aliphatic amine, aromatic amine and alicyclic amine.

3. The method for purifying a crude bisfluorosulfonyl imide containing fluorosulfonic acid according to claim 2, characterized in that: Meet at least one of the following conditions: The fatty amine includes at least one of triethylamine, diethylamine and n-butylamine; The aromatic amine includes at least one of aniline and diphenylamine; The alicyclic amine includes at least one of cyclohexylamine, morpholine and piperidine.

4. The method for purifying a crude bisfluorosulfonyl imide containing fluorosulfonic acid according to any one of claims 1 to 3, characterized in that: The organic amine includes at least one of triethylamine, diethylamine and n-butylamine.

5. The method for purifying a crude bisfluorosulfonyl imide containing fluorosulfonic acid according to claim 1, characterized in that: The molar ratio of the amino group in the organic amine to the fluorosulfonic acid is 1.5-2.

0.

6. The method for purifying a crude bisfluorosulfonyl imide containing fluorosulfonic acid according to claim 1 or 5, characterized in that: The heating temperature is 20°C-130°C.

7. The method for purifying a crude bisfluorosulfonyl imide containing fluorosulfonic acid according to claim 1 or 5, characterized in that: Meet at least one of the following conditions: The pressure during the reduced pressure distillation is 0-40KPa; The temperature during the reduced pressure distillation is 80°C-130°C.

8. The method for purifying a crude bisfluorosulfonyl imide containing fluorosulfonic acid according to claim 1 or 5, characterized in that: The method further comprises: before mixing the crude bisfluorosulfonyl imide containing the fluorosulfonic acid with the organic amine in the reactor, introducing an inert gas or nitrogen into the reactor.

9. The method for purifying a crude bisfluorosulfonyl imide containing fluorosulfonic acid according to claim 1 or 5, characterized in that: After the crude bisfluorosulfonyl imide containing fluorosulfonic acid is purified by the purification method, the content of fluorosulfonic acid in the obtained bisfluorosulfonyl imide is less than or equal to 1000 ppm.

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