Method for purifying bis (fluorosulfonyl) imide, and purified bis (fluorosulfonyl) imide and bis (fluorosulfonyl) imide salt

Abstract

The invention belongs to the technical field of chemical engineering, and provides a purification method of imidodisulfuryl fluoride, purified imidodisulfuryl fluoride and imidodisulfuryl fluoride salt. The purification method provided by the invention comprises the following steps: reacting to-be-purified imidodisulfuryl fluoride with an impurity removal agent to obtain a mixture; the impurity removing agent comprises resin with nitrogen-containing aromatic ring groups; the bis (fluorosulfonyl) imide to be purified comprises fluorosulfonic acid; and separating the mixture to obtain the purified bis (fluorosulfonyl) imide. The impurity removal agent provided by the invention contains the resin with the nitrogen-containing aromatic ring group, the resin with the nitrogen-containing aromatic ring group can react with the fluorosulfonic acid to finally form the ammonium fluorosulfonate salt, and the fluorosulfonic acid is chemically adsorbed on the resin with the nitrogen-containing aromatic ring group, so that the separation of the fluorosulfonic acid and the bis (fluorosulfonyl) imide is conveniently realized, and the impurity removal efficiency is improved. New anion impurities are not introduced.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical industry, and in particular relates to a method for purifying fluorosulfonyl imide, purified bisfluorosulfonyl imide, and bisfluorosulfonyl imide salt. Background Art

[0002] Lithium bis(fluorosulfonyl)imide is an important lithium battery material. Its usage has gradually increased in recent years, and there is a trend from electrolyte additives to becoming the main salt of electrolyte. At present, most manufacturers use bis(fluorosulfonyl)imide to prepare lithium bis(fluorosulfonyl)imide. Therefore, the level of impurities 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. Under normal pressure, the boiling point of fluorosulfonic acid is 165.5℃, while the boiling point of bis(fluorosulfonyl)imide is 170℃. The boiling points of the two are very close. If the traditional distillation method is used, the equipment investment is large and the production efficiency is low. Therefore, a salt is added to the crude bis(fluorosulfonyl)imide, and the salt is used to react preferentially with fluorosulfonic acid to obtain a high-boiling-point fluorosulfonate salt, which is retained in the heavy component, thereby achieving the purpose of removing the fluorosulfonate ion.

[0003] For the method of removing fluorinated sulfonic acid with salt, the main options are halogenated salts (such as sodium chloride, potassium chloride, etc.), sulfates (sodium sulfate, potassium sulfate, etc.) and organic acid salts (sodium acetate, potassium acetate). Using the above salts to remove impurities will introduce other acidic substances, such as chlorides will produce hydrogen chloride tail gas, sulfates will produce sulfuric acid, and acetates will produce acetic acid, which will make the waste gas and waste liquid composition more complicated and cause safety and environmental protection problems. Summary of the invention

[0004] The present invention aims to solve, at least to some extent, the technical problem that a method for removing fluorinated sulfonic acid from salt introduces new impurities. To this end, one object of the present invention is to provide a method for purifying bisfluorosulfonyl imide, purified bisfluorosulfonyl imide, and a bisfluorosulfonyl imide salt. The method for purifying bisfluorosulfonyl imide does not introduce new anionic impurities.

[0005] The first aspect of the present application provides a method for purifying bis(fluorosulfonyl)imide. According to an embodiment of the present invention, the purification method comprises:

[0006] The bisfluorosulfonyl imide to be purified is reacted with an impurity remover to obtain a mixture; the impurity remover includes a resin having a nitrogen-containing aromatic ring group; the bisfluorosulfonyl imide to be purified includes fluorosulfonic acid;

[0007] The mixture was separated to obtain purified bis(fluorosulfonyl)imide.

[0008] The impurity remover provided in the present application includes a resin having a nitrogen-containing aromatic ring group. The resin having a nitrogen-containing aromatic ring group will react with fluorosulfonic acid to eventually form ammonium fluorosulfonic acid salt. The fluorosulfonic acid is chemically adsorbed on the resin having a nitrogen-containing aromatic ring group, thereby facilitating the separation of fluorosulfonic acid and bis(fluorosulfonyl)imide without introducing new anionic impurities.

[0009] According to an embodiment of the present invention, the above-mentioned method for purifying bis(fluorosulfonyl)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 an impurity remover to generate ammonium fluorosulfonic acid salt, thereby achieving chemical adsorption of fluorosulfonic acid on the resin.

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

[0012] In some embodiments, in the step of reacting the bisfluorosulfonyl imide to be purified with the impurity remover, the control parameters include: the reaction temperature is 20° C. to 50° C.; and / or the reaction time is greater than 30 min.

[0013] In some embodiments, in the resin having a nitrogen-containing aromatic ring group, the nitrogen-containing aromatic ring group comprises an amine 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 vinyl pyridine, polyvinyl imidazole, and polypyrrole.

[0015] In some embodiments, the mixture is separated using a separation method comprising filtration.

[0016] In some embodiments, after the mixture is separated, the method further includes regenerating the impurity-removed resin.

[0017] The second aspect of the present application provides a purified bisfluorosulfonyl imide obtained by using the above-mentioned method for purifying bisfluorosulfonyl imide.

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

[0019] The third aspect of the present application provides a bisfluorosulfonyl imide salt, wherein the raw material for preparing the salt includes the bisfluorosulfonyl imide obtained by the above purification method, or includes the above bisfluorosulfonyl imide.

[0020] The present application adopts the above-mentioned bisfluorosulfonyl imide to prepare lithium bisfluorosulfonyl imide, which has low impurity content and low cost.

[0021] In some embodiments, the bisfluorosulfonylimide salt comprises lithium bisfluorosulfonylimide.

[0022] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] 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:

[0024] Figure 1 It is a flow chart of a purification method according to an embodiment of the present application.

[0025] Figure 2 It is a flow chart of a purification method according to an embodiment of the present application.

[0026] Figure 3 It is a flow chart of a purification method according to an embodiment of the present application. DETAILED DESCRIPTION

[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 understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0029] The endpoints and any values ​​of the ranges disclosed in this article 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 endpoint values ​​of each range, the endpoint values ​​of each range and the 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 as specifically disclosed in this article.

[0030] In this document, the terms “include” or “comprising” are open expressions, that is, including the contents specified in the present invention but not excluding other contents.

[0031] As used herein, the terms "optionally", "optional" or "optionally" generally mean that the subsequently described event or circumstance may but need not occur, and that the description includes instances where the event or circumstance occurs and instances where it does not.

[0032] The scheme of the present invention will be explained below in conjunction with the embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Where specific techniques or conditions are not indicated 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 are not indicated by the manufacturer and are all conventional products that can be obtained commercially.

[0033] The first aspect of the embodiment of the present application provides a method for purifying bisfluorosulfonyl imide, comprising:

[0034] The bisfluorosulfonyl imide to be purified is reacted with an impurity remover to obtain a mixture; the impurity remover includes a resin having a nitrogen-containing aromatic ring group; the bisfluorosulfonyl imide to be purified includes fluorosulfonic acid;

[0035] The mixture was separated to obtain purified bis(fluorosulfonyl)imide.

[0036] In the prior art, for the method of removing fluorinated sulfonic acid with salt, mainly halide salts (such as sodium chloride, potassium chloride, etc.), sulfates (sodium sulfate, potassium sulfate, etc.), and organic acid salts (sodium acetate, potassium acetate) can be selected. Using the above salts to remove impurities will 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, which will more or less make the waste gas and waste liquid components more complicated, causing safety and environmental protection problems. In addition, after the impurity removal is completed, distillation is required to separate the bisfluorosulfonyl imide, and the obtained heavy components are viscous and difficult to handle.

[0037] The impurity remover provided in the embodiment of the present application includes a resin having a nitrogen-containing aromatic ring group. The resin having a nitrogen-containing aromatic ring group will react with fluorosulfonic acid to eventually form ammonium fluorosulfonic acid salt. Fluorosulfonic acid is chemically adsorbed on the resin having a nitrogen-containing aromatic ring group, thereby facilitating the separation of fluorosulfonic acid and bis(fluorosulfonyl)imide without introducing new anionic impurities.

[0038] The mechanism of the reaction between the resin having a nitrogen-containing aromatic ring group and fluorosulfonic acid provided in the examples of the present application is:

[0039] 1) After the resin with nitrogen-containing aromatic ring groups contacts bisfluorosulfonyl imide, it adsorbs bisfluorosulfonyl imide or fluorosulfonic acid and reacts quickly to form bisfluorosulfonyl imide ammonium salt or fluorosulfonate. In the crude product (i.e., the bisfluorosulfonyl imide to be purified), bisfluorosulfonyl imide is present in large quantities while fluorosulfonate is present in small quantities. When the resin with nitrogen-containing aromatic ring groups is just added, a large amount of organic amine will react with bisfluorosulfonyl imide to form the corresponding ammonium salt, while fluorosulfonic acid may not be completely converted due to its low concentration.

[0040]

[0041] 2) When the contact continues, the fluorosulfonic acid that has not yet participated in the reaction will collide with the ammonium salt of bisfluorosulfonyl imide. Since the acidity of fluorosulfonic acid is stronger than that of bisfluorosulfonyl imide, according to the principle of strong acid to weak acid, an ion exchange reaction will occur to obtain ammonium salt of fluorosulfonic acid and bisfluorosulfonyl imide. In this way, it can be ensured that all the fluorosulfonic acid in the crude product is converted into ammonium salt with a high boiling point. The obtained ammonium fluorosulfonic acid salt matrix is ​​still a resin in a solid form, and pure bisfluorosulfonyl imide can be obtained by subsequent separation means (such as filtration).

[0042]

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

[0044] 1) No new anionic impurities are introduced after impurity removal. First, after impurity removal of bisfluorosulfonyl imide salt, fluorosulfonate and bisfluorosulfonyl imide will be generated, and bisfluorosulfonyl imide is the product itself. Secondly, in chain fatty amines, the carbon-nitrogen bond is a single bond with a small bond energy. It is easily broken by external energy stimulation (light, electricity or other substances), and irreversible changes occur. For resins with nitrogen-containing aromatic ring groups, nitrogen participates in the formation of conjugated regions in the nitrogen-containing aromatic structure, in which the carbon-nitrogen bond energy is larger and is not easily destroyed. Therefore, compared with resins with chain fatty amines, resins with nitrogen-containing aromatic rings have a more stable structure, are more difficult to be destroyed during use, have high separation efficiency, and do not produce impurities.

[0045] 2) High separation efficiency. After impurities are removed, fluorosulfonic acid is adsorbed on the resin, and a simple separation method (such as direct filtration) can be used to obtain bis(fluorosulfonyl)imide, which does not require distillation and has no difficult-to-handle distillation heavy components. The industrial production efficiency is high. In industrial production, a resin tower can be used to circulate the defluorinated sulfonic acid, which is more efficient.

[0046] 3) Convenient for regeneration and recycling. The present embodiment uses a resin having a nitrogen-containing aromatic ring group, which can be recycled after impurities are removed, thereby reducing costs.

[0047] According to the embodiment of the present application, the bis(fluorosulfonyl)imide to be purified is reacted with an impurity remover to generate ammonium fluorosulfonate, thereby achieving chemical adsorption of fluorosulfonic acid on the resin.

[0048] In the embodiment of the present application, a resin having a nitrogen-containing aromatic ring group is used to remove fluorosulfonic acid, so that the fluorosulfonic acid is converted into ammonium fluorosulfonic acid salt. The fluorosulfonic acid is adsorbed on the resin through ionic bonds, and the obtained ammonium fluorosulfonic acid salt matrix is ​​still a resin in a solid form. Pure bis(fluorosulfonyl)imide can be obtained subsequently by a simple separation method.

[0049] According to an embodiment of the present application, the molar ratio of the nitrogen-containing aromatic ring group in the resin having the nitrogen-containing aromatic ring group to fluorosulfonic acid is 4 to 1:1; in a specific example, the molar ratio of the nitrogen-containing aromatic ring group in the resin having the nitrogen-containing aromatic ring group to fluorosulfonic acid is 4:1, 3.5:1, 3:1, 2.5:1, 2:1, 1.5:1 or 1:1, etc.

[0050] In the embodiments of the present application, the molar ratio of the resin having a nitrogen-containing aromatic ring group and fluorosulfonic acid meets the above conditions, which is conducive to fully consuming the fluorosulfonic acid and converting it into ammonium fluorosulfonic acid salt, effectively removing the fluorosulfonic acid, and improving the reaction efficiency; the more resin having a nitrogen-containing aromatic ring group is added, the more conducive it is to improving the effect of removing fluorosulfonic acid, but when the molar ratio of the nitrogen-containing aromatic ring group and fluorosulfonic acid is higher than 4:1, a balance is reached, avoiding the waste caused by adding too much bis(fluorosulfonyl)imide.

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

[0052] In the embodiments of the present application, the molar ratio of the nitrogen-containing aromatic ring group and fluorosulfonic acid in the resin satisfies the above conditions, ensuring effective removal of fluorosulfonic acid impurities without consuming or consuming a minimum amount of bis(fluorosulfonyl)imide.

[0053] According to an embodiment of the present application, in the step of reacting the bisfluorosulfonyl imide to be purified with the impurity remover, the control parameters include: the reaction temperature is 20° C. to 50° C.; and / or the reaction time is greater than 30 min.

[0054] In a specific example, the reaction temperature is 20° C., 25° C., 30° C., 35° C., 40° C., 45° C., or 50° C., etc. In a specific example, the reaction time is 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 the embodiments of the present application, the impurity removal reaction temperature meets the above conditions, which is beneficial to ensure that the structural integrity of the resin having a nitrogen-containing aromatic ring group is not destroyed. At the same time, the bisfluorosulfonic acid imide is in a liquid state and can fully contact with the resin having a nitrogen-containing aromatic ring group, thereby improving the reaction efficiency and the impurity removal effect.

[0056] In the embodiments of the present application, the impurity removal reaction time meets the above conditions, which is conducive to the resin having nitrogen-containing aromatic ring groups and fluorosulfonic acid to fully participate in the reaction, converting fluorosulfonic acid into ammonium fluorosulfonic acid salt, thereby ensuring thorough impurity removal.

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

[0058] In a specific example, the impurity removal reaction temperature is 25° C., 27° C., 29° C., 31° C., 33° C., 35° C., 37° C., 39° C., or 40° C. In a specific example, the impurity removal reaction time is 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.

[0059] In the embodiments of the present application, the impurity removal reaction temperature is controlled to meet the above conditions, and while ensuring the structural integrity of the resin having the nitrogen-containing aromatic ring group, the liquid bisfluorosulfonic acid imide is promoted to fully contact with the resin having the nitrogen-containing aromatic ring group, thereby further improving the reaction efficiency and the impurity removal effect.

[0060] In the embodiments of the present application, the impurity removal reaction time is controlled to meet the above conditions, thereby ensuring the impurity removal effect while avoiding excessive time consumption and increased costs.

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

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

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

[0064] The pyridine group and the pyrrole group contain an imine group, which can react with the acidic substances fluorosulfonic acid and bisfluorosulfonic acid imide to generate fluorosulfonic acid ammonium salt and bisfluorosulfonic acid imide ammonium 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 lines represent single covalent bonds.

[0070] According to an embodiment of the present application, the resin having a nitrogen-containing aromatic ring group includes at least one of poly-4-vinylpyridine, polyvinyl imidazole and polypyrrole.

[0071] The embodiments of the present application use any one or a combination of the above-mentioned agents as the impurity remover, which will react with fluorosulfonic acid to eventually form ammonium fluorosulfonic acid salt. The fluorosulfonic acid is chemically adsorbed on the resin having a nitrogen-containing aromatic ring group, thereby facilitating the separation of fluorosulfonic acid and bis(fluorosulfonyl)imide without introducing new anionic impurities.

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

[0073] The embodiment of the present application uses poly-4-vinylpyridine to remove fluorinated sulfonic acid. Poly-4-vinylpyridine is a commercial product with low price and stable structure, which is conducive to industrial removal of fluorinated sulfonic acid.

[0074] According to an embodiment of the present application, the mixture is separated, and the separation method adopted includes filtration.

[0075] In the embodiment of the present application, a resin having a nitrogen-containing aromatic ring group is used to remove fluorosulfonic acid, and the fluorosulfonic acid in the crude product is converted into a high-boiling-point ammonium salt. The obtained fluorosulfonic acid ammonium salt matrix is ​​still a resin in a solid form, and pure bis(fluorosulfonyl)imide can be obtained subsequently by simple separation methods such as filtration.

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

[0077] S1000: adding a resin-containing impurity remover to the bisfluorosulfonyl imide to be purified to perform an impurity removal reaction to obtain a liquid mixture; wherein the resin refers to a resin having a nitrogen-containing aromatic ring group, and the bisfluorosulfonyl imide to be purified contains fluorosulfonic acid impurities;

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

[0079] Furthermore, the filtration includes at least one of normal pressure filtration, suction filtration and pressure filtration.

[0080] In the embodiment of the present application, some conventional filtering means can be used to separate the bis(fluorosulfonyl)imide from the resin for chemically adsorbing fluorosulfonic acid to obtain purified bis(fluorosulfonyl)imide. The separation operation is simple, the cost is low, and it is conducive to industrial application.

[0081] Furthermore, suction filtration or nitrogen pressure filtration is adopted.

[0082] Fluorosulfonic acid and resin are ionically bonded and exist in solid form; unreacted resin will react with bis(fluorosulfonyl)imide, but the amount of bis(fluorosulfonyl)imide involved in the reaction is small. Some of the bis(fluorosulfonyl)imide liquid is physically adsorbed onto the resin. Try to filter it dry during filtration to reduce physical adsorption, or remove the bis(fluorosulfonyl)imide liquid physically adsorbed on the resin by suction filtration or nitrogen pressure filtration to reduce the waste of bis(fluorosulfonyl)imide.

[0083] According to an embodiment of the present application, after the mixture is separated, the process further includes a step of regenerating the resin after impurities are removed.

[0084] In the embodiments of the present application, fluorosulfonic acid is chemically adsorbed on the resin having nitrogen-containing aromatic ring groups through ionic bonding. In addition, a small amount of bis(fluorosulfonyl)imide may be physically adsorbed on the resin. Therefore, the resin can be regenerated after impurities are removed for easy recycling. After regeneration, the resin having nitrogen-containing aromatic ring groups exhibits a higher adsorption retention rate.

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

[0086] S1000: adding a resin-containing impurity remover to the bisfluorosulfonyl imide to be purified to perform an impurity removal reaction to obtain a liquid mixture; wherein the resin refers to a resin having a nitrogen-containing aromatic ring group, and the bisfluorosulfonyl imide to be purified contains fluorosulfonic acid impurities;

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

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

[0089] Furthermore, the regeneration treatment includes: using an inert gas to purge the resin; washing with a weak alkaline aqueous solution to a weak alkaline state, then washing with water to a neutral state, and dehydrating the resin.

[0090] In the embodiment of the present application, the resin is first purged with an inert gas to facilitate the removal of impurities physically adsorbed on the surface of the resin; then, the resin is washed with a weak alkaline aqueous solution to a weak alkaline state, and then washed with water to a neutral state to further remove impurities chemically adsorbed by ionic bonding, thereby achieving effective regeneration of the resin. Finally, the water content of the resin is removed to meet the use requirements of the defluorinated sulfonic acid, and no impurities such as water are introduced.

[0091] The regenerated resin can be recycled.

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

[0093] S1000: adding a resin-containing impurity remover to the bisfluorosulfonyl imide to be purified to perform an impurity removal reaction to obtain a liquid mixture; wherein the resin refers to a resin having a nitrogen-containing aromatic ring group, and the bisfluorosulfonyl imide to be purified contains fluorosulfonic acid impurities;

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

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

[0096] S4000: adding an impurity remover containing the regenerated resin in step S3000 to the bisfluorosulfonyl imide to be purified to perform an impurity removal reaction to obtain a liquid phase mixture;

[0097] S5000: Separate the liquid phase mixture to obtain purified bis(fluorosulfonyl)imide. The liquid phase mixture can be separated by filtering.

[0098] Experiments have shown that after the resin of the present application is regenerated once, the impurity removal efficiency retention rate of the resin is not less than 85%.

[0099] In a specific example, the inert gas is nitrogen.

[0100] In a specific example, the weak alkaline aqueous solution is, for example, a sodium hydroxide aqueous solution or a sodium carbonate aqueous solution.

[0101] A second aspect of the embodiments of the present application provides a purified bisfluorosulfonyl imide obtained by using the above-mentioned method for purifying bisfluorosulfonyl imide.

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

[0103] A third aspect of the embodiments of the present application provides a bisfluorosulfonyl imide salt, wherein the raw materials for preparation include the bisfluorosulfonyl imide obtained by the above-mentioned purification method, or include the above-mentioned bisfluorosulfonyl imide.

[0104] According to an embodiment of the present application, the bisfluorosulfonyl imide salt includes lithium bisfluorosulfonyl imide.

[0105] 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, most manufacturers use bis(fluorosulfonyl)imide to prepare lithium bis(fluorosulfonyl)imide. The embodiment of the present application uses the above-mentioned bis(fluorosulfonyl)imide to prepare lithium bis(fluorosulfonyl)imide, which has low impurity content and low cost.

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

[0107] Example 1

[0108] This embodiment provides a method for purifying bis(fluorosulfonyl)imide, and the specific steps are as follows:

[0109] The reactor was replaced with nitrogen, 300.00 g of crude bis(fluorosulfonyl)imide was added, the content of fluorosulfonic acid in the crude bis(fluorosulfonyl)imide was 10300 ppm, 12.98 g of poly(4-vinylpyridine) (CAS No. 25232-41-1) was added for reaction, the reaction temperature was set to 25° C., and the reaction time was 1 h.

[0110] After the reaction is completed, the resin is filtered off at normal pressure to obtain purified bis(fluorosulfonyl)imide.

[0111] Example 2

[0112] This embodiment provides a method for purifying bisfluorosulfonyl imide. The specific steps are as shown in Example 1, except that: the amount of poly 4-vinyl pyridine added is 9.73 g.

[0113] Example 3

[0114] This embodiment provides a method for purifying bisfluorosulfonyl imide. The specific steps are as shown in Example 1, except that: the amount of poly 4-vinyl pyridine added is 8.11 g.

[0115] Example 4

[0116] This embodiment provides a method for purifying bisfluorosulfonyl imide. The specific steps are as shown in Example 1, except that: the amount of poly 4-vinyl pyridine added is 6.49 g.

[0117] Example 5

[0118] This embodiment provides a method for purifying bisfluorosulfonyl imide. The specific steps are as shown in Example 1, except that: the amount of poly 4-vinyl pyridine added is 3.25 g.

[0119] Example 6

[0120] This embodiment provides a method for purifying bis(fluorosulfonyl)imide. The specific steps are as 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 method for purifying bis(fluorosulfonyl)imide. The specific steps are as 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 method for purifying bisfluorosulfonyl imide, and the specific steps are as shown in Example 3, except that: the reaction temperature is set to 20°C.

[0125] Example 9

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

[0127] Example 10

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

[0129] Embodiment 11

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

[0131] Example 12

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

[0133] Example 13

[0134] This embodiment provides a method for purifying bisfluorosulfonyl imide. The specific steps are as shown in Example 3, except that the resin used is polyvinyl imidazole, and the amount of polyvinyl imidazole added is 7.26 g.

[0135] Embodiment 14

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

[0137] Embodiment 15

[0138] This embodiment provides a method for purifying bis(fluorosulfonyl)imide, which is specifically as follows:

[0139] First, a purification treatment is performed, such as the specific steps provided in Example 3.

[0140] Secondly, the resin is regenerated. The specific method is as follows:

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

[0142] Finally, the regenerated resin was used to perform purification treatment according to the specific steps provided in Example 3, and the impurity removal retention rate of the regenerated resin was 89.8%.

[0143] Comparative Example 1

[0144] This case provides a method for purifying bis(fluorosulfonyl)imide. The specific operation is as shown in Example 3, except that sodium chloride is used to replace poly(4-vinylpyridine).

[0145] Comparative Example 2

[0146] This case provides a method for purifying bis(fluorosulfonyl)imide. The specific operation is as shown in Example 3, except that polystyrene is used to replace poly-4-vinylpyridine.

[0147] Detection method:

[0148] 1. Detection method of fluorosulfonic acid: Use anion chromatography to test the content of fluorosulfonate.

[0149] 2. Detection method for other impurities: Other anions are tested by anion chromatography.

[0150] 3. Impurity retention rate of regenerated resin: the ratio of the amount of fluorosulfonate removed when the resin is activated and impurities are removed again to the amount removed when it was first used (resin of the same quality).

[0151] Test results:

[0152] The results of the purification tests of the various embodiments and comparative examples are shown in Table 1.

[0153] Table 1 Test results of purification effects of various embodiments and comparative examples

[0154]

[0155] The test results show that Examples 1-15 of the present application use a resin with a nitrogen-containing aromatic ring group to remove fluorinated sulfonic acid, which has a good removal effect. Among them, when the molar ratio of the nitrogen-containing aromatic ring group and fluorinated sulfonic acid in the resin is 2.5:1, the impurity removal effect has reached the best, and increasing the ratio has no obvious effect. When the temperature is too high, it has little effect on the effect of removing fluorinated sulfonic acid, but it will have an adverse effect on the resin itself, causing yellowing, which may affect regeneration. The effect of polypyrrole is not as good as that of poly-4-vinylpyridine. It is initially speculated that this is because there is a large conjugated area, the properties are not so stable, and it may change in the system.

[0156] In Comparative Example 1, sodium chloride was used to remove fluorinated sulfonic acid, which had a certain effect, but the impurity chloride ion was obviously introduced. In Comparative Example 2, polystyrene had no nitrogen-containing basic group, and the impurity removal reaction could not occur.

[0157] 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. A method for purifying bis(fluorosulfonyl)imide, characterized in that: include: The bisfluorosulfonyl imide to be purified is reacted with an impurity remover to obtain a mixture; the impurity remover includes a resin having a nitrogen-containing aromatic ring group; the bisfluorosulfonyl imide to be purified includes fluorosulfonic acid; The mixture is separated to obtain purified bis(fluorosulfonyl)imide.

2. The method for purifying bis(fluorosulfonyl)imide according to claim 1, characterized in that: The molar ratio of the nitrogen-containing aromatic ring group in the resin having the nitrogen-containing aromatic ring group to the fluorosulfonic acid is (4-1):

1.

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

4. The method for purifying bis(fluorosulfonyl)imide according to claim 1 or 2, characterized in that: In the resin having a nitrogen-containing aromatic ring group, the nitrogen-containing aromatic ring group comprises an amine group or an imine group.

5. The method for purifying bis(fluorosulfonyl)imide according to claim 1 or 2, characterized in that: The resin having a nitrogen-containing aromatic ring group includes at least one of poly-4-vinylpyridine, polyvinyl imidazole and polypyrrole.

6. The method for purifying bis(fluorosulfonyl)imide according to claim 1 or 2, characterized in that: The mixture is separated, and the separation method adopted includes filtration.

7. The method for purifying bisfluorosulfonyl imide according to claim 1, characterized in that: After separating the mixture, the method further includes a step of regenerating the resin after impurities are removed.

8. A purified bis(fluorosulfonyl)imide, characterized in that: The bis(fluorosulfonyl)imide is obtained by the purification method of any one of claims 1 to 7.

9. A bisfluorosulfonyl imide salt, characterized in that: The preparation raw material comprises the bisfluorosulfonyl imide obtained by the purification method according to any one of claims 1 to 7, or comprises the bisfluorosulfonyl imide according to claim 8.

10. The bisfluorosulfonyl imide salt according to claim 9, characterized in that The bisfluorosulfonylimide salt includes lithium bisfluorosulfonylimide.

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