Purification method of bis(fluorosulfonyl)imide and purified bis(fluorosulfonyl)imide salt

Abstract

This application belongs to the field of chemical technology. It provides a method for purifying bis(fluorosulfonyl)imide, as well as the purified bis(fluorosulfonyl)imide and its salt. The purification method includes: reacting the bis(fluorosulfonyl)imide to be purified with a decontaminating agent to obtain a mixture; the decontaminating agent includes a resin with a nitrogen-containing aromatic ring group; the bis(fluorosulfonyl)imide to be purified includes fluorosulfonic acid; and separating the mixture to obtain purified bis(fluorosulfonyl)imide. The decontaminating agent provided in this application contains a resin with a nitrogen-containing aromatic ring group. This resin reacts with fluorosulfonic acid to ultimately form an ammonium fluorosulfonate salt. The fluorosulfonic acid is chemically adsorbed onto the resin with the nitrogen-containing aromatic ring group, thus facilitating the separation of fluorosulfonic acid and bis(fluorosulfonyl)imide without introducing new anionic impurities.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology, specifically relating to a purification method for fluorosulfonylimide, purified bisfluorosulfonylimide, and bisfluorosulfonylimide salt. Background Technology

[0002] Lithium difluorosulfonylimide is an important lithium battery material, and its usage has been gradually increasing in recent years, with a trend towards it becoming a primary electrolyte salt rather than an electrolyte additive. Currently, most manufacturers use difluorosulfonylimide to prepare lithium difluorosulfonylimide. Therefore, the impurity level in difluorosulfonylimide largely determines the quality level of lithium difluorosulfonylimide. One major impurity in difluorosulfonylimide is fluorosulfonic acid. At normal pressure, fluorosulfonic acid has a boiling point of 165.5 °C, while difluorosulfonylimide has a boiling point of 170 °C. Their boiling points are very close, and using traditional distillation methods results in large equipment investment and low production efficiency. Therefore, a salt is added to crude difluorosulfonylimide, which preferentially reacts with fluorosulfonic acid to obtain a high-boiling-point fluorosulfonate, which remains in the heavier components, thereby achieving the purpose of removing the fluorosulfonate ion.

[0003] For methods of removing fluorosulfonic acid using salts, the main options are halides (such as sodium chloride, potassium chloride, etc.), sulfates (sodium sulfate, potassium sulfate, etc.), and organic acid salts (sodium acetate, potassium acetate). However, using these salts for purification introduces other acidic substances. For example, chlorides produce hydrogen chloride tail gas, sulfates produce sulfuric acid, and acetates produce acetic acid. These factors can lead to more complex compositions of waste gas and waste liquid, creating safety and environmental problems. Summary of the Invention

[0004] This invention aims to at least partially address the technical problem that methods for removing fluorosulfonic acid using salts introduce new impurities. Therefore, one object of this invention is to provide a method for purifying difluorosulfonylimide, the purified difluorosulfonylimide, and a difluorosulfonylimide salt. This method for purifying difluorosulfonylimide does not introduce new anionic impurities.

[0005] This application provides a method for purifying bis(fluorosulfonyl)imide. According to embodiments of the invention, the purification method includes:

[0006] The bis(fluorosulfonyl)imide to be purified is reacted with a purification agent to obtain a mixture; the purification agent includes a resin having a nitrogen-containing aromatic ring group; the bis(fluorosulfonyl)imide to be purified includes fluorosulfonic acid;

[0007] The mixture was separated to obtain purified difluorosulfonamide.

[0008] The impurity removal agent provided in this application contains a resin with a nitrogen-containing aromatic ring group. The resin with the nitrogen-containing aromatic ring group reacts with fluorosulfonic acid to form ammonium fluorosulfonate. The fluorosulfonic acid is chemically adsorbed onto the resin with the nitrogen-containing aromatic ring group, thereby facilitating the separation of fluorosulfonic acid and difluorosulfonyl imide without introducing new anionic impurities.

[0009] According to embodiments of the present invention, the purification method for difluorosulfonyl imide may further include at least one of the following additional technical features:

[0010] In some embodiments, the bis(fluorosulfonyl)imide to be purified is reacted with a purifying agent to generate ammonium fluorosulfonate, thereby achieving the chemical adsorption of fluorosulfonic acid onto the resin.

[0011] In some embodiments, the molar ratio of nitrogen-containing aromatic ring groups to fluorosulfonic acid in the resin having nitrogen-containing aromatic ring groups is 4 to 1:1.

[0012] In some embodiments, the steps of reacting the bis(fluorosulfonyl)imide to be purified with the impurity remover include controlling parameters such as: a reaction temperature of 20 °C to 50 °C; and / or a reaction time of more than 30 min.

[0013] In some embodiments, the nitrogen-containing aromatic ring group in the resin contains an amino group or an imine group.

[0014] In some embodiments, the resin having a nitrogen-containing aromatic ring group includes at least one of poly-4-vinylpyridine, polyvinylimidazole, and polypyrrole.

[0015] In some embodiments, the mixture is separated, and the separation method includes filtration.

[0016] In some embodiments, after separating the mixture, a regeneration step is also included for the purified resin.

[0017] The second aspect of this application provides a purified bis(fluorosulfonyl)imide obtained by the above-described purification method for bis(fluorosulfonyl)imide.

[0018] The purified difluorosulfonyl imide provided in this application is obtained by the purification method of difluorosulfonyl imide provided in the first aspect above. No new impurities are introduced into the purified difluorosulfonyl imide, and the content of fluorosulfonic acid impurities meets the requirements.

[0019] A third aspect of this application provides a bis(fluorosulfonyl)imide salt, the raw materials of which include bis(fluorosulfonyl)imide obtained by the above purification method, or include the above-described bis(fluorosulfonyl)imide.

[0020] This application uses the aforementioned bisfluorosulfonylimide to prepare lithium bisfluorosulfonylimide, which has low impurity content and low cost.

[0021] In some embodiments, the bisfluorosulfonyl imide salt includes lithium bisfluorosulfonyl imide.

[0022] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0023] 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:

[0024] Figure 1 This is a flowchart of a purification method according to an embodiment of this application.

[0025] Figure 2 This is a flowchart of a purification method according to an embodiment of this application.

[0026] Figure 3 This is a flowchart of a purification method according to an embodiment of this application. Detailed Implementation

[0027] 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 understood as limiting the present invention.

[0028] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0029] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0030] In this document, the terms “comprising” or “including” are open-ended expressions, meaning that they include the contents specified in this invention, but do not exclude other aspects.

[0031] In this document, the terms “optionally,” “optionally,” or “optionally” generally refer to an event or condition that may, but may not, occur, and the description includes both cases in which the event or condition occurs and cases in which the event or condition does not occur.

[0032] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0033] The first aspect of this application provides a method for purifying difluorosulfonyl imide, comprising:

[0034] The bis(fluorosulfonyl)imide to be purified is reacted with a purification agent to obtain a mixture; the purification agent includes a resin having a nitrogen-containing aromatic ring group; the bis(fluorosulfonyl)imide to be purified includes fluorosulfonic acid;

[0035] The mixture was separated to obtain purified difluorosulfonamide.

[0036] In existing technologies, methods for removing fluorosulfonic acid using salts mainly employ halides (such as sodium chloride, potassium chloride, etc.), sulfates (sodium sulfate, potassium sulfate, etc.), and organic acid salts (sodium acetate, potassium acetate). However, using these salts for purification introduces other acidic substances. For example, chlorides produce hydrogen chloride tail gas, sulfates produce sulfuric acid, and acetates produce acetic acid. These factors inevitably lead to more complex waste gas and waste liquid compositions, creating safety and environmental problems. Furthermore, after purification, distillation is required to separate the difluorosulfonamide, and the resulting heavy components are viscous and difficult to handle.

[0037] The impurity remover provided in this application includes a resin containing a nitrogen-containing aromatic ring group. The resin containing the nitrogen-containing aromatic ring group reacts with fluorosulfonic acid to form ammonium fluorosulfonate. The fluorosulfonic acid is chemically adsorbed onto the resin containing the nitrogen-containing aromatic ring group, which facilitates the separation of fluorosulfonic acid and difluorosulfonyl imide without introducing new anionic impurities.

[0038] The mechanism by which the resin with nitrogen-containing aromatic ring groups reacts with fluorosulfonic acid, as provided in the embodiments of this application, is as follows:

[0039] 1) When a resin with a nitrogen-containing aromatic ring group comes into contact with difluorosulfonyl imide, it adsorbs difluorosulfonyl imide or fluorosulfonic acid, reacting rapidly to form difluorosulfonyl imide ammonium salt or fluorosulfonate. In the crude product (i.e., the difluorosulfonyl imide to be purified), difluorosulfonyl imide is present in large quantities, while fluorosulfonate is present in small quantities. Upon initial addition of the resin with the nitrogen-containing aromatic ring group, a large amount of organic amine reacts with difluorosulfonyl imide to form the corresponding ammonium salt, while fluorosulfonic acid may not be completely converted due to its low concentration.

[0040]

[0041] 2) Upon continued contact, the fluorosulfonic acid that had not yet participated in the reaction will collide with the ammonium bis(fluorosulfonyl)imide salt. 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 displacing weak acid, yielding ammonium fluorosulfonate salt and bis(fluorosulfonyl)imide. This ensures that all fluorosulfonic acid in the crude product is converted into a high-boiling-point ammonium salt. The resulting ammonium fluorosulfonate salt matrix remains a resin in solid form, which can be further separated (e.g., by filtration) to obtain pure bis(fluorosulfonyl)imide.

[0042]

[0043] In summary, the purification method provided in this application has the following beneficial effects:

[0044] 1) No new anionic impurities are introduced after impurity removal. First, after impurity removal of bis(fluorosulfonyl)imide salt, fluorosulfonate and bis(fluorosulfonyl)imide are generated, with bis(fluorosulfonyl)imide being the product itself. Second, in chain aliphatic amines, the carbon-nitrogen bond is a single bond with low bond energy, making it easily broken by external energy stimulation (light, electricity, or other substances), resulting in irreversible changes. Resins with nitrogen-containing aromatic ring groups, however, have nitrogen participating in the conjugated region of the nitrogen-containing aromatic structure, where the carbon-nitrogen bond energy is higher, making them less susceptible to breakage. Therefore, compared to resins with chain aliphatic amines, resins with nitrogen-containing aromatic rings are more structurally stable, less prone to breakage during use, have higher separation efficiency, and do not generate impurities.

[0045] 2) High separation efficiency. After impurity removal, fluorosulfonic acid is adsorbed onto the resin, and difluorosulfonamide can be obtained using simple separation methods (such as direct filtration). Distillation is not required, and there are no difficult-to-handle heavy distillation components, resulting in high efficiency for industrial production. In industrial production, a resin tower can be used for circulating defluorosulfonic acid removal, further increasing efficiency.

[0046] 3) Facilitates regeneration and recycling. The embodiments of this application use resins with nitrogen-containing aromatic ring groups, which can be recycled after impurity removal, thus reducing costs.

[0047] According to the embodiments of this application, the bis(fluorosulfonyl)imide to be purified is reacted with a purification agent to generate ammonium fluorosulfonate, thereby achieving the chemical adsorption of fluorosulfonic acid onto the resin.

[0048] In this embodiment, a resin with a nitrogen-containing aromatic ring group is used to remove fluorosulfonic acid, so that all fluorosulfonic acid is converted into ammonium fluorosulfonate. The fluorosulfonic acid is adsorbed onto the resin through ionic bonds, and the resulting ammonium fluorosulfonate parent material is still resin, which is in solid form. Pure bisfluorosulfonylimide can then be obtained by a simple separation method.

[0049] According to the embodiments of this application, the molar ratio of nitrogen-containing aromatic ring groups to fluorosulfonic acid in the resin containing nitrogen-containing aromatic ring groups is 4 to 1:1; in specific examples, the molar ratio of nitrogen-containing aromatic ring groups to fluorosulfonic acid in the resin containing nitrogen-containing aromatic ring groups is 4:1, 3.5:1, 3:1, 2.5:1, 2:1, 1.5:1 or 1:1, etc.

[0050] In this embodiment, the molar ratio of the resin with nitrogen-containing aromatic ring groups to fluorosulfonic acid satisfies the above conditions, which is conducive to the full consumption of fluorosulfonic acid and its conversion into ammonium fluorosulfonate, effectively removing fluorosulfonic acid and improving reaction efficiency. The more resin with nitrogen-containing aromatic ring groups added, the better the effect of removing fluorosulfonic acid. However, when the molar ratio of nitrogen-containing aromatic ring groups to fluorosulfonic acid is higher than 4:1, an equilibrium is reached to avoid adding too much difluorosulfonyl imide and causing waste.

[0051] Furthermore, the molar ratio of nitrogen-containing aromatic ring groups to fluorosulfonic acid in the resin containing nitrogen-containing aromatic ring groups is 2 to 3:1; in specific examples, the molar ratio of nitrogen-containing aromatic ring groups to fluorosulfonic acid in the resin is 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1 or 3:1, etc.

[0052] In the embodiments of this application, the molar ratio of nitrogen-containing aromatic ring groups and fluorosulfonic acid in the resin satisfies the above conditions, ensuring effective removal of fluorosulfonic acid impurities while consuming little or no bisfluorosulfonylimide.

[0053] According to the embodiments of this application, in the step of reacting the bis(fluorosulfonyl)imide to be purified with the impurity remover, the control parameters include: the reaction temperature is 20 ℃ to 50 ℃; and / or the reaction time is greater than 30 min.

[0054] In specific examples, the reaction temperatures are 20 ℃, 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, or 50 ℃, etc. In specific examples, the reaction times are 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h, 9.5 h, or 10 h, etc.

[0055] In this embodiment, the impurity removal reaction temperature meets the above conditions, which helps to ensure that the structural integrity of the resin containing nitrogen-containing aromatic ring groups is not damaged. At the same time, the difluorosulfonate imine is in a liquid state, which can fully contact the resin containing nitrogen-containing aromatic ring groups, thereby improving the reaction efficiency and the impurity removal effect.

[0056] In this embodiment, the impurity removal reaction time meets the above conditions, which is beneficial for the resin with nitrogen-containing aromatic ring groups to fully participate in the reaction with fluorosulfonic acid, converting fluorosulfonic acid into ammonium fluorosulfonate salt, and ensuring thorough impurity removal.

[0057] Furthermore, the control parameters include: a reaction temperature of 25 ℃ to 40 ℃; and / or a reaction time of 0.5 h to 2 h.

[0058] In specific examples, the impurity removal reaction temperatures are 25 ℃, 27 ℃, 29 ℃, 31 ℃, 33 ℃, 35 ℃, 37 ℃, 39 ℃, or 40 ℃, etc. In specific examples, the impurity removal reaction times are 0.5 h, 0.6 h, 0.8 h, 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h, or 2.0 h, etc.

[0059] In this embodiment, the impurity removal reaction temperature is controlled to meet the above conditions. While ensuring the structural integrity of the resin containing nitrogen-containing aromatic ring groups, the liquid difluorosulfonate imine is brought into full contact with the resin containing nitrogen-containing aromatic ring groups, thereby further improving the reaction efficiency and the impurity removal effect.

[0060] In this embodiment, the impurity removal reaction time is controlled to meet the above conditions, so as to ensure the impurity removal effect while avoiding excessive time consumption and increased costs.

[0061] According to embodiments of this application, in a resin having a nitrogen-containing aromatic ring group, the nitrogen-containing aromatic ring group includes an amino group or an imine group.

[0062] In the purification method provided in this application, the nitrogen-containing aromatic ring group includes an amino group or an imine group, which is located in the repeating unit of the resin and can react with acidic substances such as fluorosulfonic acid and difluorosulfonate imine to generate ammonium fluorosulfonate salt and ammonium difluorosulfonate imine salt, thereby improving the impurity removal effect.

[0063] Furthermore, the nitrogen-containing aromatic ring group includes at least one of a pyridine group and a pyrrole group.

[0064] The pyridine and pyrrole groups contain imine groups, which can react with acidic substances such as fluorosulfonic acid and difluorosulfonate imine to produce ammonium fluorosulfonate salt and ammonium difluorosulfonate imine salt, thereby improving the impurity removal effect.

[0065] Resins containing pyridine groups, such as:

[0066] ;

[0067] Resins containing pyrrole groups, such as:

[0068] ;

[0069] The wavy line represents a covalent single bond.

[0070] According to embodiments of this application, resins having nitrogen-containing aromatic ring groups include at least one of poly-4-vinylpyridine, polyvinylimidazole, and polypyrrole.

[0071] In this application embodiment, any one or more of the above-mentioned combinations are used as impurity removal agents, which will react with fluorosulfonic acid to finally form ammonium fluorosulfonate. The fluorosulfonic acid is chemically adsorbed on the resin with nitrogen-containing aromatic ring groups, thereby facilitating the separation of fluorosulfonic acid and difluorosulfonyl imide without introducing new anionic impurities.

[0072] Furthermore, the resin having nitrogen-containing aromatic ring groups is poly-4-vinylpyridine.

[0073] The embodiments of this application use poly-4-vinylpyridine to remove fluorosulfonic acid. Poly-4-vinylpyridine is a commercially available product that is inexpensive, structurally stable, and conducive to the industrial-scale removal of fluorosulfonic acid.

[0074] According to an embodiment of this application, the mixture is separated by a separation method including filtration.

[0075] In this embodiment, a resin with a nitrogen-containing aromatic ring group is used to remove fluorosulfonic acid, converting all the fluorosulfonic acid in the crude product into high-boiling-point ammonium salts. The resulting ammonium fluorosulfonate parent material is still resin, which is in solid form. Pure difluorosulfonyl imide can then be obtained by simple separation methods such as filtration.

[0076] In a specific example, the purification steps provided in the embodiments of this application are as follows: Figure 1 As shown, it includes:

[0077] S1000: Add a resin-containing impurity remover to the difluorosulfonamide to be purified to carry out an impurity removal reaction, and obtain a liquid mixture; wherein, the resin refers to a resin with a nitrogen-containing aromatic ring group, and the difluorosulfonamide to be purified contains fluorosulfonic acid impurities.

[0078] S2000: Separates the liquid phase mixture to obtain purified bis(fluorosulfonyl)imide. The liquid phase mixture can be separated by filtration.

[0079] Furthermore, filtration includes at least one of atmospheric pressure filtration, vacuum filtration, and pressure filtration.

[0080] The embodiments of this application can use some conventional filtration methods to separate bisfluorosulfonyl imide from the resin that chemically adsorbs fluorosulfonic acid, thereby obtaining purified bisfluorosulfonyl imide. The separation operation is simple, low in cost, and conducive to industrial application.

[0081] Furthermore, vacuum filtration or nitrogen pressure filtration can be used.

[0082] Fluorosulfonic acid and resin are ionicly bonded, existing in solid form. Unreacted resin will react with bis(fluorosulfonyl)imide, but the amount of bis(fluorosulfonyl)imide participating in the reaction is relatively small. A portion of the liquid bis(fluorosulfonyl)imide is also physically adsorbed onto the resin. During filtration, filtering to a minimum can reduce physical adsorption. Alternatively, vacuum filtration or nitrogen pressure filtration can be used to further remove the liquid bis(fluorosulfonyl)imide physically adsorbed onto the resin, minimizing waste.

[0083] According to an embodiment of this application, after separating the mixture, the process further includes a step of regenerating the purified resin.

[0084] In this embodiment, fluorosulfonic acid is chemically adsorbed onto a resin containing nitrogen-containing aromatic ring groups via ion bonding. In addition, a small amount of difluorosulfonamide may be physically adsorbed onto the resin. Therefore, the resin can be regenerated after impurity removal, making it easy to recycle. After regeneration, the resin containing nitrogen-containing aromatic ring groups exhibits a high adsorption retention rate.

[0085] In a specific example, the purification steps provided in the embodiments of this application are as follows: Figure 2 As shown, it includes:

[0086] S1000: Add a resin-containing impurity remover to the difluorosulfonamide to be purified to carry out an impurity removal reaction, and obtain a liquid mixture; wherein, the resin refers to a resin with a nitrogen-containing aromatic ring group, and the difluorosulfonamide to be purified contains fluorosulfonic acid impurities.

[0087] S2000: Separates the liquid phase mixture to obtain purified bis(fluorosulfonyl)imide. The liquid phase mixture can be separated by filtration.

[0088] S3000: Regenerate the resin obtained in step S2000.

[0089] Furthermore, the regeneration process includes: purging the resin with an inert gas; washing with a weak alkaline aqueous solution until it is weakly alkaline, then washing with water until it is neutral, and finally dewatering.

[0090] In this embodiment, the resin is first purged with an inert gas to remove impurities physically adsorbed on the resin surface. Then, it is washed with a weak alkaline aqueous solution until it becomes weakly alkaline, followed by a water wash until neutral, to further remove impurities chemically adsorbed through ion bonding, thereby achieving effective resin regeneration. Finally, moisture is removed to ensure the resin's moisture content meets the requirements for use with fluorosulfonic acid, preventing the introduction of moisture and other impurities.

[0091] The regenerated resin can be recycled.

[0092] In a specific example, the purification steps provided in the embodiments of this application are as follows: Figure 3 As shown, it includes:

[0093] S1000: Add a resin-containing impurity remover to the difluorosulfonamide to be purified to carry out an impurity removal reaction, and obtain a liquid mixture; wherein, the resin refers to a resin with a nitrogen-containing aromatic ring group, and the difluorosulfonamide to be purified contains fluorosulfonic acid impurities.

[0094] S2000: Separates the liquid phase mixture to obtain purified bis(fluorosulfonyl)imide. The liquid phase mixture can be separated by filtration.

[0095] S3000: Regenerate the resin obtained in step S2000.

[0096] S4000: Add a purification agent containing the regenerated resin from step S3000 to the difluorosulfonyl imide to be purified to carry out a purification reaction, and obtain a liquid phase mixture;

[0097] S5000: Separates liquid mixtures to obtain purified bis(fluorosulfonyl)imide. The liquid mixture can be separated by filtration.

[0098] Experiments show that after one regeneration, the impurity removal efficiency of the resin in the embodiments of this application is not less than 85%.

[0099] In a specific example, nitrogen may be used as the inert gas.

[0100] In specific examples, weak alkaline aqueous solutions may be sodium hydroxide aqueous solution or sodium carbonate aqueous solution, etc.

[0101] The second aspect of this application provides a purified bis(fluorosulfonyl)imide obtained by the above-described purification method for bis(fluorosulfonyl)imide.

[0102] The purified bis(fluorosulfonyl)imide provided in this application embodiment is obtained by the purification method of bis(fluorosulfonyl)imide provided in the first aspect above. No new impurities are introduced into the purified bis(fluorosulfonyl)imide, and the content of fluorosulfonic acid impurities meets the requirements.

[0103] The third aspect of this application provides a bis(fluorosulfonyl)imide salt, the raw materials of which include bis(fluorosulfonyl)imide obtained by the above purification method, or include the above-described bis(fluorosulfonyl)imide.

[0104] According to embodiments of this application, the bisfluorosulfonyl imide salt includes lithium bisfluorosulfonyl imide.

[0105] Lithium bisfluorosulfonylimide is an important lithium battery material, and its usage has been gradually increasing in recent years, with a trend towards it evolving from an electrolyte additive to a primary electrolyte salt. Currently, most manufacturers use bisfluorosulfonylimide to prepare lithium bisfluorosulfonylimide. The embodiments of this application use the aforementioned bisfluorosulfonylimide to prepare lithium bisfluorosulfonylimide, resulting in low impurity content and lower cost.

[0106] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the invention in any way. The reagents used in the embodiments are all from Aladdin Biochemical Technology Co., Ltd.

[0107] Example 1

[0108] This embodiment provides a method for purifying difluorosulfonyl imide, the specific steps of which are as follows:

[0109] The reactor was purged with nitrogen, and 300.00 g of crude difluorosulfonylimide was added. The crude difluorosulfonylimide contained 10300 ppm of fluorosulfonic acid. 12.98 g of poly(4-vinylpyridine) (CAS No. 25232-41-1) was added to carry out the reaction. The reaction temperature was set at 25 °C and the reaction time was 1 h.

[0110] After the reaction is complete, filter off the resin under normal pressure to obtain purified difluorosulfonamide.

[0111] Example 2

[0112] This embodiment provides a purification method for bis(fluorosulfonyl)imide, the specific steps of which are shown in Example 1, except that the amount of poly(4-vinylpyridine) added is 9.73 g.

[0113] Example 3

[0114] This embodiment provides a purification method for bis(fluorosulfonyl)imide, with the specific steps as shown in Example 1, except that the amount of poly(4-vinylpyridine) added is 8.11 g.

[0115] Example 4

[0116] This embodiment provides a purification method for bis(fluorosulfonyl)imide, the specific steps of which are shown in Example 1, except that the amount of poly(4-vinylpyridine) added is 6.49 g.

[0117] Example 5

[0118] This embodiment provides a purification method for bis(fluorosulfonyl)imide, the specific steps of which are shown in Example 1, except that the amount of poly(4-vinylpyridine) added is 3.25 g.

[0119] Example 6

[0120] This embodiment provides a purification method for bis(fluorosulfonyl)imide, the specific steps of which are shown in Example 1, except that the amount of poly(4-vinylpyridine) added is 16.25 g.

[0121] Example 7

[0122] This embodiment provides a purification method for bis(fluorosulfonyl)imide, the specific steps of which are shown in Example 1, except that the amount of poly(4-vinylpyridine) added is 2.60 g.

[0123] Example 8

[0124] This embodiment provides a purification method for bis(fluorosulfonyl)imide, the specific steps of which are shown in Example 3, except that the reaction temperature is set to 20 °C.

[0125] Example 9

[0126] This embodiment provides a purification method for bis(fluorosulfonyl)imide, the specific steps of which are shown in Example 3, except that the reaction temperature is set to 40 °C.

[0127] Example 10

[0128] This embodiment provides a purification method for bis(fluorosulfonyl)imide, the specific steps of which are shown in Example 3, except that the reaction temperature is set to 50 °C.

[0129] Example 11

[0130] This embodiment provides a purification method for bis(fluorosulfonyl)imide, the specific steps of which are shown in Example 3, except that the reaction temperature is set to 60 °C.

[0131] Example 12

[0132] This embodiment provides a purification method for bis(fluorosulfonyl)imide, the specific steps of which are shown in Example 3, except that the reaction time is set to 0.5 h.

[0133] Example 13

[0134] This embodiment provides a purification method for difluorosulfonylimide, the specific steps of which are shown in Example 3, except that the resin used is polyvinylimidazole and the amount of polyvinylimidazole added is 7.26 g.

[0135] Example 14

[0136] This embodiment provides a purification method for bis(fluorosulfonyl)imide, the specific steps of which are shown in Example 3, except that the resin used is polypyrrole and the amount of polyvinylimidazole added is 5.02 g.

[0137] Example 15

[0138] This embodiment provides a purification method for bis(fluorosulfonyl)imide, as detailed below:

[0139] First, purification is performed, as detailed in Example 3.

[0140] Secondly, the resin undergoes a regeneration process, the specific method of which is as follows:

[0141] 1) Dry the resin with nitrogen gas; 2) Wash with sodium carbonate aqueous solution until pH is 8-10, then wash with water until neutral; 3) Finally, dry until the moisture content is within acceptable limits.

[0142] Finally, the regenerated resin was used for purification using the specific steps provided in Example 3, and the impurity retention rate of the regenerated resin was 89.8%.

[0143] Comparative Example 1

[0144] This case provides a purification method for bis(fluorosulfonyl)imide, the specific operation of which is shown in Example 3, except that sodium chloride is used instead of poly(4-vinylpyridine).

[0145] Comparative Example 2

[0146] This case provides a purification method for bis(fluorosulfonyl)imide, the specific operation of which is shown in Example 3, except that polystyrene is used instead of poly(4-vinylpyridine).

[0147] Detection method:

[0148] 1. Detection method for fluorosulfonic acid: The content of fluorosulfonate ions is determined by anion chromatography. 2. Detection method for other impurities: Other anions are tested using anion chromatography.

[0149] 3. Impurity retention rate of regenerated resin: The ratio of the amount of fluorosulfonate removed when the activated resin is purified again to the amount removed during the first use (for the same mass of resin).

[0150] Test results:

[0151] The results of the purification effects of each embodiment and comparative example are shown in Table 1.

[0152] Table 1. Detection results of purification effects in each example and comparative example.

[0153]

[0154] Test results show that the resins with nitrogen-containing aromatic ring groups used in Examples 1-15 of this application effectively remove fluorosulfonic acid. The optimal removal effect is achieved when the molar ratio of nitrogen-containing aromatic ring groups to fluorosulfonic acid in the resin is 2.5:1; further increasing the ratio has little effect. High temperatures have little impact on the removal of fluorosulfonic acid but can negatively affect the resin itself, causing yellowing and potentially affecting regeneration. Polypyrrole is less effective than poly(4-vinylpyridine), preliminarily speculated to be due to a large conjugated region, making its properties less stable and potentially subject to changes within the system.

[0155] In Comparative Example 1, sodium chloride was used to remove fluorosulfonic acid, which was somewhat effective, but it significantly introduced chloride ions as an impurity. In Comparative Example 2, polystyrene lacked nitrogen-containing basic groups and therefore could not undergo the impurity removal reaction.

[0156] 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 difluorosulfonyl imide, characterized in that, include: The bis(fluorosulfonyl)imide to be purified is reacted with a purifying agent to obtain a mixture; the purifying agent includes a resin having a nitrogen-containing aromatic ring group; the bis(fluorosulfonyl)imide to be purified includes fluorosulfonic acid; The mixture was separated to obtain purified difluorosulfonyl imide. The molar ratio of the nitrogen-containing aromatic ring group in the resin to the fluorosulfonic acid is (4~1):

1.

2. The purification method for difluorosulfonyl imide according to claim 1, characterized in that, In the step of reacting the bis(fluorosulfonyl)imide to be purified with the impurity remover, the control parameters include: The reaction temperature is 20 ℃~50 ℃; and / or the reaction time is greater than 30 min.

3. The purification method for difluorosulfonyl imide according to claim 1, characterized in that, The resin having nitrogen-containing aromatic ring groups includes at least one of poly-4-vinylpyridine, polyvinylimidazole, and polypyrrole.

4. The purification method for difluorosulfonyl imide according to claim 1, characterized in that, The separation of the mixture is performed by a separation method including filtration.

5. The purification method for difluorosulfonyl imide according to claim 1, characterized in that, After separating the mixture, the process further includes a step of regenerating the purified resin.

Images