Impurity removal agent for removing fluorosulfonic acid in difluorosulfonyl imide and purification method of difluorosulfonyl imide crude product containing fluorosulfonic acid

Abstract

The invention provides an impurity removal agent for removing fluorosulfonic acid in bis (fluorosulfonyl) imide and a purification method of a bis (fluorosulfonyl) imide crude product containing fluorosulfonic acid. The impurity removal agent comprises liquid organic amine. Therefore, when the impurity removal agent is used for purifying the difluorosulfonyl imide crude product containing the fluorosulfonic acid, the removal effect on the fluorosulfonic acid can be improved on the premise of not introducing other impurity ions, and the purity of the difluorosulfonyl imide is further improved.

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 purification method for a crude bisfluorosulfonyl imide containing fluorosulfonic acid. Background Art

[0002] Lithium bis(fluorosulfonyl)imide is an important lithium battery material. Its usage has gradually increased in recent years, and it has a trend from being an electrolyte additive to becoming the main electrolyte salt. At present, bis(fluorosulfonyl)imide is mainly used to prepare lithium bis(fluorosulfonyl)imide. Therefore, the impurity level in bis(fluorosulfonyl)imide will largely determine the quality level of lithium bis(fluorosulfonyl)imide. One of the main impurities in bis(fluorosulfonyl)imide is fluorosulfonic acid. The relevant technology mainly removes fluorosulfonic acid by distillation or introducing salt, but the efficiency is low and the fluorosulfonic acid content in bis(fluorosulfonyl)imide is relatively high. 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, wherein the impurity remover comprises a liquid organic amine. Thus, the impurity remover is used to purify the crude bisfluorosulfonyl imide containing fluorosulfonic acid, thereby improving the removal effect of fluorosulfonic acid without introducing other impurity ions, thereby improving 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 types of 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. Therefore, the above-mentioned saturated fatty amines have fewer side reactions during the removal of fluorosulfonic acid, which can improve the removal efficiency of fluorosulfonic acid and reduce the content of fluorosulfonic acid in bis(fluorosulfonyl)imide.

[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 performing reduced pressure distillation on the mixture to obtain the bisfluorosulfonyl imide. Thus, by making the molar ratio of the amine group in the organic amine to the fluorosulfonic acid within the above range, the removal effect of fluorosulfonic acid can be improved, the content of 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 fluorosulfonic acid and the yield of 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 comprises: 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, thereby preventing moisture from entering the system and preventing the hydrolysis of bis(fluorosulfonyl)imide from generating 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 easily understood from the description of the embodiments in conjunction with the following drawings, in which:

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

[0017] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. If no specific techniques or conditions are specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used that do not specify the manufacturer are all 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 utilizes 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 utilize the salt to preferentially react with fluorosulfonic acid to obtain a high-boiling-point fluorosulfonate salt which is then retained in the heavy component, thereby achieving the purpose of removing the fluorosulfonate ion.

[0019] For the first method, since the boiling points of fluorosulfonic acid and bis(fluorosulfonyl)imide are very close, the number of plates required for distillation will be large, that is, the equipment and civil engineering investment will be large. In addition, the operation of the distillation tower is also extremely complicated, the reflux ratio is large, the overall energy consumption of the process is very high, and the efficiency is low.

[0020] For the second method, mainly halide salts (such as sodium chloride, potassium chloride, etc.), sulfates (sodium sulfate, potassium sulfate, etc.), organic acid salts (sodium acetate, potassium acetate) can be selected as impurity removers. Fluorosulfonic acid is an impurity. Compared with the bisfluorosulfonyl imide product, its content is less. Too much impurity remover will cause product loss, and insufficient addition will cause high residual fluorosulfonic acid. Therefore, the amount of impurity remover needs to be accurately controlled to achieve a better deacidification effect. The current impurity removers are all solids, and the amount added is difficult to accurately control. In addition, the water content of commercially available salts is generally difficult to reach the ppm level, which contains a certain amount of water. The introduction of water will cause the bisfluorosulfonyl imide to decompose and produce additional impurities. Thirdly, the use of salt to remove impurities will also introduce other acidic substances, such as chloride salts 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] The first aspect of the present application provides an impurity remover for removing fluorosulfonic acid from bisfluorosulfonyl imide, comprising a liquid organic amine. Thus, the impurity remover is used to purify the crude bisfluorosulfonyl imide containing fluorosulfonic acid, which can improve the removal effect of fluorosulfonic acid without introducing other impurity ions, thereby reducing the content of fluorosulfonic acid in the bisfluorosulfonyl imide and improving the purity of the bisfluorosulfonyl imide.

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

[0023] The present application uses liquid organic amine to remove fluorosulfonic acid from bisfluorosulfonyl imide, and fluorosulfonic acid and bisfluorosulfonyl imide react rapidly with the organic amine at the same time to obtain the corresponding ammonium salt. Since bisfluorosulfonyl imide is present in large quantities and fluorosulfonate is present in small quantities in the crude product, when it is first added, a large amount of organic amine reacts with bisfluorosulfonyl imide to form the corresponding ammonium salt, and fluorosulfonic acid is not completely reacted to form ammonium fluorosulfonic acid salt.

[0024]

[0025] As the reaction proceeds, the fluorosulfonic acid that has not yet participated in the reaction will collide with the ammonium salt of bis(fluorosulfonyl)imide. Since the acidity of fluorosulfonic acid is stronger than that of bis(fluorosulfonyl)imide, an ion exchange reaction will occur according to the principle of strong acid to weak acid, and fluorosulfonic acid ammonium salt and bis(fluorosulfonyl)imide will be obtained. In this way, all the fluorosulfonic acid in the crude product can be converted into high-boiling ammonium salt, which can be separated from 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. Therefore, the above-mentioned saturated fatty amines can improve the removal effect of fluorosulfonic acid and reduce the content of fluorosulfonic acid in bisfluorosulfonyl imide on the one hand; on the other hand, the above-mentioned saturated fatty amines have no other active groups except the amino group, and other side reactions are not 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 performing reduced pressure distillation on the mixture to obtain the bisfluorosulfonyl imide. Thus, the purification method is simple, has high reaction efficiency, does not need to introduce other anionic impurities, can reduce the content of fluorosulfonic acid in bisfluorosulfonyl imide, and improves the purity of bisfluorosulfonyl imide.

[0034] The following is a detailed description of each step of the method. 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 the mixture 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 amine group in the organic amine to the fluorosulfonic acid is 1.5 to 4. Thus, by controlling the molar ratio of the amine 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 improved.

[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, and the yield of bisfluorosulfonyl imide is improved. 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 can be a range of any of the above values. Thus, the rate of homogeneous reaction is increased, and the removal efficiency of fluorosulfonic acid impurities is improved.

[0039] According to some specific embodiments of the present application, the method may further include: 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. Thus, introducing the inert gas or nitrogen in advance can prevent moisture from entering the system and avoid the hydrolysis of bis(fluorosulfonyl)imide to produce additional impurities.

[0040] S20: subjecting the mixture 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 a range of any of the above values. Thus, the separation efficiency of the bis(fluorosulfonyl)imide in the mixture is improved, the distillation time is shortened, and the energy consumption is reduced.

[0043] As an example, the temperature during the reduced pressure distillation can be 80°C, 90°C, 100°C, 110°C, 120°C or 130°C, or can be any range of the above values. Thus, the separation efficiency of the bis(fluorosulfonyl)imide in the mixture is improved, the distillation time is shortened, and the energy consumption is reduced.

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

[0045] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. If no specific techniques or conditions are specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used that do not specify the manufacturer are all 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 (containing 8600 ppm of fluorosulfonate according to ion chromatography, equivalent to 3.44 g of fluorosulfonic acid, 34.4 mmol) was added. Stirring was started, 6.25 g of triethylamine (61.8 mmol) was added, and the reaction was maintained at 50 °C for 30 min.

[0048] Vacuum distillation: The reactor is equipped with a distillation head, a condenser, and a receiving bottle, and a vacuum pump is connected at the same time. The vacuum pump is turned on. When the pressure is less than 4 kPa and stable, the temperature is raised to 95°C, and liquid begins to flow out. High-quality bis(fluorosulfonyl)imide is obtained by collecting. When no liquid flows out, a total of 394.8 g of high-quality bis(fluorosulfonyl)imide is collected (yield 98.7%, ion chromatography detection of fluorosulfonate 330 ppm). The residue in the reactor is liquid after cooling.

[0049] The methods in Examples 2 to 15 are the same as those in Example 1, and the differences are detailed 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 amine 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 in Example 1, except that the molar ratio of the amino group in the organic amine to the fluorosulfonic acid is 4.5:1.

[0054] Comparative Example 3

[0055] Take 400g of crude bis(fluorosulfonyl)imide from the same batch in Example 1, place in a 500mL stainless steel flask replaced with nitrogen, load a 60cm high φ20 stainless steel distillation column containing tetrafluoro filler, connect a vacuum pump, turn on the vacuum pump, and when the pressure in the system is evacuated to below 4kPa and stable, start to heat up to reflux in the distillation column, at this time, the temperature in the flask is 95°C, and the system continues to reflux stably for a period of time, and after the flask temperature and the distillation column top temperature are stable, start to carry out vacuum distillation, and collect fractions at different temperatures. When the column top temperature is 60°C, some liquid comes out, and a total of 325.2g liquid (detected by ion chromatography, wherein fluorosulfonate 10600ppm) is collected. When the column top temperature is 64°C, there is liquid outflow again, and a total of 28.2g liquid (detected by ion chromatography, wherein fluorosulfonate 4700ppm) is collected, and the remainder is the kettle residue that cannot be steamed 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 (same batch as Example 1, ion chromatography detected 8600 ppm of fluorosulfonate, equivalent to 3.44 g of fluorosulfonic acid, 34.4 mmol) was added, stirring was started, 5.03 g of sodium chloride (86.0 mmol) was added, and the reaction was maintained at 50 ° C for 30 min to complete.

[0058] The reactor was equipped with a distillation head, a condenser, and a receiving bottle, and a vacuum pump was connected at the same time. The vacuum pump was turned on. When the pressure was less than 4 kPa and stable, the temperature was raised to 95°C, and liquid began to flow out. High-quality bis(fluorosulfonyl)imide was obtained by collecting. When no liquid flowed out, a total of 378.4 g of high-quality bis(fluorosulfonyl)imide was collected (yield 94.6%, ion chromatography detected 970 ppm of fluorosulfonate). The residue in the reactor was a paste-like solid after cooling.

[0059] Table 1

[0060]

[0061]

[0062] Performance Testing

[0063] Test 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 ​​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] It can be seen from the comparison between Examples 1 to 15 and Comparative Examples 1 to 4 that the present application can improve the removal effect of fluorosulfonic acid and the yield of bisfluorosulfonyl imide by adding organic amines during the purification process and controlling the amount of organic amines added. This indicates that the addition of organic amines can convert all fluorosulfonic acid in the crude product into high-boiling ammonium salts, which are then separated from bisfluorosulfonyl imide by distillation, thereby improving the removal effect 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] It can be seen from the comparison between Examples 9 to 12 and Comparative Examples 1 and 2 that 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] It can be seen from the comparison between Examples 1 to 3 and Examples 4 to 8 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, bis(fluorosulfonyl)imide with low fluorosulfonic acid content and high yield can be obtained simultaneously.

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

[0074] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means 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 may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

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

Claims

1. An impurity remover for removing fluorosulfonic acid from bis(fluorosulfonyl)imide, characterized in that: Includes liquid organic amines.

2. The impurity remover according to claim 1, characterized in that The organic amine includes at least one of aliphatic amine, aromatic amine and alicyclic amine.

3. The impurity remover according to claim 2, characterized in that Satisfy 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 impurity remover 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. 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 the impurity remover according to any one of claims 1 to 4 in a reactor, and heated 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; The mixture is distilled under reduced pressure to obtain the bisfluorosulfonyl imide.

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

0.

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

8. The method for purifying a crude bisfluorosulfonyl imide containing fluorosulfonic acid according to claim 5 or 6, characterized in that: Satisfy 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.

9. The method for purifying a crude bisfluorosulfonyl imide containing fluorosulfonic acid according to claim 5 or 6, 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.

10. The method for purifying a crude bisfluorosulfonyl imide containing fluorosulfonic acid according to claim 5 or 6, 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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